PENGELOLAAN KEMASAMAN TANAH

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1 PENGELOLAAN KEMASAMAN TANAH
BAHAN KAJIAN - MKT PENGELOLAAN KEMASAMAN TANAH & PENGAPURAN Soemarno – Okt 2013

2 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

3 Apa itu pH Tanah? pH adalah kemasaman atau kebasaan relatif suatu bahan. Skala pH mencakup dari nilai 0 (nol) hingga 14. Nilai pH 7 dikatakan netral, di bawah nilai 7 dikatakan asam, sedangkan di atas 7 dikatakan basa. Asam menurut teori Bronsted dan Lewry adalah suatu bahan yang cenderung untuk memberi  proton (H+) ke beberapa senyawa lain, demikian sebaliknya apabila basa adalah suatu bahan yang cenderung untuk menerimanya. Teori asam basa ini sangat baik untuk diterapkan dimedia cair termasuk larutan tanah. Teori asam basa lain yang sangat baik diterapkan dalam tanah adalah Arrhenius, yaitu asam adalah suatu bahan yang menghasilkan H+ atau menurunkan pH apabila terdisasosiasi dalam air, sebaliknya apabila basa dalam disosiasinya akan menghasilkan OH- atau menaikkan pH.

4 Kemasaman di dalam tanah dapat dihitung berdasarkan kedudukan ion H+.
KEMASAMAN (pH) tanah Kemasaman di dalam tanah dapat dihitung berdasarkan kedudukan ion H+. Apabila yang diukur adalah ion H+ yang ada dilarutan tanah (sebelah kanan, bebas) dikatakan sebagai kemasaman aktual. Apabila ion H+ yang diukur terdapat di komplek jerapan tanah (sebelah kiri, tidak bebas) dikatakan sebagai kemasaman potensial, yang nilainya jauh lebih besar dari kemasaman aktual. Sedangkan apabila kedua kemasaman tersebut dijumlahkan disebut kemasaman total.

5 KEMASAMAN (pH) tanah Kemasaman pH tanah secara sederhana merupakan ukuran aktivitas H+ dan dinyatakan sebagai -log10[H+]. Secara praktikal ukuran logaritma aktivitas atau konsentrasi H+ ini berarti setiap perubahan satu unit pH tanah berarti terjadi perubahan 10 kali dari jumlah kemasaman atau kebasaan. Pada tanah yang mempunyai pH 6.0 berarti tanah tersebut mempunyai H+ aktif sebanyak 10 kali dibandingkan dengan tanah yang mempunyai pH 7.0

6 KEMASAMAN (pH) tanah Sebagian besar tanah tanah produktif, mulai dari hutan humid dan sub humid hingga padang rumput di semiarid, mempunyai pH bervariasi antara 4.0 hingga 8.0. Nilai di atas atau di bawah variasi tersebut disebabkan oleh garam Ca dan Na atau ion H+ dan Al+3 dalam larutan tanah. Pengaruh utama pH di dalam tanah adalah pada ketersediaan dan sifat meracun unsur seperti Fe, Al, Mn, B, Cu, Cd dll terhadap tanaman atau mikroorganisme.

7 pH = - log [H+] Kisaran Nilai pH tanah: 0 - 14 pH = 7.0 : Tanah Netral
[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

8 SUMBER KEMASAMAN TANAH
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:

9 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

10 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

11 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.

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

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

14 TOKSISITAS ALUMINIUM 1. Konsentrasi Al dlm larutan tanah > 1 ppm menyebabkan penurunan hasil tanaman 2. Tembakau dan kentang sangat peka thd Al+++ dlm tanah, terutama akarnya. Gejalanya akar menjadi tebal, kaku dan becak-becak jaringan mati 3. Pertumbuhan akar jagung mulai terganggu pada kondisi 60% kejenuhan Al. 4. Al cenderung terakumulasi dalam akar dan menghambat penyerapan dan translokasi Ca dan fosfat menuju tajuk, sehingga mendorong defisiensi Ca dan P.

15 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.

16 TOKSISITAS Al & DEFISIENSI Ca thd AKAR TEMBAKAU
% 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

17 EFEK Al thd PERTUMBUHAN AKAR
Tanah pH Aldd % Kejenuhan Berat kering akar tanaman: me/100 g Al Jagung (mg/pot) Sorghum Ultisol Oxisol Sumber: Brenes & Pearson,

18 MENGUKUR KEMASAMAN (pH) tanah
Ada 2 metode yang paling umum digunakan untuk pengukuran pH tanah yaitu kertas lakmus dan pH meter. Kertas lakmus sering di gunakan di lapangan untuk mempercepat pengukuran pH. Penggunaan metode ini di perlukan keahlian pengalaman untuk menghindari kesalahan. Lebih akurat dan secara luas di gunakan adalah penggunaan pH meter, yang sangat banyak di gunakan di laboratorium. Walaupun pH tanah merupakan indikator tunggal yang sangat baik untuk kemasaman tanah, tetapi nilai pH tidak bisa menunjukkan berapa kebutuhan kapur. Kebutuhan kapur merupakan jumlah kapur pertanian yang dibutuhkan untuk mempertahankan variasi pH yang di inginkan untuk sistem pertanian yang digunakan. Kebutuhan kapur tanah tidak hanya berhubungan dengan pH tanah saja, tetapi juga berhubungan dengan kemampuan menyangga tanah atau kapasitas tukar kation (KTK).

19 MENGUKUR KEMASAMAN (pH) tanah Metode untuk mengukur kemasaman tanah.
1. pH meter - Only measures soil pH and is not used to determine LR by itself. 2. Extraction Techniques KCl - Gives an estimate of exchangeable aluminum and hydrogen only. BaCl2 - TEA Widely-used in soil survey, but usually overestimates LR for most soils. Incubation - Requires a great amount of time to allow the soil-water-base suspension to equilibrate. Buffer Techniques Mehlich - Several different formulations of this strong acid technique are used. The WVU Soil Testing Laboratory uses the Mehlich III method. SMP - Schumacher-McClean- Pratt were the names of the scientists that developed this extraction fluid. Used in Midwestern US soil testing laboratories Woodruff - This buffer technique was developed for calcareous soils and is used extensively in arid Western US soil testing laboratories. 5. Acid-Base Accounting This laboratory procedure measures both the acid-producing (potential acidity) and acid-neutralizing materials in soils. It is not generally used by itself to determine LR. 6. H2O2 Oxidation Another method used in a few laboratories to measure potential acidity, especially those containing unweathered pyritic materials.

20 Pembentukan Kemasaman Tanah
“Old soil” “Young soil” Waktu Al3+ melarut dari mineral Ca2+, Mg2+, K+ tercuci dari tanah Mineral liat dengan kation dapat ditukar: Ca2+, Mg2+, K+ dan Al 3+, H+ Mineral liat dengan kation dapat ditukar Ca2+, Mg2+, K+

21 KATION DAPAT DITUKAR Ca2+, Mg2+, Na+, dan K+ tidak menghasilkan H+ dalam tanah, sehingga disebut “kation basa” Al3+ and Fe3+ react to produce H+ in soils, and so are called the “acid cations” The “base saturation” is the percentage of the CEC occupied by the basic cations. It is highly related to soil pH.

22 “PERSENTASE KEJENUHAN BASA”
8 Low CEC Soil Soil pH High CEC Soil 2 100 Percent base saturation

23 Mengapa Al3+ disebut “MASAM” ?
Al3+ ions in solution are surrounded by water molecules (octahedral coordination). The high positive charge of Al3+ causes it to pull electrons from O on H2O. Menghakibatkan H2O menjadi lebvih masam. Disebut “Al hidrolisis” Perilakunya menyerupai seperti Fe3+.

24 3+ Al(H O) 2 6 + H + [Al(H 2 O) 5 OH] 2+ 3+ Al H O 2

25 2+ 2+ + H + [Al(H 2 O)4(OH) ] [Al(H O) OH] 2 5 3+ Al H O 2

26 + [Al(H O) OH] + H + [Al(H 2 O) 3 (OH) ] 2 5 3+ Al H O 2

27 Kurva Titrasi— Tanah Masam
Alkaline “ The amount of buffering capacity will determine the lime requirement. Soils with higher CEC will have a higher L.R. pH Buffering due to Al hydrolysis Acid Lime added

28 Soil Acidity Al3+ Ca2+ H+ Clay Solution

29 Al 3+ H+

30

31 Kisaran pH tanah

32 Toksisitas Al Below a pH of ______, Al3+ may be present in concentrations that are toxic to plants. Al solubility is inversely proportional to pH. Menghambat pertumbuhan akar, mengganggu penyerapan hara P. Al toxicity is the #1 problem in acid soils. Mn and Fe may be toxic as well, because they become more __________ under acid conditions. 5.5 soluble

33 pH Tanah dan Ketersediaan Hara

34 pH dan Ketersediaan Hara

35 Preferensi Tanaman terhadap pH
Tanaman dan pH Kisaran pH tanah <4 5.5 6.5 7.5 8.5 Strongly Acidic Moderately Slightly Neutral Alkaline Highly Preferensi Tanaman terhadap pH Most crop plants and plants of temperate regions Most tropical plants. Tea, Coffee, azaleas Alfalfa Halophytes

36 Tanaman dan pH Perbedaan toleransi tanaman terhadap kemasaman terurtama disebabkan: Perbedaan ekebutuhan hara Kemampuannya meng-immobilisasi Al3+ dalam rhizosfirnya dan men-detoksifikasi Al3+ di dalam tubuh tanamanm.

37 Mengoreksi Kemasaman Tanah
Ada dua komponen kemasaman tanah yaitu : __________ acidity, which is ____ in the soil solution, and ____________ acidity which is _______ on the soil clay cation exchange sites. Both of these have to be neutralized to correct soil acidity. To do this, ________ is added to acid soils. active H+ reserve Al3+,H+ lime

38 Al 3+ H+

39 PENGELOLAAN KEMASAMAN (pH) tanah
Tanah masam adalah tanah ber-pH rendah (pH di bawah 6), semakin rendah pH tanahnya maka semakin ekstrim kemasamannya. Kendala Tanah Masam Unsur hara makro (terutama N,P,K,Ca,Mg) tidak tersedia dalam jumlah cukup, efektifitas dan efisiensi pemupukan makro (urea, TSP, KCl) juga rendah. Beberapa unsur (terutama Al dan Fe) tersedia berlebih sehingga sering meracun pada tanaman. Menghambat perkembangan mikroorganisme tanah.

