Effects of Intercropping and Melon Sowing Date on Crop Growth, Soil Micro-Environment and Rhizosphere Fungi and Bacterial Populations of Maize and Cassava

Abstract

ABSTRACT The rhizosphere fungi and bacterial populations, soil micro-environment and crop growth during the late-season cropping of 2002 and 2003 in south-western Nigeria were studied by assessing the effects of melon grown in monoculture or in mixed stands with maize or cassava. Melon was sown on 28 August, 11 September and 25 September 2002, and on 20 September and 4 October 2003. Intercropping did not reduce the growth and yields of maize or cassava, but of melon irrespective of the sowing date. Melon seed yield and yield components were generally reduced by 18–66 and 8–31% in mixed stands with maize and cassava, respectively. The rhizosphere fungi and bacterial populations, growth and seed yield of melon and soil moisture content were generally enhanced by early sowing compared with late sowing of melon in both cropping systems. Late sowing led to greater melon seed yield reduction than early sowing in monocropping or intercropping systems, with greater effect occurring in intercropping in both years. Number of fruits per plant, seeds per fruit and seed yield of melon were significantly reduced by 12–52, 10–75 and 10–67% by late sowing in monoculture, mixed stands with maize and mixed stands with cassava, respectively. Intercropping with melon decreased soil temperature by 3.6–10.4 °C and soil bulk density by 0.09–0.16 g cm3, and increased soil moisture content by 12–45 g kg1and the rhizosphere fungi and bacterial populations of maize by 10–20% and cassava by 38–46%, with early sowing showing greater effects than late sowing. Land equivalent ratios were greater than 1, irrespective of the crop combination and sowing date of melon in both years. However, increased mixture productivity of 46–55 and 69–75% in maize/melon and cassava/melon mixtures, respectively, was obtained by early sowing of melon, without a negative effect on maize grain and cassava root tuber yields. Conclusively, intercropping provided favourable soil micro-environment and increased the rhizosphere fungi and bacterial populations of maize and cassava and total crop productivity, but this depended on sowing date of melon.