Managing water to supply the correct amount of water at the proper time is essential to produce maximum grain yields.
Water, whether provided via rainfall or irrigation, is essential for corn production. In the Midwestern Corn Belt, a successful corn crop consumes about 25 acre-inches of water – 680,000 gallons per acre – during its life cycle. According to research at Iowa State University, about 55 percent to 60 percent of this water transpires through the corn plant – about 400,000 gallons of water per acre – while the remainder evaporates from soil.
If the field yields 300 bushels per acre, corn plants transpire about 1,300 gallons of water for each bushel of grain. On a per-plant basis, if the field population is 32,000 plants per acre each corn plant transpires about 12.5 gallons of water between germination and maturity. If we also include the amount of water lost through evaporation from soil, each bushel of corn requires about 2,300 gallons of water – 19,000 pounds – or about 21 gallons of water per corn plant. If we assume a yield of 300 bushels per acre and a nitrogen-conversion factor of 1.1 pounds of nitrogen per bushel of corn, the water-to-nitrogen-use ratio is about 58:1 – or 19,000 pounds of water per 330 pounds of nitrogen.
Although water is often viewed as a “resource.” corn producers may need to think of water more as a “nutrient” that should be managed. Climatologists are predicting more occurrences of extended periods of excessive rainfall as well as periods of dry and droughty conditions. Corn producers may need to adapt water-management programs to continue to produce corn under those more-varied and stressful environments. A better understanding of what water does in the corn plant contributes toward making the correct decisions.
Water serves four major functions in corn production.
• evaporative cooling to maintain proper plant temperatures for growth
• carrier for nutrient and sugar transport
• hydraulic force for cell growth, development and expansion
• source of hydrogen for sugars, starches and plant-cell components
Evaporative cooling – Temperature is a measure of the average speed of molecules in a system. The more heat that’s applied to a system, the faster the molecules move, and the warmer the temperature. As faster-moving molecules escape from the system those molecules do two things – they extract heat from the system as they escape, and their leaving the system reduces the average speed of the molecules left behind in the system, thus reducing the temperature.
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