DroughtSilage

Utilizing Drought Damaged Corn

Beef Consultant

Jeff Heldt, Ph.D., PAS

The drought of 2002 has left us all scratching our heads on what to do with our field crops that have received very little moisture this year. I have put together a summary of some key issues available on the web and through various publications to help determine how to best use drought damaged corn to get the most out of the hard work and expenses it took to put the crop into the ground.

The moisture content of early harvested/stressed corn can be >70%, which is far above the recommended range of 60% to 65%. Plant material ensiled at moisture content above 70% will cause excessive seepage. Seepage losses occur at an increasing rate with higher moisture contents, Excessively wet silage often undergoes an undesirable and less efficient fermentation, with greater dry matter losses, greater chances of clostridial contamination, formation of butyric acid fermentation end products (causes palatability concerns), and more rapid deterioration at feed out. Dry grains or chopped hay can be blended with excessively wet silage to ‘soak up the excess water, however, it requires a lot of added substrate, and thorough blending to achieve the desired result. For example, to bring chopped immature corn of a moisture contend of about 80% down to about 65% moisture, it would require 400 to 500 lbs of dry shelled corn per ton of chopped wet corn. For best results, this grain should be coarsely ground and thoroughly blended with the chopped corn as the silo is being filled. This is just not a practical solution for most producers, because silos should be filled and packed quickly to minimize extended exposure to air. Alternatively, you can wait for the moisture content to drop. However, grain development typically guides the whole plant moisture decisions. Without grain present, this becomes more of a challenge. If all plants survive, but are barren, it is best to wait until leaves begin to dry in the fall. If only some stalks form grain, or some plants die in mid- summer, determining the average moisture content of the remaining combination of mixed moisture content plant material is very difficult. The best method is to actually chop some of the material and get a moisture test on the mixed material.

The ideal method for determining moisture is to use a Koster crop tester or microwave to determine whole plant dry matter. However as a visual guide, if the corn has any grain, kernel milk line can be used to determine the proper time to chop. When the milk line is 1/3 of the way down to the kernel tip, it’s ready for the bunker. When the milk line is 2/3 to 3/4 of the way down to the kernel tip, whole plant moisture is 63 to 68%. Whole plant moisture is 50 to 60% as the black layer begins to appear at the tip of the kernel and chopping should be underway for sealed structures. Green, barren stalks will contain 75 to 90% moisture. If weather remains hot and dry, the moisture of the plant can drop quite rapidly. However, if rains follow, the plants may remain green until a frost in northern environments. Under these conditions, there is a general tendency to ensile the crop too wet. Therefore, on a chopped sample, use a microwave oven to get an accurate measure of whole plant moisture.

Drought obviously affects yields, but how much? If the corn has little or no grain, then a rough pre-harvest estimate may be made by assuming that 1 ton of 70% moisture silage may be obtained for each foot of plant height (excluding the tassel). Therefore, corn that is only 3 to 4 feet tall might yield 3 to 4 tons of 70% moisture corn silage. Generally speaking you will se a 50-90% reduction from normal silage yields.

Since fermentation by bacteria relies on simple sugars as found in the leaves and stalks of the corn plants and not on starch as found in the corn kernel, fermentation of stressed few-eared silage should be equal to well-eared corn silage. However, due to the hot temperatures and added stress on crops, it’s likely that yeast and fungus found on the corn plants will be elevated. These yeast are harmful to the fermentation process since they consume the lactic acid produced by the beneficial bacteria, thus inhibiting the proper drop in pH of the silage. Ensiling the corn in the upper range of the recommend moisture levels will be beneficial in reducing yeast affects. The fungus should have limited impact on the fermentation and quality of silage. The use of innoculants will speed up the fermentation process and will reduce the harmful effect of yeasts on the silage.

Because the potential for nitrate toxicity exists, grazing or green chopping should be done only when emergency feed is needed. A nitrate test should be taken before feeding green-chopped corn. Also, weather conditions should be accounted for before green chopping begins, since rainfall stimulates nitrate uptake from the soil following a rain, always wait one week before green chopping drought-stressed corn. Se our Beeflinks web site for Nitrate related articles.

Due to earlier than normal harvesting for silage this year, the labels of the pesticides should be reviewed before harvesting to make certain you are not breaking a harvest restriction when ensiling or green-chopping corn.

Determining the value of the drought stressed crop as silage is difficult since yield is less predictable and pricing scenarios for silage are not standardized. The value of the corn crop needs to be determined in order to calculate the value of the silage. Traditionally, most corn silage has been priced in relationship to corn grain. Simply multiplying the bushel price of corn grain by some factor has been used as a guideline. Generally, the multiplier has been somewhere between 6-8 times the bushel price of December corn futures when pricing delivered to the feedlot. Most corn silage pricing equations historically have not been based on any adjustment for nutrient value. Unlike hay, that is based on a standard quality measurement; RFV (relative feed value), protein or fiber content (ADF), corn silage is generally priced the same whether it contains 30% or 50% grain. Most feeders are now adjusting the price of corn silage to a standard moisture content (generally 65-70%). Since the animal derives the entire nutrient from the dry matter it doesn’t make since for the feeder to pay for water. Example, a comparison between the as-is value of silage having 65% vs. 72% moisture. Silage valued at $25/ton on a wet basis results in a dry matter cost for the 65% moisture silage of $.036/lb of DM vs. $.045/ lb DM for the 72% moisture silage. That’s a 25% increase in the actual cost of the silage dry matter.

Drought years, more than any other time, are extremely important to analyze feedstuffs rather than rely on book values. Wet chemistry will be more accurate this year than infrared analysis due to increased variation in the samples. If you are making major ration decisions based on a limited number of forage analyses; it might be justified to pay the slightly higher cost for wet chemistry analysis.

Besides the precautionary measures, forage analysis information can provide quality rankings to inventoried feedstuffs. This increases the accuracy of ration formulations and allows the producer to maximize all inventoried feedstuffs.