Long-Term Study Shows Benefits of Poultry Manure as Fertilizer

A 20-year study by Iowa State University researchers showed that fertilizing crops with poultry manure can benefit soil health and farm profits when compared to a commercial fertilizer. In the study’s first decade, experiments compared three treatments in a corn-soybean rotation, and in the second 10 years, treatments for continuous corn cropping were compared. After 20 years, the study found particulate organic matter and several other measures of soil quality were significantly better in the manured plots. Corn yields increased from manure treatment during the continuous corn phase of the study, and were similar during the corn-soybean phase. Although the manure treatment was generally more expensive, the increased yields helped offset this cost. Additionally, nitrate-nitrogen losses were 7% to 16% lower from the cropland fertilized with manure.