Critical decision When to harvest

With drought ravaging corn crop, you must gauge moisture carefully

With drought ravaging corn crop, you must gauge moisture carefully

August 20, 2002|by DON SCHWARTZ

Field corn is the single most important field crop in Washington County, in the state, and in the entire country for that matter.

Locally, it is harvested for silage to feed our 16,000 dairy cows, our larger dairy heifers, and several thousand beef cattle. It is also harvested as high moisture shelled corn for these animals.

When harvested as dry shelled corn, it is used to feed all of our livestock from cows to catfish, pigs to poultry, horses to hares, and goats to gerbils. Corn is processed into virtually all pet foods.

And it is the same corn processed into our corn flakes, corn starch, corn oil, and hundreds of other products.

Because it is such an important crop, is grown virtually everywhere, and is very visible-sensitive to weather, the corn crop is often the field barometer of our summer weather, particularly rainfall.


This year's dry spell began in the spring of 1998. The cumulative effect of several dry summers and dry winters allowed 2002 to begin with very dry conditions both on the soil surface and deep in the soil. Spring rains initiated the growing season, but some areas began missing rains in June and conditions worsened in July and August.

As corn silage harvest is beginning across the region, corn conditions are quite variable. There are a few areas in southern Washington County where fields will reach yields of 20 tons of silage, and some dry areas of Pennsylvania, where corn silage yields will be as low as four tons per acre.

Much of the corn crop across the county will average in the 8 to 10 tons per acre range.

Each farmer will need to carefully access their feed needs and harvest enough corn silage to last until September 2003! As corn grain prices increase and milk prices remain low, corn silage is the most economical feed to supply energy and fiber in the dairy ration.

Of the 18 years I have worked in Washington County, 12 have been dry years. Over that time, I have developed a general formula to assist producers in pricing corn silage.

Local elevator price paid for corn multiplied by 7 equals the value of corn silage in the field.

So, if corn is $2.75 per bushel, that times 7 equals $19.25 per ton of standing corn silage. Silage harvest, hauling, and storage costs are added to this figure.

Because of our strong basis and the declining estimates of the nation's corn crop, I am suggesting that producers use a $3 per bushel figure and see what the market will stand.

Generally, an acre of corn is worth more sold as silage than harvested as grain. Severely droughted corn with no ears should be discounted. But corn only six feet tall with a small ear on most stalks will still make good corn silage.

The key to making corn silage, especially in a drought year, is harvesting at the proper moisture.

Most upright silos require a moisture range of 65 percent to 70 percent. Larger tower silos need to decrease moisture by about 2 percent for each additional 10 feet of height over 50 feet. Using a 68 percent moisture standard for a 50-foot silo, then an 80-foot silo would need a moisture content close to 62 percent.

Bunker silos or ag bags can afford to have silage cut at moistures over 70 percent. But if the moisture content approaches 75 percent, then you had better construct a holding pond for the corn squeezings!

Corn is a grass. So, if it can be cut just a few days sooner, especially under hot droughty conditions, then there is more plant sugar to aid in ensiling process and less lignin in the stalk.

Determining the optimum time to harvest corn silage can be based on total plant moisture or by corn maturity as determined by the advancement of the "milk line" down the kernel. This may be just a bit wet for tower silos but perfect for bunkers.

The problem with severely droughted corn is that the plant dies before the corn grain matures so there is no milk line to follow. In this case, monitor moisture by chopping or grinding samples.

Dry leaves do not determine plant moisture that is stored in the stalk. Also keep in mind that a rain several days before harvest can increase the stalk moisture content.

A quick moisture test can be done in the field if a more precise method is not available. A handful of chopped silage should be squeezed as tightly as possible for 90 seconds. Release your grip and observe:

-- If moisture seeps between your fingers, the level is over 75 percent - too wet!

-- If the silage stays in a ball and your hand is moist, the moisture content is 70 to 75 percent.

-- If the silage ball expands slowly and there is no free moisture on your hand, the moisture level is 60 to 70 percent.

--n If the silage ball just falls apart, moisture is less than 60 percent - too dry.

All of the other factors required to make good corn silage need extra attention in a drought year.

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