Symbiotic nitrogen fixation and nitrogen benefits by nodulated soybean (Glycine max (L.) Merrill) to interplanted crops in northern India

An experiment was conducted during the rainy seasons of 1982-1983 and 1983-1984 to study the effect of nodulation of the soybean (Glycine max (L.) Merrill) cv. Shilajeet on plant dry matter, grain yield and nitrogen benefits in terms of mineral-nitrogen-equivalent (MNE), nitrogen uptake and nitrogen-harvest-index (NHE) in interplanted ragi (Eleusine coracana (L.) Gaertn.) cv. PES-176 and non-nodulated soybean cv. Lee. Symbiotically fixed N2 by nodulated soybean was also determined. Nodulated soybean significantly increased plant dry matter and grain yield of interplanted crops. The average beneficial effect in terms of mineral-nitrogen-equivalent, was 41.1 and 82.4 kg N ha-1 for non-nodulated soybean and 43.2 and 78.6 kg N ha-1 for ragi, respectively, associated with one and two rows of nodulated soybean between the intercrops. Average nitrogen benefit in terms of N-uptake was 61.8 and 73.1 kg N ha-1 for non-nodulated soybean and 32.0 and 45.1 kg N ha-1 for ragi associated with one and two rows of nodulated soybean, respectively. Application of N at the rate greater than 20 kg ha-1 decreased nitrogen-harvest-index in both interplanted crops. Nodulated soybean, however, slightly improved nitrogen-harvest-index. The quantity of symbiotic N2 fixed by nodulated soybean cv. Shilajeet was estimated to be 128.1 kg N ha-1.