Nitrogen-Sulfur Relations in Soft White Winter Wheat. I. Yield Response to Fertilizer and Residual Sulfur1
- R. E. Ramig,
- P. E. Rasmussen,
- R. R. Allmaras and
- C. M. Smith2
Sulfur deficiency occurs in some soils in the northwestern United States. Wheat (Triticum aestivum L.) responses to S applications are highly variable and apparently related to N fertilization. Our objective was clarification of this variability by measuring yield responses of wheat (grain and straw) to S applied with a range of N (deficient to excess) for the first wheat crop and monitoring residual S effects on yields of three subsequent wheat crops.
A factorial combination of four rates of S (0, 17, 34, and 68 kg S/ha) as gypsum and four rates of N (0, 45, 90, and 180 kg N/ha) as ammonium nitrate was applied to the first wheat crop at seeding. Wheat was grown in rotation with peas (Pisum sativum L.), wherein the peas were not fertilized and subsequent wheat crops received only a blanket application of N at the optimum rate (56 kg N/ha).
First wheat crops after fertilization did not respond to S when N was deficient or optimum. Sulfur applied with excess N increased straw but not grain yield. Significant N to S interactions were noted. Residual S increased straw yield in all wheat crops and grain yield in 1 of 4 second, 3 of 3 third, and 2 of 2 fourth-wheat crops. All S application rates gave similar yield increases in the second wheat crop. Residual S from 17 kg S/ha gave responses below maximum in the third wheat crop and residual S from 34 kg S/ha was marginally adequate in the fourth wheat crop.
Wheat response to residual S was influenced by N rates applied to the first wheat crop. High N and S fertilization resulted in early drought and curtailed yields. Gradual release of residual S from recent organic matter apparently provided S at a rate adequate for efficient water use and maximum yield.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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