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KEMASAMAN TANAH pH Tanah Bahan Kajian MK. Dasar Ilmu Tanah smno.jurtnh.fpub.nop2013.

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Presentasi berjudul: "KEMASAMAN TANAH pH Tanah Bahan Kajian MK. Dasar Ilmu Tanah smno.jurtnh.fpub.nop2013."— Transcript presentasi:

1 KEMASAMAN TANAH pH Tanah Bahan Kajian MK. Dasar Ilmu Tanah smno.jurtnh.fpub.nop2013

2 pH = - log (H + ion concentration) Sumber: Brady and Weil, 2002 As pH increases… As pH decreases… pH = 7 neutral

3 Kisaran pH optimum untuk berbagai jenis tanaman

4 ^ Mo lebih tersedia kalau pH naik

5 Toksisitas Aluminum Toxic forms of Al are bioavailable at low pHs Aluminum toxicity is minimal above pH 5.5

6 Bentuk-bentuk Kemasaman Tanah pH tanah mengukur kemasaman aktif Kemasaman Cadangan Kemasaman Aktif Brady and Weil, 2002

7 Kemasaman Cadangan Reserve acidity Reserve acidity Active acidity Active acidity Very little lime is needed to neutralize the active acidity in soils Kemasaman cadangan mensuplai kemasaman aktif Tanah dengan KTK tinggi Tanah dengan KTK rendah ΔpH

8 exchangeable cations soil solution Humus Clay - - - - - - - - - - Al +3 Ca +2 H+H+ K+K+ Mg +2 K+K+ H20H20 H20H20 H20H20 H20H20 H20H20 + SO 4 -2 + - - H20H20 Apakah Kejenuhan Basa ? Exchangeable acidity Setiap muatan yang ditandai pada diagram ini mencerminkan 1 centimol muatan per kg tanah + H 2 O ↔ Al(OH) 3 + 3H +

9 Apakah pH berhubungan dengan kejenuhan basa? 100 80 60 40 20 0 Acid Saturation, %

10 Muatan yang tergantung pH The dominant clay minerals in IL have mostly permanent charge

11 Brady and Weil (2002) Muatan tergantung pH Ion H + berdisosiasi kalau pH tanah naik dan re-asosiasi kalau pH turun. Muatan listrik pada substansi humik (dan liat yg aktivitasnya rendah) sangat tergantung pH

12 Soil acidity increases when H + producing processes exceed H + consuming processes. H + producing processes H + consuming processes

13 Banyak proses yang menambah ion H + ke tanah 1) Carbonic acid forms when carbon dioxide dissolves in water. H + ions are released when carbonic acid dissociates: H 2 CO 3 → HCO 3 - + H + 2) Organic acids form during the decomposition of organic matter. H + ions are released when these organic acids dissociate. 3) Sulfuric and nitric acids form during the oxidation of reduced forms of N and S (e.g., NH 4 + from fertilizer, elemental S). NH 4 + + O 2 → NO 3 - + 2H + S 0 + O 2 → SO 4 -2 + 2H + 4) Sulfuric and nitric acids form when sulfur oxides and nitric oxides (released into the atmosphere by automobile emissions, industry smoke stacks, volcanoes, forest fires) dissolve in precipitation. H 2 SO 4 and HNO 3 are strong acids and fully dissociate in water. 5) Roots release H + to balance internal charge when cation uptake exceeds anion uptake. VERY IMPORTANT PART OF SOIL FORMATION

14 Banyak proses yang mengkonsumsi ion H + dalam tanah (1) Weathering of most minerals (e.g., silicates, carbonates…) (2) Decomposition of organic anions (3) Reduction of oxidized forms of N, S and Fe. (4) Roots release OH - or HCO 3 - to balance internal charge when anion uptake exceeds cation uptake (5) Inner sphere adsorption of anions (especially sulfate) which displaces hydroxyl (OH - ) groups

15 Oksida-oksida C, N dan S menyebabkan hujan asam Brady and Weil, 2002

16 Chadwick and Chorover ( 2001) Sumber-sumber penyangga pH dalam tanah Carbonates

17 K+K+ H+H+ NO 3 - ? pH rizosfir tanaman berubah kalau mengatur keseimbangan muatan listrik internalnya.

18 Mana tanaman yang dipupuk nitrat? Mana tanaman yang dipupuk ammonium ?

19 Masukan asam mendorong pencucian kation basa Brady and Weil, 2002 Mengapa pencucian kation basa memicu kemasaman tanah ?

