Unloading manure (IMAGE) American Society of Agronomy Caption The researchers used excess cattle manure from local producers. Here a donor deposits composted cattle manure prior to spreading it over the field sites. Credit Paul Green Usage Restrictions For use with this story only. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.