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Presentasi berjudul: "REAKSI TANAH (pH Tanah) BAHAN KAJIAN MK Dasar Ilmu Tanah"— Transcript presentasi:

1 REAKSI TANAH (pH Tanah) BAHAN KAJIAN MK Dasar Ilmu Tanah

2 pH tanah merupakan indikator kemasaman atau kebasaan suatu tanah.
Apakah pH tanah? pH tanah merupakan indikator kemasaman atau kebasaan suatu tanah. Kondisi kemasaman atau kebasaan yang ekstrim mempengaruhi pertumbuhan tanaman. Some plants can grow over a wide range of pH; others are sensitive to acidity, or alkalinity. It is hard to overestimate the importance of pH in agricultural systems. pH tanah dipengaruhi oleh kimia tanah dan biologi tanah. pH tanah juga dipengaruhi oleh karakteristik fisika tanah melalui aerasi tanah dan air tanah. Diunduh dari: ………… 11 sept 2012.

3 pH TANAH pH tanah merupakan ukuran kemasaman atau kebasaan suatu tanah. pH didefinisikan sebagai logaritma negatif (base 10) aktivitas kation hidrogen (H+ atau, H3O+ aq) dalam sistem larutan. It ranges from 0 to 14, with 7 being neutral. A pH below 7 is acidic and above 7 is basic. Soil pH is considered a master variable in soils as it controls many chemical processes that take place. It specifically affects plant nutrient availability by controlling the chemical forms of the nutrient. The optimum pH range for most plants is between 5.5 and 7.0,[1] however many plants have adapted to thrive at pH values outside this range. (1). Perry, Leonard. “pH for the Garden". 11 December 2012. Diunduh dari: 11 Des 2012.

4 EMPAT KOMPONEN TANAH Padatan An-organik: Mineral & Bukan mineral
Padatan Organik : Bahan Organik Tanah (Senyawa organik mati) Organisme hidup Udara tanah …… Aerasi Tanah Air tanah = Larutan tanah Soil Solution, Elektrolit tanah Sifat fisiologik penting dari Larutan tanah adalah “REAKSINYA” (pH) ……. Kemasaman / kebasaan tanah

5 pH = - log [H+] [H+] dlm larutan tanah ………. Kemasaman aktif
[H+] dijerap koloid tanah ………. Kemasaman potensial Total keduanya ………………….. Kemasaman total Misel -H [H+] Ion H+ terjerap, Hdd Ion H+ terlarut Kisaran Nilai pH tanah: pH = 7.0 : Tanah Netral pH < 7.0 : Tanah Masam pH > 7.0 : Tanah basa/ Alkalin/Alkalis Biasanya: Tanah masam : di daerah iklim basah Tanah alkalis: di daerah kering

Hdd H+ Kation aluminium: MISEL Al Al 3+ Al H2O Al(OH)2+ + H+ Al OH Al(OH)2+ Al(OH)2+ + OH Al(OH)2 + Al(OH)2+ + H2O Al(OH) H+ Al(OH)2+ + H2O Al(OH)3 + H+ Bahan Organik Tanah:

7 Bagaimana pH tanah mempengaruhi pertumbuhan tanaman?
Kondisi ideal kemasaman tanah bagi kebanyakan tanaman adalah agak masam atau agak alkalis. At extreme pH the availability of some nutrients is decreased, e.g. phosphorus and molybdenum at low pH, and zinc at high pH; and the solubility of elements toxic to plants is increased, e.g. aluminium and manganese at low pH. Extremes in alkalinity and acidity present problems for the production of many agriculturally important plant species and their symbiotic Rhizobia. Diunduh dari: ………… 11 sept 2012.

The United States Department of Agriculture Natural Resources Conservation Service, formerly Soil Conservation Service: Klasifikasi pH tanah : Tata nama Kisaran pH Ultra acid < 3.5 Extreme acid 3.5–4.4 Very strong acid 4.5–5.0 Strong acid 5.1–5.5 Moderate acid 5.6–6.0 Slight acid 6.1–6.5 Neutral 6.6–7.3 Slightly alkaline 7.4–7.8 Moderately alkaline 7.9–8.4 Strongly alkaline 8.5–9.0 Very strongly alkaline > 9.0 Diunduh dari: 11 Des 2012.

Kemasaman dalam tanah berasal dari kation-kation H+ dan Al3+ yg ada dalam larutan tanah dan terjerap pada permukaan koloid tanah. pH merupakan ukuran H+ dalam larutan, Al3+ penting dalam tanah masam karena pd kondisi pH antara 4 dan 6, Al3+ bereaksi dnegan air (H2O) menghasilkan AlOH2+, dan Al(OH)2+, melepaskan ion H+. Every Al3+ ion can create 3 H+ ions. Many other processes contribute to the formation of acid soils including rainfall, fertilizer use, plant root activity and the weathering of primary and secondary soil minerals. Acid soils can also be caused by pollutants such as acid rain and mine spoilings. Curah hujan: Tanah-tanah masam seringkali ditemukan di daerah dg curah hujan tinggi. Air hujan yg berlebihan dapat mencuci kation basa ke luar tanah,, meningkatkan persentase Al3+ dan H+ relatif dibandingkan kation lainnya. Air hujan reaksinya sagak masam, pH = 5.7 karena reaksi air dnegan CO2 di udara membentuk asam karbonat. Penggunaan pupuk: Ammonium (NH4+) fertilizers react in the soil in a process called nitrification to form nitrate (NO3−), and in the process release H+ ions. Diunduh dari: 11 Des 2012.

AKTIVITAS AKAR TUMBUHAN: Plants take up nutrients in the form of ions (NO3−, NH4+, Ca2+, H2PO4−, etc.), and often, they take up more cations than anions. However plants must maintain a neutral charge in their roots. In order to compensate for the extra positive charge, they will release H+ ions from the root. Some plants will also exude organic acids into the soil to acidify the zone around their roots to help solubilize metal nutrients that are insoluble at neutral pH, such as iron (Fe). PELAPUKAN MINERAL: Both primary and secondary minerals that compose soil contain Al. As these minerals weather, some components such as Mg, Ca, and K, are taken up by plants, others such as Si are leached from the soil, but due to chemical properties, Fe and Al remain in the soil profile. Highly weathered soils are often characterized by having high concentrations of Fe and Al oxides. HUJAN ASAM: Kalau air di atmosfir bereaksi dnegan senyawa-senyawa sulfur dan nitrogen yg dihasilkan oleh emisi industri, maka hasilnya adalah pembentukan asam sulfat dan asam nitrat dalam air hujan.. Akan tetapi rata-rata jumlah kemasmaan yang ada dalam air hujan lebih kecil (lebih sedikit) dibandingkan dnegan yg dihasilkan oleh aktivitas pertanian. Mine Spoil: Severely acidic conditions can form in soils near mine spoils due to the oxidation of pyrite. Diunduh dari: 11 Des 2012.

Hara yang diperlukan tanaman dalam jumlah besar disebut hara makro, termasuk nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg) dan sulfur (S). Unsur hara yg diperlukan tanaman dalam jumlah sedikit disebut hara mikro. Trace nutrients are not major components of plant tissue but are essential for growth. They include iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), cobalt (Co), molybdenum (Mo), and boron (B). Ketersediaan unsur hara makro dan mikro dalam tanah sangat dipenagruhi oleh pH tanah. In slightly to moderately alkaline soils, molybdenum and macronutrient (except for phosphorus) availability is increased, but P, Fe, Mn, Zn Cu, and Co levels are reduced and may adversely affect plant growth. In acidic soils, micronutrient availability (except for Mo and Bo) is increased. Nitrogen disuplai sebagai ammonium (NH4) atau nitrate (NO3) dalam bentuk pupuk, dan N yang terlarut konsentrasinya tertinggi dalam tanah yang mempunyai pH 6–8. Diunduh dari: 11 Des 2012.

Konsentrasi N-tersedia kurang dipengaruhi oleh pH tanah, dibandingkan dengan efek pH tanah terhadap konsentrasi P-tersedia.. In order for P to be available for plants, soil pH needs to be in the range 6.0 and 7.5. If pH is lower than 6, P starts forming insoluble compounds with iron (Fe) and aluminium (Al) and if pH is higher than 7.5 P starts forming insoluble compounds with calcium (Ca). Ketersediaan hara dalam atanah dipengaruhi oleh pH tanah. Defisiensi hara tidak terjadi pada kondisi kisraan pH , asalkan mineral atanah dan bahan organik tanah cukup mengandung unsur hara esensial. Diunduh dari: 11 Des 2012.

13 Diunduh dari:………… 11 Des 2012.
TANAMAN & pH TANAH pH 4.5–5.0 Blueberry, Bilberry, Heather, Cranberry, Orchid, Azalea, for blue Hydrangea (less acidic for pink), Sweet Gum, Pin Oak. pH 5.0–5.5 Parsley, Potato, Heather, Conifers, Pine, Sweet Potato, Maize, Millet, Oars, Tye, Radish, Ferns, Iris, Orchids, Rhododendron, Camellia, Daphne and Boronia. pH 5.5–6.0 Bean, Brussels Sprouts, Carrot, Choko, Endive, Kohl Rabi, Peanuts, Rhubarb, Soybean, Crimson Clover, Aster, Begonia, Canna, Daffodil, Jonquil, Larkspur, Petunia, Primrose, Violet and most bulbs. pH 6.0–6.5 : Broccoli, Cabbage, Cannabis, Cauliflower, Cucumber, Aubergine, Pea, Sweet Corn, Pumpkin, Squash, Tomato, Turnip, Red Clover, Sweet Clover, White Clover, Candytuft, Gladiolus, Iceland Poppy, Pansy, Rose, Snapdragon, Viola, Wallflower, Zinnea and Strawberry. pH 6.5–7.0 : Asparagus, Beet, Celery, Lettuce, Melons, Onion, Parsnip, Spinach, Alfalfa, Carnation, Chrysanthemum, Dahlia, Stock, Sweet Pea and Tulip. pH 7.1–8.0 untuk jenis-jenis Lilac, brassica. Diunduh dari: 11 Des 2012.

14 What is an optimum soil pH?
Kebanyakan hara menunjukkan ketersediaan maksimum pada kondisi tanah agak masam, netral atau agak alkalis. Bentuk paling fitotoksik aluminium dan manganese mempunyai konsnetrasi paling minimum pada kondisi kisraan pH ini. Emil Truog did some outstanding work over 60 years ago and his conclusions on how pH affects the availability of nutrients are still widely used today. Diunduh dari: ………… 11 sept 2012.

15 Bagaimana mengukur pH tanah?
Soil pH may be measured on site using a colorimetric kit and a fresh sample. More reliably, it can be measured in a laboratory, using a prepared sample and a pH probe. As pH is usually measured as one of a suite of soil tests to assess fertility, the laboratory option is quite practical. Bagaimana pH tanah beragam dnegan kedalaman? pH beragam di dlaam profil tanah. pH di seluruh profil tanah atau pada suatu horison tidak dapat diprediksi dengan mengukur pH lapisan tanah permukaan. Nilai pH yang ekstrim pada tanah lapisan bawah dapat menjadi kendala bagi pertumbuhan tanaman. Diunduh dari: ………… 11 sept 2012.

16 Bagimana perubahan pH tanah ?
The most common way of increasing soil pH is applying agricultural lime. It is, however, an activity that requires a good application of science to be both effective and economic. Keberhasilan pengapuran dapat terjadi kalau petani: Knows the target pH for the plants being grown Incorporates lime by cultivation Matches the quantity and quality of lime with amount needed for the pH buffering capacity of the soil Can get it on the ground at a sufficiently cheap price (i.e. including transport and spreading costs) Management decisions on the application of lime must consider many factors. Aside from business objectives, important factors include: Jenis Kapur = The type of lime its effective neutralising value (a product of fineness and composition) the moisture content of the lime application method depth of soil to be ameliorated soil texture (e.g. coarse textured soils like sands need less lime than fine textured soils) organic matter content (e.g. low organic matter content soils require less lime to ameliorate acidity than peaty soils) Waktu = timing Respon tanaman = plant response Biaya = cost Diunduh dari: ………… 11 sept 2012.

