Corn is a relatively drought-sensitive crop with a relatively high water demand. Corn responds well to irrigation. Where water from irrigation and rainfall are insufficient or unreliable, extra care in risk management assessment is recommended.
- Increase understanding of water requirements (peak water use, seasonal water use, critical growth stages, drought sensitivity/tolerance, and water quality requirements) of corn produced for grain or for silage.
- Increase water use efficiency and profitability in corn production through application of appropriate best management practices.
- Key Points:
- Corn is relatively sensitive to drought and salinity.
- Seasonal water use for corn in the Texas High Plains is approximately 28 to 32 inches per season.
- Peak water use rates occur a few days before; water demand begins to decline about midway through the grain-fill period (dent stage).
- The most critical period during which water stress will have the greatest effect on yield corresponds with the maximum water demand period, approximately two weeks before and after silking.
- Best Management Practices with regard to irrigation method and management (timing, rate, etc.) can minimize risk, optimize water use efficiency and minimize risk of water resource contamination.
- Assess your knowledge:
- What is the peak water use of corn in you area? When (growth stage and calendar range) does this occur?
- How do peak water use and seasonal water use of full season corn compare to those of short-season corn?
- What is the maximum effective root zone depth for corn? Are there other factors in your field or management program that you would expect to limit this effective root zone depth? What practical significance do these limitations have with respect to your irrigation and nutrient management programs?
- Are there water quality (salinity) concerns for corn production on your farm? If so, what are they? How can they be managed?
- What irrigation method do you currently use to irrigate corn? What best management practices (BMPs) are you using to optimize water use efficiency? Identify other methods and BMPs that would be applicable to your operation.
- Corn Water Demand and Irrigation Management
Corn is a relatively high water use crop, with relatively high sensitivity to drought. Seasonal water use for corn in the Texas High Plains is approximately 28 to 32 inches per season. Peak water use rates occur a few days before tasseling (concurrent with maximum leaf area index); water demand begins to decline about midway through the grain-fill period (dent stage). The most critical period during which water stress will have the greatest effect on yield potential corresponds with the maximum water demand period, approximately two weeks before and after silking. The general trend of crop water demand during the season is shown in Figure 1.
The root zone of corn can be as deep as 5-6 feet, if soil conditions allow. Roots are generally developed early in the season, and will grow in moist (but not saturated or extremely dry) soil. Like most crops, corn will extract most (70% – 85%) of its water requirement from the top one to two feet of soil, and almost all of its water from the top 3 feet of soil, if water is available. Deep soil moisture is beneficial primarily when the shallow moisture is depleted in high water demand periods.
Soil moisture profile (moist, but not saturated zone), plow pans, caliche layers, etc. often limit the effective root zone depth. A shallow-rooted crop is more susceptible to drought and related injury.
Irrigation capacity to meet peak water demand
Where irrigation system capacity is limiting, planted acreage may be limited to that which can be supplied by the irrigation capacity and soil moisture storage. Peak water demand for corn can exceed 0.35 inches per day (6.4 gpm/acre) in some areas of the state. Because soil moisture storage (3 to 6 inches of water in the top 3 ft. of soil) can help meet water need during the high demand period, irrigation capacities of 5 to 6 gpm/acre are generally adequate for corn production, provided highly efficient irrigation equipment and management are used.
Irrigation water quality: salinity
Corn is moderately sensitive to salinity in soil and irrigation water. Grain yield is adversely affected by irrigation water salinity above 1.1 dS/m electrical conductivity (EC), or soil salinity above 1.7 dS/m EC. A 50% yield reduction is expected with irrigation water EC of 3.9 dS/m. Corn is also moderately sensitive to foliar injury from sodium (tolerance between 230 and 460 ppm) and chloride (tolerance between 350 and 700 ppm) in irrigation water. Spray irrigation applications present a higher risk of foliar damage from marginal quality waters. Periodic excess applications of water (irrigation and/or precipitation) can facilitate leaching of accumulated salts from the root zone.
Compiled by Dana Porter, PhD, PE, Department of Biological and Agricultural Engineering and Texas A&M AgriLife Research and Extension Center – Lubbock.