With all the rain we have seen this summer, it seems like water has been in just about every conversation. “How much rain did you get in that last storm? Did you see the flooding up north? We had enough rain that the basement has started to flood.” With summer moving quickly towards fall, another type of moisture might be on some folk’s mind, “Is my corn the right moisture for silage?”
Some of you might be asking, why do we care what the moisture content of silage is when we head out to harvest and pack? As with just about anything in agriculture, silage has a sweet spot we need to hit to produce an optimal product. Too wet and the chopped pile can seep, loosing nutrients and affecting fermentation creating an end result less palatable to our animals. To dry and forcing air out of the pile during packing is difficult. This affects fermentation in a different way, resulting in increased spoilage, decreased protein and energy, and heat. If you’ve ever felt a warm silage pile or seen one steaming on a cold winter day, chances are it was chopped too dry.
Bruce Anderson, a forage specialist at UNL puts the ideal moisture content for harvesting silage at 60-70%. Figuring out exactly where this sweet spot is can be difficult. For sure we want to wait until the plant has begun drying down before harvest is even attempted. Green stocks, leaves, and husks are more likely than not over 80% moisture. Anderson shares that for most hybrids, start by looking at the ear. After dent around one-half milk line is ideal. In hail damaged fields, plants might appear to be drier than normal due to the physical beating from the hail. That and our eagerness to save damaged plants before they become unusable often puts us in the field a bit too early.
Another way to check if our silage is ready for harvest is to figure its dry matter content at home. This can be done with specialized tools like a Koster moisture tester that come with instructions or everyday items like you’re microwave or a food dehydrator. If you’re wanting to give it a go at home, first get a sample to run. This means either take a test pass with the harvester or go out and do some hand sampling. Next, weigh out a set amount on a scale, 100 grams is a good size and makes things easier at the end. Select a scale that will show differences to at least the ones place. If it can go to tenths, all the better. Next you have to remove as much moisture from the sample as possible. Spread out the sample in your dehydrator and turn it on and let it sit overnight and weigh it in the morning. If you’re using a microwave, go for 2-3 minutes on medium-low power. If the sample starts to char, you’ve gone too long or need to lower the power setting. After 2-3 times begin weighing the sample after each run. Your goal is to get to a point where the sample you put in to the microwave is less than 2 grams heavier than the one you pulled out.
Once you have a final weight simply divide this by your initial (that 100 g we started with) and multiply by 100 and voila, you have dry matter content. For example, a sample that started at 100 g ended up weighing 34 g will give us a dry matter content of 34%. You can see how that 100 g starting weight is helpful and really makes the math easy. When we consider dry matter content, which is the inverse of the moisture content we were talking about above, we want to shoot for 30-40%.
One final thing that those harvesting or feeding silage this year need to be aware of are any possible toxins that may negatively affect cattle, especially in fields that have received hail damage. Two I’ve been hearing quite a lot about are nitrates and mycotoxins. Without drought stress and the fact that they are normally reduced during a proper fermentation, nitrates shouldn’t be a big concern this year. Mycotoxin on the other hand is a real concern in hail damaged fields. Both nitrates and mycotoxin can be tested for by commercial labs, a good check to anyone with concerns. For those who would like more information about mycotoxins and feeding hail damaged corn, Dr. Mary Drewnoski from the UNL Animal Science Department has put together a great article for our monthly BeefWatch publication which can be found at beef.unl.edu under the BeefWatch tab at the top or stop in to the extension office and we can print out a copy for you. If you have any specific questions about putting up or feeding silage this year, stop in or give us a call and we’d be happy to help you out.
-Ben Beckman is a beef systems Extension Educator serving the counties of Antelope, Cedar, Knox, Madison and Pierce. He is based out of the Cedar County Extension office in Hartington. You can reach him by phone: (402) 254-6821 or email: firstname.lastname@example.org .