Nitrogen nutrition and rhizobial inoculation on soybean

Abstract

An experiment was conducted at the Research Station and Instructional Farm, Mannuthy during 1976 on the nitrogen nutrition and rhisobial inoculation on soybean ( Glycene max (L.) Marrill). The investigation was undertaken to assess the nitrogen requirement of the crop under inoculated and uninoculated conditions. Also the study was aimed to arrive at the fertiliser equivalent of rhisobial inoculation. The experiment was laid out in factorial in randomized block with 12 treatments and 4 replications. The study revealed that nitrogen fixed symbiotically, was adequate for the crop. Application of nitrogen depressed symbiotic nitrogen fixation and with increasing levels of nitrogen, there was depression in symbiotic nitrogen fixation. The study also revealed that introduced strain of Rhizobium japonicum was less effective in nitrogen fixation on soybean than the strains already present in the soil. Application of nitrogen didi not influence the stover yield. Inoculation of an ineffective strain tended to depress the stover yield. Application of nitrogen increased the plant height in the early stages when symbiotic nitrogen fixation could not make any substantial contribution towards nitrogen supply. Significant increase is test weight with increasing levels of nitrogen indicated that enhanced soil nitrogen supply was beneficial towards the later stages of crop growth. The quality of nitrogen fixed by the soybean plant appears to exceed the fertiliser equivalent of 250 kg N/ha applied basally.