Soil physical. conditions and physiological performance of cowpea following organic matter amelioration of sandy substrates

Mulch was added to sand and sandy loam soil in order to simulate repeated additions of organic matter into soils of the tropics where high temperatures cause rapid decomposition. The experiments used pots (0.003 m(3)) and lysimeters (0.18 m(3)) to investigate the effect of farmyard manure (FYM) and municipal waste compost (MWC) incorporation on temperature, soil water retention and evaporation, and MWC on transpiration, photosynthetic rate and yield as performance indicators for cowpea [Vigna unguiculata (L)]. Incorporation of FYM and MWC in un-cropped pots increased early stage evaporation compared with surface mulch treatments and compost mulch conserved soil water at depths between 0.05 and 0.6 m. Repeated incorporation of compost in lysimeters increased crop water availability between 7 and 10% and yield increased 3 to 5 times, despite organic matter content remaining below 1%. Results show cowpea performance indicators in light, low fertility soils of the tropics would benefit substantially from repeated incorporations of compost.