• Use of Tissue Testing to Prevent Low Grain Protein Content in Durum, 2003

      Ottman, Michael J.; Husman, Stephen H.; Clay, Pat A.; Ottman, Michael J. (College of Agriculture, University of Arizona (Tucson, AZ), 2007-10)
      Low grain protein content in durum can be prevented by applying nitrogen fertilizer after heading. Tentative guidelines were established from previous research for nitrogen fertilizer applications after heading based on the lower stem nitrate content near heading. Ten commercial durum fields were selected for testing the use of these guidelines to ensure grain protein contents greater than 13%. Only one field had grain protein content less than 13% (12.83%), and this field had herbicide damage and had to be over-irrigated due to surface unevenness. The average protein content was 13.62% but the amount of nitrogen fertilizer actually applied by the growers after heading averaged 74.5 lbs N/acre, whereas the amount recommended by the tentative guidelines averaged 53.1 lbs N/acre. If the tentative guidelines had been followed, we estimate that the average grain protein content would have been about 13.04%. Our tentative nitrogen fertilizer recommendations based on stem samples near heading appear accurate, but another year of testing would add more certainty.
    • Use of Tissue Testing to Prevent Low Grain Protein Content in Durum, 2004

      Ottman, Michael J.; Husman, Stephen H.; Clay, Pat A.; Ottman, Michael J. (College of Agriculture, University of Arizona (Tucson, AZ), 2007-10)
      Low grain protein content in durum can be prevented by applying nitrogen fertilizer after heading. Tentative guidelines were established from previous research for nitrogen fertilizer applications after heading based on the lower stem nitrate content near heading. Ten commercial durum fields were selected for testing the use of these guidelines to ensure grain protein contents greater than 13%. The average protein content was 14.00%, the amount of nitrogen fertilizer actually applied by the growers after heading averaged 44.5 lbs N/acre, whereas the amount recommended by the tentative guidelines averaged 41.5 lbs N/acre. If the tentative guidelines had been followed, we estimate that the average grain protein content would have been about 13.92%, and two fields would have been slightly below 13% protein (about 12.8% protein). Our tentative nitrogen fertilizer recommendations based on stem samples near heading appear accurate.
    • Use of Tissue Testing to Prevent Low Grain Protein Content in Durum, 2005

      Ottman, Michael J.; Husman, Stephen H.; Ottman, Michael J. (College of Agriculture, University of Arizona (Tucson, AZ), 2007-10)
      Low grain protein content in durum can be prevented by applying nitrogen fertilizer after heading. Tentative guidelines were established from previous research for nitrogen fertilizer applications after heading based on the lower stem nitrate content near heading. Three durum fields in Pinal County were selected for testing the use of these guidelines for ensuring grain protein contents greater than 13%. These fields were split into plots that either received late N fertilization after heading or not. The stem nitrate content at heading for two of the fields averaged 6337 ppm, indicating no need for late N fertilizer application to achieve grain protein content above 13%, and the grain protein content for these fields averaged 15.1% with or without late N fertilizer. The stem nitrate content at heading was 894 ppm for the third field, the stem nitrate guidelines called for a late N application of about 63 lbs N/a, and a late N application of 46 lbs N/a increased grain yield protein from 11.54 to 13.34%. Our tentative nitrogen fertilizer recommendations based on stem samples near heading appear accurate.
    • Variety Mixtures for Reduced Input Barley, 2006

      Ottman, Michael J.; Ottman, Michael J. (College of Agriculture, University of Arizona (Tucson, AZ), 2007-10)
      Variety mixtures may lessen competition among plants and reduce effects of stress particularly in environments where resources are limiting. Mixtures of four barley varieties were grown under low input conditions at the Maricopa Agricultural Center. The barley varieties seeded were Barcott, Solum, Solar, and an experimental low input line designated Entry 9. The highest yields were not obtained with mixtures in this experiment, but rather when the varieties were grown alone. Barcott and Entry 9 decreased yield when part of the mixture more than Solum or Solar. When Solum was grown in a mixture rather than alone, test weight and lodging were improved, but yield was decreased.