Crop Water Use in Corn – What Do We Know?

When traveling across the state, many corn fields show well-developed tassels. Hopefully, closer field inspection also finds emerged silks that are needed to pollinate ovules on the developing ears (Figure 1). On July 10, USDA reported 7% of the Ohio Corn silking. In the July 18 report, the percentage of silked corn fields is expected to be much higher as a lot of crop progress can occur in a week if adequate conditions exist (e.g., water, temperatures).

Figure 1. Corn fields approaching or at pollination across the state of Ohio. Pictures: Osler Ortez.

Water availability can be a critical challenge at this point in the season. Crop water use is a significant factor in obtaining high yields (Figure 2). A 200-bushel corn yield is estimated to utilize about 20 inches of water throughout the season. Crop water use consists of two components: water losses from the soil (evaporation) and water losses from the crop (transpiration), which can occur simultaneously. If crop canopies have closed, the primary route of crop water use is through transpiration (direct losses of water from soil evaporation are much lower as most light energy is absorbed by the canopy).

Figure 2. Relationship between corn yields and evapotranspiration. Source: https://crops.extension.iastate.edu/cropnews/2017/06/corn-water-use-and-evapotranspiration

Yield components in corn are determined during both vegetative and reproductive stages. Corn requirements vary depending on the development stage, with corn's water use reaching its peak daily need during the pollination period (when tassels are developed and silks are receptive to pollen). Hence, water availability at the tasseling and silking stage is critical. Previous research has shown that corn at tasseling/silking can use 0.28 to 0.30 inches of water per day (Table 1), which is ~2 inches per week.

Table 1. Water use rates for corn at different growth and developmental stages using the leaf collar method.

Stage

Water Use Rate
Inches per day

Prior to 12-leaf stage (<V12)

<0.20

12-leaf stage (V12)

0.24

Early tassel (VT)

0.28

Silking (R1)

0.30

Blister (R2)

0.26

Milk (R3)

0.24

Dent (R5)

0.20


Any water deficits or drought issues can affect the crop in multiple ways that at the end would reduce crop yields. If drought conditions are a concern, Drought-Tolerant Corn Hybrids can be a resource to mitigate some of that. Research in Ohio on drought tolerant corn can be found here:

AGF 516 - Drought-Tolerant Corn Hybrids: A Risk Management Tool for Ohio? Part 1

AGF 517 - Drought-Tolerant Corn Hybrids: A Risk Management Tool for Ohio? Part 2

On the other hand, if good moisture conditions are available for your crop, that is excellent news. However, be aware that some pests and diseases may be benefitted too. Monitoring fields and making timely decisions will be essential to keep any potential issues under control. If there is too much water, that can be a concern too though flooding during grain fill stages typically results in less yield loss than flooding during early vegetative stages.

References

Licht, M., and Archontoulis, S. 2017. Corn Water Use and Evapotranspiration. Integrated Crop Management News, Iowa State University Extension and Outreach. https://crops.extension.iastate.edu/cropnews/2017/06/corn-water-use-and-evapotranspiration

Lindsey, A., Thomison, P., Minyo, R., and Geyer, A. 2014. Drought-Tolerant Corn Hybrids: What is the Fit for Ohio?. C.O.R.N. Newsletter. https://agcrops.osu.edu/newsletter/corn-newsletter/2014-40/drought-tolerant-corn-hybrids-what-fit-ohio

Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.