Many areas of Pennsylvania are experiencing a severe drought due to the lack of rain since late May. Corn growth has stopped in many areas and in the worst areas corn fields are beginning to dry up. Other grain and forage crops are drought-stressed as well.

Although we can do little to change the weather, we can make some management decisions now to help minimize losses and salvage as much from a bad situation as possible. Some key questions that silage and grain producers should consider are listed below.

What should be done now?
There are several things that should be initiated immediately. The condition and yield potential of the crop should be assessed. Dairy and livestock producers may want to collect a forage sample to assess moisture, forage quality and nitrate levels. Grain farmers may want to begin identify ways to market their crop as silage. All producers should be check with their crop insurance or FSA representative before harvesting the crop.

What is the yield potential of the field?
This will be variable depending on the severity of the drought. For corn fields that are losing leaves and not unrolling at night, the yield potential will be likely low – from 0-50 bushels per acre or so. For fields that have a good stand and are exhibiting leaf rolling only during the day, there may still be good yield potential if the drought is broken soon. Even many of these fields have lost a significant amount of their top end yield potential, perhaps 50 bushels per acre or more, if conditions would be perfect until the end of the season.

When should you decide to salvage the crop and harvest for silage?
When 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 itself. Producers should probably consider harvesting it for silage.

Delaying harvest will reduce yield and quality and reduce the potential for planting a second crop. The moisture content may be higher than desired, so a dry feedstuff like chopped ear corn or hay may need to be to adjust the silage moisture and energy for good fermentation. If the forage is extremely wet (greater than 75 to 80 percent), then harvest should likely be delayed. No definitive guidelines are available, but I would suggest that if half the leaves are dead or dying it would be a good candidate for evaluating for silage harvest.

What is the yield potential of this type of crop?
A rough 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 (one to three feet tall) crops.

What kind of silage will this crop produce?
This crop will likely be higher in protein than normal silage and lower in energy.  A ballpark estimate of silage quality might be  an NEL of 0.60 to 0.64 and a crude protein of 9 to 12 percent. Some preharvest forage testing may be appropriate to assess the quality, the level of nitrates, and the potential use of the forage. If it were to rain, fields that have some recovery potential could produce some good-quality silage. In these drought stressed crops that recover the ear to stover ratio will be good and the fiber digestibility is usually high.

Are nitrates a concern in this kind of crop?
Yes. The potential is greatest for high nitrate levels in young plants, especially in the stalks and especially in heavily manured fields. The potential is generally greatest for three to four days following a drought-ending rain but can be a problem any time. High nitrates can contribute to animal feed problems and deadly silo gas.

Producers should be especially cautious when filling silos with these suspect crops. Nitrates can be reduced by leaving a 12-inch stubble in the field – this would reduce yields, however, and may not be advisable unless a forage test confirms the presence of nitrates. Because the nitrate potential can be reduced through ensiling, grazing and green chopping drought stressed corn are less desirable harvesting alternatives.

Is it worth harvesting these crops?

On some fields it may be a toss-up. 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.

What should grain producers be assessing?
Grain producers in the worst areas may need to be identifying silage markets for their crop. This will help to alleviate potential feed shortages and provide a market for drought damaged corn crops that will produce little grain. They could also be considering plans for establishing other fall forage crops – there may be a significant market for these crops this fall.

What crops are a potential for replanting following corn?
This will depend on the herbicide program used for corn. Generally, sorghum-sudan grass may be the most viable option if planting can be achieved by early August. Small grains or soybeans are also alternatives in some situations, but the dry weather may make atrazine carryover high which will damage the more sensitive crops like oats and soybeans.

Check herbicide labels for replanting restrictions. If corn fields are unsatisfactory for planting fall forage crops, producers may want to consider no-tilling into small grain stubble fields – although these soils may be hard until it rains again.  FG

—From Penn State Field Crop newsletter, Vol. 12, No. 19

Greg Roth
Associate Professor
Department of Agronomy
Penn State University