Theory question 102
Soil Properties(a) With the aid of a pH scale, explain the term soil pH.
(b)(i) What are cover crops? (ii) Mention five advantages of planting cover crops on the farm.
(c) Complete the table below: give the botanical name of each weed: wild marigold; spear grass; stubborn grass; pig weed; carpet grass.
Show the model answer
(a) Soil pH is the measure of the acidity or alkalinity of the soil (the hydrogen ion concentration), on a scale of 0 to 14: below 7 is acidic, 7 is neutral and above 7 is alkaline; most crops grow best at about pH 6–7.
(b)(i) Cover crops are low-growing, usually creeping leguminous plants grown to cover and protect the soil surface.
(ii) Any five: control erosion; suppress weeds; conserve soil moisture; add nitrogen and organic matter; reduce soil temperature; improve soil structure; serve as livestock feed/green manure.
(c) Wild marigold: Tithonia diversifolia. Spear grass: Imperata cylindrica. Stubborn grass: Sporobolus pyramidalis. Pig weed: Amaranthus spinosus (or Boerhavia diffusa). Carpet grass: Axonopus compressus.
Draw the 0–14 scale with 7 marked neutral.