By James Isleib
Get more from your corn silage by meeting crop nutrient needs during the growing season and optimizing your harvest methods.
“Plan now for corn silage success – Part 1: Hybrid selection” discussed how hybrid selection leads to good success with corn silage, but crop nutrient management and corn silage harvest methods are two other important components. These topics have been extensively researched by universities and companies. The following is a brief summary of these points and links to good online sources for deeper reading.
Corn silage crop nutrition
As with all commercial crops, a good soil testing program is the backbone for development of a good crop nutrition program. Take time to collect a good, representative sample from sampling sites based on topography, soil type and past management, and submit to a reputable soil testing lab. Michigan State University Extension recommends no more than 20 acres be included in a single soil sample. Remember, you’re sending the lab a sample of approximately 1 pound of soil to represent 48 million pounds of soil (20 acres at an 8-inch depth).
Livestock manure is often used to fertilize corn silage. Be sure to take full advantage of nutrient credits from manure. Collecting a good representative manure sample and having it analyzed allows farmers to manage their manure resource more efficiently. If manure analysis information isn’t available, check the book values for nutrient content of different species in the Midwest Plan Service MWPS-18 “Manure Characteristics” publication.
Also, make sure those responsible for hauling and spreading keep accurate records of loads hauled on each field. Timely incorporation will have a major impact on retention of the nitrogen component in manure. Following the recommendations based on a quality soil test and using good fertilizer practices will maximize the growth and development of your corn silage crop.
“Corn fertilization,” University of Wisconsin Extension publication A3340, provides an interesting comparison of phosphorus (P) and potassium (K) requirements between silage corn and grain corn at various soil P and K levels and yield goals. Manure Management and Air Quality, a webpage from the University of Minnesota Extension, provides a good overview of manure management.
Harvest management
There are several considerations when setting up for corn silage harvest. A few key points from the University of Wisconsin Extension’s Corn Agronomy – Silage Harvesting and Storage webpage follow.
- Harvest timing: Moisture content at harvest should be determined to ensure good quality of silage coming out of your storage. The following are recommended silage moisture contents for various storage methods: upright silo—60-65 percent; upright oxygen-limiting silos—50-60 percent; horizontal silo—65-70 percent; and bag silo—60-70 percent. Stage of grain maturity is also an important factor in quality silage. The following are visual indicators of moisture: early dent—73 percent; half milkline—66 percent, three-fourths milkline—63 percent; and no milkline—60 percent.
- Harvest height: Increasing cutting height decreases yield, but results in higher concentration of nutrients and improved cow performance. Also, more crop residue is left behind following harvest. This is a tradeoff between yield and corn silage quality that should be carefully considered.
- Silage inoculants: Corn silage fermentation occurs naturally, but the speed and efficiency of the process may, at times, be improved by using inoculants. The inoculants contain bacteria selected to dominate the fermentation process in the silo.
- Kernel processing: A properly adjusted kernel processor damages more than 90 percent of the kernels, allowing for more efficient utilization by the cow. It pulverizes cob pieces, which allows for longer length of cut and requires less power.
- Frosted or drought-stressed corn: Moisture content can be higher than the appearance of the crop indicates. Early-frosted corn can often be left in the field to accumulate additional dry matter. Late-frosted corn at or near the proper maturity should be harvested immediately. Drought-stressed corn can accumulate excess nitrates, especially if high rates of nitrogen are available to plants, or when a drought-stressed crop is chopped within three days of rain.
- Rate of filling: In short, the quicker the better. Rapid filling improves fermentation, lowers overall ensiling costs and minimizes losses due to weather and advancing crop maturity.
- Packing: Proper and prompt packing is required to exclude oxygen and promote fermentation. Silage in upright silos creates its own packing pressure while being loaded. Silage bag loaders include adjustments to ensure even bag filling. In bunker silos, wheel tractors with front end loaders or blades should be used to level and pack silage. Crawler tractors do not provide enough compaction. The time and effort spent compacting silage in the bunker affects fermentation. Spending 5 minutes per ton, running across the surface several times, does a better job than simply spreading off the silage with minimal compaction.
- Sealing the silo: Prompt and effective exclusion of oxygen from the filled silo will result in improved quality and lower losses. It usually pays to take pains with this part of the process.
These and many more important considerations can be reviewed on the University of Wisconsin Extension’s Corn Silage webpage.