Pigeonpea in simultaneous fallow-cropping systems in the subhumid forest-savanna mosaic zone of West Africa

The potential of pigeonpea (Cajanus cajan (L.) Millsp.) as a simultaneous fallow component in cropping systems is unique in that, being a shrubby grain legume, it combines food production with ease of establishment, fast growth and high biomass productivity. A study was carried out under on-farm conditions at three different sites in southern Benin, West Africa over two years to evaluate the biomass productivity and recycled nutrients of a local pigeonpea cultivar, managed as annual hedgerows. Pigeonpea was sown between a standard cassava-maize intercrop and compared with two other agroforestry systems and annual intercrops with and without mineral fertilizer. The number of cuts taken at a height of 1 m was doubled from two in 1991-92 to four in the 1992-93 season, leading to an increase in total cut dry matter by a factor of eight (1908 g m(-2)) and cut leaf dry matter by a factor of fourteen (1317 g m(-2)) in 1992-93. There were no trade-offs in subsequent dry grain (9.5 g m(-2)) and firewood yields (96.2 g m(-2)) for cutting hedges earlier and more often during the second year, despite much lower precipitation. In pigeonpea recycled nutrients, N, P, Ca, Mg and K, increased proportionally to cut dry matter yields. Yield increases over two years with pigeonpea were highest among all evaluated cropping systems for maize (+ 150%) and significant for cassava (+ 66%). Pigeonpea as a simultaneous fallow component in cassava-maize intercropping, can help to sustain moderate yields of maize and cassava, provided thar. insects, nematodes and diseases do not lower its high biomass productivity with continued cropping after two years.