Engaging Farming Networks (IMAGE) Stanford University Caption Farmers in Mexico's Yaqui Valley use a nitrogen sensor to optimize fertilizer application, thus reducing costs and agricultural runoff. Credit Ivan Ortiz-Monasterio, Stanford University Usage Restrictions Photographs provided by the Woods Institute for the Environment at Stanford University are to be used - with appropriate credit - for editorial purposes only. Flopping, altering or otherwise embellishing these photos in any way that changes the photographs' editorial content is prohibited. Images provided for web use must be resized to low resolution. Permission is for one-time use only. Supplied image file must be deleted after use. 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.