The microclimate and productivity of a groundnut/millet intercrop during the rainy season

Abstract

The microclimate of a pearl millet/groundnut intercrop (1:3 row arrangement) was monitored for three successive rainy seasons, 1985–1987, at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Hyderabad, India. The main objective was to quantify the changes in microclimate in intercrop and to relate these changes to the performance of the component crops in terms of growth and yield. Major changes in microclimate of intercrop were in the wind speed and the relative duration of leaf wetness. Reduction in wind speed just above the groundnut crop was dependent on the height of the pearl millet canopy. Wind speed was reduced by 50% at 35 days after sowing (DAS) in 1985 and by 70% at 60 DAS in 1987. Leaf wetness duration of the groundnut was increased by intercropping but this appeared to have little effect on defoliation. The effect of temperature on crop development was estimated by calculating thermal time. This showed that the intercropped groundnut developed 2.5–2.8 days earlier than sole groundnut. The effect of saturation deficit on crop growth was small. Intercropping increased the radiation use efficiency of groundnut by 21–35%. Yield loss from foliar diseases of groundnut was 37–40% in 1985, negligible in 1986 and 33–35% in 1987. However, intercropping appeared to have no significant effect on the severity of foliar disease in groundnut, largely because defoliation occurred after the pearl millet was harvested. Therefore the grain yield of intercrop sprayed with fungicide was similar to that of the unsprayed control. The land equivalent ratio of the intercrop ranged from 1.67 in 1985 to 0.94 in 1987. The discussion highlights differences between observations made during the rainy and post-rainy seasons.