The production of grain legumes is becoming a popular practice in the humid south western Nigeria. Apart from the decreasing trends observed in rainfall amount and duration as a result of climate change, solar radiation interception also constitutes a limitation to crop production because of persistent cloud cover. A trial was conducted at the University of Ibadan experimental site to determine the effect of different plant densities of Arachis spp. on solar radiation interception, dry matter production and yield in Ibadan, Nigeria with the aim of ascertaining the best practice for groundnut production in the zone. The treatments were three plant spacings (60 cm×20 cm,75 cm×20 cmand75 cm×40 cm), and three Arachis varieties (Samnut 10, Samnut 21 and Pintoi) arranged in a split plot, randomized complete block design with Arachis varieties as the main plot while plant densities formed the subplot and replicated three times. Growth parameters (number of leaves, dry leaf weight and dry stem weight) were measured at two weeks interval while yield parameters (number of pods, dry pod weight, dry seed weight and total dry matter) were determined at harvest. Intercepted radiation by plants (PAR) was also taken along with the growth parameters. The highest light interception from 42 - 105 days after planting (DAP) among the Arachis spp. was recorded by Samnut 10, while at 42 - 87 DAP, plant density of75 cm×20 cmhad the highest light interception. Dry matter production increased with light interception and was highest at 105 DAP when light interception was between 55% and 60% for all Arachis varieties and all plant densities. In terms of pod weight and grain yield, Samnut 10 performed better than Samnut 21 and also recorded the highest Radiation Use Efficiency (RUE) for pod, seed and total dry matter. However, Arachis pintoi, a sterile and forage plant with slower growth rate served as a cover crop capable of replenishing soil nutrients and physical properties.
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