Corn Silage Harvest Management: Key Points to Consider

Timing: Kernel Maturity and Whole Plant Moisture

Healthy plants can be harvested closer to ¾ milk line to capture more starch. Depending on weather, there is about 7 days between milk line stages with only 85% of final kernel weight reached at ½ milkline. Whole plant moisture drops 0.5-1% per day as a result of healthy plants accumulating 0.5-1% starch per day until reaching black layer. Starch deposition, rather than drying of stalks and leaves results in the reduction of moisture in healthy corn plants. Focus first on monitoring kernel milk line in healthy plants and second on whole plant moisture, especially in diseased or stressed plants. Harvesting healthy plants at ¾ milk line will not significantly lower fiber digestibility (NDFD).

Chop Length and Kernel Processing: If chopping longer and/or harvesting more mature (to capture more starch), it is important to have the kernels adequately processed.

1. The industry standard for corn silage chop length is 19 mm (3/4”) unless using specialized processors. Shorter length (15-17 mm) may slightly increase fiber digestibility but reduces peNDF (effective fiber). Longer chop adds peNDF, but makes compaction more difficult. Miner Institute research indicates chopping > 22 mm does not improve rumen buffering but will extend dairy cow eating times.
2. Check roller mill wear on kernel processors.
3. Processor roller mill gap ideally set at between 1-3 mm depending upon kernel maturity.
4. Check the roller mill differential. A minimum of 40-50% differential depending upon processor and desired degree of kernel damage.
5. Don’t forget to frequently monitor the quality of processing during harvest using the Pioneer Kernel Processing Cup. Ideal is 2 or fewer whole or half kernels in the 1-liter cup.

Corn silage is preserved due to the fermentation of sugars to acids. Proper fermentation requires absence of oxygen (anaerobic process). Compaction removes air and increases density while adequate moisture prevents silage porosity to enable fermentation, prevent spoilage and preserve valuable nutrients (dry matter).

Minimum compaction goal for bunkers/piles is 15 lb. DM/ft3.

1. Proper compaction requires adequate minimal weight (known as the “800 lb. rule”): If a chopper delivers 100 ton/hr to the pile, times 800, then 80,000 lb. of pack tractors (not counting push tractors) are need.
2. Good compaction is achieved with overlapping paths and packing in thin (6 inch) layers.
3. Drive-over pile slope should be ~ 30% (1 ft rise per 3 ft run; a 10-foot-tall pile would be a total of 60 feet wide) and allow for driving over the pile in all directions.
4. Avoid “over-packing” the very top of the piles or bunkers. It is not effective in improving densities and only serves to mash and damage plant cells releasing water and nutrients that fuel aerobic, spoilage microbes that lead to increased top spoilage.
5. Use a science-backed inoculant. See your local Pioneer Representative for information on Pioneer brand 11C33 or 11CFT.

Cover and seal the pile or bunker tightly and quickly after harvest. Entry of air and water will negatively affect the ensiling process and the nutrient quality of silage during storing and feeding. Research from Kansas State University reported a return on investment (ROI) of 8:1 for covering a silo with basic (6-mil polyethylene) plastic sheets. Use oxygen barrier film for enhanced protection against oxygen penetration. Bunker sidewalls should be covered with plastic to prevent oxygen and rain or snowmelt penetration. Dry matter losses in uncovered bunkers can be over 30%. This loss does not include the cost of spoiled feed or the negative effects of decreased nutritive value on intake, weight gain, milk production or reproduction.

Delaying covering will result in excessive heating, quality decline and loss of valuable nutrients. Plastic must be weighed down with pea gravel bags or tires (or sidewalls) and the front face should be tightly sealed with bags or tires to prevent air billowing under the plastic.

As much as 50% of corn silage dry matter loss can occur at feed-out due to improper methods that disrupt the integrity of the compaction. Using a mechanical facer can significantly improve feed stability/palatability and serve to “blend” the silage reducing the nutrient variability inherent from ensiling multiple hybrids/fields.