Effect of nitrogen fertilization and plant population on the yield of soybeans

Abstract

Field experiments were conducted, over a 5-year period at 8 different sites of Greece, to determine the effects of N fertilization (0, 30, 60 kg N per ha) and plant population (10, 20, 30 plants per m) on the yield of soybeans. In general, the soybean yields were not affected by N fertilization, except in some sites with low soil fertility, where a supplementary N fertilization at the beginning of pod filling phase, resulted in a 3–20% yield increase. On an average, soybean yields were increased significantly with 20 or 30 plants per m in comparison with 10 plants per m, although the increase of plant population from 20 to 30 plants per m did not affect yields. It was concluded that, in soils with a sufficient number of rhizobia, from previous crops or from seed inoculation, N fertilization is not necessary under Greek conditions.