Fortunately, our livestock based agriculture means we have many ways to salvage corn. If you’re faced with a crop of drought-stunted corn, consider some of the ideas below in managing this kind of crop.
Assessing the situation
The condition and yield potential of the crop should be monitored as the season progresses. This allows you to begin to consider other options for harvesting or meeting feed needs well in advance. Usually are short term in nature and the main effects are reduced grain and silage yields. In the most severe cases, however, drought stress can result in the need for an early salvage harvest for silage.
As the drought progresses, consider identifying ways to market your crop as silage, since returns are often greater than harvesting for grain. Check with your Crop Insurance representative or FSA office before harvesting the crop. Livestock producers should begin to assess winter feed inventories and explore opportunities for purchasing corn silage, western hay, or other forages.
Estimating yield potential of drought stressed corn
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. A rough estimate of the potential grain yield can be obtained using the kernel count method (see box below).
An estimate of wet (70 percent moisture) silage yield is about one ton per foot of height of corn without ears or poorly pollinated ears. This estimate may be high on very short (1 to 3 foot 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 0 to 50 bushel per acre or so.
For fields that have a good stand and are exhibit leaf rolling only during the day, there may still be good yield potential if the drought has been relieved by mid August.
Fields that experience drought well into August often will have lost a significant amount of their top end yield potential, perhaps 50 bushels per acre or more, even if conditions would be perfect from then until the end of the season.
Fields following soybeans or hay (not double cropped) often will tolerate the drought much better than fields following corn.
Salvaging drought stressed corn for silage
Corn has a remarkable ability to recover from drought stress, so delay a salvage harvest as long as possible. If the corn has tasseled and leaves cease to unroll at night and the tops start to brown out, the plants are probably not going to recover.
As browning of the crop continues, the forage quality will decline as the plants are using stored carbohydrates in the leaves and stalk to sustain themselves. If half the leaves were dead or dying it would be a good candidate for evaluating for silage harvest. At this point you should probably consider harvesting it for silage. Delaying harvest will reduce yield and quality and reduce the potential for planting a second crop.
Moisture testing is essential in these situations because corn is often wetter than it appears. If the forage is extremely wet (greater than 75 to 80 percent), then harvest should likely be delayed since this will result in seepage and a loss in silage quality.
Excessively wet silage like this has caused silos to collapse in some situations. Avoid chopping when the moisture is below 60 to 63 percent. If a drought ending rain occurs just before a planned salvage harvest, the moisture content of drought stressed, immature corn will increase, so harvest should be delayed in this situation.
Potential silage quality
Drought stunted corn will likely be higher in protein and some minerals than normal silage and lower in energy. The fiber levels are often higher in silage with less grain content but often the digestibility of that fiber is higher.
Forage quality differences are less if drought stunted corn develops some grain and is harvested near normal maturity. Without grain, starch concentrations will be very low.
When drought stunted corn is allowed to reach maturity and has some grain formation, forage quality will be impacted as well. When feeding drought stressed corn silage, be sure to get a forage test so that you can have rations adjusted effectively.
Drought-stunted, low grain corn silage also tends to be less dense- as a result; truck and silo capacities are often lower. Because of the lower grain content, drought stressed corn will be less responsive to kernel processing.
Nitrate concerns
Elevated nitrate concentrations are common in drought stressed corn crops. The potential is greatest for high nitrate levels in young plants, especially in the stalks and especially in heavily manured fields. Typically elevated nitrate levels are common in Pennsylvania but only occasionally at toxic levels. The potential is generally greatest for three to four days following a drought ending rain, but can be a problem anytime.
Leaving a 12-inch stubble in the field can reduce nitrates but this would also reduce yields and may not be desirable unless a forage test confirms the presence of high levels of nitrates. Because the nitrate potential can be reduced through ensiling, grazing and green chopping drought stressed corn are not desirable harvesting alternatives.
Even though nitrates are a concern, experience from testing and feeding past drought stricken crops indicates that excessive nitrate levels (greater than 1700 ppm NO3-N) are not that common and that with good management most nitrate related problems can be avoided with careful feeding management.
High nitrates can contribute to animal feed problems and deadly silo gas. Be especially cautious when filling silos with these suspect crops. Silo gas is produced during the first four to five days after silo filling when nitrates are converted to oxides of N (NO, NO2, and N2O4).
Of these, NO2, or nitrogen dioxide is the most common and is a yellow orange gas with a bleach-like odor. This gas is heavier than air and can form in the silo and then escape down the unloading chute into the barn, endangering both humans and cattle.
Exposure to silo gas can cause immediate death or severe lung injury due to the formation of nitric acid in the lung. To avoid exposure to silo gases, keep the door between the feed room and the barn closed, ventilate the silo by running the blower for at least 20 minutes before entering the silo and learn to recognize the bleach –like odor and yellow-orange color as signals of silo gas.
Pricing silage
Values of drought stunted corn will vary but in one recent scenario of prices, drought stunted corn with few ears was worth about 91 percent of normal silage, while drought stunted corn with no ears was worth only 66 percent of the value of normal corn silage. When pricing corn silage be sure to consider harvesting and hauling costs as well as the moisture content of the silage.
Standability
Frequently drought stressed grain crops will have lower than average resistance to stalk rots. This results because the plant uses carbohydrates reserves from the stalk to fill the grain during periods of late season stress. It may pay to scout fields during the early fall to determine if any are at risk for stalk lodging problems.
Typical symptoms will include some broken stalks and light and hollow stalks pink coloration in the inside of the stalk or some discoloration at the nodes inside the stalk. Fields with these symptoms would be good candidates for early harvest.
Economics of harvesting
Usually is still worthwhile to harvested drought stricken corn, but on some of the most drought stressed fields it may be a tossup. The variable costs such as fuel, labor and repairs, associated with chopping a light corn crop are in the $15 to $25 per acre range, so if producers can harvest at least one ton of silage per acre valued at perhaps $20 per ton they will break even. To achieve this yield may require corn about two feet tall. FG
Written by Greg W. Roth, Professor of Agronomy, Department of Crop and Soil Sciences, Pennsylvania State University