40 PENGELOLAAN KEMASAMAN (pH) tanah
Pengapuran untuk Meningkatkan pH Tanah Perbaikan pH tanah bisa diakatakan menyelesaikan 50% masalah kesuburan tanah. Salah satu cara meningkatkan pH tanah dengan pengapuran menggunakan kapur pertanian (kaptan) atau dolomit. Beberapa hal yang perlu diperhatikan : Idealnya paling lambat pengapuran dilakukan 2 minggu sebelum tanam, karena bahan kapur termasuk bahan yang lambat bereaksi dengan tanah. Setelah pengapuran sebaiknya tanah dicangkul (dibajak) agar kapur bisa merata masuk dekat zona perakaran. Pengairan setelah pengapuran sangat diperlukan. Peningkatan pH tidak bisa terjadi seketika, melainkan pelan dan bertahap. Dosis kapur disesuaikan pH tanahnya, tetapi sebagai pedoman praktis dosis berkisar 500 kg/Ha 2 ton/Ha. Catatan : Dolomit juga harus secara rutin digunakan pada tanah pH normal, karena unsur Ca dan Mg pada dolomit sangat dibutuhkan tanaman.

41 PENGELOLAAN KEMASAMAN (pH) tanah
Kapur pertanian merupakan mineral yang berasal dari alam yang merupakan sumber hara kalsium. Kaptan yang mempunyai reaksi basa dapat menaikkan pH tanah. Kaptan yang banyak digunakan dalam pertanian adalah kalsit (CaCO3) Manfaat : Untuk menetralkan pH tanah pada tanaman sayuran⁄hortikultura dll . Untuk menanggulangi beberapa jenis jamur ⁄bakteri pada tanah. Untuk menetralkan tanah gambut sehingga menambah tingkat kesuburan tanah dll Spesifikasi : Kadar CaCO3 + MgCO % , Kadar CaO + MgO 58.8 %, Kadar Air Saat dikemas 1.00 %, Mesh 40 – 100, Berat bersih kemasan 50 kg

42 KAPTAN Kapur Pertanian (Kaptan) memiliki kandungan kalsium dan magnesium yang tinggi, ukiran butiran (mesh) yang halus dan sesuai dengan standar yang telah ditetapkan oleh SNI (Standar Nasional Indonesia) KAPTAN dapat diproduksi dengan menggunakan mesin crusher dan milling yang mampu memproduksi kaptan sekitar ton per bulan. Spesifikasi Kaptan Kadar CaCO3 + MgCO3 : 91.53% Kadar CaO + MgO : 50.23% Kadar air saat dikemas : 1.00% Mesh 40 – 100 : 82.01% Berat bersih perkemasan    50 Kg Kapur Pertanian merupakan mineral yang berasal dari alam yang merupakan sumber hara kalsium. Kaptan yang mempunyai reaksi basa dapat menaikkan PH tanah. Kaptan yang umum banyak digunakan dalam pertanian adalah Kalsit (CaCo3)

43 KAPTAN Dosis Kaptan 1. Sebelum melakukan pengapuran, sebaiknya terlebih dahulu dilakukan pemeriksaan PH tanah dengan menggunakan kertas lakumus atau PH soil tester, dapat meminta bantuan penyuluh terdekat dari dinas pertanian/ perkebunan/ perikanan 2. Pengapuran dengan dosis tersebut untuk jangka panjang atau 3 tahunan keatas, baru dilakukan pengapuran ulang. Ada anjuran para ahli sebaiknya dilakukan penambahan KAPTAN sebanyak 10% – 20% dari dosis diatas pada setiap 6 bulan sekali atau bersamaan dengan waktu pemupukan dilakukan 3. Untuk tanah marginal, umumnya berwarna terang atau pada tanah podsolik merah dan kuning atau pada tanah yang miskin kandungan bahan organik, dianjurkan pemberian kompos, bokasi atau pupuk organik 4. Mutu KAPTAN yang tepat selain kandungan kalsium (CaCO) yag tinggi kisaran 42% sampai 51%, tingkat kehalusan dan kelembutan (mesh) yang terbaik adalah 60 sampai 100 mesh 5. KAPTAN berkualitas tinggi bereaksi lebih cepat dan sempurna, sedangkan KAPTAN berkualitas renddah memerlukan waktu sangat lama untuk dapat merubah PH tanah, bahkan bisa sampai tahunan. Adapun KAPTAN yang memenuhi standar, dapat langsung bermanfaat dengan cara pemberian yang tepat

44 KALSIUM KARBONAT Kalsium karbonat adalah bahan aktif dalam kapur pertanian, dan biasanya merupakan penyebab utama air keras. Hal ini biasanya digunakan secara medis sebagai kalsium suplemen atau sebagai antisida, namun konsumsi yang berlebihan dapat membahayakan Kalsium karbonat memunyai beberapa sifat khas khususnya : 1. Bereaksi dengan asam yang kuat, dan melepaskan karbon dioksida CaCO3(s) + 2HC1(aq) CaC12(aq) +  CO2(g) + H2O(1) 2. Ia melepaskan karbondioksida pada pemanasan (diatas 840 C dalam kasus CaCO3), untuk membentuk kalisum oksida, yang biasa disebut kapur, dengan reaksi 178 KJ/ Mol CaCO CaO + CO2

45 KALSIUM KARBONAT Kalsium karbonat akan bereaksi dengan air yang penuh dengan karbon dioksida untuk membentuk larut kalsium bikarbonat CaCO3 + CO2 + H2O ? Ca(HCO3)2 Reaksi ini penting dalam erosi dari batuan karbonat, membentuk gua gua, dan menyebabkan air keras di berbagai daerah Sebagian besar dari kalsium karbonat yang digunakan dalam industri diekstraksi dengan pertambangan atau penggalian. Kalsium karbonat murni (misalnya untuk keperluan makanan atau farmasi), dapat dihasilkan dari sumber yang digali murni (biasanya marmer) atau kalisum karbonat disusun oleh kalsinasi mentah oksida kalsium. Air ditambahkan untuk memberikan kalsium hidroksida, dan karbon dioksida dilewatkan untuk mengendapkan kalsium karbonat yang diinginkan, sebagaimana dimaksud dalam industri sebagai endapan kalsium karbonat

46 Prinsip yang sama dapat diterapkan pada kalsit di laut.
KALSIUM KARBONAT Karbonat sering ditemukan dalam pengaturan geologi, kalsium karbonat terjadi sebagai polimor aragonit dan kalsit. Polimorf adalah mineral dengan rumus kimia yang sama tetapi struktur kimia yang berbeda. Mineral karbonat membentuk jenis batu : kapur, marmer, travertine, tufa, dan lain lain. Kalsit umumnya terjadi sebagai sedimen dalam pengaturan laut. Kalsit biasanya ditemukan di sekitar lingkungan tropis yang hangat. Endapan kalsit di lingkungan dangkal hangat lebih dari itu tidak dalam lingkungan yang lebih dingin karena lingkungan lebih hangat tidak mendukung pembubaran CO2. Hal ini dianalogikan dengan CO2 yang larut dalam soda. Ketika anda mengambil tutup botol soda, CO2 bergegas keluar. Sebagai soda menghangat, & karbon dioksida dilepaskan. Prinsip yang sama dapat diterapkan pada kalsit di laut.

47 SUPER DOLOMITE Super Dolomite adalah pupuk magnesium berkadar tinggi, digunakan baik untuk tanah pertanian, tanah perkebunan, kebutuhan industri dan bahkan untuk perikanan /tambak. Bahan baku Super Dolomit berasal dari batuan dolomit yang ditambang dari kawasan pertambangan di Gresik. Menurut pusat Penelitian dan Pengembangan Geologi Direktorat Jenderal Pertambangan Umum Bandung, batuan dolomit di Gresik adalah jenis batuan dolomit yang berkualitas tinggi, yakni dengan kadar MgO 18% - 21%

48 Keunggulan Pupuk Super Dolomit
1. Ukuran butir seragam, dan minimal 95% lolos ayakan 100 mesh Kadar MgO minimal 18% Daya larut dalam air cepat, sehingga cepat tersedia bagi tanaman Sebagai pupuk Mg memiliki efektifitas tinggi Daya tangkal pengasaman cepat Untuk mencapai produktifitas yang sama hanya memerlukan 60% super dolomit bila dibandingkan dengan dolomit biasa, sehingga mengurangi biaya aplikasi pemupukan dan biaya pengiriman 2. Pemakaian Kieserite dapat digantikan oleh super dolomit, jika super dolomit telah dicampur dengan ZA. Selain itu dapat memberikan manfaat lebih tinggi sebagai berikut : Pemakaian kombinasi super dolomit + ZA mampu memasok hara Magnesium (Mg) dan Sulfat Nitrogen pada tanaman dan tidak mengasamkan tanah Penghematan biaya produksi karena pemakaian Super Dolomit + ZA harganya lebih murah dibandingkan dengan Kieserite Penghematan devisa, karena import Kieserite dapat ditiadakan.

