Abstract
The nitrogen uptake and yielding ability of non-nodulating soybean genotype (En1282) were investigated under field conditions. Dried cattle feces were applied at levels ranged from 192 to 960 kg N/ha for seven years. No-fertilizer and inorganic fertilizer treatments were used as controls in this experiment. The grain yield of non-nodulating En1282 increased as the application of cattle feces was increased up to 384 kg N/ha. The maximum grain yield of non-nodulating soybean was 3.6t/ha, and the maximum nitrogen uptake was 250kg N/ha. Nitrogen uptake of upland rice, maize (sweet corn), maize (dent corn), radish, wheat, rye, guinea grass and non-nodulating soybean, cultured in the same field over a seven-year period, were compared. The nitrogen uptake ranged from 100 to 300kg N/ha among the crops; it was lowest in upland rice, and highest in guinea grass, followed by soybean. The nitrate content of guinea grass was very high and exceeded the toxic limits for animal feed. In soybean, the shoot nitrate level was high and close to toxic limits during flowering, but nitrate levels of grain, pod and stem were low at maturity. This fitted for animal feed. Our results indicate that non-nodulating soybean can be effectively used to retrieve inorganic nitrogen that is derived from organic nitrogen (such as animal feces), and can play some role in reducing nutrient load on the farming systems.
