Basing nitrogen (N) applications on actual plant growth provides savings of about $18/acre, says a recent British survey. Wheat farmers there face dwindling crop prices and tight environmental regulations. The savings resulted from both reduced N application and improved yields. The three-year study used Leaf Area Index (LAI), a satellite measurement of actual plant biomass, rather than by soil type.

"A soil map alone doesn't reflect recent temperatures or nitrogen uptake," explains Simon Griffin, Soyl Precision Farming. His company takes LAI readings at each of three liquid N applications during the wheat growing season, and optimizes N application to the actual plant biomass. The company's website is