Harvest Moisture, Maturity Affect Silage Quality
By Kevin Putnam, Dairy Specialist, DuPont Pioneer
Silage harvest moisture and maturity can have a huge impact on silage nutritive value. They affect yield and quality out of the field as well as losses during fermentation. Differences can lead to lower-quality forage and poor animal performance.
Timing is everything
Harvest should occur at about 36% dry matter. Harvesting corn silage before plants reach optimal moisture reduces yield per acre and starch levels, resulting in a “hidden” economic loss. As they mature, healthy plants lay down starch at a rate that’s just under the dry matter percentage. As the percentage of starch in silage increases, ear weight increases, raising yield.
However, fiber digestibility of today’s hybrids won’t change as significantly. Research shows a rise from 30% to 38% dry matter will change neutral detergent fiber (NDF) by 2 percent at most. In some samplings studied, the change was only 0.5% to 1.5%.
Harvesting corn silage when dry matter is below 30% reduces yield and also may result in seepage and extended fermentation, causing greater dry matter loss in storage. This destroys significant amounts of valuable nutrients, including soluble sugars.
Factors influencing dry matter
Some hybrids dry down faster or slower than others, affecting kernel maturity at different moisture levels. Studies in northeastern states show hybrids with a shorter silage comparative relative maturity (CRM), compared to their grain CRM, tend to gain more dry matter as they mature in the field.
Another consideration is grain-to-stalk ratio. Hybrid stature and relative grain yield can alter dry matter levels even among hybrids of similar CRM. For instance, a short-stature hybrid with a faster-maturing ear may dry more quickly than a taller hybrid with the same ear characteristics.
Leaf diseases and frost damage also can affect dry matter. Plants may look dry or dead; however, if the ear is not fully mature, total plant dry matter can still be low. The ear can account for half of plant mass, drastically altering dry matter percentages.
Healthy leaves allow the plant to exhaust moisture from the ear. Damaged leaves limit the ability to lower kernel milk line. Death of leaves before the ear matures can result in kernels at full milk. In some studies, dry matter stalled at 28% for more than two weeks even though the plants were brown. If a leaf blight or frost occurs when the ear is almost fully mature, dry matter can rise very quickly.
How to manage maturity
Chopper technology helps producers track dry matter and potential yield increases in corn that’s more mature. Growers can track dry matter levels, but they must use the information to make management decisions. For example, if the crop is too wet, it’s best to harvest a different field first.
Harvest timing is critical. Harvesting too early can jeopardize starch and feed quality. Harvesting too late risks lower feed quality and improperly packed bunkers. Keep a careful watch on plant moisture and growing conditions before and during harvest.
With many farms consisting of large numbers of acres, it may be impossible to hit an exact dry matter target. However, if Mother Nature cooperates, waiting a couple of days before chopping can result in more tons of a higher-quality feed.