Soil Physical Conditions and Physiological Performance of Cowpea Following Organic Matter Amelioration of Sandy Substrates

Abstract

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 m³) and lysimeters (0.18 m³) 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.

Keywords:

• Cowpea (Vigna unguiculata L.)
• Evaporation
• Municipal waste compost
• Sandy soil
• Soil organic matter
• Soil water

Acknowledgments

We would like to thank Sarah Brocklehurst, Keith Hart, and Pam Kite for technical assistance and Dr. Liz Baggs, Alan Clewer, Dr. Stuart McRae, and Dr. Trudy Watt for their advice. The first author held a scholarship from the Second Agricultural Extension Project from the Department of Agriculture, Sri Lanka.