49 Kegunaan Super Dolomite
1. Penyembuhan Untuk tanaman, kekurangan Magnesium (Mg) berakibat sangat fatal. Tanaman yang menderita kekurangan Magnesium ditandai dengan daun yang menguning, sehingga kehilangan kemampuan menghasilkan CO2, dengan demikian, pemberian pupuk Super Dolomite akan mampu menambah unsur hara Magnesium yang diperlukan tanaman, sehingga warna daunnya menjadi hijau lagi 2. Amelioran Pada tanah masam atau PH rendah, selain pertumbuhan tanaman akan terganggu, juga keracunan A1 dan Fe sering terjadi. Dengan pemberian Super Dolomit, selain dapat menetralisir A1 dan Fe, juga menaikkan pH tanah sehingga penyerapan unsur unsur hara, N Fosfor (P), K oleh tanaman menjadi baik 3. Pembenah Pemberian pupuk berbentuk Amonium (UREA/DAP) dan kalcium (KCl) yang terlalu banyak, dapat mengakibatkan kekurangan Magnesium (Mg). Selain itu pupuk nitrogen mempunyai kecenderungan menciptakan suasana masam. Pemberian pupuk Super Dolomit mampu menetralisir reaksi tanah yang bersifat masam akibat pemberian pupuk yang berlebihan.

50 CARA PENGGUNAAN SUPER DOLOMITE
1. Disebar/ Dicampur merata Cara ini dilakukan apabila pupuk super dolomit digunakan untuk memperbaiki tanah yang buruk. Pupuk ini disebar/ dicampur merata diatas tanah pada waktu tanah terakhir yang bisanya dilakukan sebelum tanaman ditanam atau benih ditabur 2. Dimasukkan pada lubang tanaman Bila sebagai pupuk dasar pada tanaman perkebunan, Super Dolomit ditempatkan pada dasar lubang tanaman, kemudian diaduk merata dengan pupuk dan tanah pada dasar lubang, setelah itu ditimbun sedikit dengan tanah, baru diatas timbunan ditempatkan bibit tanaman 3. Super Dolomit dicampur dengan ZA / Pupuk lainnya Bila super dolomit diperlukan dalam pencampuran pupuk maka cara pemberiannya dilakukan dengan cara sebar merata dalam larikan sejajar baris tanaman, sekeliling batang tanaman atau ditempatkan pada lubang yang dibuat dikanan – kiri tanaman Untuk meniadakan reaksi tanah masam, Pupuk Super Dolomit dicampurkan pada waktu pengolahan tanah secara merata dan dilakukan 2 minggu sebelum tanam.

51 BENTUK BAHAN KAPUR Kapor Oksida: Kapur Sirih Kemurniannya: 85 - 95%
Pembuatannya: CaCO3 + panas CaO + CO2 CaMg(CO3)2 + panas CaO +MgO + CO2 Reaksinya dlm tanah: MISEL - H + CaO MISEL - Ca + H2O CaO + H2O Ca(OH)2 Ca(OH)2 + 2 H2CO3 Ca(HCO3)2 + 2 H2O % Oksida CaO : 77% Ekuivalen oksida Ca : 102 Daya netralisasi : (kesetaraan CaCO3) Persentase unsur Ca : 55 % Oksida MgO : 18% Persentase unsur Mg : 10.8

52 BENTUK BAHAN KAPUR Kapor Hidroksida: Kapur Tembok
Kemurniannya: % Pembuatannya: CaO + MgO + H2O Ca(OH) Mg(OH)2 Reaksinya di udara lembab terbuka: Ca(OH)2 + CO CaCO3 + H2O Mg(OH)2 + CO NgCO3 + H2O Reaksinya dlm tanah: MISEL - H + Ca(OH) MISEL - Ca + 2H2O Ca(OH)2 + 2 H2CO3 Ca(HCO3)2 + 2 H2O % Oksida CaO : 60% Ekuivalen oksida Ca : 76.7 Daya netralisasi : (kesetaraan CaCO3) Persentase unsur Ca : 42.8 % Oksida MgO : 12% Persentase unsur Mg : 7.2

53 BENTUK BAHAN KAPUR Kapor Karbonat : Kapur Kalsit = CaCO3
Kapur Dolomitik = CaMg(CO3)2 Dolomit = MgCO3 Kemurniannya : % Pembuatannya: Batuan CaCO3 digiling Kapur giling Reaksinya dlm tanah: MISEL - H + CaCO MISEL - Ca + H2O + CO2 Oksida CaO = 44.8%; MgO = 6.70% Ekuivalen oksida Ca : Daya netralisasi : 96.6 (kesetaraan CaCO3) Persentase unsur Ca = 32; Mg = 4.03 Karbonat: CaCO3 = 80%; MgCO3 = 14% Total = 94%

54 PENGARUH KAPUR PADA TANAH
Pengaruh Fisik: - Membantu granulasi - agregasi - Memperbaiki struktur tanah - Tata Udara (Aerasi) - Tata Air / Pergerakan air Pengaruh Kimia: (Bila tanah dg pH= 5.0 dikapur hingga ph naik menajdi 6.0) - Kepekatan kation hidrohen menurun - Kepekatan anion hidroksil meningkat/ naik - Daya larut Fe, Mn dan Al akan menurun - Ketersediaan fosfat dan Mo akan diperbaiki - Cadd dan Mgdd akan naik - Persentase kejenuhan basa (KB) akan naik - Ketersediaan kalium berubah tgt keadaan. Pengaruh Biologik: - Merangsang kegiatan jasad tanah, termasuk mikroba tanah - Membantu pembentukan humus - Aminisasi, amonifikasi, oksidasi belerang dipercepat - Fiksasi nitrogen dari udara secara biologis dirangsang - Nitrifikasi dipercepat

55 JENIS TANAMAN yg SESUAI TANAH MASAM dg KEBUTUHAN KAPUR MINIMUM
Kebutuhan Kejenuhan pH Varietas tnm yg toleran kapur Al (t/ha) (%) Gogo, ubikayu, mangga, mente Jeruk, Nanas, Desmodium, Cen- trosema, Paspalum Cowpea, Plantain Jagung, Black bean Sumber: Spain et al

56 MEKANISME TOLERANSI / KEPEKAAN TANAMAN thd Al dlm TANAH
1. Morfologi akar. Varietas yg toleran Al mampu menumbuhkan dan tidak mengalami kerusakan ujung-ujung akar pd kondisi tanah masam kaya Al 2. Perubahan pH rhizosfer. Varietas yg toleran Al mampu menaikkan pH zone rhizosfernya, sdg varietas yg peka menurunkan pH tsb. Perubahan pH ini diduga akibat dari penyerapan anion diferensial-selektif, sekresi asam organik, CO2 dan HCO3-. 3. Lambatnya translokasi Al ke tajuk. Varietas yg toleran Al mengakumulasikan Al dlm akar, dan mentranslokasikan ke tajuk secara lebih lambat dp jenis yg peka.

57 MEKANISME TOLERANSI / KEPEKAAN TANAMAN thd Al dlm TANAH
4. Al dalam akar tidak menghambat penyerapan dan translokasi Ca, Mg dan K dlm varietas yg toleran Al. 5. Toleransi varietas kedelai thd Al berhubungan dengan penyerapan dan translokasi Ca. 6. Toleransi varietas keNTANG thd Al berhubungan dengan translokasi Mg dan K . 7. Toleransi varietas padi thd Al berhubungan dengan tingginya kandungan Si dlm tanaman. 8. Varietas yg toleran Al tidak mengalami hambatan penyerapan dan translokasi fosfat; tdk dmk varietas yg peka.

58 PENGAPURAN 1. Tujuan utama pengapuran adalah menetralisir Aldd, dan biasanya diikuti oleh kenaikan pH hingga 5.5. 2. Kalau diduga ada keracunan Mn, maka pH dinaikkan 6.0 3. Faktor-faktor yg harus diperhatikan: 1. Jml bahan kapur yg diperlukan untuk menetralkan Aldd hingga tingkat yg sesuai bagi tanaman 2. Kualitas bahan kapur 3. Cara penempatan / aplikasi bahan kapur ke tanah.

59 pH TANAH DAN PENGAPURAN
pH tanah mempengaruhi ketersediaan hara dalam tanah. Most elements are at maximum availability at pH 6 – 7 except for some minor elements. This is the ideal pH and therefore should be the aim for good soil management. Pengapuran sangat penting un tuk mencuci asam dari tanah.

60 pH TANAH DAN KETERSEDIAAN HARA

61 pH TANAH DAN PENGAPURAN
Pengapuran dilakukan setiap 5 – 10 tahun, depending on the soil and rainfall and evaporation amounts. Pengapuran meningkatkan pH tanah, by replacing H+ ions (acid ions) with Ca++ ions. Kation H+ kemudian tercuci ke luar tanah. It takes up to two years for the liming to take full effect. Ground limestone is the main source of lime

62 pH TANAH DAN PENGAPURAN
Bahan batu-kapur yang digiling harus memenuhi syarat: Harus mempunyai TNV (Total Neutralising Value) tidak klurang dari 90% Semua partikel ukurannya harus kurang dari 3.35mm Minimal 35% harus lolos ayakan 0.15 mm. Kandungan airnya lebih dari 3.0%.

63 Meningkatkan pH tanah Kation H+ pada tapak jerapan digantikan oleh Ca++ atau Mg++, sehingga kemasaman tanah dinetralkan

64 RESPON TANAMAN thd PENGAPURAN
Umumnya pertumbuhan tanaman menjadi lebih baik. Tnm kacang-kacangan menyukai kapur, termasuk kedelai dan kacang tanah Alasan terjadinya respon tanaman: 1. Pengaruh langsung unsur hara Ca dan Mg 2. Dinetralkannya senyawa-senyawa toksik 3. Penekanan gangguan penyakit tanaman 4. Ketersediaan beberapa unsur hara meningkat 5. Rangsangan kegiatan jasad mikro akan meningkatkan ketersediaan hara 6. Beberapa tanaman tertentu tidak senang pengapuran, misalnya semangka. 7. ……. Dll.

