Agricultural Soil Science Study Point For Competitive Exam
Agricultural Soil Science Study Point For Competitive Exam
1.Basic Properties of Major Silicate Minerals
| Kaolinite | Illite | Montmorillonite |
| Type of silicate clays | ||
| 1:1 type non expanding | 2:1 non expanding type | 2:1 expanding type |
| Total surface area m2/g | ||
| 37-45 | 120-170 | 580-750 |
| External surface | ||
| Very low | Low | Medium |
| Internal surface | ||
| None | Low | High |
| Cohesion, plasticity, swelling | ||
| Very low | Low | High |
| CEC (meq/100 g soil) | ||
| 2-15 | 30-40 | 60-150 |
| Size (in micron) | ||
| 0.1-5.0 | 0.1-2.0 | 0.01-1.0 |
| P fixing | ||
| Highest | Low | — |
2.Basic Properties of Major Silicate Minerals
| Vermiculate | Humus |
| Type of silicate clays | |
| 2:1 limited expanding | — |
| Total surface area m2/g | |
| 780-900 (highest among silicates) | 1200 |
| External surface | |
| High | — |
| Internal surface | |
| High | — |
| Cohesion, plasticity, swelling | |
| Medium | Low |
| CEC (meq/100 g soil) | |
| 100 -150 | >200 |
| P fixing | |
| Medium | — |
3.Composition of Organic Residues
| Organic residues | Composition % |
| Moisture | 75% |
| Dry matter | 25% |
| Dry matter Composition | |
| Carbon | 10-12% |
| Oxygen | 9-10% |
| Hydrogen | 1.5-2.5% |
| Nitrogen | 1-2% |
| Mineral matter | 1-3% |
4.Composition of Plant Tissues
| Plant tissues | Composition % |
| Celluloses | 20-50% |
| Hemicellulose | 10-30% |
| Starch, Sugar | 1-5% |
| Proteins | 1-15% |
| Fats, waxes, tannins | 1-10% |
| Lignins | 10-30% |
5.The organic matter is classified on the basis of their rate of Decomposition
| Rate of decomposition | Examples |
| Rapidly decomposed | Sugars, starches, proteins etc. |
| Less rapidly decomposed | Hemicelluloses, celluloses etc. |
| Very slowly decomposed | Fats, waxes, resins, lignins etc |
6.Crop Related To Salinity Hazard (dsm-1)
| Crops | Threshold salinity (dsm-1) | Rating |
| Barley | 8.0 | Tolerant |
| Cotton | 7.7 | Tolerant |
| Guar | 8.8 | Tolerant |
| Rice | 3.0 | Semi-Tolerance |
| Sorghum | 6.8 | Moderate tolerant |
| Soybean | 5.0 | Moderate tolerant |
| Sugar beet | 7.0 | Tolerant |
| Sugarcane | 1.7 | Tolerant |
| Wheat | 6.0 | Moderately Tolerant |
| Vegetables | ||
| Cabbage | 1.8 | Semi tolerant |
| Carrot | 1.0 | Semi tolerant |
| Onion | 1.2 | Semi tolerant |
| potato | 1.7 | Semi tolerant |
| tomato | 2.5 | Semi tolerant |
| Other crop | ||
| Date-palm | 4.0 | Tolerant |
| Grape | 1.5 | Semi tolerant |
| Citrus | 1.7 | Senstive |
7.Alkalinity classes based on RSC/RSBC ratio
| Water Quality | Quantity of RSC/RSBC (Mel/lit.) |
| Very high alkalinity water | >10.0 Mel/lit. |
| High alkalinity water | 5.0-10.0 Mel/lit. |
| Medium alkalinity water | 2.5 5.0 Mel/lit. |
| Low alkalinity water | 2.5 Mel/lit. |
| Normal water | 0 Mel/lit. |
| Non-alkaline water | Negative |
Chlorides:- In irrigation water chloride ions increases with increase in EC and sodium ions. So ions are more dominant in very high salinity water.
8.Chloride concentration ( Mel/lit. )
| Water quality | Quantity of Chloride (Mel/lit.) |
| Not suitable | > 20 |
| Not suitable | 12-20 |
| Slightly usable | 7-12 |
| Moderately good water | 4-7 |
| Excellent water | 4 |
9.Sulphate Concentration ( Mel/lit. )
| Sulphate Mel/lit. | Remarks |
| >12 | Injurious to unsatisfactory |
| 4-12 | Good to injurious |
| <4 | Excellent water |
10.Nitrate (NO3 – ) Concentration Mel/lit.
| Nitrate Mel/lit. | Remarks |
| > 30 | Intensity of problem is severe |
| 15-30 | Intensity of problem is moderate |
| <5 | No problem |
11.Major soil orders in India and their area
| Soil order | Region State |
| Entisols | Rajasthan, Gujarat, Haryana |
| Inceptisols | Uttar Pradesh |
| Vertisols | Kovilpatti (T.N.), Rajasthan, Gujarat Maharashtra, Madhya Pradesh, Karnataka, Andhra Pradesh |
| Aridisols | Haryana, West Rajasthan, Gujarat, Anantapur (A P.) |
| Alfisols | Andhra Pradesh, Jhansi (U.P.). Tamil Nadu, Karnataka |
| Oxisols | Ranchi (Jharkhand), Bhubaneswar (Orissa) |
12.Classification of rainfall zones in India
| Rainfall (in mm) | Zone | Rainfall % |
| <500 | Arid | Very low |
| 500-750 | Semi-arid | Low |
| 750-1100 | Dry sub-humid | Medium |
| 1100-1400 | Moist sub-humid | High |
| >1400 | Humid mountain | Very high |
Agricultural Soil Science Study Point For Competitive Exam
| Soil Science Important Table – 1 | Cl;ick |
| Soil Science Important Table – 2 | Cl;ick |
| Soil Science Important Table – 3 | Cl;ick |
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