Collecting additional data to calibrate and refine current guidelines for interpreting soil and plant test values for P is an ongoing need in Arizona. An experiment was conducted at the Safford Agricultural Center during the 1987 -88 crop year to evaluate the response of 'Aldura' durum wheat to P fertilizer applications on a clay loam soil testing low in available P. Maximum grain yields of more than 5,500 lbs. /A were obtained by banding 40 lbs. P₂O₅/A as triple super phosphate with the seed at planting. A December 9 planting date subjected plants to cold soil temperatures early in the season (up to 80 days after planting), rendering soil P less available for plant utilization. Preplant soil P analyses predicted the yield increase observed with P fertilization (11.2 %);however, economic returns were not sufficient to offset the cost of P fertilizer. The recommended preplant soil test for P proved accurate in predicting P status and stem PO₄⁻P tissue analyses seemed reliable in monitoring P nutrition of durum wheat. A critical nutrient range of 1200 - 2000 ppm PO₄⁻P is proposed for basal stem tissue sampled prior to the joint growth stage, and 1500 - 1706 ppm PO₄⁻P is suggested for flag leaf tissue sampled at the boot stage.

Eleven oat varieties were tested for grain and forage yields at the Safford Agricultural Center. Cayuse, the predominant variety grown in the area was the top producer of total dry matter. Four other varieties had higher grain yields than Cayuse.

No description available.

Durum grain quality is affected by many factors, but water and nitrogen are factors that the grower can control. The purpose of this research was to determine 1) the nitrogen application rate required at pollen shed to maintain adequate grain protein levels if irrigation is excessive or deficient during grain fill and 2) if nitrogen applications during grain fill can elevate grain protein. Field research was conducted at the Maricopa Agricultural Center using the durum varieties Duraking, Minos, and Turbo. The field was treated uniformly until pollen shed when nitrogen was applied at rates of 0, 30, and 60 lbs /acre. During grain fill, the plots were irrigated based on 30, 50, or 70% moisture depletion. In a separate experiment, nitrogen fertilizer was applied at a rate of 30 lbs N /acre at pollen shed only, pollen shed and the first irrigation after pollen shed, and pollen shed and the first and second irrigation after pollen shed. Increased irrigation frequency during grain fill decreased HVAC from 93 to 81%. Increasing nitrogen rate at pollen shed from 0 to 30 and 30 to 60 lbs N /acre increased protein from 11.6 to 12.5% and 12.5 to 13.3% and increased HVAC from 79 to 89% and 89 to 94 %. Nitrogen fertilizer application at the first irrigation after pollen shed increased grain protein content from 12.9 to 13.6% and application at the first and second irrigation after pollen shed increased grain protein content further to 14.1% averaged over varieties. Nitrogen fertilizer application during grain fill may not be too late to increase grain protein content.

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 %.

Nitrate content of the lower stem tissue of small grains is used as a guideline for nitrogen fertilization. The turnaround time for nitrate analysis in a commercial lab is usually 1 to 3 days. Nitrate quick tests have been suggested as a means of obtaining results on a more timely basis. The quick tests analyze nitrate in the sap or juice squeezed out of the tissue. A nitrate test conducted by a commercial lab is performed on the dried and ground tissue. In this study, I found that the quick tests on plant sap are not as accurate as conventional tests on dried tissue since the moisture content of the fresh plant tissue varies depending on its nitrate content and the growth stage of the plant. We compared the following quick test methods: nitrate test strips, a colorimetric procedure, and a hand held nitrate electrode. Nitrate test strips were not sensitive enough to be useful and were difficult to compare to the color charts. An electronic strip reader could alleviate this difficulty and make the strips a viable option. Colorimetric procedures, or those that rely on nitrate producing a colored solution with certain chemicals added, are not adapted to analyzing plant sap since the green color and organics in the sap interfer with the color produced by the nitrate. The hand held nitrate electrode, or Cardi meter, was the simplest and most accurate method we experimented tested. Quick tests for nitrate in the sap have the following disadvantages: 1) It is not easy to squeeze the sap out of the plant tissue, 2) The sap needs to be diluted to fit into the analytical range of the test, and 3) The moisture content of the tissue needs to be accounted for somehow for the results to be most accurate.

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.