17 Does soil pH change with time (and should I worry)?
Praktek pertanian seringkali menurunkan pH tanah (yaitu asidifikasi). Praktek budidaya pertanian yg seringkali menimbulkan efek pengasaman tanah: Sowing annual dominant pastures Pertanaman yang melibatkan legumes Aplikasi pupuk N (termasuk pupuk cair N dan pupuk N lewat irigasi, fertigasi) Panen produk/hasil, terutama hay dan biji-bijian. There is therefore an imperative to monitor pH changes and take action to remediate as required. In some instances, soil acidification has affected the subsoil as well as the surface soil. This presents difficulties for farmers as it is not easy to ameliorate acidified subsoils. Lime does not readily move down the profile. Diunduh dari: ………… 11 sept 2012.

18 Tanah-tanah alkalin biasanya ditemukan di daerah iklim semiarid.
SEKALA pH TANAH Konsentrasi H+ dalam tanah diukur dengan sekala pH.  Nilai pH tanah berkisar dari 3 hingga 10. Air murni mempunyai pH = 7 yamng dianggap “netral”, nilai-nilai pH yg lebih besar dari 7.0 dianggap “basa atau alkalin”, nilai pH kurang dari 7.0 disebut “masam”. Most good agricultural soils have a pH between 5 and 7. Though acidic soils pose a problem for agriculture due to their lack of nutrients, alkaline soils can pose a problem as well. Alkaline soils may contain appreciable amounts of sodium that exceed the tolerances of plants, contribute to high bulk density and poor soil structure. Tanah-tanah alkalin biasanya ditemukan di daerah iklim semiarid. Diunduh dari:

19 PENGUKURAN pH TANAH pH dapat diukur dengan menggunakan pH meter atau dengan indikator; kedua cara ini dipakai untuk uji tanah. pH meter biasanya dipakai dilaboratorium. Metode indikator warna lazimnya dipakai oleh petani atau petugas lapangan untuk menguji tanahnya.

20 Mengukur dan Menginterpretasi pH Tanah
Kimiawi pH tanah pH merupakan ukuran aktivitas H+ dalam larutan tanah. Kalau konsentrasi H+ tinggi, medium ini disebut masam. If it is low, it is said to be alkaline. pH is defined on a logarithmic scale, which means that a 1 unit change in pH is in effect a ten-fold change in acidity. Dalam simbol matematika, pH = log10 1/[H+] Kisaran pH dalam tanah While pH is measured on a scale of 1 to 14, most agricultural soils are found between the range 4 to 10 (when measured in water). For practical purposes, soil is neutral when pH is between 6 to 8, depending on plant requirements, and it is acidic when pH is less than 6 and alkaline when it is greater than 8. Diunduh dari: …………… 23/3/2013

21 Mengukur dan Menginterpretasi pH Tanah
Kisaran nilai pH dalam biologi Acid fluids include vinegar (pH 3), gastric fluids (pH 1.2), lemon juice (pH 2.2), rain water in equilibrium with atmospheric CO2 (pH 5.6), and even egg yolks (pH 5.6). Contoh cairal alkalis adalah air laut (pH 8), darah (pH 7.4), ammonia pembersih (pH 11.5) dan soda kue (pH 8.2). Diunduh dari: …………… 23/3/2013

22 Mengukur pH pH ditentukan dnegan jalan mengukur aktivitas ion H+ dalam larutan air. Untuk ini dapat dipakai elektrode gelass yang dikalibrasi dengan standard pH. Mengukur pH tanah di laboratorium A sub-sample of soil is mixed with water or CaCl2 at a ratio of 1 part soil to 5 parts liquid and the pH of the suspension is measured after 1 hours shaking. Most laboratories are equipped to automatically measure electrical conductivity and pH in 1 part soil to 5 parts 0.01 M CaCl2 at the same time. Metode ekstraksi 0.01 M CaCl2 juga telah banyak dipakai: metode ini dianggap lebih “kuat” mengukur pH tanah karena kurang dipengaruhi oleh garam-garam tanah. Metode pengukuran pH tanah sangat penting dalam kaitannya dnegan interpretasi hasilnya. (misalnya pHw: metode ekstraksi air). Diunduh dari: …………… 23/3/2013

23 Mengukur pH tanah di lapangan
A field pH test kit with a colorimetric indicator can be used on site, or the laboratory method can be roughly imitated by shaking 1 part soil in 5 parts water by hand and inserting a pH probe into the suspension. To use a field pH test kit, a small sample of soil is collected and an indicator solution is added to form a paste. The paste is then coated with barium sulphate powder. The powder changes colour depending on the pH of the soil, and the colour of the powder is compared with a colour chart. Ketelitian metode ini lebih rendah dibandingkan dnegan di laboratorium. Perlengkapan “kits” mengalami kerusakan dnegan waktu, sehingga harus diganti setelah masa kerja bulan. Diunduh dari: …………… 23/3/2013

24 pH dan Konsentrasi kation H+
pH menghitung proton ion hidrogen (H+ ). It only measures those hydrogen ions free in the soil solution. Protons that are bound to molecules are not counted. However, there is a continual slow release of hydrogen ions into the soil solution from other molecules. In addition, some hydrogen ions leave the soil solution to bind with chemical molecules. Thus there is a dynamic equilibrium where each hydrogen ion is free in solution for a very short time of approximately 2 x10^12 seconds. pH measures this trading activity in and out of the soil solution. Larutan netral mempunyai konsentrasi ion hidrogen 10^7 (moles per litre). Signifikansi sekala log ini , misalnya pH 5 adalah sepuluh kali lebih masam dibandingkan dnegan pH 6, tetapi seratus kali lebih masam dibanding dnegan pH 7, sehingga memerlukan jauh lebih banyak kapur untuk menaikkan pH. Diunduh dari: pdf…………… 23/3/2013

25 Hubungan antara pH dengan beberapa jenis material
Konsentrasi H+ Reaksi tanah pH Contoh substansi 10^-0 Asam murni Asam sulfat 10^-1 Asam ekstrim 1 10^-2 Asam Ekstrim 2 10^-3 Asam sangat kuat 3 10^-4 Asam kuat 4 Orange 10^-5 Asam Moderat 5 Urine 10^-6 Asam ringan 6 Air hujan jernih 10^-7 Netral 7 Air suling 10^-8 Alkalin ringan 8 Air laut 10^-9 Alkalin moderat 9 Larutan sabun 10^-10 Alkalin kuat 10 10^-11 Alkalin sangat kuat 11 10^-12 Alkalin ekstrim 12 Garam berbau ammonia 10^-13 13 Larutan soka kaustik 10^-14 Alkalin murni 14 Na hidroksida pekat Diunduh dari: pdf…………… 23/3/2013

26 METODE PENGUKURAN pH Ada abanyak metode untuk mengukur pH tanah. Some use a saturated paste extract, others use a 1:5 dilution of soil: water, and then take a pH measurement on the resulting solution with a laboratory meter. Others use the 1:5 dilution, but instead of water they use a dilute Calcium Chloride (CaCl²) solution. Sebagai pedoman umum, nilai pH dalam CaCl² biasanya 0.8 pH lebih rendah dibandingkan dengan pH dalam air, tetapi dapat lebih rendah 2.0 unit pH pada tanah-tanah pasir kelabu. Diunduh dari: 23/3/2013

27 Larutan CaCl2 untuk Uji Tanah
Menggunakan larutan encer CaCl² memberikan hasil lebih konsisten daripada menggunakan air hujan atau air biasa. Kalau tanah diencerkan dalam air , kebanyakan ion H+ cenderung tetap terikat pada partikel tanah dan tidak dilepaskan ke dalam larutan tanah. Penambahan sedikit CaCl2 menyediakan kation Ca++ untuk menggantikan kation H+ pada partikel tanah, memaksa ion H+ memasuki larutan dan konsnetrasinya dalam larutan lebih mendekati kondisi lapangan. pH yang diukur dalam larutan CaCl² hampir selalu lebih rendah daripada pH yg diukur dalam air, karena konsnetrasi H+ dalam larutan lebih tinggi. Prosedur ekstraksi ini lebih mendekati kondisi lapangan, karena larutan tanah di lapangan juga mengandung Ca++ larut dan ion-ion lainnya. Make up a dilute CaCl² solution with distilled/deionised water to use as you need it. Ready made calcium chloride solutions often do not keep for very long, so buy CaCl² and make the solution yourself. The calcium chloride is usually the dehydrate form (water is attached to the crystals - it will have this written on the label of the container - CaCl².2H²O). Dissolve approximately 7.5g of the salt in 5 litres of distilled/deionised water. If you are using a form of calcium chloride crystals without any water attached (CaCl²), dissolve about 5.5g of the salt in 5 litres. Diunduh dari: …………… 23/3/2013

28 Metode-metode untuk pH Tanah
Use the spoon to weigh out about 10g (to the nearest half gram), of your soil into the container. Add 50ml of distilled water to the soil. Any rough measurement ensuring a 1:5 diluted will suffice. Shake the container for about 2-3 minutes then allow the soil to settle for 2 minutes. Kalau tanah mempunyai kandungan liat yg tinggi dan diperlukan hasil analisis yang akurat, maka tidak perlu menyaring suspensi. Kalau tidak perlu disaring, ukurlah nilai pH pada air di atas tanah dalam tabung. Ensure you get a steady reading on the digital readout. Always wash your containers out before testing your next sample. Diunduh dari: …………… 23/3/2013

29 Lingkup Prinsip Dasarnya
Pengukuran pH tanah : Metode Suspensi ---- Tanah : Air = 1:5 Lingkup This is the activity of the negative log of the hydrogen ion in a suspension of 1:5 soil:water. It is the de facto standard pH measurement for most soil test interpretations. The pH measured in 1:5 soil:water suspension is sensitive to seasonal variations in the pH of soil solutions. Prinsip Dasarnya pH ditentukan pada suspensi tanah:air bebas ion 1:5. Pengyukuran pH melibatkan deteksi muatan dalam potensial dari elektrode kombinasi silver/silver chloride atau elektrode gelas / electrode referensi menggunakan pH meter atau millivolt meter yang distandardisir dnegan larutan buffer tertentu. Peralatan khusus: • pH meter dan pH electrode. • Pengaduk Mekanis Diunduh dari: lab/pH.pdf …………… 23/3/2013

30 Pengukuran pH tanah : Metode Suspensi ---- Tanah : Air = 1:5
Reagen-reagen pH 4.01 Buffer (25 °C) Dry potassium hydrogen phthalate AR (KHC8H4O4) for 2 hours at 105 °C and cool in a desiccator before the initial weighing. Dissolve g in deionised water and make to 1 L in a volumetric flask. The solution is stable for 6 weeks. Discard if fungus appears. Record the date the buffer was made up on the container. pH 6.86 Buffer (25 °C) Dry potassium dihydrogen phosphate (KH2PO4) and disodium hydrogen phosphate (Na2HPO4) for 2 hours at 105 °C and cool in a desiccator before the initial weighing. Dissolve 3.38 g of KH2PO4 and 3.35 g of Na2HPO4 in about 800 mL of deionised water and make up to 1 L in a volumetric flask. pH 9.18 Buffer (25 °C) Larutkan g sodium tetraborate (Na2B4O7.10H2O) dalam sekitar 800 mL air bebas ion dan encerkan menjadi 1 L dalam tabung volumetrik. Larutan buffer ini harus dilindungi sehingga tidak menyerap CO2 dari udara. Larutan buffer yg tersedia secara komersial dapat digunakan. Diunduh dari: lab/pH.pdf …………… 23/3/2013

31 Pengukuran pH tanah : Metode Suspensi ---- Tanah : Air = 1:5
Prosedur Menyiapkan suspensi tanah : air dengan rasio 1:5. Weigh 10 g air-dry soil (<2 mm) into a bottle and add 50 mL deionised water. (Other amounts can be used e.g. 20 g:100 mL provided the 1:5 ratio is maintained.) Mechanically shake for 1 hour at 15 rpm. (Lihat catatan No. 1.) Calibrate the pH meter according to manufacturer's instructions using the buffer at pH 6.86 and either the 4.0 or 9.18 buffer depending on the expected values for the soils. Stir these solutions with a mechanical stirrer during measurement. Thoroughly wash the electrode between measurements with deionised water. (Lihat catatan No. 2.) Immerse the electrode into the soil suspension. Record the pH value obtained when the equilibrium is reached while stirring with a mechanical stirrer. (lihat Catatan No. 3.) Diunduh dari: lab/pH.pdf …………… 23/3/2013

