ALKALINITAS CHAPTER VIII PENGELOLAAN TANAH BERLANJUT

Transkripsi

1 ALKALINITAS CHAPTER VIII PENGELOLAAN TANAH BERLANJUT

2 Orders Tanah :Aridisols, Entisols, Mollisols, Alfisols, and Vertisols, dll Suborders: Ustic, Xeric, and Natric (SAR>15)

3 OUTLINE Batasan Alkalinitas Tanah : Definisi, proses terbentuknya dan Penyebabnya Karakteristik dan permasalahan alkalinitas tanah Tanah Salin dan Sodik Pengelolaan Alkalinitas Tanah

4 H 2 O 2 H O -2 ph = -log [ H ] H OH - H OH - H OH - Acid ph = 6.0 Neutral ph = 7.0 Alkaline ph = 8.0

5 Acidity Neutrality Alkalinity

6 Alkaline and Saline Soils Saline soils occur in soils with ph>8.5 Ca 2, Mg 2, K and Na do not produce acid upon reacting with water They do not produce OH-ions either, but in soils with ph>8.5, there are higher concentrations of carbonateand bicarbonate anions (due to dissolution of certain minerals) CaCO 3 Ca 2 CO 2-3 or NaCO 3 2Na 2 CO 2-3 CO 2-3 H 2 O HCO 3- OH - HCO 3- H 2 O H 2 CO 3 OH - ph rises more for most soluble minerals (eg. NaCO H 2 CO 3 H 2 O CO 3 ) 2(gas) ph rise is limited by the common ion effect

7 Sumber Alkalinitas Di daerah arid dan semiarid komplek pertukaran didominasi: Ca 2, Mg 2, K, Na Adanya karbonat dan bikarbonat pada tanah alkalin terkait dengan disolusi CO 2 : 2 Kisaran ph reaksi tsb adalah antara 4,6 dan juga 8,6 (Ca-carbonates) atau 10 (Na-carbonates)

8 Calcium carbonate accumulation in the lower B horizon

9 N P K Mg and Ca S Soil ph & nutrient availability B Cu and Zn Mo Fe Mn Al Fungi Bacteria & Actinomycetes Soil ph

10 PERMASALAHAN PADA TANAH ALKALIN 1. DefisiensiUnsurHara 2. Dispersiliat

11 DefisiensiUnsurHara 1. Zn, Cu, Fe, dan Mn tidak terlarut pada ph tinggi

12 Defisiensi Fe pada pohon

13 2. Ketersediaan Mo meningkat pada taraf meracuni tanaman, 3. Ketersediaan Cu menurun

14 PERMASALAHAN PADA TANAH ALKALIN 4. Peningkatan kelarutan Ca dan Mg menghambat pelarutan ion P 5. P berikatan dengan Ca membentuk ikatan Ca-P yang tidak terlarut 6. Fungi, bakteri dan tanaman Brassica mengeluarkan asam organik untuk memecah ikatan Ca-P

15 CEC of alkaline soils Higher CEC than acid soils (assuming similar texture and SOM) 2:1 type clays common in alkaline soils have high permanent charge (e.g., smectite) High ph will stimulate high levels of phdependent charge

16 Soilclaydispersion Penghancuran agregat Penurunan makroporositas Penurunan aerasi Penurunan perkolasi Retakan

17 The white, rounded "caps" of the columns are comprised of soil dispersed because of the high sodium saturation

18 Stabilitas Agregat (dispersi dan flokulasi) tergantung keseimbangan SAR (antara Ca 2 dan Mg 2 ) dan Na sama dengan jumlah garam terlarut (EC) dalam tanah and Ca 2 Mg 2 S Na EC Lower EC Higher EC Flocculated soil Dispersed soil

19 Partikel tanah akan terflokulasi jika konsentrasi Ca 2 dan Mg 2 lebih besar daripada konsentrasi Na (Nilai SAR rendah) Na Ca and Mg 2 SAR EC Flocculated soil Dispersed soil

20 Partikel tanah akan terdispersi jika konsentrasi Ca 2 dan Mg 2 lebih rendah daripada konsentrasi Na (Nilai SAR tinggi) Ca 2 and Mg 2 S A R EC Na Flocculated soil Dispersed soil

21 Sodium adsorption ratio Compares Na relative to Ca and Mg SAR = [Na ]/ (0.5[Ca 2 ] 0.5[Mg 2 ]) 1/2 SAR of 13 = ESP of 15 K could be included with Na

22 Types of Alkaline soils TYPE Soil EC (mmhos/cm) ESP (%) SAR SALINE < SODIC 0-4 >15 >12 SALINE- SODIC No saline no sodic >4 >15 >

23 How to manage alkaline soils Difficult to manage Before identify the type of management we have to identify the type of alkaline soil Every type (saline, sodic, saline-sodic) has a different management. In general any practice that reduces salt content will be needed. Adding amendment (gypsum, OM) Leaching salts with clean water Irrigation techniques Utilizing salt tolerant crops

24 Types of Alkaline soils TYPE Soil ph Typical ions Management SALINE <8.5 Ca, Mg, K SODIC SALINE- SODIC No saline no sodic >>8.5 can reach 10 (chlorides and sulfates) >>Sodium >8.5 Ca, Mg, K and >>> Na Irrigation Gypsum Very diff. Add water Gypsum >7<8.5 Ca. Mg, K none

25 Alkaline soils can be black, why? Because the high ph levels and high salt levels the organic matter becomes very disperse. The disperse humus moves upward in the capillary water flow, and when the water evaporates leaves a very intense black color on the soil surface. So, not always black soils are good soils for food production.