Corn damaged by drought: Use as grain crop or forage?

Farmers, agronomists and others are evaluating cornfields hit by drought and planning when and how to harvest them for greatest economic advantage. This involves assessing condition of the crop in individual fields relative to normal, and to think through several harvest scenarios such as: Will this field have a harvestable grain crop? Are there other concerns? What use or management alternatives do you have?

Corn damaged by drought: Use as grain crop or forage?

Farmers, agronomists and others are evaluating cornfields hit by drought and planning when and how to harvest them for greatest economic advantage. This involves assessing condition of the crop in individual fields relative to normal, and to think through several harvest scenarios such as: Will this field have a harvestable grain crop? Are there other concerns? What use or management alternatives do you have?

Key Points

Farmers with drought-damaged corn can consider using it for forage alternatives.

Options are green chop it, or use the corn for silage or as dry corn stover.

Harvesting drought-damaged corn as silage is not a good option for everyone.


To help answer those questions and more, Iowa State University Extension forage agronomist Steve Barnhart and Extension corn agronomist Roger Elmore provide the following information.

With enough grain on ears, corn is more valuable harvested for grain. Most of Iowa’s corn crop is intended for use as dry grain. If it has sufficient grain content and quality, a field will be more valuable as harvested grain. If the field or parts of it fall short of economic grain potential, some farmers can harvest the crop as low-yield corn for silage or graze it.

Predicting grain yield during mid-season is difficult. It involves assessing what you have in the field and comparing that with normal crop growth and development. With normal corn development, the number of pollinated kernels should be visible at about 10 to 12 days after silking (blister stage). This represents potential grain set. If weather conditions have adversely affected pollination, it will be evident at blister stage.

For the remainder of the summer, weather conditions influence how many of the pollinated kernels develop and the stage of development. Harvest decisions can then be based on knowledge of seed development gained by monitoring. If the crop doesn’t appear to be developing well, and you’re making early forage harvest decisions, use the following guidelines for estimating silage yield of moisture-stressed corn.

Grain yield method for estimating silage yield. For moisture-stressed corn, about 1 ton of silage per acre can be obtained for each 5 bushels of grain per acre. For example, if you expect a grain yield of 50 bushels per acre, you will get about 10 tons per acre of 70% moisture silage (3 tons per acre dry matter yield). For corn yielding more than 100 bushels per acre, about 1 ton of silage per acre can be expected for each 6 to 7 bushels of grain per acre. For corn yielding 125 bushels of grain per acre, corn silage yields will be 18 to 20 tons per acre at 70% moisture (5 to 6 tons per acre dry matter yield).

Plant height method for estimating silage yield. If little or no grain is expected, a rough estimate of yield can be made assuming 1 ton of 70% moisture silage can be obtained for each foot of plant height (excluding tassel). For example, corn at 3 to 4 feet will produce about 3 to 4 tons per acre of silage at 70% moisture (about 1 ton per acre of dry matter).

In addition to yield, consider other factors. Stage of development or condition of growth also influences the feed value of the harvested crop. Compared to normal corn, corn that would yield 20 to 40 bushels per acre would have about the same pound-for-pound feed value. Very poorly pollinated stalks with 0 to 20 bushels per acre yield potential would have about 80% to 90% the feeding value of normal corn. Short, barren stalks have only about 70% to 80% of the feed value of normal corn.

In what form will the corn be harvested and used? The three most practical options for using drought-damaged corn are green chopping, ensiling and storing as dry stover. Each system has advantages and disadvantages. Consider the fungicides, herbicides or insecticides used on the field. Each of these products has a legal preharvest interval. Early harvest or grazing may violate the intervals. Carefully check the label for any restrictions that may affect harvest or harvest timing.

Green chopping corn. This provides an immediate source of feed for dry lot or supplementing animals on pasture. A disadvantage may be a potentially high level of nitrates in drought-damaged, fresh forage. Have fresh-chopped corn tested for nitrates at a nearby commercial feed testing lab if there is any concern about high levels.

Chopping corn for silage. This provides a less immediate feed source, but a form that can be stored and fed over a longer period. One of the main management challenges of harvesting drought-damaged corn for silage is cutting the plant at proper moisture content for the type of silo structure where the forage will be stored. Corn should be stored at 65% to 70% moisture in a bunker or trench silo and at 60% to 65% moisture in upright silos.

In plants with at least some grain, the drydown rate of the grain will provide a rough guide for predicting whole-plant moisture. Plants with no grain but with some live green leaf tissue still evident will have surprisingly high moisture content (75% to 80%), too high for direct-cut ensiling.

In some cases even when all visible leaves have turned brown, the whole-plant moisture is still above 70% moisture. Plants that have died will lose moisture very quickly and could drop below 50% moisture in a short time, too low for best nutrient conservation as silage.

Get an accurate moisture test

An accurate moisture test from a representative field sample is an important piece of information needed to manage the harvesting of a corn crop for silage, says ISU Extension forage agronomist Steve Barnhart. It is difficult to estimate the whole-plant moisture content in the field. He says the best method may be to chop a representative area of the field with the silage chopper to be used and send the representative sample of chopped forage to a test lab for moisture determination.

Moisture determinations can be made at a feed testing lab or with a home check using an accurate scale, and a microwave oven or heat lamp to dry the sample. Use caution when drying forage in a microwave oven or under a lamp at home, advises Barnhart. As the plant material dries, it becomes more combustible. Take special precautions to avoid permanent damage to microwave ovens.

If nitrate concentrations are a concern in the chopped crop, ensiling can diminish the nitrate concentration by 30% to 50%, he says. Good management would be to have the silage tested by a commercial feed testing laboratory, after ensiling, to estimate nitrate concentration and nutritive value for livestock.

Not good option for everyone

Harvesting drought-injured corn as silage will not be a good option for everyone, notes Barnhart. Making good silage from a normal corn crop requires some degree of skill and attention to detail. If you do not already have the harvest machinery, a silage storage structure in good condition, experience in making corn silage and a well-defined plan for silage use, then making silage from drought-damaged corn may be a high-risk venture.

Too often farmers who are looking for a “cheap way” to salvage a crop as silage choose to store silage in a wide, low pile on the ground, possibly even bounded on each side by a row of large round hay bales. These piles may seem to be low cost initially, but spoilage and waste is often high, and as a result, the “cost” per ton of usable, good-quality silage is higher than expected.

Stacking or baling stover

Stacking or baling as dry corn stover is the third option. Drought-damaged corn has dried quickly in many areas. Corn that has dried below 55% to 60% moisture is not a good material for ensiling. Rather, it should be considered for possible stacking or baling as dry corn stover, says Barnhart. Timeliness is not quite as critical when harvesting stover. It should be dried to 20% moisture or less to avoid spoilage in storage and harvested before excessive leaf loss occurs.

High nitrates can be a concern with stover. If you’re concerned, Barnhart advises you have a nitrate test done on a representative sample. Other suggestions are to store stover at a dry location near the site of feeding, and provide limited access to stover during feeding to stretch feed supplies and reduce feeding waste while allowing livestock to adapt to potentially high nitrate-concentration forage.


08121646A.tif

CRIPPLED CROP: Farmers with drought-damaged corn can consider forage alternatives such as green chopping, or corn for silage or using it as dry corn stover.

This article published in the August, 2012 edition of WALLACES FARMER.

All rights reserved. Copyright Farm Progress Cos. 2012.

Hide comments

Comments

  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.
Publish