Drought And Heat Effects On Corn Production

Jul 10, 2017

By Jonathan Kleinjan www.iGrow.org website

Nearly every season in South Dakota there are periods of hot, dry weather in at least part of the state. If this hot and dry weather occurs during corn pollination and fertilization, negative effects on yield may be substantial. Yields may be reduced at any point in the growing season when water usage exceeds supply. Early season drought stress may reduce total plant size, ear size, and the number of rows of kernels on the ear. However, as a rule, drought stress in the vegetative growth stage (up to V12) has minimal effect on final yield (Lauer, 2006).

Pollination & Fertilization

Corn is the most susceptible to stress during pollination and fertilization, with daily potential yield losses of 3 – 8%. This period actually begins about 2 weeks prior to silk emergence, with a potential loss of up to 4% per day. During silking and pollen shed, the losses can be as high as 8% per day, depending on the severity of the stress. In the 2 weeks following silking, losses can be as high as 6% a day if the stress continues (Nielsen, 1996).

Pollination for a corn plant is the process of conveying the pollen from the tassel to the ear silks. The germination of pollen grains on the silks results in a pollen tube that transfers genetic material to the respective ovules on the ear. The fertilized ovule will then become a kernel of corn (Nielsen, 2016). Drought and heat stress may cause problems with this process by 1) slowing silk emergence while accelerating pollen shed, 2) dessicating silks to the point where they are no longer viable, and 3) killing pollen directly. All of these issues may cause reduced kernel set or even a blank ear in extreme cases.

While growers worry about the effects of extreme heat on the pollination process, the fact is that high temperatures should not severely affect pollination if there is adequate soil moisture. Pollen shed occurs primarily in the morning when temperatures are relatively cool and the pollination process occurs over an extended period of time, with fresh pollen available each morning. In addition, one corn plant can provide enough pollen to fertilize ten other plants, which helps to provide a natural buffer against stressful conditions. Producers who wish to obtain an early assessment of pollination can use the Ear Shake Technique described by Dr. Bob Nielsen (2016). Late rainfall events will not correct the damage caused by poor pollination and fertilization.

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Video: Spring 2026 weather outlook for Wisconsin; What an early-arriving El Niño could mean

Northeast Wisconsin is a small corner of the world, but our weather is still affected by what happens across the globe.

That includes in the equatorial Pacific, where changes between El Niño and La Niña play a role in the weather here -- and boy, have there been some abrupt changes as of late.

El Niño and La Niña are the two phases of what is collectively known as the El Niño Southern Oscillation, or ENSO for short. These are the swings back and forth from unusually warm to unusually cold sea surface temperatures in the Pacific Ocean along the equator.

Since this past September, we have been in a weak La Niña, which means water temperatures near the Eastern Pacific equator have been cooler than usual. That's where we're at right now.

Even last fall, the long-term outlook suggested a return to neutral conditions by spring and potentially El Niño conditions by summer.

But there are some signs this may be happening faster than usual, which could accelerate the onset of El Niño.

Over the last few weeks, unusually strong bursts of westerly winds farther west in the Pacific -- where sea surface temperatures are warmer than average -- have been observed. There is a chance that this could accelerate the warming of those eastern Pacific waters and potentially push us into El Niño sooner than usual.

If we do enter El Nino by spring -- which we'll define as the period of March, April and May -- there are some long-term correlations with our weather here in Northeast Wisconsin.

Looking at a map of anomalously warm weather, most of the upper Great Lakes doesn't show a strong correlation, but in general, the northern tiers of the United States do tend to lean to that direction.

The stronger correlation is with precipitation. El Niño conditions in spring have historically come with a higher risk of very dry weather over that time frame, so this will definitely be a transition we'll have to watch closely as we move out of winter.