EFFECTS OF NITROGEN SUPPLY AND SPATIAL ARRANGEMENT ON THE GRAIN-YIELD OF A MAIZE SOYBEAN INTERCROP IN A HUMID SUBTROPICAL CLIMATE

Cereal/legume intercropping is a common practice in low-input agricultural systems. Under appropriate conditions, it usually results in higher overall productivity as compared with pure stands. Appraisal of agronomic practices is of particular importance, since component crops sometimes differ considerably in their structure and fertilization needs. An experiment was conducted under the subtropical conditions of Southern Nepal, in the Terai belt, in 1988 and 1989. Maize (Zea mays L.) and soybean (Glycine max (L.) Merr.) received 0, 35 or 70 kg N ha-1 when grown either in pure stands or when intercropped in two spatial arrangements differing in spatial intimacy. Nitrogen fertilization resulted in similar grain yield increases for maize either in pure stands or in intercropping with soybean, indicating that the availability of nitrogen for the cereal was comparable in both cropping systems. Soybean yields were 22% lower in the presence of maize, as compared with a pure stand. The overall productivity of intercropping, as assessed by ATER (area-time equivalent ratio), was significantly higher than that of pure stands in 1988 and 1989. Land-use efficiency was higher when maize was intercropped with nodulating soybean, as compared to non-nodulating soybean, but only at 0 and 35 kg N ha-1.