Soil Fertility and Productivity:
Soil Fertility:
Soil fertility is the ability of the soil to provide all essential plant nutrients in available forms and in a suitable balance.
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Soil productivity:
The capability of soil to produce specified crop yield under well defined and specified systems of management of inputs and environmental conditions.
Factors Governing Soil Fertility:
Parent material:
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Fertility of a soil depends on the chemical composition of parent material from which it derived.
Topography:
Soils on the upper slope are less fertile than the soils on lower slope because high leaching and erosion on upper slope.
Climate:
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In tropical climate decomposition of organic matter is faster than temperate climate. Thus soils of tropical regions are less fertile when compared to temperate region.
Depth of Soil Profile:
Deep soils are more fertile than the shallow soils and the roots are spread well enough in deep soils than the shallow soils.
Physical Condition of Soil:
The soil texture and soil structure influence the soil fertility.
Artificial Factors:
i. Water logging
ii. Cropping system
iii. Toxic chemicals and pesticides in the soil.
Difference between Soil Fertility and Productivity:
| Soil Fertility | Soil Productivity |
| 1. It is an index of available nutrient to plants | 1. It is used to indicate crop yields. |
| 2. Influenced by the physical, chemical and biological factors of the soil. | 2. Depends upon fertility and location. |
| 3. It is the function of available nutrients of the soil. | 3. It is the function of soil fertility, management and climate. |
| 4. All fertile soils are not productive. | 4. All productive soils are fertile. |
| 5. It is an inherent property of the soil. | 5. It is not the inherent property of the soil. |
Soil Fertility Evaluation:
It is the assessment of nutrient supplying capacity of the soil.
Soil Fertility Evaluation:
It is assessment of nutrient supplying capacity of the soil
I. A. Biological Methods (using higher plants as indicator):
1. Field Trials:
Direct way to assess the nutrient status in soil.
i. Trials with graded doses of nutrients will determine the exact requirement.
ii. The effect is very much location specific.
iii. Expensive and time consuming and growth condition can’t be fully controlled.
2. Pot Culture Methods:
i. Same as field trials except that plants grown in pots with small volume of soil or under controlled field condition like greenhouse.
ii. Limitations Preferential root growth Limited volume of soil Problems during packing of soil.
3. Neubauer Seedling Method:
i. Soil is exhausted of the available nutrients and entire plant is then analysed for the uptake.
II. B. Biological Methods (using Micro organism as indicator):
1. Aspergillus Niger Method:
i. For P, K and Mg in soils.
ii. The amount of ‘k’ extracted in mycelium compares favourably with the content of exchangeable ‘k’ in soil under investigation.
2. Soil Plaque Method:
By sockett and stewart for study of mineral deficiencies in soil.
i. If soil is deficient in ‘k’ or ‘p’ or both, the calories of the Azotobactor will not develop.
ii. The intensity of growth of calories indicates the degree of deficiency.
3. Visual Symptoms:
i. Indicator plants
ii. Hidden hunger.
III. Plant Analysis Method:
1. Total Elemental Analysis:
i. Leaf Analysis widely used.
ii. Approach
Visual Symptoms
Deficiency
Toxicity
Critical nutrient level (CNL)
‘CNL’ is a range of concentration at which growth of plants is restricted in comparison with that of plant at a higher nutrient level.
2. Plant Tissue Tests/Rapid Chemical Analysis.
i. The conductive tissue consisting un assimilate nutrients in sap or extracts are analysed.
ii. N, P and К have been tested by this technique.
IV. Soil Analysis:
1. Chemical Methods:
(a) Phosphorous – Olsen’s method,
(b) Micro nutrient – Chelate DTPA
(b) Gypsum requirement – Schoonover’s method
2. Tracer Technique:
i. The plants of few supplied the phosphatic fertilizers with P.
ii. The harvested plants tested for total ‘P’ as well as 32P.
A = В (1 –Y / Y)
Where, A – available ‘P’ in soil
В – Amount of fertilizer ‘P’
Y – Fraction of ‘P’ in plant desired from fertilizer ‘P’
(1 – Y) – Fraction desired from soil.
Land Capability Classification:
Evaluation of land for land use planning is a consequent step following the soil survey and mapping process. In the recent years, it has been popularised in almost every land development programme. The system of land capability classification requires that every acre of land be used in accordance with its capability and limitations. The land capability classification is a broad grouping of soils based on their limitations and also serves as a guide to assess suitability of the land for cultivation, grazing and forest plantation.
The land capability classification scheme developed by soil conservation service. United States Department of Agriculture (USDA).The classification scheme has four categories namely land suitability class, land capability classes (comprising eight classes). Land capability subclass and land capability units.
