The impact of combined N application and inoculation on BNF, growth, yield, residual N content of plant material and pod N yield of cowpea were studied, using two varieties of cowpea in two separate experiments. In the 1st experiment, local brady-rhizobium multi strain was used for the inoculation with five levels of fertilizer N (40, 80, 120, 160, and 200 Kg N ha'1) applied in split doses. A control treatment was also included without N application as well as without inoculation. There was another treatment that excluded N fertilizer but inoculated with local brady-rhizobium multi strain. In the second experiment same treatments were used but inoculated with two introduced braby-rhizobium strains i.e. THA-291 and THA 230. Both experiments were arranged in a Randomized complete block design with 4 replicates. Nodule fresh weight, stover dry weight at physiological maturity, pod yield, pod N yield at harvesting and percent 15N atom excess and total N in experiment 2 were determined at physiological maturity. Applied fertilizer N inhibited nodulation significantly but contributed positively to stover dry matter production, pod yield and plant N yield. Seed inoculation enhanced nodulation in MI 35 but did not affect nodulation of Bombay. In 2nd experiment, two introduced inoculums i.e., THA-291 and THA-230 were used with same levels of fertilizer N, with a reference crop of Setaria italica. The %Ndfa was significantly higher in variety, Bombay compared to variety, MI-35 and increased application of fertilizer N significantly reduced %Ndfa in both varieties. N fixation was significantly higher in Bombay compared to MI-35.
The impact of combined N application and inoculation on BNF, growth, yield, residual N content of plant material and pod N yield of cowpea were studied, using two varieties of cowpea in two separate experiments. In the 1st experiment, local brady-rhizobium multi strain was used for the inoculation with five levels of fertilizer N (40, 80, 120, 160, and 200 Kg N ha'1) applied in split doses. A control treatment was also included without N application as well as without inoculation. There was another treatment that excluded N fertilizer but inoculated with local brady-rhizobium multi strain. In the second experiment same treatments were used but inoculated with two introduced braby-rhizobium strains i.e. THA-291 and THA 230. Both experiments were arranged in a Randomized complete block design with 4 replicates. Nodule fresh weight, stover dry weight at physiological maturity, pod yield, pod N yield at harvesting and percent 15N atom excess and total N in experiment 2 were determined at physiological maturity. Applied fertilizer N inhibited nodulation significantly but contributed positively to stover dry matter production, pod yield and plant N yield. Seed inoculation enhanced nodulation in MI 35 but did not affect nodulation of Bombay. In 2nd experiment, two introduced inoculums i.e., THA-291 and THA-230 were used with same levels of fertilizer N, with a reference crop of Setaria italica. The %Ndfa was significantly higher in variety, Bombay compared to variety, MI-35 and increased application of fertilizer N significantly reduced %Ndfa in both varieties. N fixation was significantly higher in Bombay compared to MI-35.
