OFRA 52 (IMAGE) American Society of Agronomy Caption Researchers from Niger are doing an in-field assessment of the soil at one of their on-farm trial sites testing the sand content, soil pH and electrical conductivity and depth. Farmers often have trees in their fields for soil conservation and cycling of nutrients. Photo credit Charles Wortmann. Credit Charles Wortmann. Usage Restrictions Please use with 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.