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Kick-start your nutrient management planKick-start your nutrient management plan
Use your manure analysis to calculate the amount of nutrients to be applied.
3 Min Read
CHECK FIRST: Before you spread or inject manure, use your manure analysis to know how much of each nutrient is being applied. Or take the analysis to calculate how many tons of manure should be spread to hit a target nutrient amount. Tom J. Bechman
Sampling manure is just the start to better management of your nutrients. Now that you know how to gather and submit manure samples, you must understand and apply based on the analysis you receive from the lab. Utilizing that analysis will equip you with the knowledge of what you’re applying to your fields, keeping you from blindly spreading manure.
“We all have good intentions, but we need to know what we’re actually applying,” says Melissa Lehman, certified crop adviser and technical service provider at the Natural Resources Conservation Service. She also owns Agronomic Solutions LLC, based in Topeka, Ind.
Known as the “manure lady,” Lehman helps farmers better understand their manure and strategically plan how to best use it. She walks through an example of how to use your beef cattle manure analysis to understand what nutrients will be applied to a group of fields. From there, consult your NRCS technical service provider to develop a nutrient management plan.
Evaluate parameters. In this example, the spreader used is a New Holland 165. It has an 8-ton capacity. The fields to be covered span 65 acres, and it will take 122 full loads of manure to cover that acreage. These are simply parameters set forth in this example based on previous manure applications.
Get the per-acre amount. Given these parameters, Lehman says that you would first multiply the number of loads by the spreader capacity. Multiplying 122 by eight yields 976 total tons to be applied. You will then divide that amount by the acreage: 976 tons per 65 acres = 15 tons per acre.
Consult your analysis. The analysis in this example showed a first-year availability of 6.7 pounds of nitrogen per ton of manure, 14.1 pounds of phosphorus per ton and 20.8 pounds of potassium per ton. The phosphorus amount is in the form of phosphate and the potassium amount is in the form of potash.
Calculate the amount applied. To find how much of each nutrient will be spread per acre, you will multiply each one by the amount of manure applied per acre. Here are the calculations:
Nitrogen: 6.7 pounds per ton N x 15 tons per acre = 100 pounds per acre of N
Phosphorus: 14.1 pounds per ton P2O5 x 15 tons per acre = 211 pounds per acre of P2O5
Potassium: 20.8 pounds per ton K2O x 15 tons per acre = 312 pounds per acre of K2O
“You need to know where your numbers come from,” Lehman says. “A lot of times I work with producers, and they just have somebody pull their samples and give them recommendations. But they don’t know what they’re based upon or where they came from. So, you want to know where your numbers are coming from.”
Additionally, you can follow the formula in reverse to calculate how many tons per acre and total loads should be spread, based on the manure analysis. Say you want to apply 100 pounds per acre of nitrogen. In this example, you would multiply that by 6.7, found in the manure analysis, to equal about 15 tons per acre of manure that needs to be spread to achieve 100 pounds per acre of nitrogen.
Having these fertilizer numbers will allow you to go to your NRCS technical service provider and take an active role in understanding and developing your nutrient management plan.
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