(a) A farmer in a tropical region is preparing land that was previously under bush fallow for maize cultivation. (i) State two methods the farmer could use ...

(a)(i) Two methods to clear bush vegetation (any two for [2]):

1. Slashing with cutlasses or machetes [1].
2. Mechanical clearing using a bulldozer or tractor with a front-mounted blade to push down trees [1].

Also acceptable: uprooting stumps with chains/winch; ring-barking large trees; applying herbicide before clearing.

(a)(ii) Three reasons why burning cleared vegetation may not be the best option:

1. Destroys organic matter - the vegetation, if incorporated into the soil instead, would decompose to form humus that improves soil structure, water-holding capacity and nutrient cycling [1].
2. Kills soil organisms - intense heat from burning destroys beneficial organisms such as earthworms, mycorrhizal fungi and decomposer bacteria that maintain soil health [1].
3. Nutrient loss - the mineral ash released by burning is highly soluble; if rain falls before planting, much of the potassium, calcium and other nutrients can be leached or washed away before the crop can use them [1].

(b)(i) How a mouldboard plough turns the soil:

1. The ploughshare (the pointed, horizontal blade) cuts a slice of soil horizontally along the base of the furrow [1].
2. The mouldboard (the curved plate behind the share) lifts the cut furrow slice and turns it over [1].
3. The inverted furrow slice is laid upside-down beside the open furrow, burying surface vegetation, weeds and crop residues beneath the soil [1].

(b)(ii) Two effects of primary tillage on soil physical condition (any two for [2]):

1. Breaks up compacted layers, increasing the volume of air spaces between soil particles (improved aeration) [1].
2. Improves water infiltration and drainage by loosening the soil structure [1].

Also acceptable: buries surface weeds and residues; loosens soil for easier root penetration.

(c) Secondary tillage is needed because primary ploughing leaves the field rough, with large clods of soil. Secondary tillage (harrowing) breaks these clods into a fine tilth [1], creating a level, crumbly seedbed that provides good seed-to-soil contact for even germination and allows uniform planting depth [1].