Effect of Lablab purpureus L. cover crop and imidazolinone resistant (IR) maize on weeds in drought prone areas, Kenya

•Weed density (count m−2) was significantly (P < 0.05) higher 21 days after planting than at 42 in 2011.•Coated-IR-maize, dolichos & time interaction significantly reduced weed species (count m−2).•Lablab purpureus significantly reduced the density of Paraknoxia parviflora & Portulaca quadrifida.•L. purpureus significantly increased yield (kgs ha−1) for coated IR-maize than uncoated.•Weed residues acted as a resource and provided eco-services similar to those of cover crops.

Weeds compete for nutrients and soil moisture resulting to low maize yields in dry lands. A three year field study was initiated in 2009 at Kenya Agricultural and Livestock Research Organization, Kiboko to evaluate the effect of dolichos bean (Lablab purpureus L.) and open pollinated imazapyr herbicide coated imidazolinone-resistant (IR)1 maize on weed species composition, density, and maize yield. Initially, weed species were identified, and then controlled using glyphosate at 1.6 kg ai ha−1. Twenty four plots were marked, each measuring 4 × 5 m. Six treatments 1) IR-maize coated, 2) IR-maize coated + brown dolichos, 3) IR-maize coated + black dolichos 4) IR-maize uncoated, 5) IR-maize uncoated + brown dolichos, 6) IR-maize uncoated + black dolichos were laid out in a randomized complete block design replicated four times. IR-maize was planted at a spacing of 90 × 45 cm and 2 seeds per hole. Weeds were sampled from a one meter squared quadrat 21 and 42 days after planting (DAP). The data was subjected to analysis of variance using Genstat version 12.0. Eighteen (18) weed species were prevalent before the experiment. Interaction of dolichos and herbicide coated IR-maize had no significant (P > 0.05) effect on weed species composition and density. Dolichos significantly (P < 0.05) reduced the density of Portulaca quadrifida L. and Paraknoxia parviflora L., and increased Eleusine indica L. Weed species composition decreased by 14% (21 DAP) and 33% (42 DAP) in plots with dolichos compared to no cover. Maize yields were significantly (P < 0.05) higher in plots with dolichos than without. From the findings, this study recommends dolichos integration with coated IR-for weed management and increased maize yields in drylands.