Theory question 103
Soil Properties(a) What is soil consistency?
(b) Explain how each of the following soil properties influences crop growth: (i) soil texture; (ii) soil pH.
(c)(i) List four methods by which soil fertility could be maintained. (ii) Explain two ways in which each of the methods listed in 3(c)(i) contributes to the maintenance of soil fertility.
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(a) Soil consistency is the way soil particles hold together, i.e. the soil's resistance to being deformed or broken, shown by its stickiness, plasticity, friability or hardness at different moisture levels.
(b)(i) Texture affects water-holding capacity, drainage and aeration, nutrient content, ease of root penetration and workability.
(ii) pH affects availability of nutrients, activity of micro-organisms (e.g. nitrogen fixers) and the kind of crops that grow well; very low pH makes Al and Mn toxic.
(c)(i) and (ii) any four with two ways each: crop rotation – different rooting depths use different layers; legumes add nitrogen; manuring (organic) – adds nutrients and humus, improves structure; fertilizer use – replaces nutrients removed by crops quickly; liming – raises pH and supplies calcium; cover cropping – checks erosion and adds organic matter; mulching – conserves moisture and adds humus; fallowing – lets soil recover nutrients and organic matter; erosion control – keeps the fertile topsoil.
Two ways are needed for each method in (c).