“If there is one thing you must know about whole-plant corn at harvest, it’s dry matter.” – Dr. Keith Bolsen, Kansas State University, Professor Emeritus
Choppers are rolling, trucks are roaring, pack tractors traverse back and forth over carefully shaped drive-over piles. Before you started, you made a determination of the dry matter (DM) in your corn. But what has time, heat and wind done to % DM? And why is it crucial to know this value?
Keep in mind that variables like corn hybrid, chop length, kernel processing, size and shape of the pile, packing method, and inoculant use will figure into YOUR target % DM. Work with your nutritionist to arrive at a target that fits your silage program then try to stay within two percentage points plus or minus. If Mother Nature (or any other unforeseen circumstance) pulls one way or the other, have a backup plan in place to make the best of it. Take charge, do the best you can and then don’t sweat it.
Why is % DM so important?
1. Rate and extent of fermentation. Silage should go from the aerobic to anaerobic state quickly. Respiration ceases and fermentation starts to lower the pH. Lactic acid is the desired result. Silage that is too wet results in visible seepage (loss of digestible nutrients) and extensive acid production; too dry will not allow proper packing and increased oxygen in the pile (high mold and yeast counts, insufficient acid production).
2. Preservation efficiency. We aim for a quick move from aerobic to anaerobic state to complete the ensiling process, and chopping in the correct % DM range will help get corn silage there and minimize shrink loss.
3. Packing density. As a drive-over pile is formed, the goal is to layer four to six inches at a time, and pack each layer well before the next layer is put on. Chopping at a % DM that is too dry makes it difficult to get a sufficient pack (and it might never pack as well as silage with a more correct % DM). The result is too much oxygen in the pile. Oxygen is not a friend of good silage but is best buddies with mold and yeast.
4. Surface spoilage. Silage put up at incorrect % DM is more likely to have excessive surface spoilage. Remember that visible surface spoilage is indicative of lower quality silage within the top foot to two feet (or more) of the pile.
5. Aerobic stability at feedout. Silage, from chopping to feedbunk, moves through a chain of reactions. If % DM is out of whack to start with, chances are the feed in the bunk is not going to be perfect. If the silage is so-so under the plastic, it’s not going to get any better when air (oxygen) hits it at feedout. Starting with the right % DM alleviates a lot of headache (and heartache).
How to monitor DM at harvest?
Dedicate ONE PERSON to sampling and determining DM content. Sample at least once an hour from each field, record all the DM values and average them to come up with the field average % DM. It is imperative that you have one person who processes all samples so there is no variability in method. Precision is paramount. Be fussy, be accurate.
What is the process? The method used to dry down samples is up to you. Get a digital gram scale for accuracy, a stack of cheap paper plates. Dry samples down in a microwave or with a Koster tester. Use this handy record-keeper and place it in a binder for easy reference.
BIG HINT: DO NOT use the microwave in your own kitchen. Get an inexpensive one and install it in a convenient location, like a farm shop or office.
Microwaves provide a relative quick means of drying forages. The greatest challenge with the use of a microwave is the possibility of burning (note: samples dried in a microwave should not be submitted to a laboratory for nutrient analyses). A microwave requires constant monitoring. Thus, it is difficult to do other tasks while drying samples. Drying time is about 5 to 10 minutes for forage samples.
A Koster tester is an electrical appliance that blows heated air through a screen on which the forage is placed. It provides a relatively quick and inexpensive means of drying forages. Some loss of forage particles can occur, which increases the likelihood of errors. Some people use timers to turn off the Koster tester so that they can do other tasks while the sample dries. It takes about 25 to 50 minutes to dry a sample using a Koster.
Calculating Dry Matter
Weigh the empty container selected to hold the sample and record the weight.
Place the forage in the container.
Weigh and record the container and forage weight.
Subtract the weight of the container from the total weight (Step 3) to determine the weight of the forage before drying.
Thoroughly dry the forage.
Weigh and record the container and sample weight immediately after drying.
Subtract the weight of the container from the total weight (Step 6) to determine the weight of the forage after drying.
Divide the weight of the dry forage (Step 4) by the weight of the wet forage (Step 7).
Multiply by 100 to get a percentage.
Record all DM values and calculate the average for the field. Keep the records to compare with the next fields and to plan next year’s silage program.
So there you have it. Knowing % DM takes the guesswork out of knowing when adjustments need to be made to your harvest plan. Now, charge on!