Collect Soil Samples (IMAGE) American Society of Agronomy Caption Researchers collect soil samples from a crimped -- or flattened -- cover crop plot. Farmers can use cover crops to choke weeds and retain soil fertility. Credit Photo credit Kerry Clark. 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.