65 PENENTUAN KEBUTUHAN KAPUR
1. Kamprath (1970): Dosis kapur = 1.5 x ( me Aldd topsoil) = m.e. Ca yg harus diaplikasikan sbg kapur 2. Dosis kapur yg dihitung dg cara ini mampu menetralkan % Aldd dlm tanah yg mengandung 2 - 7% bahan organik 3. Faktor 1.5 digunakan untuk menetralkan H+ yg dilepaskan oleh bahan organik atau hidroksida Fe dan Al kalau pH tanah meningkat 4. Dalam tanah yg kaya bahan organik, faktor tersebut menjadi 2.0 atau 3.0, karena adanya Hdd. 5. Untuk setiap satu m.eq. Aldd dlm tanah diperlukan aplikasi 1.5 meq Ca atau setara dg 1.65 ton CaCO3 per ha. 6. Faktor penting lain adalah kandungan Aldd dlm tanah yang dapat ditolerir oleh tanaman tertentu 7. Jagung sensitif terhadap kejenuhan Al %. Pengapuran hingga kejenuhan Al = 0% dapat menguntungkan, namun pengapuran untuk menurunkan kejenuhan Al menjadi 20% dapat lebih ekonomis.

66 RESPON HASIL TERHADAP PENGAPURAN
% Hasil maks. 100 80 60 40 20 00 Rumput gajah Jagung Sorghum % kejenuhan Al Sumber: Abruna et al. 1975 Oxisols & Ultisols

67 PLACEMENT 1. Kapur biasanya dibenamkan sedalam 15 cm beberapa hari sebelum tanam. 2. Tanah Oksisol sangat masam yg topsoilnya telah dikapur hingga pH 5.5 , sebagian besar akar jagung tumbuh dalam topsoil. Tingginya kandungan Aldd dalam subsoil mencegah pertumbuhan akar lebih dalam. 3. Penempatan kapur pada lapisan tanah yg lebih dalam mengakibatkan perakaran tanaman tumbuh lebih dalam dan hasil tanaman lebih baik 4. Deep placement kapur dimungkinkan pada tanah-tanah berpasir yang strukturnya baik. 5.

68 PENGAPURAN & HASIL JAGUNG
Hasil biji , t/ha 6 5 4 3 2 1 Zone pengapuran 0-30 cm Zone pengapuran 0-15 cm Dosis kapur ( ton/ha) Sumber: Gonzales, 1973 Tanah Oxisols

69 EFEK RESIDU KAPUR 1. Efek residu pengapuran tergantung pada seberapa cepat Ca dan Mg digantukan oleh residu kemasaman dari pupuk nitrogen. 2. Pada tanah Hydrandept Selama lima tahun sejak aplikasi 2 ton kapur/ha ternyata nilai Aldd dalam tanah dipertahankan sekitar 1 meq, semula sebesar 3 m.eq, meskipun sebagian besar Ca++ telah tercuci. Setelah lima tahun efek residu pengapuran lenyap. 3. Pada Oxisol berpasir. Jagung dan kedelai respon positif terhadap kapur enam tahun setelah aplikasi, respon hasil meningkat dg waktu, diduga karena pelarutan partikel kasar kapur.

70 KELEBIHAN Pemberian KAPUR
Kelebihan: penambahan kapur yg mengakibatkan meningkatan pH tanah melebihi yang diperlukan untuk pertumbuhan optimum tanaman. Tanaman akan menderita, terutama pada tahun pertama aplikasi kapur Biasanya terjadi pada tanah berpasir / berdebu yg miskin bahan organik Pengaruh buruk pengapuran yg berlebihan: 1. Kekurangan Fe, Mn, Cu dan Zn 2. Ketersediaan fosfat mungkin menurun karena pembentukkan senyawa kompleks dan tidak larut 3. Serapan fosfat dan penggunaannya dlm metabolisme tanaman dapat terganggu 4. Serapan B dan penggunaannya dapat etrganggu 5. Perubahan pH yang terlalu melonjak dapat berpengaruh buruk 6. ………dst. 7. ……. Dll.

71 Apakah KAPUR perlu diberikan?
Penggunaan kapur harus didasarkan pada : Kemasaman Tanah dan Kebutuhan Tanaman Apakah KAPUR perlu diberikan? 1. Sebelum mengapur tanah, karakteristik kimia tanah perlu diteliti 2. pH tanah dan Kejenuhan Basa harus ditentukan secara akurat : Lapisan atas dan Lapisan bawah 3. Cara lain adalah menentukan Aldd 4. ………. 1. Kebutuhan kapur untuk tanaman secara umum atau untuk tanaman tertentu 2. Pengelompokkan respon tanaman thd kapur : - Tanaman Senang Pengapuran - Tanaman tidak senang Pengapuran - Tanaman netral

72 Bentuk KAPUR yg dipakai
Lima faktor unt menentukan bentuk kapur : 1. Jaminan mutu kimia bahan kapur 2. Harga bahan 3. Kecepatan reaksi dengan tanah 4. Kehalusan bahan kapur 5. Hal lain-lain (penyimpangan, pembungkusan dsb. Bentuk KAPUR yg dipakai Kecepatan Reaksi: 1. Kapur kaustik (kapur tohor dan tembok) lebih cepat bereaksi dg tanah dp kapur giling 2. Kapur dolomitik bereaksi lebih lambat dp kapur kalsitik 3. Bentuk tepung halus lebih cepat bereaksi dg tanah 4. …. Dll. Pertimbangan biaya: 1. Harga bahan kapur 2. Biaya angkut ke lahan usaha 3. Biaya aplikasi bahan kapur ke lahan usaha 4. ….. dll

73 Jumlah KAPUR yg diaplikasikan
Enam faktor penting unt menentukan jumlah kapur : 1. Karakteristik tanah: Lapisan atas: pH, Aldd, Tekstur & Struktur, BOT Lapisan bawah: pH, Aldd, Tekstur & Struktur 2. Tanaman yg akan ditanam 3. Lamanya pergiliran tanaman 4. Macam bahan kapur dan komposisi kimianya 5. Kehalusan bahan kapur 6. Pengalaman praktis Jumlah KAPUR yg diaplikasikan Karakteristik Tanah : 1. Tekstur dan BOT menentukan besarnya kapasitas jerapan 2. Semakin tinggi Kapasitas jerapan dan Aldd, semakin banyak kapur diperlukan 3. Kemasaman dan Aldd tanah lapisan bawah ikut menentukan jumlah kapur Contoh: Jml kapur giling unt tanah mineral setebal 20 cm seluas 1 ha: Untuk menapai pH Jumlah kapur, ton/ha x me Aldd

74 Teknologi Aplikasi KAPUR
Cara Aplikasi : 1. Kapur disebar di permukaan tanah yg baru dibajak, kemudian dicampur rata dengan tanah olahan 2. Kapur disebar di permukaan tanah, tanah dibajak (diolah) dan dicampur rata Waktu Aplikasi : 1. Biasanya sebelum tanam 2. Kapur diberikan bila diperkirakan tidak turun hujan pd saat aplikasi 3. …… 1. Pertanaman tunggal 2. Pertanaman majemuk: Pola pergiliran tanaman Kapur diberikan pd tanaman yg paling memerlukan pengapuran

75 TEKNOLOGI PENGAPURAN TERPADU
Prinsip utama pengelolaan tanah masam adalah menaikkan pH tanah dan mengurangi kejenuhan Al yang meracun, serta meningkatkan ketersediaan hara tanaman, terutama unsur hara P sehingga sesuai dengan pertumbuhan tanaman yang optimal. Pengapuran merupakan teknologi yang paling tepat dalam pemanfaatan tanah masam di dasarkan atas beberapa pertimbangan: Rekasi kapur sangat cepat dalam menaikkan pH tanah dan menurunkan kelarutan Al yang meracun. Respons tanaman sangat tinggi terhadap pemberian kapur pada tanah masam. Efek sisa kapur atau manfaat kapur dapat dinikmati selama 3 sampai 4 tahun berikutnya. Bahan kapur cukup tersedia dan relatif murah

76 PENGELOLAAN KEMASAMAN (pH) tanah
Teknologi pengapuran terpadu meliputi topik-TOPIK : Kapur pengendali kemasaman tanah Peranan kapur dalam meningkatkan serapan P Penetapan kebutuhan kapur Manfaat kapur bagi pertumbuhan dan hasil tanaman Pengaruh sisa pupuk P bersama kapur Jenis kapur dan cara penggunaannya Pengapuran harus di sertai dengan pemupukan Peran bahan organik pada tanah masam Integrasi kapur, bahan organik, dan pupuk Efek kapur berlebihan Pengapuran dan pengaturan pola tanam Budidaya lorong "Alley cropping" memantapkan pengapuran Perhitungan keuntungan akibat penggunaan kapur

77 PENGELOLAAN KEMASAMAN (pH) tanah TEKNOLOGI PENGAPURAN TERPADU:
Teknologi pengapuran yang diintegrasikan dengan penggunaan bahan organik dan pupuk buatan yang disertai dengan budidaya lorong dengan pola tanam yang menguntungkan .

