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Environmental Constraints on the use of Anion Exchange Membranes in Dryland Wheat

Redman, A.E. 2002. M.Sc. Thesis. Dept. Soil Science, Oregon State University, Corvallis, OR


Lack of growing season precipitation and the temperate climate in north central Oregon pose challenges to growing spring wheat crops. Phosphate and sulfate fertilization can improve early growth of spring wheat in this region and soil testing aids in determining rates of fertilization. In this study, anion exchange membranes (AEM) were used to assess phosphorus and sulfur supply rates in four, minimally-tilled, annually cropped spring wheat fields innorth central Oregon. To determine the validity of AEM in this region, uptake of P and S by hard red spring (HRS) wheat was correlated with soil supply of P and S as predicted by AEM. I found that in low soil water content and cool soil temperature conditions, AEM did not accurately measure plant available P and S. Unlike plants, AEM are static instruments that cannot measure plant available nutrients when soil conditions limit mineralization and diffusion of plant nutrients. I also found that three consecutive years of drought across the study sites has led to P and S quantities sufficient for maximum yield potential of HRS wheat without fertilization. These results suggest that growers in north central Oregon may not necessarily need to fertilize wheat crops following a drought and that AEM may provide inaccurate information regarding soil nutrient status.