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
Abstract
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.
