Rainout Shelter Comparison of DroughtGard® Hybrids and AQUAmax® Corn Products
To study the yield performance and the value of applying additional irrigation water to a DroughtGard® Hybrids corn product and an AQUAmax® corn product in water-limited to full-irrigation environments.
Research Site Details:
A 114 RM DroughtGard® Hybrids corn product and a 111 RM AQUAmax® corn product were planted in four unique irrigation environments with 4, 8, 12, and 16 inches of applied water.
The Rainout Shelter is a highly controlled environment for researching the impact of irrigation water on crops.
The shelter is a 160 ft by 80 ft building on rails that can be moved to cover the corn plots to restrict rainfall, and can be moved off the plots during dry weather so the crop gets otherwise normal conditions.
Starting soil moisture was near field capacity, which was provided by irrigation and rainfall during spring rain events.
Fertilizer applied was 200 lb nitrogen/acre as 32-0-0, 40 lb phosphorus/acre as 10-34-0, 25 lb sulfur/acre as 12-0-0-26S, and 0.5 lb zinc/acre as 7-0-0-9Zn.
Weeds were controlled in the plots and no insecticide or fungicide were applied.
Irrigation treatments were applied using surface drip irrigation targeting the growth stages when the irrigation would provide the most yield. The 4-inch irrigation treatment was targeted at the V16-R3 growth stage to help the plants pollinate and set kernels.
Understanding the Results
The DroughtGard® Hybrids corn product had higher yields across all irrigation environments when compared to the AQUAmax® corn product, which provided an average yield advantage of 22 bu/acre (Figure 2).
We also saw a yield advantage with a DroughtGard® Hybrids corn product in a 2016 trial in the Rainout Shelter with irrigation environments spanning 4, 7, and 10 inches of applied irrigation.
Corn yield increased with each 4-inch increase in irrigation. The 16-inch treatment yielded higher on average, but this result was not significant, indicating that the 12- and 16-inch treatments were nearing the evapotranspiration needs of the crop (Figure 3).
As expected, increased irrigation produced higher yields, but the rate of the yield increase per inch of water applied decreased incrementally.
The 4-inch treatment returned a 39 bu increase/inch of water with the assumption that yields would be 0 bu/acre with no irrigation because the corn would not pollinate with only utilizing stored soil moisture (Figure 4).
If the bu/acre increase per inch of water were monetized using a $3.30/bu corn price, this would equate to a $128.70, $50.49, $23.10, and $6.60 return on investment for the 4-, 8-, 12-, and 16-inch treatments, respectively.
This is a unique look at what the value of irrigation water or potential precipitation can be in water-stressed environments, and, depending on application costs,these results indicate where returns diminish to the point that it no longer pays to add extra irrigation water.
What Does This Mean For Your Farm?
Understanding corn product responses to irrigation water is an important part of managing irrigation to limit water use while maximizing profits (see table 1).
The Rainout Shelter provides a great tool to help understand corn products and take a detailed look at how water application rates impact yield.