Harvesting drought-stressed corn a challenge

A record May freeze and a prolonged planting season drought, caused late planting or re-planting in as much as 25 percent of the corn crop in the Southeast.

With corn acreage up across the region, this will leave large acreages of corn in the field later than normal, typically at a time when drought is more common, and creating many management decisions for growers.

For many growers, the early season drought lingered throughout much of the corn growing season, pushing large acreages into abandonment, especially dryland corn in the lower Southeast.

Harvesting drought-stressed corn creates its own challenges, but what to do with this low-quality grain is a bigger dilemma for most growers.

Since most of this grain will go for livestock feed, it is important to check corn kernel moisture from different fields and harvest the one nearest to optimum first. Corn with higher than desirable moisture should be put on top of the storage stack, since it may be less of a problem when fed out during the winter months.

Growers should be cautious about over-processing high-moisture, late-harvested corn, because the kernels can become too fine and cause digestive problems in livestock.

In the Midwest, corn growers have used bacterial inoculants to build lactic acid in stored corn and propionic acid. Both require precise application and timing and may not be cost effective for some Southeastern growers.

University of Kentucky Grain Specialist Chad Lee says drought also produces some other management strategies that growers should consider when harvesting corn. He says there are some valid reasons to go ahead and harvest drought stressed corn for silage:

Drought-stressed corn that is unlikely to resume growth should be ensiled. Harvesting drought-stressed corn should result in 85 to 100 percent of the normal net energy content. This corn may contain more crude protein than corn harvested under less stressful conditions.

This corn may contain high nitrate concentrations, especially in the lower third of the plant. Growers should remember nitrates will accumulate in the lower part of the stalk, so the cutting height should be at least 10 inches for both silage and hay.

The ensiled corn should not be fed until at least three weeks after the silo has been filled.

Lee also says there are some guidelines to follow to determine when to harvest drought-stressed corn for silage:

• It’s ideal to harvest when the milk line is one-half to three-fourths down the kernel, which occurs during dent stage.

• Leaves above the ear should be mostly green.

• Dry matter content should be near 35 percent, slightly less for storage in bunkers, trenches, or stacks.

• In drought-stressed situations, the corn kernels may be small, but the milk line will develop quickly.

• Silage should be chopped into lengths of approximately three eighths to one half inch.

Especially in the Southeast, where early season drought was so severe, smaller-than-normal corn kernels will likely be common, reflecting canopy conditions that deteriorated before kernels were fully filled. Though reducing the marketability of this grain in most cases, kernel protein actually is higher because this reduces the dilution of protein by starch. This is a key reason drought stressed corn can be very good source of livestock feed.

Drought-stressed corn is likely to produce reduced numbers of kernels, hence yield will be reduced. However, kernel size and weight may not be reduced.

To make the most efficient harvest decisions, growers need to monitor kernel development to determine the value of drought-stressed corn before making decisions on harvesting, storing or even abandoning of fields.

When drought causes grain fill to end early, due to canopy deterioration, stalk quality can be compromised. This happens most often when leaves curl during extreme drought and in fields with highest yield potential (400 or so kernels per stalk).

In late planted fields, growers may not see this until times when corn is traditionally already harvested.

Despite the high cost of diesel fuel to pump water, in many cases late season irrigation may pay off in maintaining both yield and quality of drought-stressed corn.

Determining the value of drought-stressed and damaged corn can be tricky. Greg Roth, a professor and long-time corn expert at Penn State University, says yields will be variable depending on the timing and severity of the drought. Drought stress is most severe when it occurs within two weeks before or after silking.

Roth says an estimate of wet (70-percent moisture) silage yield is about 1 ton per foot of height of corn without ears or poorly pollinated ears. This estimate may be high on very short (1 to 3 feet tall) crops. For corn fields with no ear development that are losing leaves and not unrolling at night, the yield potential will be likely low- from zero to 50 bushels per acre or so. For fields that have a good stand and exhibit leaf rolling only during the day, there may still be good yield potential if the drought is relieved early enough.

University of Georgia Small Grains Specialist Dewey Lee agrees that in some parts of the Southeast, the best option for drought damaged corn is to chop it for silage. Whether the crop is a total loss or not sometimes depends on its proximity to dairy or other livestock operations.

Grazing or green chopping drought-stressed corn is not recommended because the risk of nitrate-nitrite toxicity to animals is too great. Nitrates used to fertilize corn aren’t taken up by the plant in drought situations. However, if corn is left for grazing or early chopping, and it gets a rain shower, the plant can take up too much of the available nitrogen, and subsequently this can cause problems when livestock graze the damaged corn or are fed silage that has gotten rain.

Ruminants consuming nitrates reduce them to nitrites which are absorbed and can cause toxicosis. Moderate levels of nitrite can be tolerated, but high concentrations overwhelm the animals' system, causing a decreased ability of the blood to carry oxygen.

The key to managing drought-damaged corn is to know the value of what is left in the field, what the options are for the crop and when to pull the trigger to make the best shot at getting out with the least economic damage.

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