Effect of application of biofertilizers to soybean (Glycine max) and nitrogen to tobacco (Nicotiuna tabacum) in soybean - tobacco cropping system

A field experiment was conducted during 2001-02 and 2002-03 at Jeelugumilli to find out the direct and residual effects of Bradyrhizobium japonicum and Pseudomonas striata inoculation on rainy season (kharif) soybean [Gly- cine max (L.) Merr.] cv 'JS 335' and of directly applied N in winter (rabr) season FCV tobacco (Nicotiana tabacum L.) cv 'Kanchan' in irrigated Alfisols of Andhra Pradesh. Co-inoculation of soybean with Bradyrhizobium + Pseudomonas recorded significantly higher growth, yield attributes and grain yield than their individual inoculation and no inoculation. Green-manuring in situ with sunnhemp [Crotalaria juncea (L.) Rotar & Joy] followed by tobacco recorded significantly higher tobacco green-leaf and cured-leaf yields, and grade index compared with other treat- ments. Combined inoculation of Bradyrhizobium and Pseudomonas to soybean increased the tobacco green leaf yield, cured leaf yield and grade index by 10.5, 7.7 and 13.2% respectively compared with no inoculation. Applica- tion of 130 kg Nlha recorded significantly higher green-leaf and cured-leaf yields, and grade index compared with that of 11 0 kg Nlha. Higher total N, nicotine, lower reducing sugars and sugar: nicotine ratio in X and L leaf posi- tions were observed in sunnhemp-tobacco system, followed by soybean (co-inoculation) - tobacco system. Higher total N, nicotine, lower reducing sugars and sugar : nicotine ratio were recorded with 130 kg Nlha than with 11 0 kg Nlha. Soybean (co-inoculation) - tobacco system gave additional net returns of Rs 1,7101ha over sunnhemp-tobacco system (Rs 40,670lha). Higher B : C ratio of 1.65 was obtained with sunnhemp - tobacco sys- tem. It was concluded that combined inoculation of Bradyrhizobium and Pseudomonas to soybean improved the growth and yield of soybean and increased the succeeding tobacco yields, and application of 130 kg Nlha would be needed for tobacco succeeding soybean.