Data from: Irrigation water used to produce cattle feeds throughout the United States

<p dir="ltr">Both beef and dairy production can require large amounts of water, primarily for irrigation of feed crops. Together these industries use about 9% of the total annual freshwater withdrawals of the United States with over 95% used for irrigation. Reducing water use in cattle systems is important to improve the long-term sustainability of beef and dairy products. Water use in feed production varies greatly across the US as influenced by climate and the resulting irrigation required. When feeding cattle, there is flexibility in the choice of feeds. Therefore, an option for reducing the water required for beef or milk production is to use feeds produced using less water. To properly assess the benefit of using alternative feeds, the water required to produce each feed must be known.</p><p dir="ltr">Important feed crops for cattle production include corn, sorghum, and wheat grains, alfalfa hay and silage, various grass hays, and corn and sorghum silages. Blue water used to produce each crop (liters per kg dry matter (DM) of feed produced) were estimated for each state and the total US considering the amount of irrigation used and the portion of irrigated crop produced within the state, region or nation. The irrigated portion was determined considering imported or exported amounts based upon the production and consumption of the feed in the state. As follows, the procedure and assumptions varied among the feed crops.</p><p dir="ltr">For each crop, land area, total production and irrigation water use were obtained for each state and the US from the 2022 Agricultural Census published by the USDA National Agricultural Statistics Service. Harvested crop areas for irrigated and non-irrigated production were used to determine the portion of each crop produced using irrigation. Total production of each crop was converted to Mg DM using standard DM contents of 85% for corn grain, 86% for sorghum grain, 86.5% for wheat, 35% for silage, and 90% for hay. The water applied per unit of irrigated crop area was multiplied by the irrigated crop area to get the total blue water used to produce that portion of the crop in each state. This total was divided by the irrigated crop DM produced to get an intensity for blue water use per unit of irrigated feed DM produced. This value was designated as the irrigated crop footprint of the feed. Total irrigation water used was also divided by the total crop DM produced (irrigated plus non-irrigated) to get an average intensity (feed footprint) for the feed produced within each state and the US.</p><p dir="ltr">Crops used in each state included those consumed by animals and those used for biofuel production. Feed consumed by animals was determined from the Animal Feed Consumption Report of Decision Innovation Solutions. For each feed, the report provided the total amount fed to all animal species in each state and the US. For corn grain, that processed and fed as corn gluten feed and corn gluten meal were included in the total, and middlings and flour were included with wheat. The water attributed to each of these feeds was determined through economic allocation among the byproducts of processed grain.</p><p dir="ltr">Large quantities of corn and sorghum grains were also used in biofuel production. National use of each crop for ethanol production was obtained from the National Agricultural Statistics Service. Corn used in each state was determined based upon the biorefinery capacity in the state published by the Renewable Fuels Association. Thus, for corn, the state capacity divided by the national capacity was multiplied by the US total used in ethanol production to estimate the amount used within the state. Sorghum used in ethanol production was assigned to Kansas, where most of this grain was produced and consumed.</p><p dir="ltr">This procedure provided a reasonable estimate for the feed use compared to that produced within each state. By comparing the amount consumed to that produced, the imported portion of the total consumed was determined. When the total produced in the state was greater than that consumed, the blue water footprint for the feed was that for all of the feed produced in the state, i.e., irrigation water used divided by the total crop DM produced. When feed was imported to the state to meet the feed consumption within the state, the consumed feed footprint was determined as the weighted average of that produced in the state and that imported. Not knowing where the imported feed originated, the imported feed footprint was set to the national footprint, i.e., the total irrigation water applied to the crop nationally divided by the national production of the feed. For example, the national footprint of corn production was 47 L/kg DM of grain produced, and the footprint of that produced in Kansas was 166 L/kg DM. With 18% of the grain imported to the state, the weighted footprint of all corn grain consumed in Kansas was 146 L/kg DM.</p><p dir="ltr">For corn and sorghum silages, feeds were assumed to be used within the state where they were produced. With the high moisture content and weight of these feeds, long-distance transport is constrained. Therefore, the consumed feed footprint was equal to the produced feed footprint, i.e., the irrigation water used divided by the total forage DM produced and fed within the state.</p><p dir="ltr">Footprints were also determined for multi-state regions of the US. Seven regions were defined as Northeast, Southeast, Midwest, Northern Plains, Southern Plains, Northwest, and Southwest. Regional values were determined by totaling production, water use and consumption values for the states within the region. Regional footprints for irrigated crop, produced feed, and consumed feed were determined following the same relationships used for determining individual state values.</p><p dir="ltr">An Excel spreadsheet provides the calculations and footprints for each feed in each state and region (Table S1). Two versions of the table are provided using either Standard International or English units of measurement. Footprints include that for irrigated crop produced, all feed produced, and all feed consumed in the state or region.</p><p dir="ltr">For states where relatively small portions of the crop were irrigated, the footprint for all feed produced was relatively small or negligible. In states where most or all of the crop was irrigated, the footprint for all feed produced was equal or nearly equal to that of irrigated crop alone. For states or regions where little or no feed was imported, the footprint of the feed consumed was that determined for the feed produced in the state. When feed was imported to meet the needs of the state or region, the footprint of consumed feed was generally less than that of the feed produced within the state or region. The footprint of imported feed was that determined over the US, which was often smaller than that of feed produced within the state or region (Table S1). For states where little irrigation was used and large portions of the feed were imported, the footprint of consumed feed was greater than that of the feed produced within the state.</p>

Tags: blue-water, cattle-feed, irrigation, water-footprint
Organization: Department of Agriculture