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Soybean Sulfur and Nitrogen Balance under Varying Levels of Available Sulfur
Author(s) -
Sexton P. J.,
Paek N. C.,
Shibles Richard
Publication year - 1998
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1998.0011183x003800040016x
Subject(s) - biology , point of delivery , glycine , dry matter , shoot , nitrogen , amino acid , field experiment , nitrogen balance , greenhouse , sulfur , zoology , agronomy , horticulture , chemistry , biochemistry , organic chemistry
Protein quality of soybean [ Glycine max (L.) Merr.] seed could be enhanced by increasing the concentration of S‐containing amino acids. The N:S ratio of soybean seed tissue is an indicator of protein quality. The objective of this study was to compare N and S accumulation and distribution in the soybean plant under varying levels of S availability. Soil S levels were varied in two greenhouse trials and tissue S and N contents were monitored. A field experi~nent with 0 and 60 kg ha −1 applied S was also conducted. In the two greenhouse trials, seed yield, rate of dry matter increase, and rate of N accrual by shoots all increased at least five‐fold as S availability increased from less than 15 (zero added S) to 60 mg available S per plant, but showed little response to higher levels of S. Rate of S accrual was strongly related to S availability. In the field trial, there were no responses to added S. Leaf, pod, and seed tissue appeared to accumulate S in proteins, whereas, root and stem tissue appeared to accumulate S as sulfate. Harvest index values for S were consistently less than those for N, indicating S is not remobilized to seed as efficiently as is N. Seed S:N ratio was linearly related to the rate of S versus N accrual on a whole‐plant basis. We estimate that a 50% increase in the amount of S‐containing amino acids in soybean seed may require a 65 to 80% increase in S accrual by shoots to satisfy the increased demand for S.