Influence of Grass Mulch on Soil Physical Attributes of a Luvisol and Water Requirement of Cowpea (Vigna unguiculata) in the Transition Zone of Ghana

The experiment was conducted to assess the influence of grass mulch on some soil physical attributes of a luvisol and water requirement of cowpea in the transition zone of Ghana at the University of Education, Winneba, Mampong campus. A Randomized Complete Block Design (RCBD) was used. The grass mulch rates were; 1 t ha-1, 3 t ha-1, 5 t ha-1 and control (no mulch) with four replications. The grass mulch was applied evenly on the soil surface under a cultivated cowpea. Parameters assessed were soil aggregate stability, bulk density, soil porosity, soil gravimetric and volumetric moisture contents, cumulative infiltration, sorptivity, organic matter content and cowpea seed yield. The study showed that mulching improved cowpea seed yield, soil gravimetric moisture content, soil volumetric moisture content, cumulative infiltration amount, infiltration rate, sorptivity and soil residual moisture. The soil physical parameters measured in both the minor and major seasons were higher on the 5 t ha-1 plots but lower on the control (no mulch) plots. There was a significant (P = .05, r = 0.61) positive correlation between the cowpea seed yield and soil gravimetric moisture content. Estimation of water requirement of cowpea using the Blaney-Criddle method produced higher values in 2010 (629.70 mm season-1), 2011 (619.60 mm season-1) than the field graphical estimated values in 2010 (399.00 mm season-1), 2011 (357.0 mm season-1) and improvised evaporation pan values in 2010 (347.90 mm season-1), 2011 (136.11 mm season-1) seasons Although cowpea is tolerant to water deficit to some extent, the use of 5 t ha-1 mulch for sustainable soil moisture management would be important in areas of erratic and inadequate rainfall.