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Table 1. Estimated seasonal water reaulrement (consumptive use) in eastern Colorado (Inches /season). Yield vs Evapotranspiration 12000 ` -- - - - -- 10000 ! Y soon SM 41W 2000 0 5 10 15 20 25 30 Evrpouuaraplraaon fwrol».i - - winter whets - - sunflower -corn Figure 1: Yield vs. ET relationship for several irrigated crops. r '+` _i kicdd rsEl' R I I ' Vicki vs 1rriKation Water (ET or Irrigation) Figure 2: Generalized Yield vs. ET and Yield vs. Irrigation production functions. In Colorado's semi -arid climate, ir- rigation is important to increasing ET and grain yields, supplementing rainfall in periods when ET is greater than precipita- tion. However, not all of the water applied by irrigation is used for ET. Inefficiencies in applications by the system result in losses. As yield is maximized, more losses occur since the soil is closer to field capacity and more prone to losses, such as deep percola- tion, which cause the deviation from the straight line (Figure.2). By applying less than needed for maximum yield, water can be saved. As seen in Figure 2, a reduction in water applied from point A to point B can save water with little or no yield reduction. In Colorado's semi -arid climate, ir- rigation is important to increasing ET and grain yields, supplementing rainfall in periods when ET is greater than precipita- tion. However, not all of the water applied by irrigation is used for ET. Inefficiencies in applications by the system result in losses. As yield is maximized, more losses occur since the soil is closer to field capacity and more prone to losses, such as deep percola- tion, which cause the deviation from the straight line (Figure 2). By applying less than needed for maximum yield, water can be saved. As seen in Figure 2, a reduction in water applied from point A to point B can save water with little or no yield reduction. Limited Irrigation When water supplies are restricted in some way, so that full evapotranspiration demands cannot be met, limited irrigation results. Reasons that producers may be limited on the amount of available water include: 1.) limited capacity of the irriga- tion well - in regions with limited saturated depth of the aquifer, well yields can be mar- ginal and not sufficient to meet the needs of the crop; 2.) reduced surface water storage - in regions that rely upon surface water, droughts and seasonal fluctuation affect the water allocations available for users. When producers cannot apply water to meet the crop ET, they must realize that with typical management practices, yields and returns will be reduced as compared to a fully irrigated crop. To properly manage the water for the greatest return, producers must understand how crops respond to wa- ter, how crop rotations can enhance water availability, and how changes in agronomic practices influence water needs. Yield vs. ET and Irrigation Crop yields increase linearly with the water that is used by the crop (Figure 1). Crops such as corn, respond with more yield for every inch of water that the crop consumes as compared to winter wheat or sunflower. High water use crops, such as corn, require more ET for plant develop- ment or maintenance before yields are produced. Corn requires approximately 10 inches of ET as compared to 4.5 and 7.5 inches of ET for wheat and sunflower. These crops also require less ET for maxi- mum production compared to corn. Irrigation is important to increasing ET and grain yields. Irrigation is used to supplement rainfall in periods when ET is greater than precipitation. However, not all of the water applied by irrigation can be used for ET. Inefficiencies in applications by the system result in losses. As yield is maxi- mized, more losses occur since the soil is nearer to field capacity and more prone to losses such as deep percolation (Figure 2). Water can be saved by applying less water than needed for maximum yield. As seen in Figure 2, a reduction in water applied from point A to point B can save water with little or no yield reduction. When producers are faced with reduced surface water supplies, they have three management options 1. reduce irrigated acreage, 2. reduce irrigation amounts to the entire field, or 3. include different crops that require less irrigation. Cheyenne Colo. Rocky Burlington Byers Weds Springs Holy Greeley Lamar Longmont Fond Springfield Sterling Trinidad Wray Alfalfa 35.64 32.13 36.14 30.04 39.34 31.58 39.06 30.91 37.75 37.44 35.24 33.29 35.24 Grass hay /pasture 31.06 27.45 31.74 26.04 34.66 26.63 34.16 26.17 32.92 32.61 28.01 28.10 30.92 Dry beans 19.22 18.42 15.83 18.75 18.75 Corn, grain 26.00 25.81 20.49 29.40 26.81 21.66 27.73 26.67 21.31 25.42 corn, silage 2282 22.11 18.22 26.12 21.74 