Monday, 7 November 2005
5

Winter Wheat Nitrogen Requirements with Reduced Irrigation.

Jason W. Ellsworth, Bradford Brown, Howard Neibling, and Bryan G. Hopkins. University of Idaho, PO Box 1827, 315 Falls Ave, Evergreen Bldg., Twin Falls, ID 83303-1827

Most fertilizer guides assume that water is not a limiting factor in making fertilizer recommendations and do not make suggestions for adjusting fertilizer requirements when irrigation water is in short supply. The purpose of this research project was to determine the adjustments in nitrogen fertilizer rates and practices based on irrigation outlook for the season for soft white winter wheat (Triticum aestivum, L.). The project consisted of four irrigation treatments (100% ET, 100% ET till flowering, 50% ET and 0% ET) and four (Parma, ID, 0, 50, 100 and 150%) or five (Kimberly, ID, 0, 33, 66, 100, 133% of the University of Idaho Recommended rate) nitrogen treatments. The studies were conducted in 2003 and 2004. In each year and in each location the 100% ET treatment yielded the highest (mean = 158 bu/ac) and a 0% ET yielded the lowest (mean = 65 bu/ac). There were no yield differences between 50% ET and 100% ET till flowering irrigation treatments at Kimberly. However, at Parma, there was no difference at the lower N rates but there was a 10-15 bu/ac decrease in the 100% ET till flowering over the 50% ET treatment at the high N rates. On the average it was better to irrigate at 50% ET all season rather than cease irrigation at flowering. There were no additional increases in yield with increasing N rate for any of the irrigation treatments except the 100% ET treatment. In this study there was no advantage to applying any N when water was limited during the growing season.

Handout (.pdf format, 62.0 kb)

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