2. Improves the soil structure through aggregation. 3. Improves the rate of infiltration and perculation. 4.
Increases the water holding capacity. 5. Reduces the plasticity, cohesion in clay. 6.
Increases the ability of soil to resist erosion. 7. Improves the porosity by changing bulk Density. 8. Reduces the losses of surface soil by wind erosion. 9. Helps to reduce alkalinity of soil.
10. Acts as buffering agent. 11. Has solubilzing effect on some mineral compounds present in the soil. 12. Acts as the store house of various nutrients essential to plant growth. 13.
Helps to clean contaminated water by adsorption of pollutants. 14. Acts as a chelate which helps to mobilize the plant nutrients.
15. Serves as a source of energy for both macro and micro-organisms. 16. Interacts with pesticides. Harmful Effects of Organic Matter: 1. Serves as source of energy and carbon for many disease organisms.
2. Excessive application creates problems in mixing with soil thoroughly and abstructs easy planting. 3. Most of the toxins identified are short chain organic acids as Butyric, propionine etc. C. N. Ratio (Carbon: Nitrogen Ratio): 1. Definition: The ratio of the weight of organic carbon to the weight of total nitrogen in a soil or organic material.
2. Ratio in soils: i. Humus (10: 1) is fairly constant in soils ii.
Arable soils 5: 1 to 15: 1 iii. Lower in warmer regions. iv. Narrow for sub soils than surface soils. 3.
Ratio in plant and microbes: i. Plant material is 20: 1 (legumes 30: 1) ii. FYM is 100: 1 iii. Microbes 4: 1 to 9: 1 4. Significance of Ñ: N ratio: i. The Ñ: N ratio helps to conserve both the nitrogen and organic matter in the soil. ii. If organic residues with high Ñ: N ratio is added, the N2 is immobilized temporarily by micro organic i.
e. ratio becomes narrow. iii. The converted N2 is reconverted to simple inorganic forms. 5. Constancy of Ñ: N ratio: a. Decomposition process continues > Ñ – lost as C02 > N – lost as leaching/absorbed by plant b.
The percentage of total N2 being depleted from soil equal to the percentage of carbon being lost. c. At this point, ratio in top soil range from 10: l to 12: 1 which is more or less constant. 6. Ñ: N ratio and Organic matter i. Organic carbon: Humus (1: 1.7) ii. For most soils, the C: N ratio and organic matter is 20: 1
Nutrition: Plant requires a supply of large number of substances from outside. 2. Total elements in plants > 60. 4. Essential Elements: CHO, NPK, Ca, Mg, Fe, Mn, Cu, Zn, Mo, B, Cl (a) Criteria: (i) A deficit of the elements make it impossible for a plant to complete it’s vegetative and reproductive cycle.
(ii) It can’t replace by another. (iii) Elements directly involve in metabolism. 5. Mineral Content of Plant (i) Water > 70% (ii) Organic matter > 27% (iii) Minerals > 3%. 6. Factors determine Nutrient availability (i) Soil characters like texture, structure moisture, pH.
atmosphere and Salinity. (ii) Interception and contact exchange. (iii) Mass flow and diffusion. (iv) Soil solution. (v) Root growth and Morphology.
(vi) Root Exudation and Rhizophore. (vii) Mycorrhizae. Macronutrients: CHO – Not mineral, structural compound source – atmosphere, water. Nitrogen: (i) Source (a) Soil (b) Biological N2 fixation (c) Industrial N2 fixation (ii) Function: Constituent protoplasm of chlorophyll and coenzyme. (iii) Forms of absorbed (a) NO–3 (b) NH+4 (iv) Deficiency Symptoms (a) Thin (b) Pale yellow (c) Protein decrease (d) Root lengthening (e) Prolonged dormancy (v) Disease (a) Starvation (vi) Corrective (a) NH4SO4 (i) CAN (c) Urea Phosphorous: (i) Function (a) Root growth and ripening (b) Help translocating of CH20. (c) Electron Transport System (ii) Forms of absorbed (a) H2 PO4– (b) HPO2-2 (iii) Deficiency symptom (a) Vein necrotic (b) Tillering decrease (c) Premature falling (d) Stunting (iv) Disease: Sickle leaf disease Potassium: (i) Source (a) Potash Feldspar (b) Mica (c) Glucomite (ii) Function (a) Cofactors for 40 Enzyme (b) Stomatal regulation (iii) Deficiency symptom (a) Spot of dead tissue at tips.
(b) Margin of leaves (lnterveinal chlorosis) (iv) Disease (a) Rosette (b) Dieback Calcium: (i) Source (a) Chalk rock (b) Ca Co3 (ii) Function: (a) Constituents of lamella and cell wall. (b) Activator for many enzyme (iii) Deficiency: (a) Brown – scorching (b) Terminal bud die (c) Roots poorly developed. (iv) Disease: (a) Tip hooking, blosom end rot of tomato Magnesium: (i) Source: Carbonate of Magnesium. (ii) Functions: Chlorophyll Synthesis. (iii) Deficiency: (a) Mottled Chlorosis (b) Withering (defoliation) (iv) Disease: Sand-drown (Tobacco) Sulphur: (i) Functions (a) Odour in Onion (c) Nodule formation (ii) Deficiency (a) Leaf fall is rapid. (b) Tea leaf turning into yellow (iii) Disease: Akiochi (Rice) Iron (Fe): (i) Source: (a) Soil oxide (b) Fe3+.
(ii) Functions: (a) N2 Fixation (b) Respiration (iii) Deficiency: (a) Interveinal chlorosis (b) Complete bleaching (c) Scorching of leaf margin Manganese: (i) Functions: (a) Enzyme cofactor (b) Formation of Chlorophyll (ii) Deficiency: (a) Dead spot scattered (b) Grain formation decreased (c) Root system become poor (iii) Disease: (a) Pahla blight- sugarcane (b) Marsh spot of pea Copper: (i) Function: (a) Compounds of plastocyanin (c) Essential for Photosynthesis, respiration. (ii) Deficiency: (a) Vegetative growth is decreased. (b) Whitening of terminal bud.
(c) Marginal chlorosis. Boron: (i) Function: (a) CH2 O transport. (b) Pollen gemination (c) Water reaction (d) N2 Metabolism (ii) Deficiency: (a) Plant dwarf (b) Dieback (iii) Disease: (a) Top sickness – Tobacco (b) Hard fruit – citrus (c) Hen chick – grape Molybdenum: (i) Function: (a) Nitrate reductase (b) N2 Fixation (ii) Deficiency: (a) Light yellow and leaf blade fail to expand.
(b) Mottling of leaves. (c) In oats, failure of grain formation. (iii) Disease: (a) Whiptail of Brassica (b) Scald of legumes. Chlorine: (i) Source: Chlorides (ii) Function: (a) O2 Evolution (b) Photosynthesis (iii) Deficiency (a) Basipetal chlorosis (b) Necrosis Zinc: (i) Functions: (a) Enzyme alcohol dehydrase (b) CO2 evolution (c) Chlorophyll synthesis (ii) Deficiency: (a) Leathery chlorosis (b) Leaf margin sickle (iii) Disease: (a) Khaira – Paddy (b) Rosette – Fruits (c) White bud-maize