2/23/2013 7:00 AM
By Laura Zoeller Southwestern Pa. Correspondent
BELLE VERNON, Pa. — One of the most important pieces of information a farmer can understand is the Law of Diminishing Returns.
This law states that there is a point at which there is no additional benefit from an action that is being taken.
Edward B. Rayburn, an Extension specialist with West Virginia University, spoke recently on that topic and how it relates to lowering the cost of cow-calf production and optimizing stocking rates.
“If your soil needs the pH improved, lime will help that,” Rayburn said. “But there is a point at which adding more lime will no longer give you an improvement.
“In all of our farming practices, we want to find that optimum point and meet it, but not exceed it,” he said. “Once we exceed it, we are just wasting money, and it is my goal to get two dollars back on every dollar I spend.”
According to Rayburn, one of the first things a farmer should do is get into the habit of testing his soil and forage.
“A good soil tester runs between $80 and $100,” he said. “That is cheaper than a ton of fertilizer, and a test may show that you don’t need to fertilize certain fields or parts of fields. Good hay tests may indicate that cows may not need grain or supplements. We want to substitute farm resources in place of cash-purchased products wherever possible.”
Rayburn suggested that breaking fields into smaller test units could be beneficial, as slopes and flats don’t always test the same.
“A whole field sample may test in the low range,” Rayburn said, “while the fact is that the slope is OK and the flat is not, or vice versa. Knowing which sections are suboptimum saves you money over fertilizing the entire field.
“Another option for adding nitrogen back into the soil is to plant legumes instead of adding urea,” he said. “A field that has had corn on it for several years will need a higher percentage of legumes before the maximum yield is reached, but in an old stand, as little as 30 percent can do the job.”
Rayburn said that the harvest of one ton of hay removes 10 to 12 pounds of phosphorus and 40 to 50 pounds of potassium from the soil, and that it can be replaced in a number of ways.
“You can apply 0-11-45 fertilizer to a field at a rate of 100 pounds per ton of hay removed,” Rayburn said. “Or, you can use your cows to replace it. There is between $50 and $75 worth of nitrogen, phosphorus and potassium in a ton of hay. You can feed the hay to your cows and then spread the manure on the hayfield.
“It is often cheaper to buy additional hay and spread the manure than it is to buy the fertilizer and apply it,” he said. “Additionally, there is approximately $270 worth of fertilizer nutrients in each ton of mineral supplement that many farmers feed their cows. You will get much of that returned to you out the back end of the cow. Use that manure on your hayfields also.”
Rayburn indicated that stocking rates depend on a number of factors as well, including grazing management, forage testing and how close cows are allowed to graze the pastures.
“One of the first things to figure out is if you have a buffer area,” Rayburn said. “Do you have fences around your hayfields and croplands that the cows can be turned onto after the harvest? Are you set up to rotational graze? Rotationally grazing and utilizing your buffer areas can nearly double the optimum stocking rate on a farm.”
Rayburn’s research indicates that the optimum grazing is begun when the grasses are between 8 and 10 inches tall, and the cows are moved when the paddock is grazed to a 2-inch height.
“Even in a drought, you do not want to open up all of the gates and allow the cows to access all of the paddocks,” Rayburn said. “Put them in an abuse area and feed them some hay instead. The grass will still make sugar and store it until it rains. Then it will make up some ground.”
Stocking rates will depend on what type of animals and their size, the forage productivity and grazing management, but there is a rule of thumb.
“Keeping fewer animals means more gain per head, but wasting forage,” Rayburn said. “Keeping more animals means they compete for the forage but may individually perform a little less.
“Finding the number where the gain per acre meets with the gain per head is the optimum number of cows,” he said.
“An old farmer’s saying is that stocking at 85 percent will get you through 85 percent of droughts,’ and that is good advice,” he said.
“I would really say, though, that as long as your cows are ending the grazing season with a body condition score of six, that they are maintaining a good body condition score at calving with no additional supplements, and that they are grazing until the deep snow hits, then you are doing some things right.”