Harvesting Corn Silage at the Correct Moisture While Being Cautious of Nitrates

Corn silage harvest is a critical time of year for dairy and beef operations, as the quality of the silage harvested determines the farm's success or failure for the following year. As drier weather sets into the state it will decrease the risk of compaction during corn silage harvest but may set up a few other challenges such as timing harvest moisture correctly and Nitrate toxicity. While we have not heard of any difficulties with nitrate toxicity in the corn silage that has been harvested, this is always a risk during drought-stressed periods. Anytime plant growth slows due to conditions such as drought or cold weather, nitrates accumulate in the lower stalk. The most significant risk then comes for the next 3 to 5 days after a soaking rain, when the plant starts growing again, moving these nitrates up the plant. Higher nitrate corn silage can be managed by increasing cutting height and making sure silage ferments for at least 21 days, during which the nitrate changes to ammonia in the feed. During this time, nitrate levels generally decline by 50-60%. However, during this time, the silage will release deadly silage gas, and during drought conditions, the silage is at a significant risk of being harvested too dry. If you need silage before it has time to ferment fully, it is a good idea to test the corn silage nitrate level. Samples should be less than 1,000 ppm Nitrate Nitrogen on a dry matter basis.

Estimating harvest moisture

Corn silage harvest moisture is critical to maintaining feed quality and achieving good fermentation, with the goal of whole plant harvest moisture being between 62-70% moisture. The kernel milk line method can help determine when to harvest corn silage, but it loses accuracy during dry conditions when plant moisture doesn’t match kernel maturity. When the kernel is at 1/3, the silage moisture is generally 68-72% and by 2/3 milk line, the whole plant moisture is 62-68% moisture, but under drought conditions, it may be less than 60% moisture. A better way to determine moisture is once kernels reach the ¼ milk line, start checking whole plant moisture. To do this, select 10 plants from uniform areas of the field, sampling obviously more mature and less mature regions separately. Cut corn plants at the same height you plan to chop; cutting too low generally underestimates moisture, while cutting too high overestimates moisture.  Chop these samples carefully either through a silage chopper or a woodchipper. Mix the sample well to achieve uniformity and sub-sample for a moisture test using a Koster tester, air fryer, or microwave to determine moisture.   

Safety

Corn silage harvest can be a stressful and dangerous time of year when long hours are mixed with large machinery operations. During fermentation, both Nitrogen Dioxide and Carbon Dioxide are released at deadly levels. Tower silo’s pose the greatest risk, but even bunker silo’s and silage bags are releasing gas. At just five ppm, Nitrogen Dioxide poses a human health risk, and Carbon Dioxide poses a risk at 1,500 ppm. When Nitrate levels in silage are elevated so are Nitrogen Dioxide levels during fermentation. When entering an upright silo, the silo blower should be run to provide oxygen, and a multi-gas meter should be used to make sure Nitrogen Dioxide levels are low enough for safe entry. When a bag is opened, even if not sealed shut, but the plastic is lying on the ground, trapped gases are released when the plastic is lifted, so stand to the side and never stick your head inside.

During silage harvest, be cautious of equipment that may suddenly back up. Always know your way out of the pay of equipment. It is a good idea to wear bright clothes or even safety vests so that you are easily seen when working around all the silage equipment. When filling a bunker silo, be careful of how steep the side walls or wedge becomes, as this increases the risk of equipment rolling over. Then, when covering the pile, be very careful near the edges. If filling against old feed, remember to stay at least 3 times farther away from the face of a silage pile than it is tall if you walk up to it. Also, when working on top of a pile, stay at least as far away from the edge as the pile is tall to protect yourself from pile collapse.   

Pricing Corn Silage

Corn silage price can be a challenge as it is not a directly traded commodity; however, we have a tool that can help you price corn silage based on the yield, price of corn grain, and low-quality hay, which can be found at: https://go.osu.edu/cornsilageprice. This tool also offers an in-depth spreadsheet that can help you refine this price to your operation based on additional information such as nutrient removal cost, harvest cost, hauling distance, and storage losses. Based on current corn prices and low-quality hay prices, corn silage has an average value of about $43.40 per ton. However, factoring in other decisions, such as harvest cost and trucking, this value could be between $27.83-$58.95 per ton. No matter how you price corn silage, getting an accurate estimate of grain yield or harvested tonnage is critical. Either of these can be used to determine price per acre. Have a safe and plentiful corn silage harvest.