Technology, fertilizer costs and energy prices are driving changes in the economics of site-specific nutrient management. In the 1990s studies generally showed modest economic benefits from variable rate application (VRA). These studies showed higher profitability when input prices increase, if VRA led to more efficient fertilizer use. Recalculation of benefits in phosphate (P) and potash (K) VRA studies in Indiana with current prices suggest that VRA is more economically competitive at 2006 prices, but P and K price increases are not yet enough to make 1990s technology generally profitable for corn and soybean producers. Because of the nitrogen dynamics in the soil, VRA nitrogen is often more a question of risk management, than expected profits. Increased nitrogen prices have stimulated farm interest in VRA nitrogen and may eventually stimulate the development of technology that deals with the stochastic nature of nitrogen response. Among the new technology changing the economics of VRA are global positioning system (GPS) guidance, soil sensors and crop “greenness” sensors. The rapid adoption of manual lightbar GPS guidance and “hands free” auto guidance technology reduces skip and overlap in fertilizer application. Auto guidance is reviving interest in strip tillage and deep placement of P & K beside strips. A pH soil sensor is on the market and at least two research groups are working on a buffer pH sensor. A K soil sensor has been developed to work on the same principles as the pH sensor. At least three companies are marketing proximate “greenness” sensors for on-the-go control of nitrogen application. In Europe and in the US there has been some adoption of greenness sensor technology for spring nitrogen applications in winter wheat, but usefulness of the technology in corn and other cereals remains to be shown.