Not a Waste Product: The nutrient value of manure is often severely discounted when making crop nutrient plans. Some soil test companies do not even consider it in their recommendations. Most of the nutrients from manure are retained in the soil. If not incorporated, the ammonia nitrogen is lost to the atmosphere.
But, the organic nitrogen is still retained and gradually becomes incorporated into the soil. This occurs by the action of tillage or earthworms and other soil organisms. The organic nitrogen becomes part of the soil biosphere.
Warmth = Conversion: If soil temperatures are warm, much of the organic nitrogen is mineralized into nitrate by soil bacteria and fungi. If you plant winter wheat or a cover crop after summer spreading, there is plenty of nitrate in the soil to get them growing. The rest of the organic and ammonium nitrogen is retained in the soil. There is usually a minimum of 4 to 6 lbs/ton available to the succeeding crop.
Phosphorus and Potassium: All manure contains phosphorus and potassium. These compounds don’t evaporate away. They become part of the soil. The analysis of manure varies, depending on the feeding program and the species of animal. But, dairy manure will normally have a minimum of 4 pounds of phosphate and 5 pounds of potash fertilizer equivalent. At 80 % availability that means a 15-ton per application is equal to 48 pounds of phosphate and 60 pounds of potash equivalence.
In a liquid system, a light application of 5 to 6000 gallons per acre will supply 65 pounds of phosphate and 80 pounds of potash equivalence per acre. These nutrients don’t leave the field except by erosion of surface particles or crop harvest.
Dollar Values: Nutrient prices have taken a substantial jump this year. Let’s take some round numbers and look at current manure values. At 45 to 50 cents per pound of N or Phosphate and 25 to 30 cents per pound of Potash, it is easy to come up with a value of $5 to $6 per 1000 gallons. If it is incorporated, the Nitrogen value is more. At 10,000 gallons per acre, that amounts to $50 to $60 per acre.
At these values, manure can be hauled much more effectively than in the old days. That way it can be used where you are likely to obtain the greatest crop response.
Test: Soil testing is the practice that makes it possible to tell where those fields are that will give a positive response. Soil test this fall to know where best to make those applications.
There are often conditions where frost tillage can be done over the winter. Last season there were several occasions when the ground was frozen with little or no snow cover. This is an ideal to inject manure and accomplish some primary tillage at the same time. Look for those conditions this winter and be prepared to apply. If you don’t have the equipment to inject, check with custom or contract manure applicators.
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