March 15, 2013
Maturity Range Effects on Seasonal Evapotranspiration
Figure 1. Crop coefficient and hybrid maturity.
An often discussed strategy for reducing seasonal crop water use is to plant a short-season corn hybrid when water is the limiting factor. Under irrigation, the relative maturity range of a particular corn hybrid has an important effect on seasonal ET. At the same location, a hybrid with a relative maturity of 120 days will use more water than a 100-day hybrid.
Longer season corn hybrids, planted in Nebraska, use approximately 1.0 inch more water for every five days difference in relative maturity, but they also produce more grain if the heat units and water supply are available. For example, a 120-day hybrid will use approximately 2 inches more water per year than a 110-day hybrid. The difference in water use is due to total days of water use, not a difference in daily ET (see Table 1). If a long-season hybrid and a short-season hybrid are both at full cover (LAI above 2.7), the daily ET rate will be the same for both until the short-season hybrid begins to mature. The shorter season hybrid begins to mature sooner, reducing drying costs and allowing for an earlier harvest.
A study in the Texas Panhandle in 1995 showed a similar water use efficiency (bushels/acre-inch) for a 98-day hybrid and a 115-day hybrid (Howell, et al. 1998). The shorter season hybrid did use 5 inches less water, but it also yielded 30 fewer bushels. The study also showed that the daily ET rates were essentially the same until the short-season hybrid began to mature. This finding demonstrates that short-season hybrids need just as much pump capacity to keep up with ET rates as a long-season hybrid during most of the growing season.
|Table 1. Reported differences of yield, ET and water use efficiency between a 98-day hybrid and a 115-day hybrid from a study conducted in the Texas Panhandle. (Howell, et al. 1998)|
|98-day hybrid||115-day hybrid|
|Grain yield (bu/ac)||180||211|
|ET, emergency to maturity (inches)||26.5||31.6|
|Water use efficiency bu/ac-in||6.8||6.7|
Selecting a shorter season hybrid does reduce seasonal ET; however, yield potential will be reduced as well and the grain produced per unit of ET is essentially the same for either situation. In most cases it is more profitable to plant a hybrid with a typical maturity for your area and allow the moisture (or lack of) to reduce your yield. If the drought subsides and you receive ample late season precipitation, the long-season hybrid will use the additional moisture and produce more grain. If you plant a shorter season hybrid, you are limiting yield potential even if moisture is available.
Source: Howell, T.A., J.A. Tolk, A.D. Schneider, and S.R. Evett. 1998. Evapotranspiration, Yield, and Water Use Efficiency of Corn Hybrids Differing in Maturity. Agronomy Journal, Vol. 90, January-February 1998.
UNL Water/Cropping Systems Extension Educator
Extension Irrigation Specialist, Northeast REC