Nitrogen and light partitioning in a maize/soybean intercropping system under a humid subtropical climate

Abstract

Land-use efficiency in a cereal/legume intercropping system is related to the complementarity of resource use in time or space. Nitrogen and light partitioning in a maize (Zea mays L.)/soybean (Glycine max (L.) Merr.) intercropping system under subtropical climatic conditions in Nepal was studied during the summers of 1988 and 1989. Factors studied included the cropping system (sole cropping vs. intercropping), three levels of nitrogen fertilization (0, 35 and 70 kg N ha−1) and two spatial arrangements of the intercrops. During the second season, a non-nodulating soybean isoline of the same cultivar was used as a control. The cropping system had a limited impact on soybean nodulation, since intercropped soybean nodules dry weights were only 11% and 6% inferior, as compared with sole cropped soybean, in 1988 and 1989, respectively. However, the seed N yield of sole cropped nodulating soybean was significantly higher than the total seed N yield of intercropped maize/nodulating soybean. The reverse effect was measured in the case of the maize/non-nodulating soybean intercropping system. Intercropping maize with soybean did not result in the interception of a higher proportion of the incident photosynthetic photon flux density (PPFD) than sole soybean, except early during the season. Intercropped nodulating soybean developed a dense underlying canopy, and was able to intercept 95% of incident PPFD after maize harvest.Key words: LER, resource capture efficiency, Bradyrhizobium japonicum, PPFD interception