Interactions between plants in intercropped maize and common bean

BACKGROUND: Intercropping maize (Zea mays L.) with common bean (Phaseolus vulgaris L.) can give silage yields that are as high as with monocropped maize, but with more crude protein. Interactions between maize and common bean intercropped in the UK were assessed at a range of plant densities (maize 100 000, 75 000 and 50 000 plants ha(-1) and beans at a fixed density of 50 000 plants ha(-1)). RESULTS: In monoculture, maize yield per plant increased as planting density decreased from 100 000 to 50 000 plants ha(-1). At a density of 50 000 maize plants ha(-1), both dry weight yield per plant and shoot N concentrations of maize were greater when intercropped with 50 000 Type III (bush-type) bean plants ha-1 than in monoculture (1196.4 g plant(-1) and 167.0 g plant(-1); 21.6 g N kg(-1) dry mass and 17.4 g N kg(-1) dry mass, respectively), but intercropping Type IV (climbing) beans at this density combination had no effects on either maize plant weight or shoot N concentration. Invariably, however, the beans grown at 50 000 plants ha(-1) were adversely affected by competition with maize at all densities. Weight per plant of both Type III (bush-type) and Type IV (climbing) beans grown in competition with 50 000 maize plants ha(-1) was only about half that of when grown alone. Intercropping gave increased mycorrhizal colonization of both species, especially in unfertilized plots, and gave higher shoot N concentration in the maize. The beans had more nodules in the intercrop than in the monocrop. CONCLUSIONS: Intercropping maize with Type III common bean at 50000 plants of each species ha(-1) increases yield per miaize plant above that of monoculture maize at 50000 plants ha(-1), despite plant density being doubled. This increase is brought about by increased maize shoot N concentration. Mycorrhizal infection of both species, and bean plant nodulation, are stimulated, and N moves from the beans to the maize. (C) 2008 Society of Chemical Industry