Soil Science and Soil Fertility Management
What the domain tests
Soil Science and Soil Fertility Management tests soil formation, physical and chemical properties, soil fertility versus productivity, nutrient availability and soil-test interpretation. Questions often ask you to read a soil-test value and choose a management practice.
Core rules
- Soil texture is the proportion of sand, silt and clay; structure is arrangement into aggregates. Clay holds more water and nutrients but drains slowly.
- CEC (cation exchange capacity) measures the soil's capacity to hold exchangeable cations; high-organic-matter and clay soils usually have higher CEC.
- Soil pH controls nutrient availability. Acid soils (low pH) may need lime; sodic/alkaline soils (high pH, high ESP) may need gypsum and drainage.
- EC measures soluble salts; a high EC indicates salinity risk, not fertility.
- Organic carbon, available N, P, K, S and micronutrients are interpreted against soil-test ratings: low, medium, high.
- Fertility is the inherent capacity to supply nutrients; productivity also depends on water, climate, variety and management.
- Management: organic matter, balanced fertilizer, crop rotation, green manure, contour bunding, mulching and avoiding excessive tillage.
Worked example
A laboratory report gives pH 8.5, EC 0.18 dS/m, organic carbon 0.35%, available N low, P medium, K high. Reasoning: pH 8.5 is alkaline but EC is low, so salinity is not the main limit; low organic carbon and low N call for FYM/compost and adequate nitrogen; P is medium and K high, so avoid unnecessary K. Gypsum is not automatically justified without exchangeable sodium percentage (ESP) data.
Traps
High pH is not the same as high salinity. A high K rating does not mean apply more K. Lime raises pH; gypsum is used for sodic soils, not ordinary acid soils. Do not confuse fertile soil with productive soil.