Manure is one of those handy resources built in on the working farm. The fertilizer that comes out of the backends of livestock can be a real boost to the nutrient profile if applied correctly. A study by Paulo Pagliari from the University of Minnesota Extension has found that the phosphorous available in manure, while subject to a number of variations, can be a legitimate source of P and has the potential to trim expenditures on commercial NPK application.
Concerns over runoff have raised questions over the environmental impact of spreading manure, but the report states that simply working in the manure right after application can minimize the risk of losing nutrient to runoff. Another benefit of manure incorporation is that P may be stored in soils with a higher clay content as the mineralization rate in these types of soils is much slower.
The U of Minn. report says, "Phosphorus in organic compounds must first be mineralized before it can become available for plant uptake. Research has shown that soils high in clay content (greater than 12 percent) might have lower mineralization of organic phosphorus. The organic phosphorus may stay stored in the soil for more than one cropping season, which would provide a source of phosphorus for following growing seasons. This is also one of the forms of manure phosphorus that has been called residual manure phosphorus.
Phosphorus in manure is a valuable resource for crop production when applied correctly and has proven to improve crop yield to higher levels than commercial fertilizer. In contrast, inappropriate use of animal manure has been reported to negatively impact the environment. Therefore, it's important to understand the forms of phosphorus in manure and how manure interacts with soil before improved manure management strategies can be developed."
As always, soil testing is recommended along with manure nutrient testing. But incorporated manure, especially in soils with high clay content can increase P levels in the soil, moderate carryover and help growers save money on commercial fertilizer.