If you plan to harvest the crop for ensiling, the main consideration will be proper moisture for storage and fermentation. The crop will look drier than it really is, so moisture testing will be critical. Be sure to test whole-plant moisture of chopped corn to ensure that acceptable fermentation will occur. Use a forced-air dryer (Koster), oven, microwave, electronic forage tester, near infrared reflectance spectroscopy or the rapid "grab-test" method for your determination.
In the "grab-test" method, squeeze a handful of finely cut plant material as tightly as possible for 90 seconds. Release your grip and note the condition of the ball of plant material in your hand. Here is how to interpret what you see:
* If juice runs freely or shows between your fingers, the crop contains 75 to 85 percent moisture.
* If the ball holds its shape and your hand is moist, the material contains 70 to 75 percent moisture.
* If the ball expands slowly and no dampness appears on your hand, the material contains 60 to 70 percent moisture.
* If the ball springs out in your open hand, the crop contains less than 60 percent moisture.
Grazing the corn field is an option, but be aware of the potential for nitrate toxicity. This is especially likely to be a problem if growth was reduced to less than 50 percent of normal and/or high levels of nitrogen were applied to the crop.
The risk of nitrate poisoning increases as pollination becomes poorer. Nitrate problems often are related to concentration (the greater the yield, the less chance of high nitrate concentrations in the forage). If pollination is poor, only about half of the dry matter will be produced, compared with normal corn forage.
Under stressful growing conditions, especially drought, this conversion process is slowed, causing nitrate to accumulate in the stalks, stems and other conductive tissue. If moisture conditions improve, the conversion process accelerates, and within a few days, nitrate levels in the plant return to normal.
The only way to know whether your silage contains nitrate is to have it tested by a testing facility such as NDSU's Plant Diagnostic Laboratory. Get samples taken for nitrate tests analyzed immediately or freeze them until they can be tested because nitrate will decline in tissue in three to four hours.
If drought-stressed corn is ensiled at the proper moisture content and other steps are followed to provide good-quality silage, nitrate testing should not be necessary. Nevertheless, feed the silage to a few cull cows before feeding it to your other animals.
Always follow precautions regarding dangers of nitrate toxicity to livestock, especially with grazing and green-chopping, and silo gasses to humans when dealing with drought-stressed corn. If the nitrate is above toxic levels, feed hay or some other forage in the morning and allow your livestock to graze the corn for a couple of hours in the afternoon.
Source: J.W. Schroeder, Dairy Specialist, NDSU Extension Service