Durum growers were surveyed in cooperation with the USDA’s National Agricultural Statistics Service to determine production practices and their effects on yield and protein in the 2006 growing season. The survey was conducted in three regions: West (Yuma and La Paz counties), Central (Maricopa, Pinal, and Pima counties), and East (Cochise and Graham counties). Most of the durum in Arizona is grown in these three regions. We obtained responses from 83 out of an estimated 166 durum growers (50%) representing 46,331 out of 79,000 acres (59%). Durum was grown following cotton (41%), vegetables (27%), lettuce (16%), or other crops. The major varieties were Orita (30%), Kronos (25%), Ocotillo (16%), and Sky (11%). Herbicide was applied on 64% of the acreage. Flood irrigation systems accounted for 69% of the acreage, followed by furrow (17%). The crop was irrigated 6-7 times on average. The predominant soil texture was a sandy clay loam (36%), followed by sandy loam (35%) and clay loam (12%). The average planting date (germination irrigation applied) was December 21 in the Central region, January 4 in the West region and February 7 in the East region. The seed was planted at an average rate of 165 lbs/acre. Phosphorus was applied to only a third of the acreage, but when it was applied, the rate averaged 71 lbs P2O5/acre. Nitrogen rate averaged 224 lbs N/acre. Increased yield was associated with amendment application in the West region; certain varieties, amendment application, seeding rate between 120 and 159 lbs/acre, and nitrogen rate over 200 lbs N/acre in the Central region; and a seeding rate between 140 and 159 lbs/acre in the East region. Increased grain protein was associated with a previous crop of lettuce, lack of phosphorus application, and irrigation number in the West region; and a seeding rate of 140 to 159 lbs/acre and lack of phosphorus application in the East region. This survey documents associations, not cause-and-effect relationships, among durum production practices, yield, and protein.

Durum growers were surveyed in cooperation with the USDA’s National Agricultural Statistics Service to determine production practices and their effects on yield and protein in the 2006 growing season. The survey was conducted in two regions: West (Yuma and La Paz counties) and Central (Maricopa, Pinal, and Pima counties). These two regions represent about 95% of the durum acreage. We obtained responses from 85 out of an estimated 170 durum growers (50%) representing 40,580 out of 70,000 acres (58%). Durum was grown following vegetables (42%), cotton (41%), lettuce (12%), or other crops. The predominant soil texture was a sandy clay loam (47%), followed by sandy loam (30%) and clay loam (16%). Herbicide was applied on 52% of the acreage. The major varieties were Kronos (26%), Ocotillo (20%), Alamo (16%), and Orita (16%). Flood irrigation systems accounted for 87% of the acreage, followed by furrow (11%). The crop was typically irrigated 6 times. The average planting date (irrigation applied) was December 27 in the Central region and January 4 in the West region. The seed was planted at an average rate of 160 lbs/acre. Phosphorus was applied to only a quarter of the acreage, but when it was applied, the rate averaged 65 lbs P2O5/acre. Nitrogen rate averaged 224 lbs N/acre. Increased yield was associated with previous crops other than cotton in the West region, certain varieties, lack of herbicide application, planting in January in the West region and November or December in the Central region, a seeding rate between 100 and 160 lbs N per acre, and an N rate between 200 and 300 lbs N per acre. Increased grain protein was associated with a previous crop of vegetables or lettuce in the West region, lack of herbicide application in the Central region, manure application, clay loam or sandy clay loam soil, December planting in the West region, lack of phosphorus application, and fewer irrigations. This survey documents associations, not cause-and-effect relationships, among durum production practices, yield, and protein.

Lower stem nitrate concentration is used as a guide for fertilization of small grains in Arizona. The objective of this study is to determine if the timing of stem sampling has an appreciable effect on stem nitrate and corresponding fertilizer recommendations. Durum and barley were grown at the Maricopa Agricultural Center and lower stems were analyzed for nitrate from 3-leaf to maturity. Stem nitrate concentration varied considerably between the 3-leaf and 2 node stages, but thereafter was relatively constant and low (averaged 765 ppm). Stem nitrate increased after rain or N application on a few occasions, but not consistently. In this study, the timing of the stem sampling could have affected fertilizer recommendations before the 2-node stage, but after the 2-node stage, fluctuations in stem nitrate would have resulted in relatively minor differences in fertilizer recommendations.