Timing is Key to Salvaging Grain Corn for Silage
Every so often, grain corn growers are faced with a decision: Allow a struggling crop to mature and harvest for grain or cut it early for silage. Most often the issue comes up when drought or other stresses threaten to devastate yields. In some cases, growers simply see a higher value in the crop as silage than as grain.
“Different growers will have different reasons to consider cutting for silage the corn they intended to harvest for grain,” says Becky Arnold, DuPont Pioneer livestock key account manager. “When conditions turn dry, growers who irrigate may decide to skip the final irrigation as a water- and cost-saving tool, thinking it won’t have a significant impact on the crop.”
Skipping the last round of irrigation could reduce yields, perhaps by 15% to 20%, Arnold acknowledges. But if a grower can get value from the crop as silage, that may not be the key factor. The priority on timing irrigation, regardless of the intended crop use, should be placed on what the crop needs to maximize yields and, therefore, profits.
In some areas, the need for silage is very high, and producers compete for acres to meet demand. If the previous year produced a small silage crop, the hybrids planted for grain may be that much more valuable as silage and producers may encourage growers to cut the crop for silage, even if an operation sees plenty of moisture for optimal grain yields.
Issues to consider
“Growers need to be aware of possible differences between hybrids bred to produce grain and those bred for silage production,” Arnold says. “A grain hybrid is typically selected for strong grain production and is also expected to stand until fall harvest. These hybrids can still produce high-quality silage but they may contain more fiber and lignin, which can reduce fiber digestibility compared to forage-specific hybrids.”
Environmental factors such as drought can actually improve fiber digestibility. If the plant is under stress, it will sacrifice stalk structure for grain production, making the stalks easier for the animal to digest.
Drought-stressed plants still offer substantial nutritional value as silage. A barren plant can produce 80% to 90% of the nutrient value of a plant with an ear.
Unfortunately, when severe drought stress or hail damage occurs, the temptation is to harvest poor-performing plants too early, before they dry down to an optimal dry matter percentage for ensiling. Barren plants that are brown and look dry can still contain as much as 75% moisture. Plants with no ears or small ears retain lots of moisture and valuable nutrients in their stalks. If harvested before they can dry down, the nutrient-rich stalk moisture is lost through seepage from the silage and ultimately they produce wet silage that ferments poorly. It pays to let these fields dry down more before harvesting and ensiling.
To emphasize this point, Arnold explains that silage that’s been harvested too wet doesn’t ferment efficiently. A poor fermentation leaves room for activity from ever-present clostridia bacteria, which thrive in wet environments. An unfavorable secondary fermentation from clostridia produces butyric acid, which has a nasty, offensive odor — one that’s sure to decrease livestock appetites and performance.
“Quality inoculants help promote more-efficient fermentation,” Arnold explains. “For instance, fermentation where optimal pH was reached in five to 10 days, rather than a couple of months, will improve animal performance for producers. Forage treated with Lactobacillus buchneri has improved aerobic stability during feedout and a reduction in spoilage activity that can cause heat damage to silage. However, the best inoculant can’t make bad forage into good silage. Proper harvest timing and bunker packing are critical to getting value out of inoculants.”
When to harvest
“The most important part of making good silage is harvesting within ideal dry matter ranges, from 32% to 37%,” Arnold says. “Knowing when to harvest has its challenges. Evaluating the crop for kernel starch fill and whole-plant health is a good place to start but testing the silage moisture is also a good idea.”
Harvesting for efficient fermentation involves striking the right balance between dry matter and moisture. Producers who manage this balance can retain the greatest percentage of nutrient value from the crop.
Arnold uses a wood chipper to process samples for testing in a Koster Moisture Tester. Bear in mind that the dry matter in these samples can be a couple of points drier than actual field levels.
Starch vs. fiber and protein
Generally, as crops mature in the field, fiber digestibility and crude protein decrease, Arnold says. If a grower harvests early, the digestible fiber and crude protein will be higher but the starch level will be lower. Maintaining good plant health to allow for more time in the field will increase starch levels. Understanding the impact that the growing environment and field conditions can have on starch production, as well as fiber digestibility and crude protein, can help you determine the ideal harvest date for the highest-quality outcome.