Open access publications in the SLU publication database

High doses of nitrogen (N) fertilizer may increase N leaching with drainage. This increase is likely to be dependent on crop N uptake and grain yield response. To study nitrate leaching with different fertilizer N rates and grain yield responses, field experiments in spring oats were conducted in 2007, 2008 and 2009 on loamy sand outside Skara in Sweden. Nitrate leaching was determined from nitrate concentrations in soil water sampled with ceramic suction cups and measured discharge at a nearby measuring station. The results showed that the increase in nitrate leaching from increased N fertilization was insignificant as long as each extra kg of fertilizer N resulted in at least a 10 kg increase in grain yield (85% DM). Above this fertilization level, the yield response gradually ceased and the nitrate leaching response gradually increased. As a consequence, nitrate leaching per kg grain produced had its minimum around this fertilization level. The economic optimum fertilization level depends on the price relationship between fertilizer and grain, which in Sweden usually vary between 5 and 15. In other words, precision fertilization that provides a 10 kg increase in grain yield per kg extra N fertilizer can be optimal for crop profitability at the same time as nitrate leaching is not elevated.