20 NH 3 1H + consumed released into the soil Siklus N 2 H + yang dihasilkan selama proses nitrifikasi diimbangi dengan 2 H + yang dikondumsi selama pembentukan NH 4 + dan serapan NO 3 - oleh tanaman

21 Sumber NitrogenKomposisi Kebutuhan Kapur (lb CaCO 3 / lb N) Anhydrous ammonia82-0-01.8 Urea46-0-01.8 Ammonium nitrate34-0-01.8 Ammonium sulfate21-0-0-245.4 Monoammonium phosphate 10-52-05.4 Diammonium phosphate 18-46-03.6 Standard jumlah kapur yg diperlukan untuk menetralkan kemasmaan yang dihasilkan oleh pupuk N. Asumsi: 1) Semua ammonium-N dikonversi menjadi nitrate-N 2) separuh nitrate tercuci.

22 Tanaman Ratio Kation : N dalam biomasa tanaman Kapur yg diperlukan untuk menggantikan alkalinitas yang diambil dalam panen tanaman (lb CaCO 3 /100 lb N yang dipanen) Corn grain0.1425 Corn stover0.73131 Soybean0.1425 Oats grain0.1425 Oats straw0.94169 Alfalfa1.41254 Panen biomasa tanaman berarti mengambil sejumlah alkalinitas dari lahan pertanian

23 Lime rates should be guided by soil testing

24 1. The soil to solution ratio used when measuring pH. 2. The salt content of the diluting solution used to achieve the desired soil to solution ratio. 3. The carbon dioxide content of the soil and solution. 4. Errors associated with standardization of the instrument used to measure pH. Sumber variasi dalam pengukuran pH tanah

25 Water pH > Salt pH Brady and Weil, 2002 Mengapa mengukur pH tanah dengan menggunakan larutan garam?

26 pH tanah tergantung pada metode pengukurnanya. As a result, the method of measurement should be reported whenever soil pH data is discussed.

27 soil colloid + CaCO 3 soil colloid + H 2 O + CO 2 H+H+ H+H+ Ca +2 When a soil is limed, Ca +2 from the lime displaces exchangeable acidity from the soil colloids. The active acidity that is generated reacts with the carbonate ions from the lime, producing water and carbon dioxide.

28 “Illinois method” untuk menentukan kebutuhan kapur How do you know which line to use ?

29 Line A: Dark colored silty clays and silty clay loams (CEC > 24) Line B: Light and medium colored silty clays and silty clay loams, dark colored silts and clay loams (CEC 15-24) Line C: Light and medium colored silt and clay loams, dark and medium colored loams, dark colored sandy loams (CEC 8-15) Line D: Light colored loams, light and medium colored sandy loams and all sands (CEC < 8) Line E: Mucks and peat (organic soils). Light colored (< 2.5% OM) Medium colored (2.5-4.5% OM) Dark colored (4.5% OM) Memilih bahan kapur yang tepat

30 Tidak semua batu-kapur sama kualitasnya ! Pure calcium carbonate has a calcium carbonate equivalency (CCE) of 100 and is the standard against which all liming materials are compared. A ton of material with a CCE of 90 % can neutralize 10% less acid than a ton of pure calcium carbonate. Liming materials that are finely ground, have more surface area in contact with the soil solution than coarser ground materials and thus will neutralize soil acidity more rapidly. Fineness of grind is rated according to the percentage of material that will pass through 8-, 30-, and 60-mesh screens.

31 Reaksi kapur dalam tanah memerlukan waktu

32 pH tanah dan Kebutuhan Kapur dapat beragam dalam suatu bentang lahan pH measurements on the fly

33 Barak P, Jobe BO, Krueger AR, Peterson LA, Laird DA 1997. Effects of long- term soil acidification due to nitrogen fertilizer inputs in Wisconsin. PLANT AND SOIL. 197(1): 61-69 Agroecosystems are domesticated ecosystems intermediate between natural ecosystems and fabricated ecosystems, and occupy nearly one-third of the land areas of the earth. Chemical perturbations as a result of human activity are particularly likely in agroecosystems because of the intensity of that activity, which include nutrient inputs intended to supplement native nutrient pools and to support greater biomass production and removal. At a long-term fertility trial in South-Central Wisconsin, USA, application of ammoniacal N fertilizer resulted in significant increases in exchangeable acidity accompanied by decreases in cation exchange capacity (CEC), base saturation, and exchangeable Ca 2+ and Mg 2+. Plant analysis shows that a considerable portion of the alkalinity generated by assimilation of N (and to a lesser extent by S) is sequestered in the above-ground plant parts as organic anions and is not returned to the soil if harvested. Elemental analysis of soil clays indicates a loss of 16% of the CEC. The reversibility of this change is doubtful if the changes are due to weathering of soil minerals.

34 pH << 5.5pH >> 7.0 Toksisitas Al pada akar tanaman Fe deficiency Toksisitas Mn pada akar tanaman Mn deficiency Defisiensi Ca dan MgZn deficiency Defisiensi Mo pada legumes*Osmotic stress from salts P terikat kuat oleh Fe dan AlP tied up by Ca and Mg Transformasi N lambatPotato scab Permasalahan kesuburan tanah pada kondisi pH tanah yang ekstrim

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