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Corn silage concerns with hail damaged corn

Fri, Aug 20th, 2010
Posted in Agriculture

Although the areas of recent hail damage were not large and were very scattered, where hail did strike, the damage was severe. The question becomes, "How to best use this corn?" Corn silage is certainly one option.

The hail damage includes loss of leaf area and stem bruising from hail stones. Unfortunately, corn is more susceptible to loss of leaf area from hail at tasseling and silking than at any other time in its life cycle. In general, complete loss of leaf area at this stage results in nearly 100 percent yield loss. This is because once the tassels have emerged, the plant has completed its vegetative growth. This means that all leaves have emerged and that there are no more leaves left to emerge if the exposed leaves are damaged. There has not been any grain fill at this point, and loss of leaf area prior to grain fill means that there will be less leaf area available to intercept the sunlight that is needed to fill the grain.

Hail stones can also result in significant stem bruising when hail is accompanied by strong winds. Stem-bruised regions on the stalk are an entry point for bacterial infection and leave the plant more susceptible to stalk breakage in the future. As a result, fields with considerable stem bruising should be harvested early to minimize the amount of stalks that break below the ear prior to harvest.

Bruises on stalks and ear husks may allow pathogen entrance that could result in stalk and ear rots, and consequently stalk and grain quality issues. In particular, there may be increased risk of mycotoxin contamination.

We know that injury to the ear does favor certain rots, namely Fusarium ear rot and Aspergillus ear rot. The fungi associated with these ear rot diseases can produce mycotoxins that are harmful to livestock.

Another ear rot to look out for, since mycotoxins are also associated with it, is Gibberella ear rot. This ear rot is not typically associated with damaged kernels. Instead, it usually infects through the silks, so it begins at the tip of the ear and appears red or pink, or occasionally white. Infections occur more commonly in cool, wet weather after silking and through the late summer. Gibberella can produce vomitoxin and zearalenone. When evaluating an ear rot problem, remember that certain ear rots are a warning sign to suspect toxins, but ear rots do not always lead to toxin problems.

Mold inhibitors can be used in silage, but they will not repair decay that has already occurred nor reduce existing mycotoxin levels. The only way to determine mycotoxin levels with certainty is to have samples tested for specific mycotoxins. The most accurate samples will be chopped silage, sampled just before ensiling. Silage samples are more time-consuming to process because of the lack of accurate quick tests for mycotoxins in silage.

Corn silage from plants with few ears will likely be wetter and have higher nitrate levels than normal. Since the highest nitrate concentrations will be found in the lower stalk, it is best to cut such plants a few inches higher than normal.

Last year there was considerable hail damage in Iowa. Recently retired ISU Extension dairy/beef/forages field specialist, Dale Thoreson, offered some tips on making silage from hail damaged crop: (1)Use good silage-making techniques such as one-fourth inch theoretical length of cut. Kernel processing will not be necessary. (2) Harvest in a timely fashion and pack the silage very well. (3) Set baggers to attain a maximum amount of packing. (4) Consider using corn silage inoculants to increase the potential for proper fermentation. (5) Cover bunkers and piles with plastic immediately after chopping is done. (6) Have a use for the silage ahead of chopping, either fed to your own livestock or an arrangement with a neighbor to use the silage.

The information in the article came from, "Wind and Hail Damage to Pollinating Corn," Jeff Coulter, Extension Corn Agronomist, University of Minnesota; "Making Silage from Hail Damaged Crops," Dale Thoreson, ISU Extension dairy/beef/forages field specialist, and "Risk of Mycotoxins Associated with Hail Damaged Corn," Alison Robertson and Gary Munkvold, Department of Plant Pathology, ISU.

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