Irrigation Scheduling on Small Grains using AZSCHED for Windows - Safford Agricultural Center, 2003

Transcription

1 Irrigation Scheduling on Small Grains using AZSCHED for Windows - Safford Agricultural Center, 23 L.J. Clark and K.F. Ellsworth Abstract The AZSCHED irrigation scheduling software was developed in the early 199'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. Introduction The DOS version of AZSCHED software has been used for more than ten years at this location and has been of tremendous value to provide irrigation water to the many small plots in a timely fashion. As computers have changed from DOS to Windows operating systems it was important to have a Windows version available for use. The Bureau of Reclamation has teamed up with the University of Arizona to produce this software. The grain growing season was already underway when the Windows version of AZSCHED was made available to the authors but the shift was made and the season was finished out with this new version. A detailed description of the software will not be given but it is sufficient to say that, like its predecessor, it is menu driven. Even though it has a very different look, it performs the operations of scheduling irrigations on crops in much the same manner. The interface with the AZMET system to download weather data is greatly improved over the older version. Kofa durum wheat and Nebula barley were the cultivars used in this trial with three different irrigation treatments applied. Materials and Methods Experimental plots were rowed-off and firmed with a roller prior to planting the variety trials so seed placement would be somewhat consistent from top of beds to bottom of furrows. Plots were planted with a 12-foot International grain drill with fertilizer attachment, over four 36" beds. The cultural practices applied are described below in the crop history. Crop History (Wheat): Previous crop: Cotton Soil type: Grabe clay loam Planting date: 13 December 22 Watered up: 16 December 22 Seeding rate: 175 lbs/ac (Kofa Durum) Fertilizer: 3 lbs/ac of lbs/ac urea at planting, 2 lbs/ac urea side dressed on 28 Feb and 27 Mar Herbicide: None Insecticide: None Irrigation: Furrow, watered up and watered according to AZSCHED schedule This is a part of the 23 Forage and Grain Report, The University of Arizona College of Agriculture and Life Sciences, index at

2 Water holding capacity: -1' = 2.3 in/ft, 1-2' = 1.8 in/ft, 2-3' = 1., 3-4' = 1. in/ft Rainfall during the growing season:.94 inches Plot size: 4 rows (12 feet) wide by 2 feet long Harvest date: 17 June 23 Heat Units (4/81EF) from watering-up to maturity: 2676 HU Crop History (Barley): Previous crop: Cotton Soil type: Pima clay loam variant Planting date: 16 December 22 Watered up: 19 December 22 Seeding rate: 175 lbs/ac (Nebula variety) Fertilizer: 3 lbs/ac of lbs/ac urea at planting, 2 lbs/ac urea side dressed on 4 Feb and 27 Mar Herbicide: None Insecticide: None Irrigation: Furrow, watered up and watered according to AZSCHED schedule Water holding capacity: -1' = 2.3 in/ft, 1-2' = 1.8 in/ft, 2-3' = 1.1 in/ft, 3-4' = 1. in/ft Rainfall during the growing season:.94 inches Plot size: 4 rows (12 feet) wide by 2 feet long Harvest date: 25 June 23 Heat Units (4/81EF) from watering-up to maturity: 2926 HU Fields in the AZSCHED program were set using our best estimates of water holding capacity throughout the rooting zone for wheat and barley (shown above in Crop History) and selecting wheat and barley, respectively, from the crop data file. The planting date was supplied to the program, AZMET data was updated approximately weekly and irrigation amounts and rainfall were input as they occurred. Weekly irrigation prediction reports were prepared and placed in the hands of the Farm Manager, Farm Supervisor and the irrigator. This group met and made final decisions on which fields were watered and when. Their decisions were made based on water availability, how many fields were needing water and the weather. The three treatments were to apply water at 4 percent, 45 percent and 5 percent soil water depletion. At maturity plant height measurements and the plots were harvested using a Gleaner Model K combine. Grain from each plot was weighed in a weigh wagon where samples were taken to determine percent moisture, bushel weight and 1 kernel weights. In the case of wheat, percent protein was also determined. Results and Discussion Table 1 shows yield, grain quality and other agronomic data on durum wheat. The 4% depletion treatment had superior numbers, even though few statistical differences were seen. The reduced height for this treatment might be related to reduced plant growth since the plants produced more grain. The yields were considered very good for our location and the grain quality as expressed in bushel weight and percent protein were acceptable for export. The first column in Table 2 lists the number of inches of irrigation water applied with the various treatments. It is noted that the same amount of water was applied to the first two treatments. So one might ask, why was there any yield difference? The answer is in the timing. Calculated soil water depletion levels from AZSCHED generated tables were analyzed and displayed in the next two columns. The average depletion level from planting to maturity is low because it starts at zero at planting, slowly working its way up to the trigger level and then drops to low values after each irrigation or rainfall event. Differences are seen in these values because of timing of irrigations even when the same amount of water was applied. The average depletion level just before irrigation uses only values on the day before an irrigation. If irrigations were applied when the software called for an irrigation, one would expect to see values of 4, 45 and 5 in this column. The values are lower than these values for two reasons: depletion levels on the day before an irrigation vary from 1 to 7 percent lower than the day of the irrigation and irrigations are normally scheduled early rather than late, especially if a weekend is involved. The next column in Table 2 shows a value related to irrigation efficiency. The higher the value the more grain was produced per inch of water applied. This indicates that the 5% depletion level was the most water efficient treatment. The last column was added for interest. AZSCHED calculates a leaching loss. If more water is added to the soil profile than can be stored in the soil or used by the plant in 2 days, that water is considered as lost and added to the leaching amount. Again, the 5% depletion treatment was the most efficient.

