Question

Soil fertility is reduced by

(a) crop rotation

(b) nitrogen fixing bacteria

(c) decaying organic matter

(d) intensive agriculture.

Answer 1

Soils lose fertility when the qualities that support plant growth and soil health are degraded:

Loss of plant nutrients - The nutrients essential for growth (N, P, K, Ca, S, Mg, B, Cl, Mn, Fe, Zn, Cu, Mo, Ni) are unavoidably lost when plants are harvested and removed. But they are also lost when soil erodes or when water leaches soluble nutrients through the soil. To minimize nutrient loss, use effective erosion control practices, and capture nutrients with the use of cover crops before and after the main crop.

Loss of organic matter - Organic matter is responsible for imparting many benefits to topsoil, including increasing water-holding capacity, maintaining soil structure, ability to hold nutrients until needed by plants, and increasing permeability to rainfall. To make sure that organic matter doesn't decay faster than it's replenished, return crop residues to the soil and use cover crops to generate additional plant matter.

Loss of soil structure - The granular, crumb-like structure of topsoil is desired by every farmer or gardener and is the product of adequate levels of organic matter. The subsoil also has structure that is formed over long periods of time by wetting and drying, freezing and thawing, the deposition of clay particles, and the mechanical action of soil organisms.

Denitrification