The effect of plant population on peanuts ( Arachis hypogaea) in a monsoonal tropical environment

Abstract

The responses in the growth of peanuts ( Arachis hypogaea L. cv. Florunner) to plant density and to spatial ratio (ratio of inter-row: intra-row spacing) in a tropical monsoonal environment were investigated. Biological yield (above-ground biomass plus pods) was unresponsive to spatial ratio over the range 1:1-1:7:19, but it increased markedly (12 600-16 900 kg ha −1), with increasing density up to the maximum density of 588 000 plants ha −1. In contrast, economic yield (commercially recoverable pods and kernels) was relatively unresponsive to plant density in the range of 88 000–394 000 plants ha −1, after which a marked decline was recorded (6 500 kg ha −1 pods or 4 900 kg ha −1 kernels, falling to 5 700 kg ha −1 pods or 4 300 kg ha −1 kernels). Economic yields were maximized at square plant-arrangements (6 900 kg ha −1 pods or 5 200 kg ha −1 kernels), but were relatively uneffected by increasing plant rectangularity from spatial ratios of 1:2.15-1:7.19 (6 100 kg ha −1 pods or 4 600 kg ha −1 kernels). The increase in biological yield with increasing plant was primarily attributed to differences in the amount of photosynthetically active radiation ( PAR) intercepted ( I), which was evident during both vegetative growth and kernel development. In contrast, I was unresponsive to spatial ratio. Neither density nor spatial ratio affected the average efficiency of conversion ( E c) of I to biological yield during vegetative growth (2.6-3.0 g MJ −1) nor during the entire life-cycle (2.1–2.3 g MJ −1). Average E cm during kernel development was 55–60% of that during vegetative growth. Thus the higher economic yield of the square plant-arrangement was not associated with changes in I and E c . Rather it was associated with greater partitioning of dry matter to reproductive yield and a greater proportion of total pods recovered at harvest.