KESUBURAN KIMIA, FISIKA DAN BIOLOGI TANAH

1. KESUBURAN KIMIA, FISIKA DAN BIOLOGI TANAH

2. Main Material Time Climate SOIL Topography Organism

3. SOIL

4. ROLE OF THE SOIL IN PLANT GROWTH ANCHORAGE/tempat berjangkar takar tanaman, STORAGE/Supply of Water, STORAGE/Supply of O2, Storage/Supply of Nutrients.

5. TANAH (YANG IDEAL) TERSUSUN OLEH : ATMOSFER UDARA 20-30% LITOSFER MINERAL 45% HIDROSFER BIOSFER PASIR AIR 20-30% LEMPUNG DEBU BAHAN ORGANIK 5%

6. PENGERTIAN KESUBURAN TANAH ( SOIL FERTILITY) • Kemampuan tanah utk menyediakan unsur hara (ability of the soil to supply nutrients) yg menyangkut kualitas hara, ketersediaan & serta upaya utk menahannya dari pelindian

7. Foth and Ellis 1997: Kesuburan tanah adalah kondisi suatu tanah yg mampu menyediakan unsur hara essensial utk tanaman tanpa efek racun dari hara yg ada.

8. Brady : Kesuburan tanah adalah kemampuan tanah menyediakan unsur hara essensial dalam jumlah & proporsi yg seimbang utk pertumbuhan tanaman • Anonymous : …bag dr ilmu yg mempelajari sumber & ketersediaan unsur hara essensial utk pertumbuhan tanaman dari aspek kualitas & kuantitas produksinya

9. Abbott & Murphy, 2003. SOIL BIOLOGICAL FERTILITY. “A key to Sustainable Land Use in Agriculture”. SOIL FERTILITY : The capacity of soil to provide PHYSICAL, CHEMICAL and BIOLOGICAL REQUIREMENTS for growth of plants for productivity, reproduction and quality relevant to plant type, soil type, land use and climatic conditions.

10. Abbott & Murphy, 2003. SOIL BIOLOGICAL FERTILITY. “A key to Sustainable Land Use in Agriculture”. SOIL CHEMICAL FERTILITY : The capacity of soil to provide a SUITABLE CHEMICAL AND NUTRITIONAL ENVIRONMENT for plants and foraging animals for productivity, reproduction and quality in a way that SUPORTS BENEFICIAL SOIL PHYSICAL AND BIOLOGICAL PROCESSES, including those involved in nutrient cycling. SOIL PHYSICAL FERTILITY : The capacity of soil to provide PHYSICAL CONDITIONS that support plant productivity, reproduction and quality WITHOUT LEADING TO LOSS of soil structure or erosion and SUPPORTING SOIL BIOLOGICAL AND CHEMICAL PROCESSES.

11. Tanah Subur : mempunyai sifat kimia, fisika dan biologiyang mendukung pertumbuhan / produksi tanaman • Kesuburan tanah : • Potensial : kesuburan dalam jangka panjang; sulit berubah dan untuk merubah perlu masukan tinggi • Aktual : kesuburan untuk jangka pendek; berubah-ubah setiap musim

12. Beberapa KOMPONEN kimiatanah : KOLOID TANAH Bahanorganik PERTUKARAN ION & Reaksitanah

13. KOLOID TANAH adalah penyusun tanah yang berperan aktif dalam reaksi kimia tanah yang mempunyai diameter < 1 mikron. • Sifatnya : • Mempunyai bidang permukaan yang luas per unit massa • Tersuspensi dalam air • Bermuatan negatif/positif

15. MACAM KOLOID TANAH : • KoloidOrganik •  Koloid Humus • Anorganik (Koloid Mineral) • Koloidsilikat(SiO2.nH2O) kristalin yang bermuatan negatif • Koloid silikat non kristalin • Hidroksida Besi [Fe(OH3)] dan hidroksida aluminium yang menimbulkan warna merah, kuning, coklat atau campurannya

17. PERTUKARAN ION Colloids are small particles in soil that act like banks: managing the exchange of nutrient currency in the soil Different soils, like checking accounts, have different capacities to hold nutrient currency: cations and anions

18. Sumber muatan : • In 2:1 clays, charge created mostly by isomorphous substitution. • Not very pH dependent • Hydroxyls (OH-) and other functional groups on the surfaces of colloidal particles that cause positive or negative charges based on releasing or accepting H+ ions. • pH dependent • Common source of charge on humus, Fe and Al oxides, 1:1 type clays, and non-crystalline silicates

19. Ion exchange • Positive and negative • Anion exchange (negative ions) • Cation exchange (positive ions) Units of : cmolc/kg (centimoles of charge per kg)

20. Cation exchange- the interchange between a cation in solution and another cation on a soil surface • Cation exchange capacity (CEC)- the total sum of exchangeable cations that a soil can adsorb.

