Theory question 103
Soil PropertiesWrite short notes on the following.
(a) soil pH.
(b) soil texture.
(c) soil organisms.
(d) soil profile.
Show the model answer
(a) Soil pH: measure of acidity or alkalinity (hydrogen-ion concentration) on a 0–14 scale; 7 neutral; most crops prefer 6–7; affects nutrient availability and soil organisms; corrected by liming (acid) or sulphur/acid fertilizer (alkaline)
(b) Soil texture: relative proportions of sand, silt and clay; determines water holding, drainage, aeration, fertility and ease of tillage; e.g. sandy, loamy, clayey soils
(c) Soil organisms: living things in soil – macro (earthworms, termites, rodents) and micro (bacteria, fungi, protozoa, actinomycetes); decompose organic matter, fix nitrogen, improve structure and aeration; some cause diseases/pests
(d) Soil profile: vertical section of soil showing layers (horizons) – O (organic), A (topsoil), B (subsoil), C (weathered parent material), R/D (bedrock); shows depth, drainage and fertility
One paragraph of definition plus importance for each.