Nitrate leaching from short-rotation coppice

In the UK, short-rotation coppice (SRQ is expected to become a significant source of 'bio-energy' over the next few years. Thus, it is important to establish how nitrate leaching losses compare with conventional arable cropping, especially if SRC is grown in Nitrate Vulnerable Zones. Nitrate leaching was measured using porous ceramic cups in each of the three phases in the lifespan of SRQ establishment, harvest and removal and was compared with conventional arable cropping. Nitrogen concentrations were increased in drainage water as soon as the crop cover was destroyed to plant the SRC (peak 70 mg L-1 nitrate-N) and increased further (peak 134 mg L-1 nitrate-N) on cultivation. Once the coppice crop was established, concentrations returned to a smaller level (average 18 mg L-1 nitrate-N). Concentrations were not affected by the harvesting operation, and annual applications of nitrogen (40, 60 and 100 kg ha(-1) N in the first, second and third years, respectively) had little effect. By contrast, concentrations in the arable rotation showed a regular pattern of increase in the autumn, and the average peak value over the 4 years was 54 mg L-1 nitrate-N. When the SRC was 'grubbed up' and roots removed, the soil disturbance resulted in a flush of mineralization which, combined with a lack of crop cover, led to increased nitrate-N in leachate (peak 67 mg L-1 nitrate-N). In a normal life-span of SRC (15-30 years), the relatively large nitrate losses on establishment and at final grubbing up would be offset by small losses during the productive harvest phase, especially when compared with results under the arable rotation.