78 Waktu Aplikasi dan Penempatan Kapur ke Tanah
Waktu Aplikasinya. Aplikasi kapur dapat dilakukan setiap saat dalam setahun. For the farmer or gardener, winter or early spring just prior to soil preparation is usually most convenient. Don't apply caustic liming materials such as burned lime, hydrated lime, or wood ashes to actively growing plants. Ground limestone will not harm plants. Penempatan Kapur ke dalam Tanah Ground agricultural limestone is relatively insoluble in water so maximum contact with the soil is necessary to neutralize the soil acidity. Lime will not move into the soil like water-soluble fertilizers. Thoroughly mix the recommended amount of lime with the top 6 to 8 inches of soil. As soon as moisture is present, the lime will begin to react. Coarse lime particles react more slowly than very fine particles. Therefore, using very finely ground limestone and thoroughly mixing it are necessary to achieve the desired soil pH change within a few months. If the soil will be turned with a bottom plow, turn it first and then apply the lime and mix. Diunduh dari: …… 23/9/2012

79 Beberapa material bahan kapur untuk tanah pertanian.
Relative Neutralizing value % Comment pure CaCO3 100 not generally available Calcitic agricultural lime,   (calcium carbonate,   CaCO3 +impurities) easily available Dolomitic agricultural lime,   CaCO3 + MgCO3 easily available; provides Mg Ground oyster shells Selma chalk/marl,   CaCO3 + clay contains clay; keep dry Burned lime, CaO very caustic; don't use Hydrated lime or   builders' lime, Ca(OH)2 caustic; use with caution; no Mg Basic slag contains some P & micronutrients; byproduct Wood stove or fireplace   ashes provides some plant nutrients Boiler wood ash By-products Variable use as specified by manufacturer Gypsum and/or   ground drywall, CaSO4 NOT A LIMING MATERIAL Diunduh dari: …… 23/9/2012

80 KLASIFIKASI KAPUR PERTANIAN
Agreement between the Directors of the New England and New Jersey Experiment Stations and the Special Committee of the National Lime Manufacturers' Association of Boston, March 3, 1909. Diunduh dari: …… 23/9/2012

81 Bedding Lime: Tepung Batu-kapur
The typical analysis and comparitive application rates for our Calcium Ground Lime and Calcium Limestone Flour: Benefits of Calcium Limestone Flour: Improves pH levels and adds Calcium to the soil Decreases dependance on fertiliser Suitable for grassland and tillage Easy to spread using your own tanker Produces a lime rich slurry Fast acting due to fineness Reduces liming costs Diunduh dari: …… 23/9/2012

82 The quantity of Ag-limestone needed to
KEBUTUHAN KAPUR: Lime Requirement (LR). The quantity of Ag-limestone needed to increase the pH of a soil to the optimal Ph (target pH) for the crop or crop rotation. Diunduh dari: …… 21/9/2012

83 Tekstur Tanah dan Kebutuhan Kapur
Diunduh dari: …… 23/9/2012

84 KEBUTUHAN KAPUR LR : lime Requirement Diunduh dari: …… 23/9/2012

85 From Adams-Evans Buffer to LR target pH = 6.5, pounds of limestone
KEBUTUHAN KAPUR From Adams-Evans Buffer to LR target pH = 6.5, pounds of limestone Diunduh dari: …… 23/9/2012

86 KEBUTUHAN KAPUR Lime Recommendations (tons/acre) for Various Soil Textural Classes in Maryland to Attain pH 6.5 (1952, Soil Science, Hoyert and Axley) Diunduh dari: …… 23/9/2012

87 target pH is 6.5; recommendation is pounds oxides
KEBUTUHAN KAPUR target pH is 6.5; recommendation is pounds oxides Diunduh dari: …… 23/9/2012

88 KEBUTUHAN KAPUR SMP SINGLE BUFFER pH
pH buffer merupakan ukuran kemasaman tanah (aktif dan cadangan), yaitu kapasitas buffer dan digunakan untuk menduga kebutuhan kapur. The method is based on the reaction of soil buffered acidity with a chemical buffer resulting in change in the pH of the buffer. Several tests have been developed to measure lime requirement including SMP Buffer, Woodruff (1967), Mehlich (1939) and Adams & Evans (1962). The SMP (Shoemaker, McLean & Pratt, ) buffer tests is one of the more popular lime requirement tests used for estimating exchange acidity including that associated with exchangeable aluminum and is used predominately on soils of the northeast. Others such as the Woodruff and Mehlich method, are dependent on geographic region or preference. Standard calibration curves exist for liming based on a SMP value to a desired pH for soil groups in a geographic area. Local calibration of the method is desirable. The procedure is generally reproducible with in 0.1 pH units. Diunduh dari: …… 23/9/2012

89 KEBUTUHAN KAPUR WOODRUFF BUFFER pH
pH buffer merupakan ukuran kemasaman tanah (aktif dan cadangan), yaitu kapasitas buffer dan digunakan untuk menduga kebutuhan kapur. The method is based on the reaction of soil acidity with a chemical buffer resulting in change in the pH of the buffer. Several methods have been developed to measure lime requirement including SMP Buffer, Woodruff (1967), Mehlich (1939) and Adams & Evans (1962). The SMP (Shoemaker, McLean & Pratt, ) and Mehlich buffer methods is one of the more popular lime requirement tests used for estimating exchange acidity including that associated with exchangeable aluminum. The Woodruff method is better suited to soils low in exchangeable aluminum with acidity associated with ammoniacal nitrogen applications. Idaho, Nebraska, Missouri and Mississippi currently use the Woodruff method to make lime recommendations. Local calibration of the method is desirable. The procedure is generally reproducible with in 0.10 pH units. Diunduh dari: …… 23/9/2012

90 KEBUTUHAN KAPUR ADAMS AND EVANS BUFFER pH
pH buffer merupakan ukuran kemasaman tanah (aktif dan cadangan), yaitu kapasitas buffer dan digunakan untuk menduga kebutuhan kapur pada tanah-tanah yang KTK nya rendah . The method is based on the reaction of soil buffered acidity with a chemical buffer resulting in change in the pH of the buffer. The Adams and Evans method (Shoemaker, McLean & Pratt, 1961) is one of the more popular lime requirement tests used for estimating exchange acidity including that associated with exchangeable aluminum. It is mainly used on the coastal plain soils of the mid-Atlantic states. This method can detect small differences in lime requirement where such differences may elicit large changes in pH. The procedure is generally reproducible with in 0.10 pH units. Diunduh dari: …… 23/9/2012

91 KEBUTUHAN KAPUR MEHLICH BUFFER pH
pH buffer Mehlich merupakan ukuran kemasaman tanah (aktif dan cadangan), yaitu kapasitas buffer dan digunakan untuk menduga kebutuhan kapur (CaCO3). The method is based on the reaction of soil buffered acidity both hydrogen and aluminum with a chemical buffer resulting in change in the pH of the buffer (Mehlich, Bowling and Hatfield, 1976). The method is particularly well suited to for determining lime requirement for neutralizing very acid soils which may be harmful to crop productivity. Calibration data presented is based on data developed by van Lierop (1990), Mehlich et al. (1976) and Ssali and Nuwamanya (1981). North Carolina uses the Mehlich Buffer pH method to make lime recommendations Local calibration of the method for lime requirement is desirable. The procedure is generally reproducible with in 0.10 pH units. Diunduh dari: …… 23/9/2012

92 Buffer SMP untuk Kebutuhan Kapur
Metode SMP semula dikembangkan untuk menentukan kebutuhan kapur pada tanah-tanah di Ohio tahun Metode ini cocok untuk tanah-tanah lempung-debu dengan beragam kandungan Al-terekstraks. Prior to 1962, the Woodruff buffer method (1948) was observed to underestimate lime requirement for Ohio soils with appreciable extractable Al (McLean et al. 1958). Shoemaker, McLean and Pratt developed the SMP buffer method to remedy this problem (Shoemaker et al., 1961). The SMP buffer is added to a soil-water slurry after measurement of soil pH. The SMP buffer has an initial pH of Bases in the buffer react with soil acidity to reduce the pH of the buffer from 7.5 to some measured soil-buffer pH. The greater a decline in soil-buffer pH from an initial value of 7.5, the greater the lime requirement for neutralizing soil acidity. A calibration of soil-buffer pH to actual lime requirement to some target soil pH from incubating Ohio soils with varying amounts of CaCO3 provided a means of estimating lime requirement from soil-buffer pH (Shoemaker, 1959; Shoemaker et al., 1961). Diunduh dari: …… 23/9/2012

93 Effect of bulk lime on soil pH
KEBUTUHAN KAPUR Effect of bulk lime on soil pH To test the effect of each lime product as purchased by farmers, bulk samples were mixed with soil and pH change measured as described previously. Again rates were adjusted to allow for differences in neutralising value.  Diunduh dari: …… 23/9/2012

94 Berapa lama ‘kapur’ bekerja dalam tanah?
TOP 10 LIMING QUESTIONS. Berapa lama ‘kapur’ bekerja dalam tanah? Since water is required for lime to react with the soil, effects of a lime application will be slower in a dry soil. It often takes a year or more before a response can be measured even under perfect conditions. However, a response may be observed within weeks of the application when soil pH is extremely low. It is important to apply lime immediately after the growing season or crop removal to allow lime to react, correcting soil pH before the next growing season. The reactivity time also depends on the type of lime used. Liming materials differ widely in their neutralizing powers due to variations in the percentage of calcium and/or magnesium. Usually, liming materials with a high calcium carbonate equivalent (CCE) tend to neutralize soil acidity faster than those with a low CCE. The coarseness of the liming material will also influence how fast the lime will react. In other words, the finer the liming material, the greater the surface area, resulting in faster reactivity. Diunduh dari: …… 23/9/2012

95 Berapa dosis kapur setiap aplikasi?
TOP 10 LIMING QUESTIONS. Berapa dosis kapur setiap aplikasi? The amount of lime needed depends on the type of crop being grown. If growing continuous wheat or bermudagrass, it is only necessary to raise the soil pH above 5.5. Therefore, one-half ton or 25 percent of the soil test deficiency amount required to raise the soil pH to 6.8 is recommended. If growing legumes, the soil pH needs to be raised to 6.8. If surface applying lime, apply no more than two and one-half tons per acre per year. Up to four tons per acre may be applied if the lime is worked into the soil. In situations where soil pH is extremely low and a large amount of lime is recommended, it may be a good idea to spread the cost over two to three years by annually applying one-third or half of the lime needed. Diunduh dari: …… 23/9/2012

96 TOP 10 LIMING QUESTIONS. Haruskah kapur dibenamkan ke dalam tanah, atau cukup di permukaan tanah? Whenever possible, tillage should be used as a tool to incorporate lime into the soil. When lime is worked into the soil, a larger portion of its surface area is exposed to the soil allowing for faster reactivity. Lime applied on the soil surface does not react as fast as lime incorporated by tillage, but what other option is there in perennial pasture systems? Surface-applied lime moves into the soil at a slow rate. It is similar to non-mobile nutrients in its movement in the soil. However, there are a few crops that have roots that feed close to the soil surface, such as bermudagrass and alfalfa. It has been documented that correcting pH in the top two to three inches of the soil has a positive effect on forage production. Even though it is best to incorporate lime whenever possible, it is still important to surface-apply lime to correct the soil acidity problem in established pastureland and no-till cropping systems. Diunduh dari: …… 23/9/2012

