Cowpea response to compaction and mulching on a sloping loamy sand soil in Southern Nigeria

Abstract

Mulching the surface of soil after machinery traffic can offset some of the adverse effect of compaction of the soil caused by the machine.  Thus, this study reported the response of cowpea (vigna-unguiculata) to compaction and mulching with elephant grass (Pennisectum purpuereum) on loamy sand soil in Southern Nigeria.  A randomized split-block design of field plots with compaction levels as the main block and the mulching levels as the sub-block was used.  The compaction treatment consisted of 0, 5, 10 and 15 passes of a tractor with a 31 kPa contact pressure while the mulching treatment consisted of 0%, 30%, 60% and 90% areal ground cover.  The zero percent treatment served as control and each treatment was replicated twice.  The soil dry bulk density, penetration resistance, soil moisture content and crop growth and yield parameters were measured.  Results showed that compaction level significantly increased the dry bulk density, penetration resistance and reduced soil moisture content, crop growth and yield parameters; while mulching significantly increased soil moisture content, dry bulk density and reduced penetration resistance (P<0.05).  The growth and yield parameter increased for 30% mulch cover and thereafter reduced for 60% and 90% mulch cover.  Both the crop dry matter and grain yield had significant correlation  (R² = 0.93 and 0.96, respectively) with mulch cover and compaction using surface response analysis.  Multiple regressions showed that a ground cover of 40% will be optimum for cowpea production on uncompacted soil while up to 65% and 92% will be needed to complement the 5 and 10 passes of tractor to produce comparative yields respectively.