32 Pengukuran pH tanah : Metode Suspensi ---- Tanah : Air = 1:5
Catatan-catatan Kalau diperlukan pH dapat ditentukan pd suspensi tanah yg sama dengan sampel untuk pengukuran konduktivitas elektrik. Karena adanya limbahan KCl dari elektrode referensi pH, maka konduktivitas elektris harus diukur lebih dahulu. Periodically confirm there is adequate leakage of KCl from the electrode otherwise inaccurate readings may be obtained on soil suspensions. This is achieved by placing the reference electrode in dilute AgNO3 solution and observing that a precipitate of AgCl forms. Waktu kesetimbangan beragam dengan umur elektrode dan kapasitas penyangga dari sampel. Diunduh dari: lab/pH.pdf …………… 23/3/2013

33 MENGUKUR pH TANAH Ada banyak faktor yang mempengaruh reaksi tanah yang diukur di laboratorium. pH dari banyak tanah cenderung meningkat kalau contoh tanah diencerkan dalam air. Perubahan pH seperti ini dapat disebabkan oleh variabel-variabel seperti tekanan potensial CO2, konsnetrasi garam, hidrolisis, dan kelarutan komponen tanah. Berbagai rasio tanah:air telah dicobakan untuk penentuan pH tanah. Rasio ini berkisar dari suspensi sangat encer (rasio tanah:air = 1:10) hingga poasta tanah. Efek secara umum menunjukkan bahwa pH tanah meningkat dnegan pengenceran, dan menjadi konstan pada rasio sekitar tanah:air = 1:5.  There is no standard procedure for measuring soil pH. Some of the details that vary from one laboratory to the next are: soil:solution ratio, use of a salt solution (e.g., 0.01 M CaCl2) rather than water, method of mixing, time of standing before reading, etc. Soil may be weighed, or measured as a volume (McLean 1982). Therefore, when reporting sol pH, it is essential to include at least a brief summary of the procedure followed. Diunduh dari: 23/3/2013

34 MENGUKUR pH TANAH The exact placement of the pH electrode in the sample may be important. When placed in the settled sediment of a suspension of soil of appreciable cation exchange capacity (CEC), a lower pH is generally measured compared to the measurement obtained in the supernatant solution (called the suspension effect). Akan tetapi, nilai pH sedimen dapat lebih rendah, sama, atau lebih tinggi daripada nilai pH supernatan-nya, tergantung pada tanah dan kondisi aktualnya. Misalnya, kalau suatu tanah mempunyai muatan neto positif, dan lebih banyak ion OH- daripada kation H+ terdisosiasi dari tanah, maka sedimen dapat mempunyai nilai pH lebih tinggi daripada supernatan-nya (Coleman and Thomas 1967). Diunduh dari: 23/3/2013

35 MENGUKUR pH TANAH . Faktor-faktor tanah di lapangan yg mempengaruhi reaksi tanah adalah kejenuhan basa, tipe koloid tanah, tekanan potensial CO2, potensial oksidasi, garam larut, dll. Nilai pH contoh tanah juga dipengaruhi oleh tindakan pengelolaan contoh tanah selama di laboratorium. pH can be determined using either colorimetric or electrometric methods. The choice of method depends upon the accuracy required, the equipment available, or convenience. Many organic dyes are sensitive to pH, the color of the dye changing more or less sharply over a narrow range of H-ion activity. These methods tends to be slower, less precise, and obscured from view by soil particles and organic matter. Hence, they are used mostly in the field where pH is to be approximated. Diunduh dari: 23/3/2013

36 MENGUKUR pH TANAH . The electrometric method involves a glass electrode that is sensitive to H+: there is an exchange of ions between solution (H+) and glass (Na+) (Westcott 1978). A reference electrode that produces a constant voltage is also required. The electrode pair produces an electromotive force (emf or voltage) that is measured by a millivoltmeter. The relation between emf and pH is governed by the Nernst equation: where E = emf produced by electrode system Eo = a constant dependent on the electrodes used R = gas constant T = absolute temperature n = number of electrons involved in equilibrium (1 in this case) F = Faraday constant  (Willard et al., 1988, p. 675). Temperatur merupakan faktor dalam persamaan. Pada suhu 25°C persamaan ini disimplifikasikan menjadi E = E° pH Hal ini berarti bahwa perubahan satu unit pH menghasilkan perubahan emf sebesar mV, pada suhu 25°C. Ketergantungan pH pada suhu ini snagat penting ketika mengkalibrasikan suatu pH meter. Diunduh dari: 23/3/2013

37 Mengukur pH tanah untuk Taksonomi Tanah
The Soil Survey Laboratory Methods Manual (USDA, 2004) describes several methods used by the laboratory at the National Soil Survey Center to measure soil pH.  Metode-metode yang berhubungan dnegan kriteria dalam Soil Taxonomy (Soil Survey Staff, 1999) dijelaskan dalam dokumen itu  The reader is advised to study the laboratory methods companion document Soil Survey Laboratory Information Manual (USDA, 1995).  This manual provides informative operational and conceptual definitions for all soil properties measured by the Kellogg Soil Survey Laboratory.  Dalam dokumen itu juga dijelaskan bagaimana aplikasi masing-masing metode untuk klasifikasi tanah, genesis tanah, dan geomorphology. Diunduh dari: 23/3/2013

38 Mengukur pH tanah untuk Taksonomi Tanah
Metode ekstraksi air (1:1 H2O) dan Metode ekstraksi CaCl2 (1: molar (M) CaCl2 ) Metode Ekstraksi Air 1:1 H2O is a mixture, by weight, of one part soil to one part distilled H2O.  It is the method most commonly used in the field because of the availability of water.  Seasonal variations in soil pH can be detected with the 1:1 H2O method; therefore, it is not used to determine family reaction classes in Soil Taxonomy.  If pH varies widely, knowledge of this variability is important because of the effect of pH on crop performance and on some other aspects of land use. Metode Ekstraksi CaCl2 1: M CaCl2 is a mixture, by weight, of one part soil to two parts 0.01 M CaCl2 solution.  Calcium chloride (CaCl2) pH is the standard used in Soil Taxonomy to differentiate acid and nonacid family reaction classes in mineral soils and euic and dysic family classes in organic soils.  The 0.01 M CaCl2 solution dampens the seasonal variation in soil pH by providing Ca2+ ions that displace the hydronium and aluminum ions from the colloid surfaces.  The result is a pH measurement that remains somewhat invariable to the seasonal changes in pH.  The use of the CaCl2 solution also diminishes the seasonal effect of soluble salt concentration. Diunduh dari: 23/3/2013

39 Mengukur pH tanah untuk Taksonomi Tanah
Metode ekstraksi KCl normal: 1:1 1 normal (N) KCl Penggunaan nilai pH metode ekstraksi dengan larutan 1:1 1 N KCl adalah untuk uji keberadaan aluminum dapat ditukar. Nilai absolut pH(KCl ) sangat berkorelasi dnegan kejenuhan aluminum.  Larutan garam yang lebih pekat ini menggantikan H+ dan Al+++ secara komplit, sedangkan larutan 0.01 M CaCl2 tidak selalu demikian.   Aluminum, yang digantikan oleh K+ pada tapak jerapan, mengkonsumsi OH– dan meningkatkan [H+].  Akibatnya, nilai pH larutan menurun.  Umumnya, aluminum dapat ditukar dapat ditemukan kalau nilai pH ekstraksi 1 N KCl nilainya atau kurang.  Kalau nilai pH tanah dnegan ekstraksi 1 N KCl lebih dari 5.2, aluminum menjadi tidak-dapat ditukar karena hidrolisis, polimerisasi, dan pengendapan.  Oleh karena itu, dalam tanah-tanah oxisols yg terlapuk lanjut, kesuburannya rendah, great-group “Acr”, kriteria “1 N KCl pH > 5.0” menyatakan bahwa toksisitas aluminium tidak penting. For soils that have a net negative charge (cation-exchange capacity), the 1:1 1 N KCl pH generally is about 1 pH unit lower than the 1:1 H2O pH.  Be aware that 1 N KCl significantly modifies the natural soil environment.  Thus, the 1 N KCl pH is not reliable for interpreting the soil’s fertility or crop production potential. Diunduh dari: 23/3/2013

40 Mengukur pH tanah untuk Taksonomi Tanah
Delta pH The comparison of KCl pH with H2O pH provides an assessment of the nature of the net charge on the colloidal system.  For example, highly weathered Oxisols with high amounts of iron oxihydrates have a net positive charge (anion-exchange capacity).  If the content of organic matter is low or negligible in such soils, the 1:1 1 N KCl pH may be higher than the1:1 H2O pH.  The difference in pH results from displacement of OH– ions by Cl– ions.  The numerical difference in the values of pH measured in KCl and H2O is referred to as the delta pH.  When this difference is negative, the colloid has a net negative charge, and when positive, it has a net positive charge.  This relationship is used as differentiae in the Anionic subgroups of the Acric great groups of Oxisols, in which the delta pH (KCl pH minus 1:1 H2O pH) is zero or positive.  Delta pH is not estimated when the pH is higher than about CATATAN:  The difference in pH between 1:1 H2O and 1: M CaCl2 may also be positive or negative.  However, the delta pH in Soil Taxonomy is not measured with 0.01 M CaCl2.  In order to completely exchange the aluminum ions, a much higher salt concentration is needed, and so 1 N KCl is used. Diunduh dari: 23/3/2013

41 Mengukur pH tanah untuk Taksonomi Tanah
Oxidation pH Acid sulfate soil formation occurs when sulfide minerals, such as pyrite, and/or elemental sulfur in reduced sulfidic sediments oxidize upon exposure to air through drainage or earth-moving operations.  The oxidation products are jarosite and sulfuric acid.  Jarosite undergoes hydrolysis in an oxidizing environment, releasing iron oxyhydrates and more sulfuric acids.  This set of reactions is one of the most acid-producing reactions in soils.  A sulfuric horizon is indicated if acid sulfate formation gives an end product pH of 3.5 or less. Oxidation pH is used to test for the presence of sulfidic material and to predict the occurrence of sulfuric horizons.  The laboratory procedure accelerates the natural formation of microbial acid sulfate.  Microbial oxidation of sulfidic material is controlled by incubating a saturated soil sample in a closed container at room temperature.  The sample is periodically stirred, so that the O2 needed for the oxidation process is incorporated, and the pH (1:1 H2O) is measured.  The sample is given ample time (up to 8 weeks) to fully oxidize.  When the change is a pH unit of less than 0.03, the oxidized pH is recorded.  For a more rapid test, hydrogen peroxide is added to the soil.  The result is violent effervescence and an extremely acid suspension, indicating the presence of acid sulfate material. Diunduh dari: 23/3/2013

42 Mengukur pH tanah untuk Taksonomi Tanah Metode: 1 molar (M) NaF Ph
The pH of a suspension containing 1 g soil in 50 mL 1 M NaF is used as a criterion for the isotic mineralogy class.  This method tests for the presence of short-range order minerals.  These minerals are commonly early products of the weathering of pyroclastic materials or are formed in spodic horizons in a humid climate.  The action of 1 M NaF on these minerals releases hydroxide ions (OH–) to the soil solution and increases the pH.  A 1 M NaF pH of more than 8.4 at 2 minutes after the NaF solution is added is a strong indicator (in non-calcareous soils) that short-range order minerals dominate the soil exchange complex. Karbonat bebas dalam tanah dapat menghasilkan tingginya nilai pH ekstraksi NaF , tanpa adanya mineral-mineral “short-range order”.  Oleh akrena itu, kelas mineralogi ISOTIK tidak termasuk tanah-tanah yg mengandung karbonat bebas.. Diunduh dari: 23/3/2013

43 Mengukur pH tanah untuk Taksonomi Tanah
.Mengukur pH tanah di lapangan Pocket pH meters, standard dyes, and paper pH indicator strips are commonly used when pH is measured in the field.  Pocket pH meters can be used in 1:1 H2O or any soil:salt solution.  The meters must be well maintained and calibrated to be reliable.  They are sensitive and can become faulty.  Clean them as specified, keep them well calibrated, and do not leave them where they will be subject to excessively hot or cold temperatures. Although they continue to improve, pH meters are less dependable than standard dyes, which are quite accurate.  Soil pH measured with pH meters in a laboratory setting and then measured with dye differs by a pH unit of no more than 0.3 when the dye is used carefully.  Temperature extremes and prolonged exposure to sunlight can affect the reliability and longevity of dyes.  Several kits are in use.  Some of them include a neutral salt.  As a result, the pH measured from different kits may vary.  The same indicator dyes that are applied to 1:1 H2O can be applied to 1: M CaCl2 and 1:1 1 N KCl soil:water suspensions. Paper pH indicator strips are bonded with dyes.  They can be used in 1:1 H2O or any soil:salt solution.  They are as accurate as standard liquid dyes and are not so sensitive to temperature and sunlight.  Unlike pocket pH meters, these strips are not subject to breakage and do not need to be calibrated and maintained.  Indicator colors are easily distinguishable. Diunduh dari: 23/3/2013