97 Bagaimana efek pengapuran thd aktivitas herbisida?
TOP 10 LIMING QUESTIONS. Bagaimana efek pengapuran thd aktivitas herbisida? Ada beberapa jenis herbisida yang aktivitasnya dipengaruhi oleh pH tanah. For example, low soil pH levels may reduce the activity or residual time of triazine (atrazine, Sencor) and sulfonylurea (Peak) herbicides. High soil pH levels (>6.8) tend to increase herbicide activity that increases the risk of crop injury and/or carryover potential. Diunduh dari: …… 23/9/2012

98 Bgm efek pengolahan tanah thd pH-tanah?
TOP 10 LIMING QUESTIONS. Bgm efek pengolahan tanah thd pH-tanah? All lime calculations are based on neutralizing the acidity in the top six inches of soil. As a result, different tillage systems affect soil acidity. A conventional tillage system involves several tillage passes over the field prior to planting. If the subsoil is calcareous, deep tillage may mix enough subsoil into the top six inches to maintain soil pH at the surface. Conventional tillage systems allow the opportunity to thoroughly mix applied lime prior to the next growing season. A conservation tillage system is not as aggressive as conventional. Fewer tillage passes may be implemented prior to planting, leaving greater than 30 percent crop residue on the soil surface. As a result, there is a limited amount of soil mixing. It is critical to closely monitor soil pH in no-till systems since most lime and dry fertilizer is surface-applied. Over time, the top inch of soil may become extremely acidic due to the surface application of fertilizer. However, soil surface pH can also become too high if a large amount of lime is applied at one time and left on the soil surface. It is best to apply small amounts of lime more frequently to maintain soil pH in a no-till system. Diunduh dari: …… 23/9/2012

99 Both calcitic and dolomitic lime sources work well in raising soil pH.
TOP 10 LIMING QUESTIONS. Apakah dolomitik (MgCO3) lebih baik dp kalsitik (CaCO3)? In general, soils in Oklahoma and north Texas are not deficient in magnesium. Therefore, the use of dolomitic lime to increase soil magnesium levels is not important. Dolomitic lime may be recommended in pastures that have a history of grass tetany to raise forage magnesium levels. Both calcitic and dolomitic lime sources work well in raising soil pH. Di berbagai daerah biasanya lebih penting efektivitas biaya daripada jenis bahan kapur. Diunduh dari: …… 23/9/2012

100 Ada tiga kelemahan penggunaan bahan kapur cair.
TOP 10 LIMING QUESTIONS. Apakah kelebihan dan kekurangan bahan kapur cair dibanding kapur padatan-kering? Liquid lime is a formulation of approximately 50 percent high quality dry Ag lime (usually greater than 90 percent) and 50 percent H2O. It has the advantage of providing better uniformity of spread over the field in comparison to dry lime. Ada tiga kelemahan penggunaan bahan kapur cair. Biasanya biaya aplikasinya lebih mahal. Biasanya akan terjadi “under-liming” karena “spread rate”. Diperlukan frekuensi aplikasi kapur lebih sering karena kapur cair bereaksi lebih cepat, tetapi dosisnya tidak cukup tinggi untuk mengoreksi semua kemasaman cadangan. One must be very careful of the rate at which liquid lime is applied. It is appealing to the producer because of its fast reaction time and uniformity advantages. Perlu diketahui seberapa besar kandungan bahan aktif atau daya netralitas dari bahan kapur. Diunduh dari: …… 23/9/2012

101 Bagaimana efektivitas bahan kapur cair dibandingkan Kapur Pertanian?
TOP 10 LIMING QUESTIONS. Bagaimana efektivitas bahan kapur cair dibandingkan Kapur Pertanian? Untuk membandingklan kedua bahan ini kita harus mengetahui: Daya netralisasi per satuan berat bahan kapur Harga dan biaya per satuan berat bahan kapur. Diunduh dari: …… 23/9/2012

102 TOP 10 LIMING QUESTIONS. Mengapa ada perbedaan antara pH tanah dan pH buffer dalam hasil uji tanah? pH is an unbuffered measure of the hydrogen ion concentration in the soil (active acidity) whereas buffer pH is a measurement of total soil acidity (active + reserve acidity). Soils with low buffering capacities (low cation exchange capacity or CEC) usually have less total acidity than soils with a high CEC if the pH is the same. Therefore, it takes less lime to correct the total acidity in a soil with a low CEC. The buffer pH on the soil test report is used to calculate how much lime is needed to correct both the active and reserve acidity. When soil pH is 6.5 or greater, the buffer index will not be reported on the soil test report due to its irrelevance. Diunduh dari: …… 23/9/2012

103 Berapa frekuensi pengapuran?
TOP 10 LIMING QUESTIONS. Berapa frekuensi pengapuran? The answer to this question depends on a variety of considerations. A soil with a low CEC does not require a lot of lime to correct soil pH, but may need to be limed frequently. A soil with a high CEC requires a large amount of lime to initially correct pH, but it may be several years before another lime application is needed due to its high buffering capacity. The level of production also dictates how often lime will be needed. As fertilizer is applied to enhance forage or crop production, the removal of essential plant nutrients from the soil also increases. As a result, lime may be needed more frequently to replenish removed nutrients. For example, the rate of nutrient removal from a pasture being hayed is much greater than a pasture being grazed. Therefore, the hay field may need to be limed more often. Diunduh dari: …… 23/9/2012

104 PENGARUH PENGAPURAN. Effect of ag lime fineness on speed of reaction
The speed with which an ag lime material reacts with the soil to neutralize acidity and thus increases soil pH is determined by the fineness of the material. The finer the material, the faster it will react because limestone’s solubility increases as it is ground finer. Also, limestone affects only a very small volume of soil around each particle, so the finer the material, the greater the total surface area that is available to come into contact with the soil and neutralize it (assuming adequate soil mixing). Ag lime should react with the soil as quickly as possible. Generally, ag lime should react completely within three years. Quicker reaction may be desirable on rented ground or for shorter-season annual crops. Diunduh dari: …… 23/9/2012

105 PENGARUH PENGAPURAN. Effect of Quarry Lime Application Rates on Soybean Yield Time between application and when soybeans were harvested was 16 months. Soybean yields varied as part of the plot area had standing water. Soybean yield from the 6-ton liming rate was significantly different from the check. Soybean yields trended higher than the check. Diunduh dari: …… 23/9/2012

106 Badal C. Saha, Michael A. Cotta.
PENGARUH PENGAPURAN. Lime pretreatment, enzymatic saccharification and fermentation of rice hulls to ethanol Badal C. Saha, Michael A. Cotta. Biomass and Bioenergy. Volume 32, Issue 10, October 2008, Pages 971–977 Effect of lime dose (25, 50, 100 mg g−1) and duration (6, 30, 60 min) of pretreatment at 121 °C on the enzymatic saccharification of pretreated rice hulls (15.0%, w/v) using a cocktail of three commercial enzyme preparations (cellulase, β-glucosidase and hemicellulase) at each enzyme preparation dose level of 0.05 ml g−1 hulls at pH 5.0 and 45 °C for 72 h. The data presented are averages of two individual experiments. (A) glucose; (B) total sugars. Diunduh dari: …… 23/9/2012

107 PENGARUH PENGAPURAN. Effect of different particle size fractions on soil pH All lime sizes significantly increased soil pH to optimum levels in comparison to the control block where no lime was applied. The <0.25mm particle size lime raised soil pH and soil exchangeable calcium levels within 35 days*, a quick response, Ag Lime 90 contains 40% of this particle size range. Pasture production is increased the sooner lime is absorbed. Particles mm increased soil pH to greater that 5.8 in less than 83 days and between 83 and less than 320 days for the largest particles 1-2mm. These pH levels remained constant for the duration of the trial work. Diunduh dari: …… 23/9/2012

108 PENGARUH PENGAPURAN. Estimated effect of AgLime 90 on pasture dry matter yield The cumulative dry matter yield is estimated to increase significantly over application periods. AgLime 90 has the potential to increase dry matter accumulation by 2000 kg of dry matter per hectare, approximately 18%, compared to the effect of no lime over a twenty two month period. Diunduh dari: …… 23/9/2012

109 Copper becomes more available at low pH.
PENGARUH PENGAPURAN. Soil pH and Mineral Nutrition of Vitis vinifera Varieties © Copyright 2000 Robert Pool Revised by Terry Bates and Lailiang Cheng, 2011 Copper Toxicity Copper becomes more available at low pH. For world viticulture, copper toxicity is most commonly associated with long term application of copper fungicides to acid soils. This is one reason that a dependence on copper fungicides to control disease is undesirable. Diunduh dari: …… 23/9/2012

110 A.E. Crawford and C.J.P. Gourley
PENGARUH PENGAPURAN. Pasture responses to lime over five years are limited and highly variable A.E. Crawford and C.J.P. Gourley Australian Agronomy Conference Concurrent Session 3, , Tuesday 30 January Effect of lime on soil pH(H2O), exchangeable Al (KCl), available P (Olsen) and extractable cations at Wyelangta in October 1999, five years after application. Depths shown are 0-5 cm (), 5-10 cm (), cm () and cm (). Diunduh dari: …… 23/9/2012

111 PENGARUH PENGAPURAN. Correcting soil acidity How does lime work?
Soil acidity is corrected by applying agricultural lime or dolomite. Lime (calcium carbonate) is the most common product applied to dairy pastures to increase the pH and neutralise the effects of soil acidity. How does lime work? 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. Figure shows a simplified version of these chemical reactions. Diunduh dari: …… 23/9/2012

112 Lime application at sowing
PENGARUH PENGAPURAN. Lime application at sowing Lime is relatively insoluble (does not dissolve easily). Thus, it is slow to react. For maximum benefit, it should be worked into the soil when resowing a pasture or sowing a summer fodder crop. Table 4.5 shows the recommended application rates of lime if applied to an area to be sown. The amount of lime with a neutralising value (NV) of 100 required, by incorporation into the soil, to raise the pH level over a particular range on various soil types. Source: Adapted from Seeliger (1973). Diunduh dari: …… 23/9/2012

