HOW TO REDUCE NITRATE LEACHING BY PRODUCTION OF PERENNIAL ENERGY CROPS

摘要

Denmark has ambitious policies on both the aquatic environment and on renewable energy. Producing perennial energy crops with low nitrate losses may combine these policies. This paper describes nitrate leaching from the energy crops Miscanthus and willow (Salix sp.) compared to leaching from traditional agricultural crops. Miscanthus is a C_4-crop originating from Southeast Asia, while willow is an indigenous crop to Europe. In the establishment phase leaching can be high from willow and Miscanthus - up to 150 kg N/ha have been measured. In fully established crops on sandy soils and at recommended fertiliser level, the nitrate-N concentration decrease to most often below 10 mg/L corresponding to an annual leaching between 0 and 20 kg N/ha. Similarly low levels were measured when the crops were fertilised with slurry or sludge. In annual agricultural crops, fertilised at recommended levels, the EU-limit for drinking water quality of 11.3 mg nitrate-N/L is often exceeded during wintertime in Denmark On sandy soils it is estimated that annual leaching from agriculture is more than 70 kg N/ha, and it is estimated that changing land use into perennial energy crops will reduce leaching with 40-65 kg N/ha.