19.74 24.28 20.29 19.15 Corn, sweet 22.75 20.37 Melons 15.85 15.80 15.13 Potatoes 28.14 Small vegetables 18.71 17.70 18.85 22.23 Sorghum, grain 21.51 20.46 15.99 25.20 19.48 22.64 22.65 16.09 Soybeans 10.41 Spring grains 12.49 11.82 11.36 14.15 10.44 14.29 15.17 Sugar beets 29.98 30.43 34.83 29.31 34.27 25.48 32.70 32.28 29.99 29.99 Wheat, winter 18.99 16.42 18.55 14.06 19.65 16.38 19.30 18.46 18.64 12.53 16.14 Av. Precipitation 16.35 18.57 16.26 15.73 15.33 12.20 5.33 12.74 12.53 15.36 14.92 12.80 18.51 Av. Effective Precipitation 11.28 10.39 11.68 10.59 10.72 7.32 11.00 6.99 8.89 10.93 6.66 8.28 12.56 Yield vs Evapotranspiration 12000 ` -- - - - -- 10000 ! Y soon SM 41W 2000 0 5 10 15 20 25 30 Evrpouuaraplraaon fwrol».i - - winter whets - - sunflower -corn Figure 1: Yield vs. ET relationship for several irrigated crops. r '+` _i kicdd rsEl' R I I ' Vicki vs 1rriKation Water (ET or Irrigation) Figure 2: Generalized Yield vs. ET and Yield vs. Irrigation production functions. In Colorado's semi -arid climate, ir- rigation is important to increasing ET and grain yields, supplementing rainfall in periods when ET is greater than precipita- tion. However, not all of the water applied by irrigation is used for ET. Inefficiencies in applications by the system result in losses. As yield is maximized, more losses occur since the soil is closer to field capacity and more prone to losses, such as deep percola- tion, which cause the deviation from the straight line (Figure.2). By applying less than needed for maximum yield, water can be saved. As seen in Figure 2, a reduction in water applied from point A to point B can save water with little or no yield reduction. In Colorado's semi -arid climate, ir- rigation is important to increasing ET and grain yields, supplementing rainfall in periods when ET is greater than precipita- tion. However, not all of the water applied by irrigation is used for ET. Inefficiencies in applications by the system result in losses. As yield is maximized, more losses occur since the soil is closer to field capacity and more prone to losses, such as deep percola- tion, which cause the deviation from the straight line (Figure 2). By applying less than needed for maximum yield, water can be saved. As seen in Figure 2, a reduction in water applied from point A to point B can save water with little or no yield reduction. Limited Irrigation When water supplies are restricted in some way, so that full evapotranspiration demands cannot be met, limited irrigation results. Reasons that producers may be limited on the amount of available water include: 1.) limited capacity of the irriga- tion well - in regions with limited saturated depth of the aquifer, well yields can be mar- ginal and not sufficient to meet the needs of the crop; 2.) reduced surface water storage - in regions that rely upon surface water, droughts and seasonal fluctuation affect the water allocations available for users. When producers cannot apply water to meet the crop ET, they must realize that with typical management practices, yields and returns will be reduced as compared to a fully irrigated crop. To properly manage the water for the greatest return, producers must understand how crops respond to wa- ter, how crop rotations can enhance water availability, and how changes in agronomic practices influence water needs. Yield vs. ET and Irrigation Crop yields increase linearly with the water that is used by the crop (Figure 1). Crops such as corn, respond with more yield for every inch of water that the crop consumes as compared to winter wheat or sunflower. High water use crops, such as corn, require more ET for plant develop- ment or maintenance before yields are produced. Corn requires approximately 10 inches of ET as compared to 4.5 and 7.5 inches of ET for wheat and sunflower. These crops also require less ET for maxi- mum production compared to corn. Irrigation is important to increasing ET and grain yields. Irrigation is used to supplement rainfall in periods when ET is greater than precipitation. However, not all of the water applied by irrigation can be used for ET. Inefficiencies in applications by the system result in losses. As yield is maxi- mized, more losses occur since the soil is nearer to field capacity and more prone to losses such as deep percolation (Figure 2). Water can be saved by applying less water than needed for maximum yield. As seen in Figure 2, a reduction in water applied from point A to point B can save water with little or no yield reduction. When producers are faced with reduced surface water supplies, they have three management options 1. reduce irrigated acreage, 2. reduce irrigation amounts to the entire field, or 3. include different crops that require less irrigation.