113 M. Toma, M. E. Sumner, G. Weeks and M. Saigusa.
PENGARUH PENGAPURAN. Long-term Effects of Gypsum on Crop Yield and Subsoil Chemical Properties M. Toma, M. E. Sumner, G. Weeks and M. Saigusa. Sssaj 1999 Vol. 63 No. 4, p.  A number of long-term experiments with gypsum incorporated into the topsoil at 10 and 35 Mg ha−1 were sampled to evaluate its effects on soil profile chemical properties and yields of corn (Zea mays L.) and alfalfa (Medicago sativa L.). Even after 16 yr, the gypsum effects were still clearly visible. Exchangeable Ca and SO4 were higher down the soil profile in the gypsum than in the control treatment. A complementary reduction in exchangeable Al was observed in the gypsum treatment to the 80-cm depth. However, pH was not greatly altered down the profile. Diunduh dari: …… 23/9/2012

114 Chances in agricultural systems on acid soils in southern Australia
PENGARUH PENGAPURAN. Chances in agricultural systems on acid soils in southern Australia D.R. Coventry "Crop and pasture production - science and practice". Edited by J.J Yates. Proceedings of the 3rd Australian Agronomy Conference, January - February 1985, The University of Tasmaina, Hobart, Tasmania. Grain yield responses to liming obtained at Rutherglen, North-east Victoria, 1984 season. Diunduh dari: /9/2012

115 Subsoil Acidity - The Next Hurdle
PENGARUH PENGAPURAN. Subsoil Acidity - The Next Hurdle Brendan J. Scott NSW Department of Agriculture, Agricultural Research Institute Wagga Wagga, NSW 2650 Cumulative yields of maize over three years at a site in Brazil, as affected by lime rates and depth of lime incorporation (CPAC 1976). Diunduh dari: /9/2012

116 Effect of Lime Products on No-till Soybean Yield
PENGARUH PENGAPURAN. Effect of Lime Products on No-till Soybean Yield Quarry lime with an ENM of 377 per ton and a pelleted lime with an ENM of 580 per ton were applied to plots. The quarry lime was applied June of 2005 as a one-time application and 200 pounds of pelleted lime material has been applied annually before planting. The pHs of the site ranged from 5.2 to 5.4. Soil samples were taken at 1-inch increments and analyzed for pHs to indicate the movement of the surface-applied materials into the soil. There were no significant differences between products and respective soybean yields. Diunduh dari: /9/2012

117 Effects of Lime on Yields
PENGARUH PENGAPURAN. Effects of Lime on Yields Limesand increased canola yields more than either G Lime or dolomite in a field trial harvested in 1997 by Chris Gazey (DAFWA).  Adjustments were made to the lime rates to compensate for the lower neutralising value of the dolomite (67%), Both G lime and limesand were applied at 1 and 2 t/ha while dolomite rates were higher and 3.0 t/ha. The results clearly show that limesand was the superior liming material with dolomite being much less effective even when applied at higher rates. In fact canola yield increase from 1 t/ha of limesand was more than the yield increase from 3t/ha of dolomite and the same as the yield increase from 2t/ha of G lime. The high neutralising value, fineness and solubility of Aglime (limesand) makes it the most effective liming material available in WA. Diunduh dari: /9/2012

118 An. Acad. Bras. Ciênc. vol.81 no.2 Rio de Janeiro June 2009
PENGARUH PENGAPURAN. Strawberry (Fragaria X ananassa Duch.) yiel das affected by the soil pH  Tomo M. Milosevic; Nebojsa T. Milosevic; Ivan P. Glisic. An. Acad. Bras. Ciênc. vol.81 no.2 Rio de Janeiro June 2009 the use of CaO for raising the soil pH had positive effect on strawberry yields. The yields obtained in all the treatments were higher than those in the control. The highest yield in all cultivars examined was obtained in the trial plot where 750 kg ha-1 CaO (A4) was applied. At this rate there was an increase in pH from 4.12 (the control) to 5.75, as well as the increase in yield of %. Diunduh dari: /9/2012

119 Diunduh dari: http://www.noble.org/ag/soils/soilacidity/…… 23/9/2012
PENGARUH PENGAPURAN. How is soil acidity corrected? Soil acidity can be corrected easily by liming the soil, or adding basic materials to neutralize the acid present. The most commonly used liming material is agricultural limestone, the most economical and relatively easy to manage source. The limestone is not very water-soluble, making it easy to handle. Lime or calcium carbonate's reaction with an acidic soil is described in figure 1, 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. The acidity reacts with the carbonate (CO3) to form carbon dioxide (CO2) and water (H2O). The result is a soil that is less acidic (has a higher pH). Diunduh dari: /9/2012

120 PENGARUH PENGAPURAN. Soil Acidity and Liming for Agronomic Production
Ohio State University Extension Fact Sheet School of Environment and Natural Resources Coffey Road, Columbus, Ohio 43210 Soil Acidity and Liming for Agronomic Production Robert Mullen, Edwin Lentz, and Maurice Watson How Lime Works Lime supplies a surplus of the basic cations Ca2+ and/or Mg2+ in a carbonated, hydroxide, or oxide form (CaCO3, MgCO3, CaOH, MgOH, CaO). As the compounds dissolve in soil solution, the carbonate (CO32-), hydroxyl (OH-), or oxide (O2-) react with active acidity (H+) to form carbonic acid (H2CO3) or water (H2O). Also, because H+ is being removed from soil solution, free Al3+ reacts with OH- to form an insoluble compound. Hydrogen held by soil-clay (potential acidity) is released into soil solution to maintain chemical equilibrium as active acidity is neutralized, and Al3+ is released from the soil to form insoluble compounds. The H+ released into the soil solution is then neutralized until the CO32-, OH-, and O2- are exhausted. Ultimately, most of the carbonic acid will dissociate to form water and carbon dioxide. Thus, excess H+ is converted into water, and free Ca2+ and/or Mg2+ replace the released H+ and Al3+ on the soil exchange sites Diunduh dari: …… 23/9/2012

121 PENGARUH PENGAPURAN. Soil Acidity and Liming for Agronomic Production
Ohio State University Extension Fact Sheet School of Environment and Natural Resources Coffey Road, Columbus, Ohio 43210 Soil Acidity and Liming for Agronomic Production Robert Mullen, Edwin Lentz, and Maurice Watson Diunduh dari: …… 23/9/2012

122 Diunduh dari: http://www.florahydroponics.com/ph.aspx …… 23/9/2012
PENGARUH PENGAPURAN. LIME WORK Lime works in a two-step process.  When lime is applied to the soil it breaks up into calcium (sometimes magnesium) and carbonate ions.  The calcium ions will then move to the cation exchange sites on the soil particles and bind to them, in the process knocking hydrogen ions and aluminum ions off the charged particle.  The hydrogen ions then move into the soil solution, where they bind to the carbonate ion to form carbonic acid, which is then quickly broken down to water and carbon dioxide.  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. Liming is extremely important in maintaining adequate soil pH.  In order to be sure that one is doing an effective job of liming, a few guidelines should be noted.    Thus, when applying lime, one should work it into the soil while tilling.  Particle size of the liming material is also very important in determining its effectiveness. Diunduh dari: …… 23/9/2012

123 Sources of negative charge
PENGARUH PENGAPURAN. Soil science Prof. Blaskó Lajos (2008) Debreceni Egyetem a TÁMOP pályázat keretein belül Sources of negative charge Diunduh dari: …… 23/9/2012

124 Sources of negative charge
PENGARUH PENGAPURAN. Soil science Prof. Blaskó Lajos (2008) . Debreceni Egyetem a TÁMOP pályázat keretein belül Sources of negative charge Diunduh dari: …… 23/9/2012

125 PENGARUH PENGAPURAN. Presence of surface and broken - edge -OH groups gives the kaolinite clay particles their electronegativity and their capacity to absorb cations. In most soils there is a combination of constant and variable charge. Cation-a positively charged ion There are two types of cations, acidic or acid-forming cations, and basic, or alkaline-forming cations. The Hydrogen cation H+ and the Aluminum cation Al+++ are acid-forming. Diunduh dari: …… 23/9/2012

126 Lime Reactions in Soil The most commonly used lime for North Carolina agriculture is the dolomitic type (CaMgCO3); calcitic lime (CaC03) is less frequently used. A liming material must have more than a high calcium content; it must also be capable of neutralizing acid (H). The chemical reaction of dolomitic lime with soils is as follows: Diunduh dari: /9/2012

127 Wassalam………. ???

128 Soil Buffering and Management of Acid Soils
The other is buffering. Soils because of exchangeable acidity have the ability to buffer pH changes that may occur naturally or artificially.

129 pH pH = - log (H+) pH = - log (H+) If (H+) = 1 x 10-3 mol/L
(H+) = mol/L (H+) = mol/L pH = - log (1 x 10-3) pH = - log (1 x 10-5) pH = - (-3) pH = - (-5) pH = 3 pH = 5 Low pH = high hydrogen ion concentration

130 1. Acids increase the H+ ion concentration in solution
2. Bases are the opposite of acids 3. Bases neutralize acids. 4. When acids and bases are in equal amounts in a solution, the pH is 7. Neutral pH. 5. When the number of acids exceeds the number of bases the pH is lowered. (acid conditions) 6. When the number of bases exceeds the number of acids, the pH is raised. (basic/alkaline conditions)

131 H+ OH- H2O + Acid (=10) Base(=10) OH- OH- H+ H+ OH- OH- H+ H+ OH- OH-
Acidic basic

132 H+ OH- H2O + Acid (=10) Base (=6) H+ H+ OH- OH- H+ H+ OH- H+ H+ OH-
Acidic basic

133 H+ OH- H2O + Acid (=10) Base(=15) OH- OH- H+ OH- H+ OH- OH- OH- H+ OH-
Acidic basic

134 Two types of acidity in soils:
Active Acidity Exchangeable Acidity

135 Acidity associated with the soil solution
Active Acidity Acidity associated with the soil solution Typically a 1:1 or 2:1 extract 10 g soil and 10 mL water 10 g soil and 20 mL water

136 Exchangeable Acidity Acidity associated with cation exchange sites on mineral or organic colloids. H+ Al+3 Si Al Si Si Al Si Al Al Si Al Al Al Al Al Al

137 Types of Acidity Exchangeable Active Acidity
Al+3 Na+ H+ K+ Ca2+ Clay minerals/Organic matter H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ There are two basic types of acidity Active and exchangeable, or “reserve” acidity. Active acidity is in soil solution and can be measured with a pH meter. We will do this today. In part I you will mix soil with water and measure the pH of the resultant solultion. This is a measurement of active acidity. From that pH measurement you will determine the concentration of hydrogen ions associated with the active acidity. The other form of acidity, exchangeable acidity, is associated with colloidal exchange sites on clay minerals and organic matter. Notice that both H and Al are cations and can participate in exchange reacitons like any other cation. Therefore, to determine the total acidity of a soil-water system requires determination of both types of acidity. H+ H+ Soil Solution

138 CEC and Acidity CEC suggests the ability of a soil to store important plant nutrients (K, Mg, Ca, Fe) Is CEC always a good indicator of fertility?

