Alternatively, it may be applied on the surface of the ground or crop (e.g. grass) using a tractor mounted centrifugal spinner or oscillating spout type applicator where the fertilizer is broadcast rather than placed in rows. Aerial application of fertilizers may also be used in locations inaccessible to tractors, as described in Fertilizer Applicators and Plant Protection Equipment (EOLSS on-line, 2002). Both pressurized (typically using ammonia) and nonpressurized liquid fertilizer applicators are also described. Protection of plants from diseases and pests is normally achieved by atomizing a liquid formulation containing the active pesticide ingredient through a small nozzle under pressure and spraying onto, beside or beneath the crop canopy, or by using granular pesticide applicators.
The lower tillage intensity in Africa may simply reflect the abundance of land: in order to maximize labor productivity, people work thinly over a large area. Under the substitution view, the profitability of mechanization and its contribution to economic growth depend on the opportunities available to workers (and sometimes draft animals) released from their tasks.