Water Requirements for Corn
What is the consumptive use of corn in Nebraska? The number varies from year to year and from location to location. ET is the total amount of water that evaporates from the plant. Consumptive Use (CU) is the amount of water that is evaporated, transpired, incorporated into crops or products, and consumed by humans and livestock. Precipitation falls. Some of the precipitation stays in the root zone where a plant can get to it. However, to maximize the yield, a farmer usually needs to supplement the plant with additional water via irrigation. The plant only takes the water that it needs. If the farmer applies more water than needed, then the excess water either runs off into the stream or seeps into the aquifer. Only the portion that is used by the plant is considered consumptive use or that is evaporated off of the lakes. In dry years, CU is higher and so is ET. Dry air with high temps increases the evaporation from the plant. The higher the humidity, the lower the ET rate. High ET levels usually translate into high CU. In the following chart, CU is about the same as NIR. However, the less efficient the delivery system, the higher the irrigation requirement is. If the plant used 100% of the water supplied, NIR would equal IR.
Keep in mind that the Model does not consider water used by a dryland crop or water used by trees and grass as consumptive use.
The ET and NIR numbers come from a report by the 2006 DNR.
Read the full report.