Determining hay and pasture yields isn’t quite as simple as looking at the combine monitor for the number of bushels per acre. But, I would argue that knowing your hay and pasture yields is just as important as knowing your grain yields.
Having a yield in tons per acre will provide you with a better understanding of how much feed you have for your livestock. If you are selling hay, the buyer needs to know how much hay they are getting. And last, but certainly not least, nutrient recommendations are given in pounds per ton per acre. Under-or over-applying nutrients does not do the crop, or your bottom line, any good.
To start, count the number of bales per field. The next step is to convert the number of bales into a weight. The type of hay, the baler used, size and density of the bale, and moisture will all play a part in determining the bale’s weight. The best way to determine bale weight is to load them onto a scale. If you are using a truck scale, be sure to note the weight of the empty truck and/or trailer and subtract it from the full weight. If there is more than one bale on the scale, divide the total weight of the bales by the number of bales on the trailer; this will give you the average weight per bale. Finally, take the average weight per bale times the number of bales per field and divide it by the number of acres in the field. If the weight is in pounds, divide by 2,000 to convert it to tons. Don’t forget to add up the amount from each harvest to get the total yield per acre per year.
What if you don’t have a truck scale? You can also weigh a smaller amount of hay. After the hay has been cut, but before it’s baled, collect the hay in a known area. For example, let’s use a windrow width of 12 feet. If you collect and weigh the hay from 10 feet long of the windrow, that would be an area of 12 feet by 10 feet, or 120 square feet. 120 square feet divided by 43,560 square feet per acre equals 0.0028 acres. If the amount of hay weighed 20 pounds, then 20 pounds divided by 0.0028 acres equals 7,142 pounds, or 3.5 tons per acre. Weigh hay from several different sections in the field in order to get a representative yield. It may help to put a box on the scale to contain all the hay collected; just be sure to subtract the empty box weight. This same collection method can be used for pasture. Take clippers and collect hay from a known area. Using the square footage and hay weight, you can then calculate yield in tons per acre.
Grazing sticks are also a handy tool to determine pasture yield. These sticks have a ruler to measure pasture grass height, a scale to determine stand thickness, and a simple table which takes the height and thickness into account and provides an estimate of the amount of forage available in pound of dry matter per acre per inch of growth. When using the grazing stick, take measurements every 25 steps, for example. Your eye will naturally be drawn to the taller and thicker grass spots, but it’s important to take samples from thinner and shorter areas, too, in order to get a more accurate yield estimate. Depending on the species and stand condition, grasses could range from 100 to 400 pounds of dry matter per acre per inch of plant growth. Using the height of the pasture, you can then calculate how many pounds of dry matter are available per acre. Keep in mind that you want to leave a few inches of growth so that you are not overgrazing the pasture.
So far, we’ve mostly talked about calculated yield on an as-is basis. In order to calculate the moisture percentage and calculate the amount of dry matter, weigh the hay after harvest; this will be the fresh weight. Next, dry the hay, either using a moisture tester or microwave. After the hay is dry, weigh it again. Dry the hay again and measure until a consistent dry weight is achieved. To calculate the moisture content, subtract the dry weight from the fresh weight. This gives you the weight of the water that was in the hay. Next, take the water weight and divide by the fresh weight and multiply by 100. For example, if the fresh weight was 1 pound, and the final dry weight was 0.40 pounds, the calculation would be as follows: 1 pound fresh (minus) 0.40 pounds dry (equals) 0.6 pounds water. 0.60 pounds water (divided by) 1 pound fresh (times) 100 (equals) 60 percent moisture, or 40 percent dry matter.
Kelly Nichols is an Ag Agent Associate with the Frederick County Extension Office. Her areas of focus are small farms and agronomy. Kelly can be reached at 301-600-3577 or email@example.com.