Wheat and Barley Response to Phosphorus
1999-2002
JUSTIFICATION:
Proposed NRCS standards and their potential adoption by the Idaho Department of Agriculture Dairy Bureau, and potentially other public agencies or government units have created a good deal of controversy about the UI fertility guides and their use as the basis for the NRCS nutrient management guidelines. The fertilizer industry and many growers commonly believe the UI fertilizer guides to be too conservative and the recommendations to be too low for maximum grower returns.
The University of Idaho fertilizer phosphorus (P) recommendations for irrigated wheat were developed in the late 60s. The P recommendations have not been extensively evaluated since then except for a number of industry conducted on-farm strip trials. These trials, using commercial laboratory soil test results, suggest that the current recommendations may need to be raised to adjust for improvements in wheat production technology.
University of Idaho fertilizer P recommendations do not reflect the influence of soil lime content on the P requirement for wheat. Increased lime reduces P solubility in soils and increases the fertilizer P requirement for some crops. Research is needed to determine the extent to which the fertilizer P recommendation needs to be adjusted for a soil’s lime content.
The relative P requirements of winter vs spring wheat have not been determined. Spring wheat is thought by some to require more P due to more rapid growth and less developed root systems. But winter wheat actually has greater yield potential. If P requirements do not differ for the two wheat types it will expedite the development of P fertilizer recommendations. Data collected for one type of wheat could then be applied to the other. If winter and spring wheat differ in P requirements, those differences need to be quantified.
Also, UI food chemists have discovered a significant association between phospholipid content of starch and starch quality. It is not clear to what extent environmental conditions influence this association, and specifically whether available soil P can influence this association. If available soil P does influence starch quality, that information would be useful in formulating P recommendations for soft white wheat destined for particular market niches.
OBJECTIVES:
Progress Reports to the Idaho Wheat Commission and Idaho Barley Commission for the years of study are available by clicking on the year below.
Idaho Wheat Commission Idaho Barley Commission