3 AZSCHED develops a crop coefficient (Kc) for the crop as a function of heat units. This Kc is used in conjunction with reference evapotranspiration (Eto) values (calculated from AZMET data) to determine the water use by the plant. The water use is then subtracted from water available in the soil profile. This is how the program works. For more information see reference 3. Figure 1 shows the Kc for wheat in this trial. Figures 2, 3 and 4 show the percent soil water depletion calculated by AZSCHED for the three irrigation scheduling treatments on wheat. Tables 3 and 4 present data for barley. Further discussion will not be made on this data. Similarly, Figures 5, 6, 7 and 8 are for the barley study and the explanation would be much the same as was given in the paragraph on wheat. References 1. Fox, F.A. Jr., T.F. Scherer, D.C. Slack and L.J. Clark Arizona Irrigation Scheduling (AZSCHED Version 1.1): Users Manual. Cooperative Extension, Agricultural and Biosystems Engineering. The University of Arizona, Tucson, AZ. Publication number, Martin, E.C., D.C. Slack, H. Detwiler and J. Jones. 23. Arizona Irrigation Scheduling System (AZSCHED Version 1.14): Users Handbook. Cooperative Extension, Agricultural and Biosystems Engineering. The University of Arizona, Tucson, AZ Clark, Lee J., Donald C. Slack, Edward Martin and Fred Fox, Jr AZSCHED Computer Software for Irrigation Scheduling. In: Irrigation and Water Resources in the 199's, Proceedings 1992 National Conference. U.S. Committee on Irrigation and Drainage. Pp Table 1. Yield and other agronomic data from the durum wheat irrigation scheduling trial, Safford Agricultural Center, 23. Yield per M Bushel Weight Percent Moisture Plant Height Percent Protein 1 Kernel Weight(g) Heads per acre 4% Depletion 546 a 61.3 a 1.2 a 29.5 b 13.6 a 5.7 a a 45% Depletion 512 a 6.5 a 9.7 a 31.5 a 13.5 a 49. a a 5% Depletion 5221 a 6.8 a 8.2 a 3.8 a 13.5 a 47.8 a 6534 a LSD (5) CV (%) Values followed by the same letter, within a column, are not significantly different at the 95% level of confidence using Duncan s Multiple Range test.

4 Table 2. Measured and calculated water data from the durum wheat irrigation scheduling trial, Safford Agricultural Center, 23. Irrigation Water Applied (Planting to Maturity) (Just Before Irrigation) Yield Divided by Applied Water Water Leached From Root Zone 4% Depletion % Depletion % Depletion Table 3. Yield and other agronomic data from the barley irrigation scheduling trial, Safford Agricultural Center, 23. Yield per M Bushel Weight Percent Moisture Plant Height 1 Kernel Weight(g) 4% Depletion 6194 a 53. a 8.1 a 24.3 a 43.3 a 45% Depletion 65 a 52.8 a 7.8 a 23.3 b 41.8 a 5% Depletion 5936 a 52.4 a 8.7 a 21. c 41.8 a LSD (5) CV (%) Values followed by the same letter, within a column, are not significantly different at the 95% level of confidence using Duncan s Multiple Range test. Table 4. Measured and calculated water data from the barley irrigation scheduling trial, Safford Agricultural Center, 23. Irrigation Water Applied (Planting to Maturity) (Just Before Irrigation) Yield Divided by Applied Water Water Leached From Root Zone 4% Depletion % Depletion % Depletion

5 1.2 CROP COEFFICIENT Figure 1. Crop coefficient curve generated by AZSCHED for the durum wheat on the Safford Agricultural Center, Figure 2. Percent soil water depletion calculated by AZSCHED for wheat in 5% depletion treatment Figure 3. Percent soil water depletion calculated by AZSCHED for wheat in 45% depletion treatment Figure 4. Percent soil water depletion calculated by AZSCHED for wheat in 4% depletion treatment.

6 1.2 CROP COEFFICIENT Figure 5. AZSCHED Crop coefficient curve for barley irrigation trial, Safford Ag Ctr, Figure 6. Percent soil water depletion calculated by AZSCHED for barley in 5% depletion treatment Figure 7. Percent soil water depletion calculated by AZSCHED for barley in 45% depletion treatment Figure 8. Percent soil water depletion calculated by AZSCHED for barley in 4% depletion treatment.