January 21, 2022

Impact of Limited Irrigation on Food Grade Corn - 2021

Trial Objective 

• Producing corn suitable for snack food production can be more difficult than producing commodity corn suitable for broader markets. 

• Selecting a corn product for food grade production may be limited to an approved list and often the premiums received for the grain is impacted by kernel characteristics important to snack food producers.  

• This trial was developed to better understand food-grade corn products in the local area and how the products respond to limited water environments in terms of yield potential and kernel quality. 

• If lowering irrigation amounts has little impact on yield potential and kernel quality, that information could make it an easier decision to try reducing irrigation even to corn destined for a high-quality end-use.  

Experiment/Trial Design 

• This trial was set up as a split plot with irrigation as the whole plot-sub plot. Each treatment was replicated four times. 

• Twelve corn products with either a food grade designation or listed as having high potential for a food grade designation were selected for the study. 

• Irrigation was applied using a variable rate irrigation system on a linear move sprinkler programmed to provide 100%, 80%, or 60% of the crop water needed per pass.

• The 100% irrigation treatment was managed conservatively so water was not over applied to the trial. A nearby moisture probe was used as well as hand probing to verify water treatments were completed correctly. 

• On the season, the irrigation amounts were as follows (Figure 1): 
  • 100%: 6.0 inches 
  • 80%: 4.8 inches 
  • 60%: 3.6 inches 

• Precipitation accumulation (Figure 1) was 15.25 inches on the growing season, but there was a long stretch from July 17th to August 18th with almost no precipitation. This occurred during the critical time of pollination and early grain fill, so a lack of water may have led to yield reducing stress. This was apparent in other trials at the Gothenburg Learning Center (GLC) that had dryland treatments compared to irrigated treatments. 

• This trial was strip-tilled on 4/26/2021 and a base fertilizer application of 27 lbs of nitrogen (N/acre), 60 lbs of phosphorus (P/acre), 25 lbs of sulfur (S/acre), and 0.25 lbs of zinc (Zn/acre) was strip-till applied. 

• An additional application of 100 lbs N/acre was broadcast with a streamer bar on 5/5/2021 and 60 lbs N/acre was applied with 360 Y-DROP® on 6/15/2021.  

• Plots were combine-harvested. Grain moisture content, test weight, and total weight were determined. 

• Additional information was gathered on kernel quality by hand-harvesting five ears randomly from row 1 of each plot, and the ears were used to rate kernel quality. Horneous endosperm (HE), crown, and dent ratings were given to each plot and recorded for analysis. 

Understanding the Results 

Corn Product Yield

Table 1. Average corn yields by product and irrigation treatment and averaged across irrigation treatments at the Bayer Water Utilization Learning Center, Gothenburg, NE (2021). 

• The average corn yield across irrigation environments (Figure 2) did not significantly change although there was a trend toward lower average yields as irrigation amounts were reduced. 

• When yields were evaluated by corn product (Table 1), there were differences between corn products. 

• Minor yield and yield stability variation was observed in the corn products when the irrigation amount was reduced, but the differences were not statistically significant.   

Grain Characteristics 

• Some grain characteristics are difficult to evaluate with the combine, but they are important to snack food end users. 

• The dent rating (Figures 3 and 4), crown rating (Figure 5), and horneous endosperm rating (Figure 6) were evaluated with hand harvested ears on a rating scale from 1 to 9 where 1 is the most desirable. 

Table 2. Grain characteristic measurements and ratings by irrigation treatment at the Bayer Water Utilization Learning Center, Gothenburg, NE (2021).

• Like the average yield results of this trial, the irrigation treatment had no impact on characteristics like grain moisture and test weight at harvest. There was only about a 0.5% change in grain moisture across treatments and only a little more than a pound per bushel of variation in test weight. 

• The crown, dent and HE ratings were also not significantly changed by the irrigation treatment indicating that the amount of irrigation water did not impact processor acceptability for the rated characteristics. 

Table 3. Grain characteristic measurements and rating by products at the Bayer Water Utilization Learning Center, Gothenburg, NE (2021). 

• Grain moisture was higher in the longer maturity products at harvest with the 114 relative maturity (RM) through 116 RM products in the 16-17% range while all products 113RM and under were 15% or lower. 

• Test weight did not differ significantly between corn products. 

• The crown dent and HE ratings differed between corn products with all ratings 6 or lower showing products of consistent high quality for food grade uses. 

Key Learnings  

• Irrigation did not significantly impact corn yield or grain quality characteristics at the irrigation levels present in this trial. 

• This indicates that lowering irrigation levels across these corn products, if necessary, may be possible without impacting the grain quality characteristics. 

• However, there are limits to this, at least on the yield side, as the 2021 dryland treatments at the Gothenburg Learning Center in similar research yielded significantly lower than the treatments with six inches of irrigation or more. 

• Adding dryland or very limited irrigation treatment to this test could be interesting to see if there is a point where grain quality for food-grade purposes starts to drop off. 

• This research continues as we strive to increase water use efficiency by decreasing the total amount of water applied while maintaining high yield potential and food grade corn quality. 

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