Growth, yield and quality of Bt cotton (Gossypium hirsutum) as influenced by different intercropping systems and nitrogen levels

A field experiment was conducted during the rainy (kharif) season of 2010 and 2011 at Ludhiana, Punjab to study the effect of intercrops and different levels of recommended dose of nitrogen (RDN). Applied to intercrops on growth, yield and quality of hybrid Bt cotton (Gossypium hirsutum L.). The main plot treatments comprised Bt cotton intercropped with fodder maize (Zea mays L., Saccharata), fodder cowpea [Vigna unguiculata (L.) Walp.], summer mungbean [Vigna radiata (L.) Wilczek], pearlmillet fodder [Pennisetum glaucum (L.) R. Br. emend. Stuntz] and long melon [Cucumis melo L. var. utilissiumus Duth. & Full.] and subplot treatments consisted of 5 levels (0, 25, 50, 75 and 100%) of recommended dose of nitrogen applied to intercrops on area basis. The maximum seed- cotton equivalent yield recorded under Bt cotton + fodder maize intercropping system (2.61 t/ha) was 10.6, 17.6, 27.3 and 39.6% higher than Bt cotton + fodder cowpea, Bt cotton + summer mungbean, Bt cotton + long melon and Bt cotton + fodder pearlmillet, respectively. The maximum net returns of 49,085 and benefit: cost ratio 2.33 obtained from Bt cotton + fodder maize intercropping system were statistically at par that obtained with Bt cotton + fodder cowpea ( 41,545 and benefit: cost ratio 2.12) but significantly higher than all the other intercropping sys- tems. The application of 50% recommended dose of nitrogen to intercrops resulted in 7.0 and 12.4% increase in seed-cotton and seed-cotton equivalent yield as compared to no fertilizer application to intercrops. In all the inter- cropping systems except Bt cotton + long melon, application of full dose of nitrogen to Bt cotton and 50% of the RDN to intercrops proved beneficial for getting higher seed-cotton equivalent yield and economic returns.