Biomass production and nutrient recycling through litter from pigeonpea (Cajanus cajan L. Millsp.)

In farm forestry trials for woody biomass production, pigeonpea (Cajanus cajan L. Millsp.) showed excellent adaptability to wide variations of inter-row or interplant spacings for stem as well as grain yields. The crucial factor determining biomass production was not spacing but planting density. Stem and grain yield increase beyond a density of ca. 20 000 plants/ha was minimal, so this is optimal. Average dry stem yields of 9•1 Mg ha−1 were obtained in a wide range of row spacings from 30 to 75 cm without diminishing the grain yields, which averaged 1•2 Mg ha−1. At maturity, inter-row or inter-plant spacings did not significantly influence nutrient concentration in stem or seed. Litter production was 1•9 Mg ha−1 and the amounts of nutrients recycled in the growth season were (kg ha−1) 39•5 N, 2•1 P, 7•3 K and 2•1 S.