139 Percent Acid Saturation
(charge basis) Na+ Acid Cations (cmol/kg) Cation exchange capacity (cmol/kg) Al+3 Na+ H+ Na+ H+ H+ H+ H+ Ca2+ K+ H+ Acid charge = 14 Exch. Cap. = 26 Ca2+ H+ Al+3 Ca2+ Ca2+ The first is base saturation. Which is simply an expression of the relative amounts of non-acidic cations to acid cations on the exchange sites. We can have a high CEC, but unless the exchange sites are occupied by the right cations, fertility can be affected. Explain % B.S. Recall the difference between alfisols and ultisols. 35% BS. Note that % BS provides an indication of the acid status of the soil with respect to the CEC. H+ % A.S. = 53.8% Clay minerals/Organic matter Acid Cations: Al, H+

140 Percent Base Saturation
(charge basis) Na+ Exchangeable bases (cmol/kg) Cation exchange capacity (cmol/kg) Al+3 Na+ H+ Na+ H+ H+ H+ H+ Ca2+ K+ H+ Base charge = 12 Exch. Cap. = 26 Ca2+ H+ Al+3 Ca2+ Ca2+ The first is base saturation. Which is simply an expression of the relative amounts of non-acidic cations to acid cations on the exchange sites. We can have a high CEC, but unless the exchange sites are occupied by the right cations, fertility can be affected. Explain % B.S. Recall the difference between alfisols and ultisols. 35% BS. Note that % BS provides an indication of the acid status of the soil with respect to the CEC. H+ % B.S. = 46.2% Clay minerals/Organic matter Base Cations: Na, K, Mg, Ca

141 You have two soils with the same CEC
Soil A has a % B.S. = 35% Soil B has a % B.S = 65% Which soil is more fertile? Which soil is more acidic?

142 Soil Buffering The ability of soils to resist changes in pH

143 Soil Buffering Due to ultimate equilibrium between solution and colloids. Na+ H+ Ca+2 Al+3 Na+ H+ Na+ H+ H+ H+ K+ H+ H+ H+ H+ Ca2+ K+ H+ Na+ Na+ H+ Ca2+ H+ Al+3 Ca2+ H+ Ca+2 For example consider a soil at pH 6. If you wanted to grow blueberries which prefer much lower pH, you might consider acidifying the soil. So you would add and appropriate acid. H+ K+ Clay minerals/Organic matter pH = 6

144 Soil Buffering Add acid: HCl => H+ + Cl-
Na+ H+ Ca+2 Al+3 Na+ H+ Na+ H+ H+ H+ H+ K+ H+ H+ H+ H+ H+ Ca2+ K+ H+ H+ H+ Na+ Na+ H+ H+ Ca2+ H+ Al+3 Ca2+ H+ Immediately upon adding the acid to the soil, the soil solution pH might drop quickly to, let’s say, pH 4. However, because H is a cation it can be adsorbed on exchange sites and the pH at equilibrium will be higher than expected. Ca+2 H+ H+ K+ H+ Clay minerals/Organic matter pH = 4 Soil solution pH initially declines due to acid addition

145 Soil Buffering Final equilibrium Clay minerals/Organic matter pH = 5.5
Ca+2 Al+3 Na+ H+ H+ H+ H+ Ca2+ H+ K+ Na+ H+ H+ H+ H+ H+ H+ H+ H+ H+ Na+ Na+ H+ H+ H+ H+ Al+3 Ca2+ H+ Ca+2 Notice the hydrogen on the exchange sites. Therefore, some of the hydrogen you added to change the pH is no longer in soil solution and the pH is higher than desired or expected. H+ K+ K+ H+ Ca2+ Clay minerals/Organic matter pH = 5.5 Soil pH does not decline as much as expected

146 Base A substance which decreases the
Hydrogen ion concentration in solution OH- CO32- SO42-

147 Bases react with hydrogen and remove it from soil solution
OH- CO32- + H+ H2O + H+ HCO3- (Neutralization of acid)

148 NaOH Na+ + OH- CaCO3 Ca2+ + CO32- OH- + H+ H2O CO32- + H+ HCO3-
Common Bases water NaOH Na+ + OH- CaCO3 Ca2+ + CO32- water OH- CO32- + H+ H2O + H+ HCO3- (Neutralization of acid)

149 A common base used to increase
the pH of soil is CaCO3 water CaCO3 Ca2+ + CO32- CO H+ HCO3- CaCO3 + H+ Ca2+ + HCO32- Adding calcium carbonate to soils is called “liming”

150 Soil Buffering Equilibrium between solution and colloids.
H+ Ca+2 Al+3 Na+ H+ Na+ H+ H+ H+ K+ H+ H+ H+ H+ Ca2+ K+ H+ Na+ Na+ H+ Ca2+ H+ Al+3 Ca2+ The same is true if we add bases to the soil. This is very typical in FL because our soils are typically of low pH. When we add base (what form?), hydrogen can leave the exchange sites and neutralize the base and prevent it from raising the system pH. H+ Ca+2 H+ K+ Clay minerals/Organic matter pH = 6

151 Soil Buffering water CaCO3 Ca2+ + CO32- CO32- + H+ HCO3-
Na+ H+ Ca+2 Al+3 Na+ H+ Na+ H+ H+ CO3-2 H+ CO3-2 K+ H+ H+ H+ H+ Ca2+ K+ H+ Ca+2 Ca+2 CO3-2 Na+ Na+ CO3-2 Immediately upon adding the base the solution pH may rise H+ Ca2+ H+ Al+3 Ca2+ H+ Ca+2 H+ CO3-2 K+ Clay minerals/Organic matter pH = 7 Soil solution pH initially rises due to base addition

152 Soil Buffering water CaCO3 Ca2+ + CO32- Clay minerals/Organic matter
Na+ H+ Ca+2 Al+3 Na+ H+ Na+ H+ H+ CO3-2 H+ CO3-2 K+ H+ H+ H+ H+ Ca2+ K+ H+ Ca+2 Ca+2 CO3-2 Na+ Na+ CO3-2 H+ Ca2+ H+ Al+3 Ca2+ H+ Ca+2 Ca+2 Immediately upon adding the base the solution pH may rise H+ CO3-2 K+ Clay minerals/Organic matter pH = 6.5 H+ removed from exchange sites returns to soil solution

153 Liming: raising soil pH
MgCO3 CaCO3 CaCO Ca CO32- Displaces cations From exchange sites Combines with Hydrogen ions (neutralization) CO H+ = HCO3-

154 Active Acidity pH Range Plant Alfalfa Sweet Clover Beets 6.0 – 8.0
Cauliflower Spinach Peas Carrots Cotton Wheat Tomatoes Potatoes Blueberries Azaleas 6.0 – 8.0 5.0 – 7.2 Notice that when you look at plant types, they have different optimum pH levels at which they will thrive. In some cases, the soil’s natural pH falls within that range, and plants grow well requiring no intervention. However, often we may be required to alter the pH of the soil to better suit the needs of the plant. In other words we can add or remove hydrogen ions from the soil solution by adding either acids or bases. This seems like a relatively simple matter, but the active acidity we measure in soil solution is not the only form of acidity in soils. 4.5 – 5.5 < 5 Adjusting soil pH requires a knowledge of exchangeable acidity

155 Buffering Capacity 1. CEC 2. % base saturation Kaolinite Smectite
Organic Matter 1. CEC So bufereing capacity of a soil, or the total ability of the soil to resist pH change is obviously a function of the CEC (high, med, low) and the original cationic composition of the exchange complex (% b.s.). 2. % base saturation

156 pH and Nutrient Availability

157 Florida Soils Tend to be Acidic
H+ (In Rainfall) H+ H+ Ca Na Mg Mg K Low %B.S. Al3+ Al3+ Na Ca Ca Mg H+ Na Al3+ Na

158 Aluminum Toxicity Aluminum most available at low pH
High concentration of aluminum will first reduce development of the roots, giving them a stubby appearance. They will often have a brownish color. Typical symptoms in the above ground portion of the plant are small leaves, and shortened and thickened internodes (99). It also is common for leaf tips to die and for old leaves to become yellow and brittle. Aluminum most available at low pH Damages cell walls, binds to phosphorus

159 Macro-Nutrients Nitrogen: NH4+ users below pH 5.5 Generalizations:
NH4+ NO3- Ammonium may accumulate at low pH Organism dependent. Phosphorus: H2PO4- and HPO42- Greatest availability at pH 6-7 Potassium: K+ Liming tends to increase availability (Increased pH increases CEC)

160 Acidity can be local: roots – acids - organisms
Micro-Nutrients manganese, iron, cobalt copper, zinc Oxides of these metals tend to be dissolved at low pH Fe(OH)3 + 3H+ = Fe H20 Availability generally increases With increasing soil acidity (low pH) These are plant essential, but can be toxic in high amounts Acidity can be local: roots – acids - organisms