Effect of nitrogen fertilization on yield, intercropping indices and produce quality of different soybean (Glycine max) + cereal intercropping systems

A field experiment was carried out during the rainy (kharif) seasons of 2009 and 2010 at New Delhi, to study the effect of nitrogen levels on yield, competition and produce quality of soybean [Glycine max (L.) Merr.] and intercrops. The sole crop of soybean recorded higher seed yield as compared to intercropping. Among the intercropping systems, soybean + maize (Zea mays L.) recorded the highest yield of soybean. Incremental N levels to cereal crops showed negative impact on the yield of soybean. While the yield of intercropped maize significantly increased with up to 100% recommended dose of nitrogen (RDN), the yield of intercropped sorghum [Sorghum bicolor (L.) Moench.] and pearlmillet [Pennisetum glaucum (L.) R.Br. Stuntz] increased only up to 75 and 50% RDN respectively. Soybean + maize intercropping supplied with 100% RDN gave the highest net returns and soybeanequivalent yield. The aggressivity and competitive ratio were higher for pearlmillet and sorghum than maize. The protein and nitrogen content in seed, N content in stover and total N uptake in intercropped maize were higher with 75–100% RDN, while these parameters increased only up to 75% RDN in intercropped sorghum. In pearlmillet, protein and N content in seed were significantly higher with 75% RDN, while total uptake of N was higher with 50% RDN than lower N levels. The optimum doses of N for intercrops were 66.6 and 70.7 kg/ha for maize, 54.0 and 56.7 kg/ha for sorghum and 35.5 and 31.6 kg/ha for pearlmillet, in 2009 and 2010 respectively.