By Ignacio Ciampitti, Eric Adee, Krag Roozeboom, Alan Schlegel and Stu Duncan

In recent years, drought conditions have raised questions about the utilization of corn as the main crop for maximizing yield production per unit of available water in dryland environments.

Non-transgenic, conventionally bred, “drought-tolerant” (DT) corn hybrids from Pioneer and Syngenta were released to the market with the expectation of increasing corn production in water-limited regions. Monsanto also released biotech transgenic DT hybrids.

Overall, the information from seed companies indicates that DT hybrids could provide from 2- to more than 15% yield increase over “competitor hybrids” in non-limiting and water-limiting environments, respectively.

Kansas State University research conducted over the 2012-15 growing seasons across the state has recently been summarized, and this summary is available in a KSU Research and Extension publication (discussed at the end of this article). The objective of this article is to present an overview of the DT vs. non-DT responses to management practices such as plant population and irrigation.

The information below is intended to provide some guidance to farmers, consultants, and agronomists in making the right decision for selecting corn hybrids. In addition, we hope to develop a better understanding of the kinds of environments in which DT hybrids could be most likely to result in a yield benefit. These hybrids are generally targeted for water-limited environments in the western Great Plains.

Results

Our research compared DT hybrids from diverse companies with a standard non-DT counterpart of similar maturity. The tests also evaluated the yield response to varying plant population and irrigation levels.

At the plant scale, our analysis did not reveal any change in the plant response to plant population between DT and non-DT hybrids. This indicates no need to change plant population when using DT hybrids. This conclusion was briefly introduced in an article on corn seeding rates in the eUpdate dated March 14, 2014 (Agronomy eUpdate 445).

We also analyzed yields at the plot level for DT vs. comparable non-DT hybrids with similar maturity. The information presented in the figure below (Fig. 1) depicts the association of the yields for the DT vs. non-DT corn hybrids: Yellow points = research plots (2012-2013); blue points = on-farm plots; green points = 2014; red points = 2015 growing season plots.

Overall, the analysis found a yield benefit of 3 percent for DT vs. non-DT hybrids under diverse environments and stress conditions across Kansas during the 2012-2015 seasons. In absolute terms, the yield advantage of using DT hybrids was around 5 bushels per acre compared to the non-DT material.

Similar yield trends were observed in research plots and on-farm demonstration plots. A great proportion of DT and non-DT yields were similar — within a 5% confidence interval as highlighted in Figure 1 — except in low-yielding and high-yielding environments. In low yielding-environments, DT out-yielded non-DT corn hybrids more often compared to the situation in higher-yield environments.

Yield Environment Analysis

The analysis of information across diverse yield environments allows us to more clearly understand where there would be a yield advantage from planting DT hybrids. It is clear from Figure 2 that the yield advantage of DT corn hybrids increases as the yield potential of the crop decreases.

This graph shows that there is basically no yield difference between DT and non-DT hybrids when yields are around 170 bushels per acre or greater. The yield advantage for DT hybrids gradually increases as the yield of the regular hybrids decreases from 170 bushels per acre.

It is important to note however, that these are generalized relationships, and that there are varied responses at each yield level. Some individual points show no difference between DT vs. non-DT hybrids at yields around 100 bushels per acre. Other points show a 30-bushel-per-acre yield advantage for non-DT hybrids at 160 to 170 bushels per acre, and still others show a 60-bushel-per-acre yield advantage for DT hybrids when non-DT hybrid yields were near 70 bushels per acre.

On the opposite side of the yield environments, under high yield environments (>220 bushel-per-acre), individual points show a 30 to 60-bushel-per acre yield advantage for non-DT hybrids when DT hybrid yields were above 220 bushels per acre. How individual hybrids respond to a specific environment is influenced by a number of factors, including the timing and duration of the stress.

One more technical clarification is important to note. The linear response and plateau (LRP) function model fitted in Figure 2 (adjusted to the 2012-2013 data), presented an R2 of 0.26 units, which can be interpreted to indicate that this model is accounting for only slightly more than one-fourth of the total variation presented in the data.

Even when including observations from studies conducted in the last two years (2014-15), the trend observed in the DT yield advantage versus the non-DT yield values (Fig. 2) is not being modified. From all these years of data collection and analysis we can conclude that there are many management factors involved in the yield results, which makes it difficult to separate out the effect of hybrid alone.

Still, we need to be cautious using and interpreting this information. More experiments and research data need to be collected, and a deeper understanding is needed to more properly analyze the main causes of the yield differences of DT vs. non-DT corn genotypes. Potential interpretations offered for the yield advantage for the DT corn hybrids in certain environments are:

• Slower vegetative growth, saving water for reproductive stages (stress avoidance)
• Greater root biomass with superior water uptake
• Differential regulation in the stomata opening, controlling water and CO2 exchange processes
• Other potential physiological modifications

For More Information

A publication titled Drought-tolerant corn hybrids: Yield benefits was published by Kansas State Research and Extension in 2017. This publication was supported by Kansas Corn Commission.

This publication presents research information conducted by KSU Research and Extension to evaluate drought-tolerant hybrids in a wide range of production environments. You can view the publication at https://www.bookstore.ksre.ksu.edu/pubs/MF3338.pdf