UPRIGHT VARIETIES OUT-YIELD CLIMBING COWPEA VARIETIES AND LEAF STRIPPING AND DETASSELLING ENHANCES PRODUCTIVITY OF MAIZE/COWPEA INTERCROPS

Abstract

An experiment to test the effect of cowpea architecture (two varieties with upright and bushy architecture and two with climbing architecture); three cropping systems (sole maize, sole cowpea and maize cowpea intercrop) and a maize leaf stripping/ detasselling treatment at anthesis (leaf stripped and detasselled, intact maize) on maize and cowpea grain yield and weed density and biomass at University of Zimbabwe Farm in the 2005/2006 season. Cowpea grain yield for the upright varieties was 2.5- 4 times higher than for the climbing varieties in maize cowpea intercrops. Cowpea vegetative biomass had a significant (P<0.01) but opposite trend with the climbing varieties having 1.46-1.62 more vegetative biomass at end of season than the upright varieties.  Leaf-stripping and detasselling, averaged across the cowpea varieties, significantly increased cowpea grain yield by 5.46%, 1000 grain weight by 11.7%, number of grains per pod (11%) and number of pods per plant (17%). Upright cowpea varieties planted as sole crops suffered significantly less yield reduction (19.5%-36.6%) when intercropped with maize than one of the climbing varieties, R ex-Mbare (68.5%). Leaf stripping and detasselling in the maize bean intercrops increased maize grain yield by 12% compared to intact maize. The climbing cowpea varieties proved to be more competitive against maize, causing greater maize grain yield reduction  (66%-67.7%) in maize cowpea intercrops than the upright cowpea varieties (29%-43%). Weed biomass was reduced by 46% in the intercropped treatments compared to the cowpea monocrop treatments. The results of the study show that new upright cowpea varieties are more adapted to be grown with maize in an intercrop than the traditional trailing and climbing cowpea varieties as they produced 2.5-4 times more cowpea grain and reduced maize grain yield by 24%-38% less than that caused by the trailing and climbing varieties.