Manure Nutrient Management Quality of Life Team

January - March 2003

Virgil Schmitt , crops field specialist

Situation
A producer was concerned with narrow profit margins and his 3,650 acre crop and livestock operation was also having cash flow problems. He contacted Iowa State University through the Quality of Life Team grant.

Response
As part of the Quality of Life Team, the extension crops specialist examined all phases of the cropping operation. He determined that commercial nitrogen, phosphorus and potassium fertilizers were being applied at rates considerably higher than recommended by Iowa State University ; fertilizer was being applied annually to all acres; no credits were being given for nutrients in animal manure; preventive treatments for black cutworms were being routinely applied to all corn acres; and the herbicide program was overly expensive.

Impact
1. Cost of commercial phosphorus and potassium fertilizer. Given the soil test levels on the farm, phosphorus and potassium fertilizer levels were adjusted, which will lower the fertilizer cost approximately $15 per acre for at least the next six years. On 3,650 acres, this is $54,750 per year.

2. Cost of Nitrogen. Nitrogen is being applied at 25 - 50 pounds per acre higher than what is most likely needed. As the producer has variable rate application capabilities, it was recommended that he conduct strip trials on several fields comparing 100 pounds, 125 pounds and 150 pounds per acre and then checking with the late spring soil nitrate test, fall corn stalk test and yield checks using his combine monitor. Assuming the tests show that he can lower rates in the long run by at least 25 pounds of nitrogen per acre on 1,825 acres and that nitrogen costs $0.25 per pound, this is $11,406.25 per year.

3. Cost of Application. It was recommended that fertilizer be applied every second year with the application for both a corn and a soybean crop being applied in front of the corn crop. This will cut the application costs in half. 1,825 acres at $4.00 per acre is a cost savings of $7,300 per year.

4. Livestock Manure Credits. The livestock on the farm produce approximately 79,000 pounds of nitrogen, 49,000 pounds of phosphorus and 66,000 pounds of potassium annually in manure. At $0.25 per pound of nitrogen, $0.26 per pound of phosphorus and $0.16 per pound of potassium, the total value of the manure if it is credited against commercial fertilizer applications is $19,750 for nitrogen, $12,740 for phosphorus and $10,560 for potassium for a total savings of $43,040 per year.

5. Preventive Black Cutworm Treatments. It was recommended that the preventive black cutworm treatments be discontinued and the fields be scouted, assuming a preventive insecticide cost of $10 per acre, and a rescue treatment cost of $14 per acre with a rescue needed every one out of 17 years (average rescue cost of $0.82 per acre per year). The $10 per acre savings, by not making the preventive treatments, would be partially offset by $2.00 scouting and $0.82 rescue costs for an average savings of $7.18 per acre over 1,825 acres for a net savings of $13,100 per year.

6. Herbicide Costs. It was recommended to change the corn herbicide program to herbicides with virtually identical active ingredients but with much lower costs. The average savings will be approximately $8 per acre over 1,825 acres for a savings of $14,600 per year.
The total annual savings for at least the next six years will be approximately $144,200.

Page last updated: July 7, 2006
Page maintained by Linda Schultz, lschultz@iastate.edu