21. Principles of Ionic Exchange 1. Reversible Reactions 2. Charge Balance 3. Ratio Law 4. Mass Action 5. Ion Selectivity 6. Complementary Cations

22. 1. Reversible Reactions K+ micelle K+ H+ micelle H+ Can go forwards or backwards Example: + 2K+ + 2H+

23. 2. Balanced by Charge K+ micelle K+ Charge for Charge….. NOT ion for ion Ca++ micelle + Ca++ + 2K+

24. 3. Ratio LawThe Ratio of Ions on Exchange Site is Equal to the Ratio of Ions in the Soil Solution Na+ Na+ micelle H+ H+ H+ 4 H : 2 Na After on colloid 2H : 1Na After in soln. 6 H : 3 Na before H+ H+ H+ H+ + Na+ and 2H+ micelle + 3Na+ H+ H+ H+

25. 4. Mass Action H+ + H2O + CO2 micelle + CaCO3 micelle Ca++ H+ CO2 is a gas and escapes from the soil easily…. This drives the reaction to the right.

26. 5. Ion Selectivity Charge of ion Selectivity = Size Al+3 > Ca+2 > Mg+2 > K+ = NH4+ > Na+ Held tightly ---------------------------------- Held loosely Based on Valence Charge and Hydrated Ionic Radius

27. 6.The Effects of Neighboring Cations

28. Cation Exchange Capacity • 1) the number of cation adsorption sites per unit weight of soil or • 2) the sum total of exchangeable cations that a soil can adsorb. • * CEC is expressed in milliequivalents (meq) per 100 g of oven dry soil. • Equivalent weight = molecular or atomic wt (g) • valence or charges per formula

29. Predicting CEC • 1) sum of cations : remove all cations and total the amount • 2) NH4+ saturation: soil is saturated with NH4+ - the NH4+ is replaced by Ca++ and the NH4+ removed is measured. • 3) Estimation based on texture: • Sand = 0-3 meq/100 g LS to SL = 3-10 • Loam = 10 - 15 Clay Loam = 10-30 • Clay = > 30 (depends on kind of clay)

30. Anion Exchange First we need to know about : Soil pH And Variable Charge Cl- chlorine NO3- nitrate SO4-2 sulfate PO4-3 phosphate Essential Plant Nutrients

31. Percentage of the total exchange capacity of the soil colloid which is occupied by basic cations %BS = [Sum total meq base/CEC]x100 %BS = [Sum (Ca + Mg + K + NH4 + Na)/soil CEC]x100 %SB = Availability of Nutrients! % Base saturation

32. The Soil Reaction

33. Soil pH • * pH - the negative log of the hydrogen ion(H+) concentration in the soil water solution. • pH = - log [ H+] • * the pH scale is how we measure acidity and alkalinity of solutions. • at neutral (pH =7) the number of H+ = OH- • Remember : • at pH of 6 there are 10x more H+ ions than at a pH 7 and there are 100x more H+ ions between pH 7 & 5

34. This gives a measure of the acidity or basicity of a soil. • 0-7 = acidic; 7-14 = basic. • Acidity is measured by determining the concentration of Hydrogen (H+) ions in the soil. • Higher concentration of H+ ions = high acidity, higher concentration of OH- ions = high basicity. • In general, the ideal pH for plant growth is about 5.5 in organic soils and about 6.5 in mineral soils.

35. Why is soil pH important? • Affects solubility of minerals. • Affects type, numbers and activity of microorganisms. • Fungi tolerate acidity better than bacteria. Bacteria often negatively affected by high acidity (i.e. low pH). • Indirectly affects aggregate stability. • Determines what happens to many soil pollutants. • CEC increases with soil pH.