45 Why is pH important to plant health?
Pentingnya pH tanah Why is pH important to plant health? pH tanah ternyata snagat penting. It affects soils fertility by controlling how well nutrients are dissolved. You can fertilize all you want but if your soils pH is out of range your plants will be unable to access or utilize that fertilizer. Also while plant nutrients are being rendered insoluble, toxic elements become more soluble and can potentially kill plants or severely damage roots. In addition, beneficial soil bacteria will not grow in either highly acidic or highly alkaline soil and without the help of these guys your soils structure will be poor. Symptoms of excessively high or low pH include plants exhibiting yellowing leaves, lack of proper growth and flowering and in severe cases death of the plant. Jenis-jenis tanaman tertentu lebih senang tanah masam, sedangkan jenis lainnya lebih senang tanah alkalis. Pengukuran nilai pH tanah dapat membantu dalam memilih jenis tanaman yang palign sesuai dnegan kondisi tanah. Diunduh dari: 22/3/2013

46 Penyangga (buffer) pH Tanah
Kapasitas penyangga suatu tanah menyatakan “kemampuan” tanah untuk melawan perubahan pH nya; kemampuan tanah ini berbeda-beda. Tanah-tanah yg kaya liat atau bahan organik mempunyai banyak tapak jerapan yg mampu mengakomodasi H+ dan dapat menahan lebih banyak H+ sebelum mengalami peningkatan konsnetrasi H+ dalam larutan tanah. Akan tetapi, kalau tanah-tanah ini telah menjadi masam, tanah-tanah seperti ini mampu melepaskan H+ ke dalam larutan tanah untuk mempertahankan kesetimbangan dan melawan peningkatan pH tanah. Clays are generally better buffered than loams, which in turn are better buffered than sands. Better buffered soils are slower to acidify but require more lime to lift pH when they do acidify. The naturally acidic peaty sands have a high buffering capacity and would require more lime to increase pH. Diunduh dari: 22/3/2013

47 pH & Ketersediaan Hara Ca dan Mg: Ketersediaan maksimum: pH = 6 - 8.5
Ketersediaan minim pada tanah dg : pH < 4.0 N, K dan S: Ketersediaan maksimum: pH > 6 Ketersediaan minim pada tanah dg : pH < 4.0 Fosfat : Ketersediaan maksimum: pH = Ketersediaan minim pada tanah dg : pH < 4.0 Fe, Mn,Zn, Cu,Co : Ketersediaan maksimum: pH < 5.5 Ketersediaan minim pada tanah dg : pH > 7.5 Mo: Ketersediaan maksimum pd pH > 6.5 Bakteri & Aktinomisetes : Ketersediaan maksimum: pH > 5.5 Ketersediaan minim pada tanah dg : pH < 4.0

48 pH dan ketersediaan hara dalam tanah
Soil acidity can cause nutrients to be changed chemically to forms that can't be used by plants. Nutrients become more soluble and are easily leached out of the soil, so they are removed when the soil water drains away. Unsur hara menjadi lebih sulit larut , tidak melarut, dan oleh karenanya tidak tersedia bagi tanaman. Pada kondisi di bawah kemasmaan tertentu, bakteri tanah menghentikan aktivitas dekomposisi bahan organik. Ketersediaan hara terganutng pada aktivitas tanah Diunduh dari:

Soil Reaction (pH) From an agricultural standpoint pH is important because it strongly affects plant growth, nutrient availability,elemental toxicity and microbial activity. In an agricultural sense, soil pH indirectly affects plant growth. Diunduh dari:

50 Diunduh dari:…………… 24/3/2013
Soil pH has direct influence on root activity, availability and absorption of nutrients by plants. Diunduh dari: 24/3/2013

51 Banyak hara menjadi mudah tersedia pada kisaran pH 6 -7.
Diunduh dari: 24/3/2013

52 pH Tanah dan Efisiensi Pupuk
Diunduh dari: 24/3/2013

Soil pH is a measurement of the acidity or alkalinity of a soil.  On the pH scale, 7.0 is neutral. Below 7.0 acid, and above 7.0is basic or alkaline.  A pH range of 6.8 to 7.2 is termed near neutral.  Daerah-daerah dnegan curah hujan terbatas biasanya mempunyai tanah alkalis, sedangkan daerah dg curah hujan tinggi mempunyai tanah masam. Kisaran pH dan efeknya pada pertumbuhan tanaman pH = 7.0 adalah netral. pH > 7.0 : alkalis pH < 7.0 : masam. pH tanah dan pertumbuhan tanaman Diunduh dari: .

54 Problem Kemasaman Tanah
Kesuburan tanah Ketersediaan Unsur Hara Suasana fisiologis larutan tanah tidak sesuai bagi proses-proses pertumbuhan akar tanaman Keracunan unsur hara mikro Gangguan akibat tingginya ketersediaan/kelarutan kation aluminium Gangguan kehidupan jasad renik tanah Menurunkan kemasaman tanah = Menaikkan pH tanah = ………… Pengapuran

55 Aldd dan % KEJENUHAN Al 1. Sumber kemasaman tanah : H+, Hdd, Aldd,
2. Aldd diendapkan pada pH > 3. % kejenuhan Al dari KTK efektif menjadi ukuran kemasaman tanah 4. Kejenuhan basa (KB) = jumlah basa dibagi KTK 5. Aldd ditentukan dengan jalan ekstraksi tanah dg 1 N KCl, dan mentitrasi ekstraksnya dengn larutan basa 6.

pH tanah 5.4 5.1 4.8 4.5 4.2 3.9 Sumber: Abruna et al. 1975 Ultisols & Oxisols % kejenuhan Al

% hasil maks. 100 80 60 40 20 Sumber: Abruna et al. 1975 Ultisols & Oxisols r = 0.93** % kejenuhan Al

58 TOKSISITAS ALUMINIUM Konsentrasi Al dlm larutan tanah > 1 ppm menyebabkan penurunan hasil tanaman Tembakau dan kentang sangat peka thd Al+++ dlm tanah, terutama akarnya. Gejalanya akar menjadi tebal, kaku dan becak-becak jaringan mati Pertumbuhan akar jagung mulai terganggu pada kondisi 60% kejenuhan Al. Al cenderung terakumulasi dalam akar dan menghambat penyerapan dan translokasi Ca dan fosfat menuju tajuk, sehingga mendorong defisiensi Ca dan P.

59 DEFISIENSI Ca DAN Mg 1. Gangguan pertumbuhan tanaman pd tanah masam dapat juga disebabkan oleh defisiensi Ca dan/atau Mg 2. Gangguan akar tembakau pd Ultisol yg tidak dikapur disebabkan oleh keracunan Al dan defisiensi Ca. 3. Kalau Al diendapkan (dg menggunakan MgCO3) dan tidak ditambahkan Ca, pertumbuhan akar tembakau akan berhenti dalam waktu 60 jam. 4. Tanah masam di daerah tropis defisien Ca tanpa menunjukkan masalah toksisitas Al. 5. Misalnya Tanah masam di Hawaii, pH < 5.0, namun Aldd nya sedikit; pengapuran berfungsi seperti pemupukan Ca 6. Tanah masam di Brazil sangat miskin Mg dan respon positif thd pupuk Mg.

% maks. pemanjangan akar 100 80 60 40 20 Dikapur CaCO3, pH 5.8, 4.4 meq Ca++ Dikapur MgCO3, pH 5.6, 0.4 meq Ca++ Tdk Dikapur, pH 4.2, 0.4 meq Ca++ waktu (hari) Sumber: Abruna et al. 1975 Ultisols & Oxisols

61 Kisraan nilai pH untuk berbgaai tipe tanah
Diunduh dari: …………… 22/3/2013

Kesetimbangan antara kemasmaan residual, tukar, dan aktif dalam suatu tanah dengan koloid organik dan mineral. Source: Centre for Teaching, Learning and Technology, UBC Diunduh dari: …………… 22/3/2013

63 pH dan ketersediaan hara dalam tanah
Setiap jenis tanaman memerlukan kondisi kemasaman optimal tertentu,– sehingga perlu kompos untuk tanaman yang cinta-asam. Most vegetables thrive when the soil is slightly acid i.e. a pH level between 6.5 and 7, Potatoes tend to prefer a lower pH, more acid soil (they are classified as "lime haters"), and Brassicas prefer a slightly alkaline soil, pH of 7.0 or even slightly higher. That's why it is suggested to lime in the autumn after potatoes and to follow with Brassicas who like the high pH. Legume ditanam di antara sayuran dalam pola rotasi yang bagus. Efek pH pada Hara tanaman pH tanah biasanya berkisar Kalau nilai pH berubah, keseimbangan hara dalam tanah juga berubah. Pita yg lebih lebar menyatakan hara “lebih tersedia” Penting bagi pertumbuhan daun Penting bagi akar dan batang Penting bagi pembentukan bunga dan buah Penting unt produksi energi , kekurangannya mengakibatkan daun menguning Diunduh dari: 22/3/2013

64 pH dan ketersediaan hara dalam tanah
The effect of pH (based on hydroponic solutions) on the availability of plant nutrients. Dalam tanah alkalis: Root growth is inhibited in strongly alkaline soils, possibly due to the plant's inability to absorb nutrient elements, such as zinc, which cannot move through the soil and must be present at the growing root tip. Diunduh dari: 22/3/2013

65 Pupuk Ammonium mengasamkan tanah
Proses-proses yang mengakibatkan kemasmaan tganah akibat pemupukan ammonium. Source: Singleton, P. Nutrient Management Concepts: pH & Nutrient Formulation, University of Hawaii Cooperative Extension Service, Hilo Jul Diunduh dari: …………… 22/3/2013

66 pH tanah dan ketersediaan hara dalam tanah
Efek pH tanah terhadap ketersediaan hara. (From Hunger Signs in Crops, edited by H.B. Sprague, 1964, pg. 18) Diunduh dari: …………… 22/3/2013

67 pH tanah dan ketersediaan hara dalam tanah
The width of the horizontal bars represents the availability of elements at any given pH. Most agricultural soils will be slightly acidic (pH 5.5 to 6.5). (Sumber: Atwell et al. (1999) in Plants in Action: adaptation in nature, performance in cultivation, Macmillan). Highly acidic soils may have adverse effects on plant growth due to aluminium toxicity. Alkaline soils may result in iron and manganese deficiency. Sources of iron and manganese applied to alkaline soils may rapidly become unavailable to plants, therefore foliar sprays are often used to correct these deficiencies in turf grown on alkaline soils. Diunduh dari: …………… 22/3/2013

68 Kisaran Optimum nilai pH tanah untuk beberapa tanaman
pH optimum Asparagus Brokoli 6.0 – 7.0 Kubis 6.0 – 7.5 Wortel 5.5 – 7.0 Mentimun Onion Kentang 4.8 – 6.5 Spinach Tomat 5.5 – 7.5 Diunduh dari: 26/3/2013

69 Bentuk-bentuk kemasaman tanah
Kemasmaan residual atau kemasmaan tidak-dapat ditukar This is comprised of weak acids not replaced by neutral unbuffered salt solution and H+ which bonds with OH-. This is the type of acidity caused by organic matter and bound Al. Bound Al occurs in soils primarily as Al polymers (long chain compounds) and is denoted as Al (OH)xx+ Al (OH)xx+ + OH Al (OH)xx+ COOH + OH COO- + H2O Diunduh dari: 22/3/2013

70 Mengoreksi kemasaman tanah
Koemasmaan tanah dikoreksi dnegan aplikasi kapur untuk mengurangi konsentrasi H+ atau menambah kation basa dalam tanah. Acid-producing hydrogen ions are adsorbed on exchange sites or present in soil solution. These hydrogen ions are in equilibrium between adsorbed and solution states. The hydrogen ions adsorbed to the cation exchange sites serve as a reservoir for neutralizable/reserve acidity that rapidly replaces the hydrogen ions in the soil solution that are neutralized by lime. Uji pH tanah menunjukkan tingkat kemasmaan suatu tanah, tetapi belum mengukur kemasaman cadangan. Diunduh dari: …………… 22/3/2013

