Growth, productivity and biological nitrogen fixation in soybean (Glycine max) under Bradyrhizobium inoculation, pendimethalin and nitrogen schedules, and their residual effect on succeeding wheat (Triticum aestivum) crop

A field experiment was conducted to study the growth and productivity of 'PK 416' soybean [Glycine max (L.) Merr.] as affected by interacting influence of Bradyrhizobium inoculation, herbicide use and nitrogen levels; and their residual effect on wheat (Triticum aestivum L. emend. Fiori & Paol.) on a loamy sand soils during 1993-96. Bradyrhizobium inoculation significantly enhanced the efficiency of biological nitrogen fixation (BNF) in soybean and fixed an additional 66.1 - 74.7 kg N/ha over the control. It helped in increasing the mean seed yield of soybean by 10.4% (2 q/ha) during both the years through attaining earlier flowering and pod formation, higher leaf-area index (LAI) and dry-matter accumulation and improvement in yield traits. Both the efficiency of BNF and seed yield were improved significantly following basal application of 60 kg N/ha. The plant attributes were unaffected at higher N levels or its application at later growth stages. Application of pendimethalin did not depress nodulation and BNF efficiency during any year. Inoculation of soybean seed with Bradyrhizobium increased the grain yield of the following wheat crop in both years. The residual effect of N (applied to soybean) on wheat yield was significant up to 60 kg/ha during both the years, while application of pendimethalin did not show any residual effect on following wheat crop. Similar residual effect as that of grain yield of wheat was also observed on yield traits and growth attributes of wheat.