|Ebelhar, Wayne -|
|Paris, Robert -|
Submitted to: World Journal of Agricultural Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 22, 2011
Publication Date: N/A
Interpretive Summary: Soybean is a major source of protein and oil. In the Mississippi Delta, U.S.A., sulfur fertilizer has not been applied to the soybean crop because Delta soil has adequate nutrients. Generally, 10 units of nitrogen taken up by the plants require 1 unit sulfur. Therefore, continuous removal of sulfur, a main component of sulfur-amino acids, from soil may affect soybean seed composition (protein, oil, and fatty acids). In addition, the change from conventional soybean production system to the Early Soybean Production System has shifted the time of oil and protein deposition to a warmer period, leading to possible change in the accumulation of protein, oil, and fatty acid rates. To test this hypothesis, a three-year field experiment was conducted in Stoneville, MS, to investigate the effects of sulfur alone or sulfur and nitrogen combined on seed composition. Addition of sulfur did not increase yield when soybean was irrigated or not irrigated, but seed composition changed. When the crop was irrigated, addition of either 44.8 kilograms per hectare sulfur (40 pounds per acre) or 44.8 kilograms per hectare sulfur with 112 kilograms per hectare (100 pounds per acre) nitrogen increased seed protein and oleic acid, but decreased oil and linolenic acid concentrations. When the crop was not irrigated, seed protein and oleic acid concentrations were higher without addition of sulfur than with it, but oil and linolenic acid concentrations were higher with addition of sulfur. This research provides useful information for the soybean processors to estimate total seed protein and oil in soybean produced in the Early Soybean Production System under irrigated or non-irrigated production, and for soybean breeders to select for specific desirable seed composition constituent under environmental stress such as drought.
Technical Abstract: Information on the effect of sulfur (S) or sulfur+nitrogen (S+N) on soybean seed composition is almost non-existent. The objective of this study was to investigate the effects of S, and S+N fertilizers on soybean [(Glycine max (L.) Merr.)] seed composition in the Early Soybean Production System (ESPS) under irrigated (I) and non-irrigated (NI) environments. Two separate field experiments were conducted from 2005 to 2007. One experiment (I) was irrigated, and the second experiment (NI) was non-irrigated. Under I condition, S at a rate of 44.8 kg/ha alone or with N at 112 kg/ha resulted in a consistent increase in seed protein and oleic acid concentrations, and a decrease in oil and linolenic acid concentrations compared with the control (C). For example, in 2006 and compared with the C, application of S+N increased protein percentage up to 11.4% and oleic acid up to 48.5%. However, oil percentage decreased by 3%. Protein and oleic acid increase was accompanied by a higher percentage of leaf and seed N and S. Under NI conditions, seed protein and oleic acid concentrations were significantly higher in C than in any S or S+N treatments, but the oil and linolenic acid were significantly lower. The results indicate that specific rate of S alone or S+N combined can alter seed composition under irrigated or non-irrigated conditions. This knowledge may help plant breeders to develop and release cultivars to suit specific target locations to grow new value-added soybeans or select for specific seed composition traits under specific environmental stress factors such as drought.