This research represents the second year of a project to determine when to irrigate barley based on soil water depletion levels. The purpose of this work is to establish the optimum irrigation timing based on depletion of plant available water in the soil. A field experiment was conducted at the Maricopa Agricultural Center testing irrigation of barley at 35, 50, 65, and 80% depletion of plant available water in the soil for two barley varieties, Baretta and Max. Grain yields for the 35, 50, 65, and 80% depletion levels were 8319, 7296, 5606, and 3404 lbs/acre for Baretta and 9164, 8403, 6463, and 3416 lbs/acre for Max, respectively. The yield increase averaged across varieties from irrigating at 35% rather than 50% depletion is 893 lbs/acre, which has a value of $45.54/acre assuming a grain price of $5.10/cwt. However, the cost of producing this grain is $54.33/acre due the cost of two additional irrigations ($44/acre), 30 lbs additional nitrogen per acre ($8.10/acre), and increased hauling cost ($2.23/acre). The profitability of irrigating at 35% rather than 50% depletion is improved with an increase in grain price or decrease in water cost.

This research was conducted to test the effect of soil water depletion levels on durum productivity. An experiment was conducted at a commercial farm in Stanfield where irrigations were applied at 35, 50, or 65% depletion of plant available soil water. These soil water depletion levels were estimated from soil texture and weather data. The grain yields obtained with 35, 50, and 65% depletion were 6718, 6324, and 4752 lbs/acre, respectively. Grain protein decreased and HVAC increased by irrigating more frequently at lower depletion levels. Irrigating at 50% depletion was the most economical in this study considering irrigation costs and grain quality discounts.

The AZSCHED irrigation scheduling software was developed in the early 1990's to be used in a DOS environment on computers (1) and has been used extensively for irrigation scheduling on the Safford Agricultural Center since its development. The new Windows version of AZSCHED (2) was first tested for barley and wheat in 2003. This is a follow-up verification to the first test using a wider range of irrigation depletion levels.

This research represents the first year of a project to determine when to irrigate barley based on soil water depletion levels. The purpose of this work is to establish the optimum irrigation timing based on depletion of plant available water in the soil. A field experiment was conducted at the Maricopa Agricultural Center testing irrigation of barley at 35, 50, 65, and 80% depletion of plant available water in the soil for two barley varieties, Baretta and Max. Grain yields averaged over the two varieties were 8415, 7735, 7512, and 4553 lbs/acre for the 35, 50, 65, and 80% depletion levels, respectively. The results of this study indicate irrigating at 35% soil water depletion is optimal for barley grain yield.

Solum is a barley bred for reduced water use that tends to have low test weight. An experiment was conducted at the Maricopa Agricultural Center to determine the effect of the number of irrigations and their timing on test weight and grain yield of Solum barley. Applying an irrigation at planting and a second irrigation at jointing resulted in the lowest test weight (44.4 lbs/bu) and nearly the highest grain yield (4315 lbs/acre) recorded in the test. All other irrigation treatments resulted in acceptable test weights above 48 lbs/bu except for irrigating at planting plus tillering, which resulted in 47.0 lb/bu test weight. Irrigating at planting and then delaying the second irrigation until boot or later resulted in acceptable test weight but decreased grain yield by 9% or more compared to applying the second irrigation at jointing. Grain yields similar to that obtained by applying a second irrigation at jointing was obtained by delaying the second irrigation until boot and applying a third irrigation at milk or soft dough. This experiment will be conducted a second year before conclusions are drawn.

This research represents the second year of a project to determine when to irrigate wheat based on soil water depletion levels. The purpose of this work is to establish the optimum irrigation timing based on depletion of plant available water in the soil. A field experiment was conducted at the Maricopa Agricultural Center testing irrigation of wheat at 35, 50, 65, and 80% depletion of plant available water in the soil for two durum varieties, Kronos and Westbred 881. Grain yields averaged over the two varieties were 6787, 6494, 5460, and 3067 lbs/acre for the 35, 50, 65, and 80% depletion levels, respectively. The results of this study indicate irrigating at 50% soil water depletion or less is optimal for wheat grain yield.

Research has not been conducted in Arizona to determine when to irrigate wheat based on soil water depletion levels. The purpose of this work is to establish the optimum irrigation timing based on depletion of plant available water in the soil. A field experiment was conducted at the Maricopa Agricultural Center testing irrigation of wheat at 35, 50, 65, and 80% depletion of plant available water in the soil for two durum varieties, Kronos and Westbred 881. Grain yields averaged over the two varieties were 6479, 5099, 4283, and 4145 lbs/acre for the 35, 50, 65, and 80% depletion levels, respectively. The results of this study indicate that more frequent irrigations may be required than is typically practiced to optimize wheat grain yields in Arizona. This work will be repeated during the 1999-2000 growing season and the results from both years will be evaluated before general conclusions are drawn.

Solum is a barley bred for reduced water use that tends to have low test weight. This is the second year of an experiment conducted at the Maricopa Agricultural Center to determine the effect of the number of irrigations and their timing on test weight and grain yield of Solum barley. A single irrigation resulted in low yield (2043 lbs/acre) and unacceptable test weight (45.2 lbs/acre). Two or three irrigations increased yield and test weight in most cases. Applying a second irrigation at the 1 node, 2-3 node, or boot stages resulted in yield of 2694, 2877, and 2670 lbs/acre and test weight of 48.5, 49.0, and 49.5 lbs/bu, respectively. Applying a second irrigation at boot and a third irrigation between flowering and soft dough resulted in an average yield of 3008 lbs/acre and an average test weight of 50.0 lbs/bu. Delaying the second irrigation of Solum barley until boot reduces the risk of lodging and low test weight, and results in high yields.

The AZSCHED irrigation scheduling software was developed in the early 1990's to be used in a DOS environment on computers (1). Since it’s development it has been extensively used for irrigation scheduling on the Safford Agricultural Center. Changes in computer systems from DOS to Windows has made it imperative that a new Windows version of AZSCHED be developed. That version has been developed and is now in use at our location (2). This report covers the use of this software in scheduling irrigation for barley and wheat.

The purpose of this research was to determine which durum growth stage is most responsive to additional irrigations (based on 35% depletion) when grown at a slightly suboptimal irrigation level of 65% plant available soil water depletion at other growth stages. A field experiment was conducted at the Maricopa Agricultural Center testing the effects of additional irrigations applied during tillering, jointing, or grain fill. Additional irrigations during tillering, jointing, grain fill, or no additional irrigations resulted in grain yields of 5964, 5419, 6301, and 4200 lbs/acre for Kronos and 5440, 5990, 5030, and 4019 lbs/acre for Westbred 881, respectively. The most responsive stage to additional irrigation was grain fill for Kronos and jointing for Westbred 881. The yield response of Kronos to additional irrigation during jointing may have been reduced by severe (78%) lodging in this treatment.