Graduate Thesis Or Dissertation

 

The effect of soil temperature and soil moisture stress on S-urea mineralization and ryegrass yield Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/np193d02x

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  • A growth chamber experiment was conducted to determine the rate of S-urea mineralization and effect of S-urea on the yield of ryegrass (Lolium multiflorum) grown in Steiwer soil as influenced by soil temperature (60, 75, and 90° F) and soil moisture stress (0. 10, 0.35, and 2.50 bars). Plant yield, nitrogen and sulphur uptake and amount of S-urea mineralized were studied. The optimum conditions for ryegrass growth appeared to vary due to the interaction between soil temperature and moisture status. Increasing root temperature indicated a higher soil moisture content was required for optimum ryegrass growth. High soil temperature and low soil water suction decreased the percent plant nitrogen in 31-day old seedlings. Ryegrass N-uptake was highest in the 31-day old seedlings maintained at 0.35 bar soil water suction and a root temperature of 75° F. Optimum conditions for S-urea mineralization to available NH₄ + NO₃ occurred at a soil temperature of 90° F and moisture stress of 0.10 bar. Moreover, the mineralization exceeded 60 percent of the S-urea added in only 9 days after application under these warm moist soil conditions. The amount of nitrogen mineralized was directly related to plant growth. While SO₄-S mineralized from S-urea varied directly with soil temperature and moisture content unlike nitrogen mineralization no interaction between these two factors was observed. Sulphur and nitrogen status in plants proved to have a close relationship. At low soil temperature and high soil moisture content luxury consumption of sulphate by ryegrass likely occurred.
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