36. pH vs. CEC and %BS • Increases in pH tends to increase CEC, however only in soils with pH dependant charges (Kaolinite, organic matter, Al/Fe oxides) • The natural leaching process of nutrients and nutrient plant uptake will decrease pH, why? • When any base is either leached or taken up from the exchangeable sites, it must be replaced! If there is not more available bases, will be replaced by H+

37. pH vs. ion solubility

38. pH and nutrient availability • As the soil pH increases from an acidic condition to pH 6.5 : • Macronutrients (N,P,K) increases in solubility • Secondary nutrients (Ca, Mg, S) increases in solubility • Micronutrients (except Molybdenum) decreases in solubility • Al decreases in availability (very important)

39. pH influence on microorganisms • Bacteria and actinomicete are reduced at low pH • Nitrification occurs at pH range 6.0 to 9.0, optimum pH 7 • Denitrification (biological loss of N) occurs at a minimu of pH 5.5, bellow this point chemical denitrification occurs • Nitrogen fixation by Rhyzobium (legume-bacteria symbiosis) optimum occurs between a pH of 6.0 to 6.5 • Organic matter decomposition: optimum pH 7.0

40. pH and fertilizer efficiency • At low soil pH’s: Al/Fe oxides reacts with phosphorus and molybdenum to form unavailable P and Mo forms • At high soil pH’s: Ca and Mg in excess tends to form unavailable form when react with phosphorus and most micronutrients • If we are not at the optimum pH for plant nutrient availability, the addition of fertilizer could be a waste of energy and resources. • Note: Every crop/plant/turf/tree has an unique optimum soil growth conditions

41. Soil pH affects many chemical and physical reactions in soil • Availability of most essential elements • Activity of microorganisms • Ability of soil to hold cations • Solubility of non-essential elements such as heavy metals • Herbicide performance

42. Suplai hara • Kapasitas : mensuplai hara semasa pertumbuhan tanaman • Intensitas : mensuplai hara secara kontinyu sesuai fase pertumbuhan

43. Sumber hara dalam tanah • Perombakan bahan organik tanah. • Pelapukan mineral tanah. • Pemupukan. • Pembenah organik: kompos • Penambatan N : legum. • Batuan: batuan fosfat, greensand. • Buangan industri: kapur, gipsum. • Pengendapan udara: N, S. • Pengendapan air: sedimen, erosi, banjir.

44. Pangkalan hara (nutrient pool) • Larutan tanah (sifatnya tersedia untuk diserap oleh akar tanaman) • Bahan organik (mengalami proses perombakan) • Organisme tanah (komponen penyusun tubuhnya) • Mineral tanah (sifat antara cukup terlarut sampai sedikit terlarut) • Permukaan jerapan (hara dipegang permukaan tanah oleh berbagai mekanisme) • Pertukaran kation (tipe yang sangat penting dari jerapan permukaan tanah)

45. Sifat /komponen kimia tanah : • Koloidtanahdapatbermuatanpositifataunegatif, berperan dalam penyediaan hara dalam tanah • Pertukaran ion berperan dalam penyediaan dan penyerapan hara oleh akar tanaman • Bahanorganikberperandalammemperbaikikesuburankimia, fisikadanbiologitanah • Reaksitanahberhubunganeratdenganketersediaanhara, aktivitasmikroorganisme, efisiensipemupukandanreaksikimiadanfisika yang terjadidalamtanah

46. Suhu Tanah Sifat / kompenen fisika Tanah : • Sumber panas tanah berasal dari : • Radiasi / pancaran matahari • Konduksi dari dalam bumi (magma) • Dari sejumlah radiasi matahari yang mencapai atmosfer bumi, hanya 47% yang dapat diabsorbsi oleh tanah. • Sedang energi panas sesungguhnya (radiasi efektif) yang diterima permukaan tanah lebih kecil, tergantung beberapa faktor.

47. TEKSTUR TANAH • Tekstur tanah sangat penting karena berkaitan dan berdampak pada: • soil structure • aeration • water holding capacity • water movement • nutrient storage and soil chemistry • etc

48. SOIL TEXTURE • Relative weight comparison of soil single particle fraction • Relative comparison between sand, silt and clay Sand Silt Clay Varied size components Soil particle =

49. Tekstur geluhan (Loam texture) comparison of sand, silt and clay is balance Sand Silt Clay (45 %) (30 %) (25 %) Mudah mengolah Penyerapan (perpindahan) air baik • Loam soil (physic) belum tentu subur • Dasar subur fisik pada struktur tanah • Tanah remah

50. Struktur Tanah Struktur tanah adalah penyusunan zarah-zarah tanah individual satu terhadap yang lain menjadi suatu pola. Struktur tanah adalah susunan pori-pori tanah kecil, sedang dan besar dalam suatu pola. Struktur tanah bukan merupakan faktor tumbuh tanaman tetapi berpengaruh terhadap semua faktor pertumbuhan tanaman, seperti dalam hal pemasokan air, aerasi, ketersediaan hara, kegiatan mikrobia, penembusan akar dll.