Graduate Thesis Or Dissertation
 

Effects of nitrogen applied on wheat straw on winter wheat (Triticum aestivum L.) yields in western Oregon

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/76537408t

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  • Nitrogen deficiency during the winter where winter wheat (Triticum aestivum L.) follows wheat and large amounts of straw have been plowed down has been a factor limiting yield in the Willamette Valley of western Oregon. Field experiments were established to determine if an application of N on the stubble or before plowing, in addition to standard practice of applying 23 kg N/ha at planting, would increase yields. Prior to fertilizer application, the stubble remaining after harvest was chopped and spread with a modified forage harvester to provide for even distribution of the straw and chaff rows. Liquid nitrogen fertilizers were sprayed on the stubble at either a 23, 45, or 90 kg N/ha rate prior to incorporation. Three fertilizer sources were used, Urea Sulfuric Acid (URS), ammonium sulfate (AMS), and sewage sludge (SS), to compare the relative efficiency of each. Various rates of spring fertilizers were applied as subplots to the fall fertilizer main plots. Whole plant samples were taken before harvest to determine the N uptake of each treatment. Samples were separated into grain and straw components, ground, and analyzed by a micro-Kjeldahl procedure for N content. Fall fertilization above the standard 23 kg N /ha applied at planting had varying effects on yield. In general, there was little or no response from the additional N during the first growing season after application. When additional fall N was applied on a field for two consecutive years, a yield response was usually realized. Yield increases from URS were equal to or better than yield increases from AMS. Sewage sludge generally yielded better than the fall check. Nitrogen uptake was not significantly influenced by the fall N in the first year of application, but did show some response where fall N was applied for two consecutive years. The additional fall N is not used with the same efficiency as spring applied N probably because the N is immobilized by the stubble, soil organic matter, and microorganisms. Further research is needed to determine the optimum rates and times of N application during the fall and/or winter. Future experiments need to compare the efficiency of N applied on the stubble compared with December, January, or February applications, which could be combined with herbicide application operations.
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