Yields and accumulations of N and P in farmer-managed intercrops of maize-pigeonpea in semi-arid Africa

Summary

Maize (Zea mays L.) is a major staple food in Sub-Saharan Africa but low soil fertility, limited resources and droughts keep yields low. Cultivation of maize intercropped with pigeonpea (Cajanus cajan L. Millsp.) is common in some areas of eastern and southern Africa. The objectives of this study were (1) to investigate dry matter, nitrogen (N) and phosphorus (P) accumulation in different plant components of maize-pigeonpea intercropping systems and (2) to report the effects of the intercrops on soil fertility. Maize-pigeonpea intercrops were compared to sole maize grown using farmers’ practices. Intercropping maize and pigeonpea increased (P<0.05) total system yield compared to sole maize in terms of biomass, N and P accumulation. Pigeonpea planted in maize did not reduce (P<0.05) the accumulation of dry matter, N nor P in the maize grain. The harvest indices of maize, calculated on basis dry matter, N or P did not differ either (P<0.05). Total soil C and N contents and inorganic N content, nitrate and ammonium, were not affected by two seasons of maize-pigeonpea intercropping compared to sole maize (P>0.11). Nitrate and ammonium levels in soil were still not affected by the treatments after the soils were incubated in anaerobic conditions for 8 days at 37ºC (P>0.11). However, pigeonpea added up to 60 kg of N ha-1 to the system and accumulated up to 6 kg of P ha-1 and only 25% of this N and P were exported in the grain. In conclusion, beside the added grain yield of pigeonpea in the intercropped systems, pigeonpea increased the recirculation of dry matter, N and P which may have a long-term effect on soil fertility. Furthermore, the stems from pigeonpea contributed to household fuel wood consumption. The intercropped system thus had multiple benefits that gave significant increase in combined yield per unit area without additional labour requirements. The main requirement in order to up-scale the maize-pigeonpea intercropping approach is sufficient supply of high-quality pigeonpea seeds.