I drove out past Merced last year to see a dairy farmer testing a new idea. He irrigated 40 acres of feed corn with drip lines, which are much more common in orchards and vineyards than annual crops. The lines did more than conserve water. They delivered fertilizer, in the form of nitrogen-rich wastewater from one of the farm’s manure lagoons. Such precise application could reduce the risk of pollutants seeping into drinking-water aquifers – a concern with the widespread practice of flood irrigating with lagoon water.