Effect of temperature and precipitation on nitrate leaching from organic cereal cropping systems in Denmark

• Nitrogen leaching was affected by seasonal changes in temperature and precipitation.
• Nitrogen leaching was also affected by location and use of catch crops.
• Autumn/winter soil management was the main determinant of N leaching.
• Nitrogen leaching increased with increases in temperature and precipitation.

The effect of variation in seasonal temperature and precipitation on soil water nitrate (NO3N) concentration and leaching from winter and spring cereals cropping systems was investigated over three consecutive four-year crop rotation cycles from 1997 to 2008 in an organic farming crop rotation experiment in Denmark. Three experimental sites, varying in climate and soil type from coarse sand to sandy loam, were investigated. The experiment included experimental treatments with different rotations, manure rate and cover crop, and soil nitrate concentrations was monitored using suction cups. The effects of climate, soil and management were examined in a linear mixed model, and only parameters with significant effect (P < 0.05) were included in the final model. The model explained 61% and 47% of the variation in the square root transform of flow-weighted annual NO3N concentration for winter and spring cereals, respectively, and 68% and 77% of the variation in the square root transform of annual NO3N leaching for winter and spring cereals, respectively. Nitrate concentration and leaching were shown to be site specific and driven by climatic factors and crop management. There were significant effects on annual N concentration and NO3N leaching of location, rotation, previous crop and crop cover during autumn and winter. The relative effects of temperature and precipitation differed between seasons and cropping systems. A sensitivity analysis revealed that the predicted N concentration and leaching increased with increases in temperature and precipitation.