Conservation agriculture I: Effects of legume crop species on ground cover, soil moisture retention, weed suppression and litter fall on maize yield in Swaziland

The reintroduction of conservation agriculture in Swaziland required information on crop species that could provide ground cover, suppress weeds and conserve soil moisture. A field experiment was conducted at the Malkerns Research Station in the 2011/2012 cropping season. The treatments were maize intercropped with dry beans [Phaseolus vulgaris (L.)], cowpeas [Vigna unguiculata (L.) Walp], velvet beans [Mucuna pruriens (L.) ] and tepary bean [Phaseolus acutifolius [A. Gray]. The design of the experiment was randomised complete block and each treatment was replicated four times. Results showed that cowpeasmaize association retained the highest moisture. It also had the best ground cover [84.3 %]. Velvet bean-maize association suppressed weeds more effectively compared to the other treatments; but caused maize lodging, reduced maize yield significantly and provided avenue for rodents to climb on maize plants and eat maize seeds. Results also showed that there was a significant difference in the maize seed yield (P< 0.05) among treatments. The highest maize seed yield [5820 kg/ha] was obtained in monoculture maize. The partial land equivalent ratio [PLER] for maize-velvet beans association was 0.872. The PLER for cowpea-maize was 0.933, tepary bean-maize was 0.884 and dry beans-maize was 0.869. It is concluded that cowpeas and velvet beans were the most effective in ground cover, moisture retention, weed suppression and litter fall. It was recommended that maize farmers, who practise conservation agriculture, should grow maize in association with cowpeas in order to improve food security because it was the most effective in ground cover, moisture retention, weed suppression and litter fall.