71 Reaksi pertukaran kation kalau tanah masam dikapur
Diunduh dari: 22/3/2013

Liming materials consist of calcium and magnesium carbonates. When applied, the carbonates slowly dissolve in the acid soil solutions and replace the hydrogen ions with the calcium and magnesium ions. As the hydrogen ions are replaced by the calcium and magnesium ions, the pH of the soil rises. Diunduh dari: 22/3/2013

Kemasaman tanah diestimasi dengan pengukuran pH. pH tanah merupakan indeks kemasaman aktif. Kemasaman aktif merupakan konsentrasi H+ dalam larutan tanah, dan diukur dalam campuran tanah dan air. pH tanah merupakan indikator umum bagi ketersediaan hara, adanya kapur bebas (calcium carbonate), dan ketersediaan yg berlebihan beberapa inon, seperti sodium, hydrogen, aluminum, dan manganese. Reserve acidity is the concentration of hydrogen ions attached to clay and organic matter and is measured as buffer pH in a buffer solution. Active and reserve acidity are related, but the relationship is not constant across soils. It is influenced by type and amount of clay and the amount of organic matter and free lime in the soil. The ratio of reserve to active acidity relates to the buffer capacity of the soil, or the capacity of the soil to resist change in pH. As the clay and organic matter content of soil increase, the cation exchange capacity and the ratio of reserve to active acidity increase. Thus, the buffer capacity, or reserve acidity, of a sandy soil is much less than that of a soil containing more clay, such as a silt loam. Kalau tanah mempunyai pH < 6.3, maka pH buffer diukur untuk menentukan jumlah kapur yang dibutuhkan untuk menetralkan sebagian besar kemasaman cadangan. Diunduh dari: 22/3/2013

Kemasaman aktif dan kemasaman cadangan: Kesetimbangan dua macam sumber kemasaman tanah. (Source: Nutrient Management for Agronomic Crops in Nebraska, EC155) Diunduh dari: 22/3/2013

75 pH Tanah dan Kejenuhan Basa It would take more lime to neutralize it
pH tanah dan kejenuhan basa merupakan faktor-faktor "intensity" yg berhubungan dnegan konsnetrasi.   Kemasaman tanah dan kebutuhan kapur merupakan faktor "capacity" yg berhubungan dnegan massa. Both soils have equal intensity (pH),  the one on the right has more capacity (Acid Content).  It would take more lime to neutralize it Diunduh dari:,liming/aastart8.htm …………… 22/3/2013

76 Paradigma kemasaman tanah
Diunduh dari: …………… 22/3/2013

77 Kemasaman dan kation H+
Kemasaman ditentukan oleh adanya H+ (atau lebih tepatnya ion hidronium, H30+). Hydrogen ions, however, can be considered as hydrogen atoms that have been stripped of their only electron. This is why hydrogen ions frequently are called "protons" and have a positive charge. Hydrogen ions, or protons, are widely reactive and, thus, acidity is an important environmental (and everyday) consideration. Hidrogen merupakan bagian dari molekul air, menjadikannya komponen kunci dalam suatu larutan, seperti halnya larutan tanah. Diunduh dari:…………… 22/3/2013

78 Hidrolisis Al dan kemasaman tanah
Hidrolisis Al3+ meningkatkan kemasaman larutan tanah karena pelepasan H+ dari air hidrasi. Hidrolisis Al dan kemasaman tanah Asam didefinisikan sebagai suatu substansi, yang kalau dilarutkan dalam air, meningkatkan konsentrasi H+. Aluminum mempunyai kemampuan meningkatkan konsentrasi H+ dalam larutan tanah melalui proses hidrolisis. Diunduh dari:…………… 22/3/2013

79 Hidrolisis selanjutnya:
Hidrolisis Aluminium Reaksi hidrolisis dapat terjadi tiga kali menghasilkan tiga H+, menyumbang kemasaman kepada larutan tanah. Hidrolisis selanjutnya: Notice that in each case, one of the waters of hydration loses a hydrogen leaving behind a hydroxide. An alternative way to illustrate the reaction is presented below. This reaction, of course, also may occur potentially two more times to yield three hydrogen ions. Diunduh dari:…………… 22/3/2013

80 Kemasaman Aktif dan Tukar
Kation-kation H+ dan Al3+ menjadi subyek reaksi pertukaran kation dalam tanah Kemasaman Aktif dan Tukar Kemasaman aktif adalah konsentrasi kation H+ dalam larutan tanah. Meskipun tanah tampak kering, namun ada selaput tipis air menyelimuti partikel tanah. Kalau tanah dicampur dnegan air atau larutan garam lemah (mis., KCl atau CaCl2), kemasmaan aktif dapat diukur dengan pH meter. Both H+ and Al3+ are cations; thus, they are subject to exchange like any other cation. The H+ and Al3+ ions held at colloid surfaces are termed exchangeable, or reserve acidity. The term “reserve” derives from the fact that acidity associated with the exchange complex, in effect, can stand in reserve to combat changes in soil solution pH. Diunduh dari:…………… 22/3/2013

81 KAPASITAS PENYANGGA Kapasitas penyangga merupakan kemampuan air untuk mempertahankan pH yg stabil. Pure water has no buffering capacity; the addition of minute quantities of acid or alkali has an immediate effect on its pH. In the laboratory buffer tablets can be added to water to enable the solution to be maintained at a specified pH which would resist change despite the addition of some acid or alkali. This is useful for standardizing a pH meter, usually setting the instrument at precisely pH 7 and pH 4 for work on soil pH. Kapasitas buffer dari air-tanah mengurangi efek kemasaman akibat hujan asam atau polusi. Tanah-tanah kapur, sangat alkalis dan dapat menetralkan asam-asam lebih efektif daripada tanah-tanah gambut masam. The cation exchange capacity of clays reduces the effect because the hydrogen ions exchange with calcium ions on the clay’s colloid surface. Since the number of hydrogen ions being released or absorbed is small compared with the clay’s reserve, the pH changes very little. Tanah-tanah yg kaya humus mempunyai keuntungan kapasitas penyangga yg tinggi. Efek-efek buffer tampak jelas kalau asam-asam, seperti asam karbonat air hujan, dimasukkan ke tanah yang mengandung kapur-bebas; asam melarutkan sejumlah kalsium karbonat tanpa mengalami perubahan pH. Diunduh dari: 22/3/2013

82 Ada beberapa sumber lain yg mempengaruhi kemasaman tanah:
Perubahan pH Tanah . The balance of hydrogen ions and basic ions determines soil acidity. A clay particle with abundant hydrogen ions acts as a weak acid, whereas if fully charged with bases (such as calcium, Ca) it has a neutral or alkaline reaction. In practice, soil pH is usually regulated by the presence of calcium cations; soils become more acid as calcium is leached from the soil faster than it is replaced. This is the tendency in temperate areas where rainfall (carbonic acid see) exceeds evaporation over the year. Hydrogen ions take over the soil’s cation exchange sites and the pH falls. Soils with large reserves of calcium (containing pieces of chalk or limestone) do not become acid because they are kept base-saturated. In contrast, calcium ions are readily leached from free-draining sands in high rainfall areas and these soils tend to go acid rapidly (see podsols). Ada beberapa sumber lain yg mempengaruhi kemasaman tanah: Hujan asam (polluted rain and snow) is directly harmful to vegetation, but also contributes to the fall in soil pH. Asam organik derived from the microbial breakdown of organic matter, e.g. humic acids, also lead to an increase in soil acidity. Pupuk. Nitrifikasi oleh bakteri bentuk ammonia menjadi nitrat menghasilkan H+. Oleh karena itu pupuk yg mengandung garam ammonium dapat menggantikan Ca++ pada kompleks jerapan koloid tanah, dan kehilangan kalsium dalam air drainage. Panen tanaman. Ca dan Mg adalah hara tanaman dan cadangan kapur tanah, sehingga secara bertahap dapat berkurang oleh panen tanaman. Diunduh dari: 22/3/2013

83 MANAJEMEN pH TANAH Foto:smno.kampus.ub.agustus2012

84 pH tanah sangat penting
pH tanah sangat penting karena beragam alasan. Tiny bacteria and fungi inhabit the soil and can not live in highly acid or alkaline conditions. Without them certain byproducts of the higher foodchain (feces , carcass') would not be broken down into usable nutrients. Larutan tanah yang menjadi sumber hara tersedia bagi tanaman, dapat dipenuhi oleh garam-garam yang tidak tersedia atau tidak berguna. Tanaman umumnya menyukai pH tanah Diunduh dari: …………… 22/3/2013

85 Mengubah pH Tanah Menaikkan pH Tanah
pH tanah dapat dinaikkan dnegan pengapuran. Lime is most commonly applied as ground chalk, ground limestone or slaked lime. When lime is added to an acid soil it neutralizes the soluble acids and the calcium cations replace the exchangeable hydrogen on the soil colloid surface (see cation exchange). Eventually hydrogen ions are completely replaced by bases and base saturation is achieved, producing a soil of pH 7 or more. However, care should be taken not to overlime a soil because of its effect on the availability of plant nutrients. The lime requirement of soil can be estimated from knowledge of the required increase in pH and the soil texture (see buffering capacity). A pH of 6.5 is recommended for temperate plants on mineral soils; pH 5.8 on peats. The amount of a liming material needed to meet the lime requirement will depend on the neutralizing value of the lime chosen and its fineness. Diunduh dari: 22/3/2013

86 Relative Average Yield
Relative yield of selected crops grown in a corn, small grain, legumes or timothy rotation at different pH levels. (adapted from Smith and Doran 1996) pH 4.7 5.0 5.7 6.8 7.5 Relative Average Yield Corn 34 73 83 100 85 Wheat 68 78 89 99 Oats 77 93 98 Barley 23 80 95 Alfalfa 2 9 42 Soybean 65 79 Timothy 31 47 66 Smith JL and JW Doran Measurement and use of pH and electrical conductivity for soil quality analysis. In Methods for assessing soil quality. Soil Science Society of America Special Publication 49: Diunduh dari: 23/3/2013

87 Mikroba Kisaran pH pH Optimum Bacteria 5 - 9 7 Actinomycetes 6.5 - 9.5
Kisaran nilasi pH dan pH optimum bagi mikroba (Sumber: Smith dan Doran, 1996) Mikroba Kisaran pH pH Optimum Bacteria 5 - 9 7 Actinomycetes 8 Fungi 2 - 7 5 Blue green bacteria 6 - 9 > 7 Protozoa 5 - 8 Smith JL and JW Doran Measurement and use of pH and electrical conductivity for soil quality analysis. In Methods for assessing soil quality. Soil Science Society of America Special Publication 49: Diunduh dari: 23/3/2013

88 Blueberry, Kentang, Ubijalar
Kisaran pH optimum bagi pertumbuhan tanaman Kisaran pH tanah 6.5 – 7.0 Blueberry, Kentang, Ubijalar Jagung, Kapas, Sorghum, kedelai, Padi, Kacang-tanah, semangka, Melon, dll Alfalfa, beet, Clvers Diunduh dari: 23/3/2013

89 SEBAB-SEBAB RENDAHNYA pH TANAH Faktor lain yg mempengaruhi pH tanah:
   Prior to applying materials that increase pH, make sure that the low pH is not caused by an inappropriate fertilization regime. Often, an adjustment of such a regime may solve the acidity problem. This is especially true for growing media (soilless media): ammonium/nitrate ratio is a major factor that can determine the media pH, and it can be controlled by proper a fertilizers application. Dalam tanah-tanah, pemupukan intensif dengan pupuk berbasis ammonium atau pupuk pembentuk ammonium (urea) dapat menurunkan pH tanah.     Faktor lain yg mempengaruhi pH tanah: Bahan induk tanah - tipe batuan asal-usulnya tanah. Curah hujan - tanah-tanah di daerah curah hujan tinggi biasanya lebih masam daripada tanah-tanah di daerah kering. Soil organic matter - soil organisms are continously decomposing organic matter. The net effect of their activity is that hydrogen ions are released and the soil becomes more acidic. Native vegetation - the type of the native vegetation under which the soil was formed affects the pH of the soil. Soils formed under forest vegetation tend to be more acidic. Diunduh dari: …………… 23/3/2013

