• Barley and Durum Response to Phosphorus at Buckey, Maricopa, and Yuma, 1997

      Ottman, M. J.; Husman, S. H.; Tickes, B. R.; Ottman, Michael (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Soil tests were developed in the 1930's as a guideline for phosphorus fertilizer application. The phosphorus soil test for the calcareous soils in the Western U.S. is based on bicarbonate extraction and is often called the Olsen P method. Phosphorus fertilizer recommendations for small grains based on this test are remarkably similar across the Western states. Despite the availability of this test, its proven accuracy (93% in California), and its low cost ($1 /acre), most farmers in Arizona apply phosphorus fertilizer to their small grains crops without the benefit of a preplant soil test. The purpose of this study was to demonstrate the effectiveness of the soil test in predicting a response to phosphorus fertilizer. At Maricopa, the soil test P was 8.1 ppm, a variable response to P fertilizer was expected, and a variable response to P fertilizer was obtained. We were able to detect a response to P fertilizer at this site with only 1 out of 4 varieties, and the response averaged across varieties was 336 lbs /acre or a 6% increase. No response to P fertilizer was obtained on a commercial farm in Buckeye where the soil test P was 22 ppm and a response was not expected. At the Yuma-Mesa site, the preplant P level was also 22 ppm, and a yield increase of29% (1442 lbs /acre) was measured on barley even though a response was not expected. The soil on the Yuma -Mesa is 95% sand and perhaps the soil test for P needs to be adjusted for this soil type, but at the other sites tested, the current soil test recommendations for P seem to be accurate.
    • Intensive Cereal Management for Durum Production, Buckeye and Yuma, 1996-97

      Ottman, M. J.; Husman, S. H.; Tickes, B. R.; Ottman, Michael (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      The highest wheat yields in the world are obtained using a growing system called intensive cereal management (ICM). High yielding varieties are planted at high seeding rates, treated with foliar fungicides, plant growth regulators are applied to control lodging, and high nitrogen fertilizer rates are used to obtain high yields. The ICM system adapted to Arizona does not include fungicide treatments due to our lack of leaf diseases. We tested the effect of ICM on yield, grain protein, and other characteristics at three commercial farms in Arizona. ICM resulted in higher protein in one case due to increased nitrogen application and reduced height in another case due to the plant growth regulator. However, in most cases, we were not able to detect an affect of ICM on the crop, and the increased input cost was not paid for by increased crop performance. Intensive cereal management does not appear to hold much promise under our conditions except perhaps in cases where lodging is predictable or yields do not reach their potential.
    • The Last Irrigation in Durum at Buckey, Casa Grande, and Marana, 1996-97

      Ottman, M. J.; Husman, S. H.; Ottman, Michael (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Based on consumptive use, the last irrigation in wheat may be applied by the soft dough stage on the average sandy loam soil without loss of yield or shriveled grain. In two of the three locations reported here, this was the case although one of the soils was a clay loam. At the Buckeye location, applying the last irrigation at the soft dough stage resulted in a yield loss of 406 lbs /acre, but this yield loss was not statistically significant at conventional probability levels. Nevertheless, terminating irrigation at the soft dough stage is somewhat risky, and a less risky time to terminate irrigations may be between soft dough and hard dough for a sandy loam soil. The problem with this generalized recommendation is that neither soft dough nor hard dough are well -defined crop growth stages and sandy loam soils may vary greatly in their water -holding capacity. Also, it may be profitable to apply a final irrigation to carry late, green tillers to maturity. Assuming a water cost of $15 per irrigation and a grain value of $8 /cwt, a yield increase of 190 lbs /acre would pay for a final irrigation. Therefore, if water is inexpensive, terminating wheat irrigations unnecessarily early is not worth the risk of decreased revenue. Once the heads have turned color from green to brown, the crop has reached maturity and additional irrigations at this time will not affect yield even if other parts of the plant are green.
    • Late Season Nitrogen Fertilizer for Durum at Buckey, Casa Grande, and Vicksburg, 1996-97

      Ottman, M. J.; Knowles, T. C.; Husman, S. H.; Ottman, Michael (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Research conducted recently suggested that application of nitrogen fertilizer from flowering until the dough stage could increase grain protein concentration in durum even if nitrogen applications earlier in the season were adequate for optimum yield. We tested the ability of late season nitrogen application to increase protein at commercial farms in Buckeye, Casa Grande, and Vicksburg. Late season nitrogen increased protein by nearly two percentage points in two out of the three locations. No response was measured at the third location possibly due to high rates or nitrogen earlier in the season. The cost of the late season fertilizer at 35 to 50 lbs N /acre was about $15 /acre. The fertilizer was paid for at the two location where a response was obtained by 1) the slight yield increase of 310 lbs /acre which was worth about $23 /acre and 2) the difference in dockage or premiums paid for protein which was worth about $38 /acre. It is possible that lower stem nitrate levels could be used to determine whether or late applications of nitrogen will increase protein, but we currently do not have a method to determine if protein will be over the critical level of 13% or if HVAC will be over the critical level of 90 %.
    • Small Grains Variety Evaluation at Marana, Maricopa, Paloma, and Yuma, 1997

      Ottman, M. J.; Husman, S. H.; Lindahl, D. A.; Ottman, Michael (College of Agriculture, University of Arizona (Tucson, AZ), 1997-10)
      Small grain varieties are evaluated each year by University of Arizona personnel at one or more locations. The purpose of these tests is to characterize varieties in terms in terms of yield and other attributes. Variety performance varies greatly from year to year and several site years are necessary to adequate characterize the yield potential of a variety. The results contained in this report will be combined with results from previous years in a summary available from Arizona Cooperative Extension.