• Durum wheat yield prediction at flowering stage for late N management

      Wang, Guangyao (Sam); Gutierrez, Mario; Ottman, Michael J.; Thorp, Kelly; Ottman, Michael J. (College of Agriculture, University of Arizona (Tucson, AZ), 2010-09)
      Managing late N application effectively in durum wheat is important to reach desirable protein content. Yield prediction at anathesis is needed to estimate N requirement for the crop and N application rate. In this project, we use canopy reflectance and image processing, measured at anthesis, to estimate yield at harvest. Our results of the growing season 2009-2010 suggested that the canopy reflectance index ‘NWI-4’ and the spike pixel size obtained from image processing at anthesis are potential approaches to predict durum wheat yield at harvest. The final goal of this research is to find a simple and rapid method to manage late N fertilizer to reach desirable grain protein content.
    • Response of wheat and barley varieties to phosphorus fertilizer, 2009

      Ottman, Michael J.; Ottman, Michael J. (College of Agriculture, University of Arizona (Tucson, AZ), 2010-09)
      Phosphorus fertilizer represents a significant portion of the cost of producing small grains. Some evidence exists that there are differences in the ability of small grain varieties to take phosphorus up from the soil and utilize this nutrient in the grain. The objective of this study is to determine if barley and wheat varieties grown in Arizona differ in their response to phosphorus fertilizer. A study was initiated at the Maricopa Agricultural Center testing the response of 7 barley and 13 wheat (12 durum wheat and 1 bread wheat) varieties to 2 phosphorus rates (0 and 100 lbs P2O5/acre). The grain yield increase due to phosphorus application averaged across varieties was 474 lbs/acre for barley and 613 lbs/acre for wheat. The barley varieties differed in their grain yield increase due to phosphorus fertilizer and the greatest increase for the commercial varieties tested was 906 lbs and the smallest increase was 245 lbs. We have no statistical evidence that wheat varieties differed in their response to phosphorus fertilizer. The lack of response to phosphorus fertilizer for a particular variety may save production costs if the fertilizer is not applied, but a significant response to phosphorus fertilizer may pay for the fertilizer cost and increase profits. In this study, the higher yielding varieties tended to have a greater response to phosphorus fertilizer, particularly for the barley. This test will be repeated in 2010 to see if the results obtained this year can be duplicated.