90 LIAT & KATION BASA Kalau koloid loiat jenuh dnegan H+, maka perilakunya sebagai asam-lemah. Semakin banyak H+ dijerap pada tapak jerapan koloid tanah, dan semakin sedikit kation basa (Ca, Mg, K), maka kemasaman tanah semakin tinggi. (Al also contributes to soil acidity, but for simplicity further discussion of soil acidity will be limited to H as the cause of soil acidity. Soils become acid when basic elements, such as calcium, magnesium, sodium, and potassium held by soil colloids are replaced by hydrogen ions. Soils formed under conditions of high annual rainfall are more acid than are soils formed under more arid conditions. Diunduh dari: 23/3/2013

Air (H2O) bergabung dnegan carbon dioxide (CO2) membentuk asam lemah — asam karbonat (H2CO3-). Asam lemah ini mengurai dengan melepaskan ion (H+) dan bicarbonate (HCO3=). The released hydrogen ions replace the calcium ions held by soil colloids, causing the soil to become acid. The displaced calcium (Ca++) ions combine with the bicarbonate ions to form calcium bicarbonate, which, being soluble, is leached from the soil. Efek akhirnya adalah meningkatnya kemasaman tanah. Diunduh dari: 23/3/2013

Sumber Nitrogen (pupuk, rabuk dan legumes) yang mengandung ammonium dapat meningkatkan kemasaman tanah , kecuali jika tanaman mampu menyerap langsung ammonium. Semakin besar dosis pupuk ini, semakin besar pula efek pengasaman tanahnya. As ammonium in converted to nitrate in the soil (nitrification), H ions are released. For each pound of nitrogen as ammonium or forming ammonium in urea, ammonium nitrate, and anhydrous ammonia, it takes approximately 1.8 pounds of pure calcium carbonate to neutralize the residual acidity. Also, the nitrate that is provided or that which forms, can combine with basic cations like calcium, magnesium, and potassium and leach from the topsoil into the subsoil. Kalau kation basa ini hilang dan digantikan oleh H+, tanah menjadi lebih masam. Diunduh dari: 23/3/2013


Mengoreksi kemasaman tanah dnegan pengapuran menjadi landasan bagi program pengelolaan kesuburan tanah. Aplikasi kapur tidak hanya sekedar untuk menaikkan pH tanah. Pengapuran juga dapat: Mensuplai Ca, dan Mg kalau yg digunakan kapur dolomitik, keduanya hara esensial bagi tanaman; it makes other essential nutrients more available; and it prevents elements such as Mn and Al from being toxic to plant growth. Diunduh dari: 23/3/2013

95 Bagaimana kapur bekerja dalam tanah?
Kapur bekerja dalam dua tahapan proses.   Kalau kapur diaplikasikan ke tanah, ia akan hancur (mengurai) menjadi ion-ion kalsium (kadangkala juga magnesium) dan anion karbonat.  Kation kalsium kemudian bergerak menuju tapak jerapan di permukaan partikel tanah dan berikatan dengannya, menggantikan posisi ion-ion hydrogen dan aluminum. Kemudian H+ bergerak memasuki larutan tanah, berikatan dnegan anion karbonat membentuk asam karbonat, yang kemudian dnegan cepat mengurai menjadi air dan CO2..  The aluminum that is knocked off the soil colloid moves into the soil solution and reacts with water to form aluminum hydroxide, which is inactive, and hydrogen ions.  These hydrogen ions then react with the carbonate ion and become carbon dioxide and water. Diunduh dari: …………… 24/3/2013

96 Reaksi Kapur dalam Tanah Koloid Tanah
Kapur (CaCO3) ditambahkan ke tanah Ca++ dijerap oleh koloid tanah, ditukar dnegan H+_ dan Al+++ Anion CO3= bereaksi dengan H+ membentuk asam karbonat Koloid Tanah Asam karbonat cepat mengurai menjadi air dan CO2 Diunduh dari: …………… 24/3/2013

97 Bagaimana kapur menaikkan pH tanah?
Limestone is calcium carbonate and magnesium carbonate: CaCO3 and MgCO3 The limestone dissolves in water to form carbonic acid (H2CO3) and calcium hydroxide (Ca(OH)2): CaCO3 + H2O ↔ H2CO3 + Ca(OH)2 Carbonic acid is unstable and converts to carbon dioxide (CO2) and water; the CO2 gas escapes: H2CO3 ↔ CO2 + H2O The remaining calcium hydroxide dissociates: Ca(OH)2 ↔ Ca2+ + 2OH- Kation Ca2+ menggantikan 2H+ dari tanah, meningkatkan kejenuhan basa Anion hidroksida (OH-) bereaksi dnegan kation asam tanah (H+), membentuk molekul air : OH- + H+ ↔ H2O Diunduh dari: …………… 24/3/2013

98 Bagaimana kapur menaikkan pH tanah?
Gas menguap Pertukaran Tanah Masam Netralisasi Tanah Netral Diunduh dari: …………… 24/3/2013

99 Bagaimana mengoreksi kemasaman tanah?
Kemasaman tanah dapat dikoreksi dnegan jalan pengapuran tanah, atau penambahan material alkalis untuk menetralisir asam-asam tanah. Bahan kapur yg lazim digunakan dalam pertanian adalah batu-kapur, bahan ini sangat ekonomis dan mudah pengelolaannya. The limestone is not very water-soluble, making it easy to handle. Lime or calcium carbonate's reaction with an acidic soil , which shows acidity (H) on the surface of the soil particles. As lime dissolves in the soil, calcium (Ca) moves to the surface of soil particles, replacing the acidity. Kemasaman bereaksi dnegan karbonat (CO3) menghasilkan CO2 dan H2O. Hasilnya adalah tanah menjadi kurang masam (mempunyai pH lebih tinggi). Diunduh dari: …………… 24/3/2013

100 Bagaimana kapur menaikkan pH tanah?
Reaksi kapur menetralkan kemasaman tanah Tanah masam + Kapur === Liat netral + Air, CO2, oksida Al Diunduh dari: …………… 24/3/2013

KAPUR merupakan bahan yg mengandung Ca dan/atau Mg dalam bentuk tertentu, yang kalau melarut dapat menetralkan kemasaman tanah. Tidak semua bahan yang mengandung Ca dan Mg mampu mengurangi kemasaman tanah. Misalnya, gypsum (CaSO4) mengandung Ca cukup banyak, tetapi tidak mampu mengurangi kemasaman tanah. The reason it does not is because when gypsum hydrolyzes in the soil, it converts to a strong base and a strong acid as shown in the following equation: CaSO4 + 2H2O = Ca (OH)2 + H2SO4 These two products formed, Ca(OH2) and H2SO4, neutralize each other and the result is a neutral soil effect. On the other hand, when calcitic (CaCO3-) or dolomitic lime (Ca Mg (CO3)2 is added to the soil, it hydrolyzes (dissolves in water) to a strong base and a weak acid. CaCO3 + 2H2O = Ca (OH)2 + H2CO3 Calcium hydroxide is a strong base and rapidly ionizes to CA++ and OH- ions. The calcium ions replace absorbed H ions on the soil colloid and thereby neutralize soil acidity. The carbonic acid formed (H2CO3) is a weak acid and slowly and partially ionizes to H+ and CO2-2 ions. Therefore, the net effect is that more Ca than H ions are released in the soil and consequently soil acidity is neutralized. Diunduh dari: 23/3/2013

102 Waktu, Penempatan dan Frekuensi Pengapuran
Dalam pola pergilrian tanaman yang melibatkan jenis-jenis legume, kapur harus diaplikasikan sebelum tanam legume, sehingga cukup waktu untuk bereaksi dalam tanah. Idealnya kapur diaplikasikan 3-6 minggu sebelum tanam benih/bibit. Applications as late as just before planting, with good soil incorporation, can still be beneficial on strongly acid soils. Some reduction in soil acidity will still occur, although maximum pH increases are not normally reached until about one year after application of typical agricultural limestone. Diunduh dari: 23/3/2013

103 PENGAPURAN Posisi penempatan kapur dalam tanah sangat penting pada aplikasi kapur pertanian. Maximum contact with the soil is essential for neutralization of soil acidity. Most common liming materials are only sparingly soluble in water. For example, ammonium nitrate is about 84,000 times more soluble than pure calcium carbonate. Even if lime is properly mixed into the plow layer, it will have little reaction if the soil is dry. Moisture must be available for the lime-soil reaction to occur. Perhaps the best way to incorporate lime or any other material with the plow layer is to use two perpendicular passes of a combination disc, followed by a chisel plow. Deep plowing of lime does not achieve desirable mixing in the upper six to eight inches of soil. However, because the plow or a heavy breaking disc inverts the lime, it can help to distribute the lime in the upper portion of the subsoil. Choice of tillage equipment will depend on the depth at which soil acidity neutralization is most needed. Good horizontal and vertical mixing of the lime provide the best results. Diunduh dari: 23/3/2013

104 Sifat & Sebab-sebab Kemasaman Tanah
“Soil acidity” is the term used to express the quantity of hydrogen (H) and aluminum (Al) cations (positively charged ions) in soils. When levels of hydrogen or aluminum become too high—and the soil becomes too acid—the soil’s negatively charged cation exchange capacity (CEC) becomes “clogged” with the positively charged hydrogen and aluminum, and the nutrients needed for plant growth are pushed out. This is why root growth and plant development suffer when soils become too acid. Diunduh dari: …………… 23/3/2013

105 pH tanah & Kemasaman Tanah
pH tanah menjadi indikator “kemasaman” tanah . pH = 7.0 didefinisikan sebagai :netral”. Values below 7.0 are acidic, and values above 7.0 are basic or alkaline. Small changes in numbers indicate large changes in soil acidity. A soil with a pH of 5 is 10 times more acidic than a soil with a pH of 6 and 100 times more acidic than a soil with a pH of 7. Kebanyakan tanaman tumbuh baik pada tanah agak masam, sehingga tujuan pengapuran tidak menaikkan pH tanah hingga netral (pH=7.0), tetapi untuk menghindari efek buruk akibat kemasaman yg berlebihan. Diunduh dari: …………… 23/3/2013

106 Kapur untuk menaikkan pH Tanah
Kapur pertanian lazim digunakan untuk menaikkan pH tanah-tanah masam. Kelarutan kapur relatif rendah, sehingga kalau kapur diaplikasikan di permukaan tanah maka ia hanya mempengaruhi lapisan tanah atas, tebalnya tidak lebih dari beberapa sentimeter saja. In soilless media, lime should be incorporated into the media prior planting and the process is usually logistically difficult. Waiting until after planting only makes it more complicated, because the lime should then be individually applied to each growing container or each plant. Again, due to its very low solubility, it's impossible to apply it through irrigation. Diunduh dari: …………… 23/3/2013

107 K2CO3 untuk menaikkan pH tanah
Unlike lime, potassium carbonate is highly soluble and therefore can be applied by drip irrigation. Due to its high solubility, potassium carbonate can be easily distributed throughout the root zone together with irrigation water and reach deeper soil profile. In both soils and growing media, potassium carbonate can rapidly affect chemical reactions in the root zone, thus elevate root zone pH. Irrigation with water that have a low buffering capacity (low bicarbonate content) might drastically decrease pH levels in growing media. In this case, and especially when using inert media, pH drop can present a constant problem. Aplikasi kaliumkarbonat secara periodik atau reguler, sebagai bagian dari program pemupukan tanaman, dapat mencegah penurunan pH tanah yg drastis.  Diunduh dari: …………… 23/3/2013

108 Berapa banyak batukapur atau belerang diperlukan?
All Cooperative Extension Service offices, any soil lab, and many lawn and garden centers have charts showing how much lime or sulfur to add to correct a pH imbalance. The charts tell you how many pounds of material to add per 1,000 square feet, so you need to measure the size of your vegetable garden first. Then use these tables to figure out how much lime or sulfur you need to add to your soil. pH Number of Pounds for: Sandy Soil Loam Soil Clay Soil 4.0–6.5 60 161 230 4.5–6.5 50 130 190 5.0–6.5 40 100 150 5.5–6.5 30 80 6.0–6.5 15 Jumlah kapur yg diperlukan untuk menaikkan pH tanah (per 1,000 Square Feet) Diunduh dari: …………… 23/3/2013

