The influence of interaction between Rhizobium tropici and fertilizer N on nutrient uptake, growth and yield of French bean (Phaseolus vulgaris L.) under salt stress

A range of management options have been applied by previous workers to manipulate N₂-fixation for renewable N in French bean-Rhizobium symbiosis under sodic soil conditions of north India, but success is still awaited. To solve this problem, a field experiment was conducted with four levels of nitrogen (N₀, N₄₀, N₈₀ and N₁₂₀) and three levels of seed inoculation (S₀-No inoculation, S_l-inoculation with BR-865 strain of Rhizobium tropici and S₂-inoculation with BR-885 strain of Rhizobium tropici) in partially reclaimed salt affected soil to study the interaction response of nitrogen and seed inoculation on biological nitrogen fixation (BNF), N-P uptake, growth and yield of French bean. Rhizobium tropici was found quite effective to nodulate French bean root. BR-885 strain of Rhizobium tropici was found more efficacious than strain BR-865 and fixed 7.85% higher nitrogen in unfertilized French bean crop. As a result of higher biological nitrogen fixation in BR-885 treated plants over BR-865 treated plants, root length: shoot length ratio decreased by 1.03% whereas leaf area index, grain yield, N uptake and P uptake increased by 3.68%, 4.35%, 6.31% and 4.75% respectively. Biological N₂-fixation was significantly affected by the levels of nitrogen. Among different levels of nitrogen, 40 Kg N ha⁻¹ was found the best with BNF point of view. Higher levels of nitrogen (> 40 kg ha⁻¹) decreased BNF. The highest root length (19.5 cm), shoot length (45.7 cm), root length: shoot length (0.427), number of leaves (30.2), leaf area (1152.71 cm²), leaf area index (2.562), grain yield (1.728t ha⁻¹), N uptake (83.47 kg ha⁻¹) and P uptake (13.73 kg ha⁻¹) were recorded with 40 kg N ha⁻¹ + seed inoculation with BR-885 strain of Rhizobium tropici. All the treatments were found significantly superior over control in increasing growth, yield and N-P uptake.