Soybean Yields with Direct and Residual Nitrogen Fertilization
1973
Welch, L. F. | Boone, L. V. | Chambliss, C. G. | Christiansen, A. T. | Mulvaney, D. L. | Oldham, M. G. | Pendleton, J. W.
The objective of this research was to determine the effect on soybean (Glycine max (L.) Merrill) yields of N added at different rates by different times and methods of application, as direct and residual, and as inorganic and organic sources. A number of studies were conducted over a period of several years at 10 field locations in Illinois. Nitrogen at rates up to 360 kg/ha added for corn (Zea mays L.) the preceding year had no effect on soybean yields. Neither were soybean yields increased by organic sources of N such as manure or alfalfa (Medicago sativa L.), or by combinations of organic and inorganic sources. Fertilizer N added for soybean as plow-down, disked-in, and side-dressed at early flowering and at pod filling did not increase yields. Nitrogen added for soybeans planted on four dates did not increase yields. High rates of N (1800 and 1440 kg/ha), broadcast and disked-in in the spring, decreased yield due to germination and seedling injury. Considering all the studies, yields were significantly increased in only 3 out of 133 instances and these occurred at high, uneconomical rates of N fertilizer. It is concluded that N available to the plant is not the growth factor that presently limits soybean yields in Illinois.
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