109 pH Number of Pounds for: Sandy Soil Loam Soil Clay Soil 8.5–6.5 45 60
Jumlah belerang yang diperlukan untuk menurunkan pH tanah (per 1,000 Square Feet) pH Number of Pounds for: Sandy Soil Loam Soil Clay Soil 8.5–6.5 45 60 70 8.0–6.5 30 35 7.5–6.5 10 20 25 7.0–6.5 2 4 7 Diunduh dari: …………… 23/3/2013

110 Manfaat penggunaan kapur secara tepat
Tanaman mengembangkan akar lebih sehat karena mereka tidak menghadapi Al toksik. Pertumbuhan akar yg lebih baik dapat menghasilkan toleransi kekeringan. Kapur menjadi sumber kalsium (dan juga magnesium, kalau digunakan batukapur dolomitik). Nutrient solubility is improved by a higher pH, so plants have a better nutrient supply. (The optimum pH for most crops is 5.8 to 6.2 when grown on mineral soils in North Carolina.) Increased soil CEC occurs, as well as reduced leaching of basic cations, particularly potassium. Nodulation of legumes is enhanced, which improves nitrogen fixation. Triazine herbicides, such as atrazine and simazine, work better. Optimal pH allows the breakdown of some herbicides, preventing damage to rotational crops. Beberapa jenis nematicida dapat bekerja lebih baik. Diunduh dari: …………… 23/3/2013

Mineral karbonat seringkali ditambahkan ke tanah untuk menaikkan pH tanah hingga sesuai bagi tanaman. Kalsium karbonat adalah bahan kapur pertanian. Pelarutan CaCO3 Anion karbonat (CO32-) yang dihasilkan dari pelarutan kalsium karbonat , bereaksi dengan ion hidrogen menghasilkan anion bikarbonat , menetralkan asam (H+). Diunduh dari:…………… 23/3/2013

Pengikatan H+ ini berarti mengurangi jumlah H+ yang ada dalam larutan tanah, dan pH larutan tanah meningkat. Kation Ca++ hasil pelarutan kalsium karbonat, juga dapat menggantikan H+ dari kompleks pertukaran koloid-tanah dan H+ ini memasuki larutan tanah; hal ini merupakan mekanisme untuk menyangga (mem-buffer) pH larutan tanah. Diunduh dari:…………… 23/3/2013

113 Larutan tanah (aktif) dan kompleks pertukaran (cadangan) berkesetimbangan
pH tanah dapat disangga (buffer) dengan jalan pelepasan kemasaman cadangan kalau kapur CaCO3 ditambahkan ke tanah. Setelah penambahan CaCO3, ion karbonat mengikat H+ dan membentuk anion bikarbonat dalam larutan, meningkatkan pH larutan untuk sementara. Ca++ dari CaCO3 yg ada dalam larutan , menggantikan H+ dari tapak jerapan dan menurunkan pH larutan Diunduh …………… 23/3/2013

Kondisi kesetimbangan awal (initial). pH sama dengan 6. Kemasaman aktif dan cadangan keduanya stabil Kondisi , segera setelah penambahan asam. pH menurun (kemasmaan aktif) hingga pH = 4 Kondisi setelah sejumlah hidrogen yg ditambahkan dapat dijerap pada tapak jerapan. pH meningkat mendekati kondisi initial. Diunduh dari:…………… 23/3/2013


116 Beberapa jenis tanaman memerlukan pH tanah yang rendah
Kebanyakan tanaman dapat tumbuh baik pada kondisi tganah agak masam atau kisaran pH tanah Akan tetapi beberapa jenis tanaman, seperti azaleas, gardenias, dan blueberries tumbuh paling baik pada nilai pH tanah yang lebih rendah. Others such as centipede turf, camellias, and potatoes grow well in a wide range of pH conditions, but seem to thrive best in more acid soils. Centipede turf is prone to iron chlorosis (iron deficiency) when soil pH is too high (above 6) and soil phosphorus is excessive due to over-fertilization. Diunduh dari: …………… 24/3/2013

117 Mengapa pH tanah begitu tinggi ?
Kalau pH tanah lebih dari 7.0 , maka perlu dikaji mengapa dan apa sebabnya?. Memang, ada beberapa jenis tanah yang secara alamiah memang bersifat alkalis, mis. Tanah berkapur , tanah yanag berasal dari bahan induk kapur. They are formed from the soft limestone known as Selma chalk. Some soils could be as much as 50% lime and have a pH value as high as 8.3. There's not much one can do about this. Just grow plants tolerant of calcareous soils - not azaleas, camellias, gardenias, and blueberries. Soils that have an artificially high pH, however, may also have a high salt content. Some waste products such as wood ashes (not agricultural lime) applied to the soil could be high in salts (salts of sodium, potassium, etc.). High salts probably caused the initial damaging effects to the plants. With time, rainfall will leach the salts out of the rooting zone. A high pH (up to about pH 8.0) would probably create severe micronutrient deficiencies (iron, zinc, and manganese) and result in a general yellowing and poor growth. High salts will kill plants. Diunduh dari: …………… 24/3/2013

118 Pupuk untuk menurunkan pH Tanah
pH tanah dapat menurun akibat pemupukan yang mengandung ammonium-N. Ammonium sulfate and sulfur-coated urea are two of the best choices for acidifying soils. Most specialty fertilizers for "acid-loving" plants contain ammonium sulfate or sulfur-coated urea. These are popular sources of nitrogen for azaleas and blueberries. Diunduh dari: …………… 24/3/2013

119 If you are desperate, try sulfur or aluminum sulfate.
In rare cases, it may be desirable to lower the pH by adding an acidifying agent such as elemental sulfur (flowers of sulfur) or aluminum sulfate. This can be done successfully on soils that do not contain large amounts of free lime. Sandy soils would require less and clayey soils would require more. Elemental sulfur is converted to sulfuric acid by soil bacteria. Therefore, in order for sulfur to work the following must be satisfied: Sulfur must be mixed with the soil to provide contact. The soil must be moist. The soil must be aerated (bacteria need oxygen). The soil must be warm for rapid bacterial growth. Time is required for the reaction to go to completion. Diunduh dari: …………… 24/3/2013

120 Acidifying effect of some common fertilizers and soil amendments.
Material Pure CaCO3 needed to neutralize acidity in 100 pounds of material pounds ammonium nitrate 60 ammonium sulfate 110 32% liquid nitrogen 55 urea 81 sulfur-coated urea 118 diammonium phosphate 70 flowers of sulfur (elemental S) 312 aluminum sulfate 45 Diunduh dari: …………… 24/3/2013

121 Alumimum sulfate may be better for the home gardener to use because he/she is less likely to over-apply the material. Six times as much aluminum sulfate is needed as elemental sulfur. Aluminum sulfat juga harus dicampur dengan tanah, tetapi reaksinya bersifat kimiawi dna bukan reaksi biologis. Diunduh dari: …………… 24/3/2013

122 Belerang – Unsur Hara esensial
Jangan dibingungkan antara “belerang” sebagai bahan pengasaman tanah dengan “belerang” sebagai hara tanaman. Semua uji tanah melaporkan rekomendasi 10 pounds belerang per acre sebagai hara tanaman. Kebanyakan pupuk belerang berbentuk sulfate (SO4-2) yang mudah tersedia bagi tanaman, mis., ammonium sulfat, calsium sulfat (gipsum), kalium sulfat, sul-po-mag, magnesium sulfat (garam epsom), dll. Sulfate sulfur is usually contained in mixed fertilizers. This form will not acidify soils. Elemental sulfur (a yellow powder), the form used for soil acidification, is not plant available until it is oxidized by soil bacteria to the sulfate form. This takes time - usually several weeks. Elemental sulfur is sometimes sold as "flowers of sulfur". Diunduh dari: …………… 24/3/2013

Pounds of elemental sulfur needed to lower soil pH of a silt loam soil to a depth of 6 inches. For sandy soils, reduce amount by 1/3; for clayey soils, increase amount by 1/2; if aluminum sulfate is used, multiply by 6.9. AKTUAL pH TANAH YANG DIBUTUHKAN pH 6.5 6.0 5.5 5.0 4.5 lb. S per 100 sq. ft 8.0 3.0 4.0 7.0 7.5 3.5 1.0 2.0 --- 2.5 Diunduh dari: …………… 24/3/2013


125 Measurement of soil pH: Problems and solutions
M. E. Sumner Communications in Soil Science and Plant Analysis Volume 25, Issue 7-8, Special Issue: 1993 International Symposium on Soil Testing and Plant Analysis: Precision Nutrient Management Part I Interpretasi hasil pengukuran pH tanah mengandung misteri yang unik. Prinsip-prinsip yang melandasi sistem elektrode gelas haryus dipahami dan dikaji secara tuntas dalam kaitannya dengan pengukuran pH tanah. The influence of the liquid junction potential and salt concentration on the pH values of soil water suspensions are discussed in detail from which it emerges that the current practice of measuring soil pH in stirred soil suspensions is likely to result in the greatest errors being incurred. This is due to the large liquid junction potential of uncertain magnitude developed in such systems. Measurements in salt solutions, such as M KCl and 0.1 M CaCl2, reduce the magnitude of the liquid junction potential substantially and make the pH values obtained more reproducible and consistent. Posisi jembatan garam elektroda kalomel sangat krusial dalam mengukur pH tanah dan harus selalu diposisikan dalam supernatan larutan yg jernih. Diunduh dari:

126 Natalia P. Rogovska, Alfred M. Blackmer and Antonio P. Mallarino
Relationships between Soybean Yield, Soil pH, and Soil Carbonate Concentration Natalia P. Rogovska, Alfred M. Blackmer and Antonio P. Mallarino SSSAJ. Vol. 71 No. 4, p.  July, 2007 Kedelai [Glycine max (L.) Merrill] seringkali menunjukkan khlorosis defisiensi besi (IDC) pd kondisi tanah pH tinggi, tanah berkapur.. The objective of this study was to assess the variation in soybean yield that could be explained by soil pH and carbonate concentration in Iowa fields. Color aerial images of soybean canopy taken from 2000 to 2002 from 12 fields having acid to calcareous soils were used to select 10 to 28 sampling areas 10 to 25 m2 in size to encompass significant variability in early soybean growth and IDC symptoms in each field. Representative areas 0.93 m2 in size were identified through field observations to collect soil samples and measure grain yield. Soil pH measured to a 15-cm depth across fields ranged from 5.6 to 8.2 and calcium carbonate equivalent (CCE) ranged from 0 to 30%. Soil CCE varied from 2.5 to 30% as pH ranged from 7.7 to 8.2. Grain yield decreased with increasing pH and CCE in 9 and 11 fields, respectively. Soil pH and CCE explained 30 and 41% of the variability in relative yield across sites, respectively. Indeks cekaman alkalinitas (alkalinity stress index, ASI) yg menggabungkan kedua pengukuran (pH CCE) dikembangkan berdasarkan pada efek relatif masing-masing pengukuran terhadap hasil tanaman, dan mampu menjelaskan 45% dari ragam hasil tanaman. Indeks yg dikembangkan dapat menjadi prediktor yang baik untuk menduga hasil kedleai di lapangan pada kondisi tanah pH tinggi. Diunduh dari:

127 Rapid Measurement of Soil pH Buffering Capacity
D. E. Kissel , L. S. Sonon and M. L. Cabrera SSSAJ. Vol. 76 No. 2, p.  Mar, 2012 Soil pH buffering capacity, described here as lime buffer capacity (LBC), is a fundamental soil property needed to estimate the change in soil pH after a known quantity of acidity or alkalinity is added to soil. Its rapid determination can be useful for many purposes, for example, estimating the lime needed to raise pH or acid needed to lower pH to a desired level. The objective of the present study was to evaluate the statistical relationship developed in previous studies between LBC from 30-min equilibration with Ca(OH)2 (LBC30) and LBC from 5-d equilibration with Ca(OH)2 (LBCeq) on a larger set of soils from Georgia. Five days was considered adequate time for true pH equilibrium and obtaining a true LBC. Eighty-seven soils from Georgia were treated with Ca(OH)2 using standard procedures for both equilibrium times, and the statistical relationship between the two LBCs were developed. The relationship developed in the first study was further tested in a second incubation of 67 soils to determine its accuracy in achieving a target pHCaCl2 of 6.0. The data from the second incubation indicated that the target pH was exceeded by an average of 0.11 pH units and that the average pH spread around the acquired pH was ±0.1 pH unit. Prediksi kapasitas buffer pH tanah berdasarkan pada protokol yg dicobakan ternyata cukup akurat untuk menyusun rekomendasi aplikasi kapur pertanian. Diunduh dari:

128 Impacts of soil acidity on qualitative and quantitative conditions of broadleaf and coniferous trees
N. Khorasani, A. Keshavarz and E. Adeli International Journal of Environmental Science & Technology. Vol. 1, No. 3, pp , Autumn 2004 To recognize the impacts of soil acidity on quantitative and qualitative conditions of broadleaf and coniferous trees in Syyahkal watershed region of northern Iran, hand-cultivated adjacent stands of different species of Pinus taeda, Acer insinge,and Alnus subcordata were compared. To gather general information about the soil type in each site, one profile and in total five soil profiles were dug, identified, and classified. In each site 35 individual plots have been selected and thus from all 175 plots available vegetative characteristics of above said tree species including height, diameter and volume have been determined. In order to determine the soil characteristiscs in each plot and based on our previous knowledge, samples from two specific horizon depths (0-15 cm., and cm.) were collected. Then, in total of 135 samples specific chemical analyses of concern (pH, N.K.P) were carried out. Next, based on appropriate statistical studies (Student t-test, Fisher F-test, or ANOVA, Tukey test or HSD and regression analysis) the relation between vegetative characteristics of forest trees and different soil parameters in each adjacent sites have been compared. \ This comparison clearly showed that the hand-cultivated stands do not share similar vegetative characteristics status and in fact due to past thinning nurturing operations Pinus taeda has gained the most volume in acre. Statistical tests reveal that an increase in the amount of soluble nitrogen as a nutrient substance with regard to the vegetative parameters for all three plant species involved translates into a direct dependent relation. This means that an increase in tree diameter, height, and volume is expected wherever more concentrations of soluble nitrogen exists. The soil profile descriptive tables clearly show that Pinus taeda has taken root deep in the soil due to the lack of nutrients at soil surface layers. Thus, it would not be logical to suggest the re-plantation of this species in ruined forested areas of interest . Diunduh dari: …………… 23/3/2013

129 Petra S. Kidd and John Proctor
Why plants grow poorly on very acid soils: are ecologists missing the obvious? Petra S. Kidd and John Proctor J. Exp. Bot. (2001) 52 (357): Factors associated with soil acidity are considered to be limiting for plants in many parts of the world. This work was undertaken to investigate the role of the toxicity of hydrogen (H+) which seems to have been underconsidered by ecologists as an explanation of the reduced plant growth observed in very acid soils. Racial differences are reported in plant growth response to increasing acidity in the grass Holcus lanatus L. (Yorkshire‐fog) and the tree Betula pendula Roth (Silver Birch). Soils and seeds were collected from four Scottish sites which covered a range of soils from acid (organic and mineral) to more base‐rich. The sites and their pH (1:2.5 fresh soil:0.01 M CaCl2) were: Flanders Moss (FM), pH 3.2±0.03; Kippenrait Glen (KP), pH 4.8± 0.05; Kinloch Rannoch (KR), pH 6.1±0.16; and Sheriffmuir (SMM), pH 4.3±0.11. The growth rates of two races of H. lanatus, FM and KP, and three races of B. pendula (SMM, KP and KR) were measured in nutrient solution cultures at pH 2.0 (H. lanatus only), 3.0, 4.0, 5.0, and 5.6. Results showed races from acid organic soils (FM) were H+‐tolerant while those from acid mineral soils (SMM) were Al3+‐tolerant but not necessarily H+‐tolerant. These results confirmed that populations were separately adapted to H+ or Al3+ toxicity and this was dependent upon the soil characteristics at their site of collection. The fact of plant adaptation to H+ toxicity supports the view that this is an important factor in very acid soils. Diunduh dari: …………… 23/3/2013

130 Appl. Environ. Microbiol. September 1976 vol. 32 no. 3 368-375
Influences of soil acidity on Streptomyces populations inhabiting forest soils. C. Hagedorn Appl. Environ. Microbiol. September 1976 vol. 32 no The Streptomyces populations inhabiting five acidic forest soils were examined. It was found that lowering the pH of a medium selective for streptomycetes (starch-casein agar) to the pH of the particular soil horizon being plated influenced both the total numbers and types of streptomycetes that were isolated from the soils examined in this study. On the acidified medium both the numbers of streptomycetes and the percentage of total bacteria on the plates represented by streptomycetes increased (as compared with the same medium with a pH of 7.2). These differences were greatest on the isolations from the most acid soils. The largest concentrations of streptomycetes were found in the surface horizon (0 to 15 cm) and the litter layer immediately over the surface mineral horizon. Acidity tolerance tests demonstrated that random samplings of isolates contained acidophilic, neutrophilic, and acidoduric strains, with the largest numbers of acidophiles being found on the acidified media from the most acid soils. There were no differences between overall utilization of selected carbohydrates among the isolates taken from either the neutral or acidic media, although a larger proportion of the acid media isolates produced acid from the carbohydrates. Evidence is presented which indicates that different types of streptomycetes were isolated on the acid media, and possible reasons for the presence of these acid-tolerant populations are discussed. Diunduh dari: …………… 23/3/2013

131 . Development, Impacts and Management of Soil Acidity in Hawaii
N. V. Hue  Department of Tropical Plant and Soil Sciences, College of Tropical Agriculture and Human  Resources, University of Hawaii at Manoa, HI 96822, USA . Soil acidity is a serious constraint to crop production and ecosystem health. Acidification can occur naturally via the formation of carbonic acid (CO2 + H2O → H2CO3 → HCO3 - + H+) and subsequent leaching of basic cations or through man-made processes. These include the formation of sulfuric and nitric acids by coal burning, automobile exhaust emission, and applying ammoniacal fertilizers. Given the warm temperatures and humid conditions, most Hawaii soils are acidic, having either aluminum (Al) and/or manganese (Mn) toxicities or calcium (Ca) deficiency. Aluminum toxicity usually damages the root system first; in contrast, Mn toxicity affects above-ground parts of a plant. Calcium deficiency shows up more clearly at growing points owing to the relative immobility of this nutrient. Productivity of these acid soils can be improved by either adding lime or planting acid-tolerant crops. Several lime titration curves are presented for Hawaiian soils, also some acidity tolerant crops are discussed Diunduh dari: …………… 23/3/2013

132 Soil Acidity and its Relations to Acid Deposition
. Effects of Accumulation of Air Pollutants in Forest Ecosystems. 1983, pp Soil Acidity and its Relations to Acid Deposition B. Ulrich The nature of soil acidity as well as measures of the capacity and the intensity terms are discussed. According to the proton buffer reactions occuring in soils, buffer ranges are distinguished. They are defined by pH values. Forest soils on limestones which should be in the calcium carbonate buffer range, acidify under the influence of acid deposition as soon as the fine earth is free of calcium carbonate. The same may be true for soils staying in the silicate buffer range if the rate of acid load exceeds the rate of acid buffering by base cation release during silicate weathering. From existing data on the rate of acid deposition in Central Europe, it is concluded that soils staying in the cation exchange buffer range should have lost considerable amounts of exchangeable Ca due to acid deposition since beginning of industrialization. The resilience of the ecosystem becomes very limited if the soil stays with all major horizons in the aluminium or even in the iron buffer range. The iron buffer range is characterized by podzolization. Diunduh dari: …………… 23/3/2013

133 Changes in soil acidity depending on amelioration measures
Bošković-Rakočević Ljiljana --- Jakovljević Miodrag D. --- Ubavić Momčilo --- Milivojević Jelena Journal of Agricultural Sciences Vol: 48 Issue: 2 Pages: Aplikasi jangka panjang pupuk mineral dg dosis tinggi, untuk memperbaiki hasil tanaman, menyebabkan pengasaman tanah, sehingga menurunkan hasil tanaman karena meningkatnya kandungan Al dan Mn dan menunrunnya BOT dan kation basa dalam tanah. Untuk mengeliminir efek buruk mini, diaplikasikan bentonite, zeolite, crude phosphates, MgO dan CaO. The trial was set up on the pseudogley type of soil with an extremely acid reaction (pH/MKCl about 3.55) and a high content of mobile aluminium (over 37 mg/100 g soil). The obtained results show that the best effect on the decrease of all forms of soil acidity was exerted by the use of the amelioration measure CaO+MgO, with a ratio of 5:1. Aplikasi “crude phosphates dan zeolite “ menunjukkan efek paling lemah. Aplikasi bahan-bahan tersebut juga mampu menurunkan aluminium-mobil hingga 1.87 mg/100 g tanah, dan dalam kaitan dnegan ketiga varian (bentonite+CaO dan CaO) kandungan aluminium berada di dalam kisaran toleransi tanaman jagung (sekitar 10 mg/100 g tanah). Diunduh dari: …………… 23/3/2013

134 S. A. Waring and J. W. Gilliam
The Effect of Acidity on Nitrate Reduction and Denitrification in Lower Coastal Plain Soils S. A. Waring and J. W. Gilliam Soil Science Society of America Journal Vol. 47 No. 2, p.  Denitrification and nitrate reduction to NH+4-N and organic N were investigated in the laboratory using surface samples of Histosols and Ultisols. A wide range of pH (3.4 to 7.3) was obtained by liming acidic virgin soils and by selecting a range of field-limied soils. When incubated under waterlogged conditions in the presence of glucose for 2 d at 25°C, there was a very low loss of NO-3-N below a pH of 4.0 and an increase in NO-3-N loss with pH up to a pH of 6.0. After 12 d of incuhation, NO-3-N loss ( mg L−1) was complete from soils at all pH values. Laboratory and field-limed soils behaved as expected from their pHs. For soils incubated for 2 d without glucose, there was a moderate effect of soil pH upon NO-3-N loss (R2 = 0.40). The correlation was even poorer at longer time periods becoming nonsignificant after 12 d. For incubations longer than 2 d soluble C appeared to be more important than pH in controlling loss of NO-3-N. Soils with pH < 4.0 showed unexpectedly high NO-3-N loss when incuhated for periods > 12 d without glucose. Experiments with 15NO-3-N showed that 16 to 20% of the NO-3-N loss in soils with pH <4.0 was due to reduction to NH+4-N and organic N but only 1 to 2% for soils with pH > 4.0. Evidence indicates that the reduction was dissimilatory and unrelated to levels of soluble C. Denitrification was substantial in the soils with pH <4.0 and of a similar level to that for moderately acidic soils (pH ). In the neutral soils (pH ) denitrification was much higher but much of the increase appeared due to the higher level of soluble C. Diunduh dari: …………… 23/3/2013

135 pH tanah tetap rendah pada perlakuan mkontrol dan menerima pupuk NPK.
Reclamation of an acidic soil of Rwanda’s central upland by composts based on natural vegetation biomass J.J.M. Mbonigaba, M. Culot Journal of Agriculture, Forestry and the Social Sciences. Vol 17 (2009) 64-81 Kompos yg berasal dari vegetasi alamiah berpengaruh terhadap pengurangan kemasaman total dan netralisasi Al-tukar dalam tanah dari Rwanda. The initial soil analysis showed that the average pHW (pH measured in water) was 4.4; the average concentration of exchangeable Al and the total acidity were respectively 3.70 and 4.45 1 of soil. Five types of composts and NPK fertilizer were applied to the soil under a splitplot experimental design. Two doses of composts (30 and 60 t.ha-1) were applied while the NPK fertilizer was applied to a dose of 300 kg.ha- 1. The experiment lasted two years and four samplings were carried out to evaluate the impact on pH, exchangeable aluminium and total acidity. Pada akhir tahun ke dua, pH(air) meningkat 0.2 unit dengan adanya aplikasi kompos pada awal percobaan dnegan dosis 60 t.ha- 1. pH tanah tetap rendah pada perlakuan mkontrol dan menerima pupuk NPK. After only five months, the Al3+ was reduced of 32 and 53 % respectively with 30 and 60 t.ha- 1 of compost. At the end of the two years of experimentation, the concentration of Al3+ increased again but without reaching the initial level except for the plots treated with the mineral manure NPK. The same trend was observed for the case of the exchange total acidity. Diunduh dari: …………… 23/3/2013

136 ……. Tanah hutan jati biasanya alkalis ………..
………….. Dan seterusnya …………… Foto: smno.hutanjati.saradan.nopember2012

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