Potential strategies to reduce nitrogen emissions to the environment in an intensive cauliflower-leek rotation system: a modeling approach

摘要

An optimally calibrated and validated mechanistic model for the simulation of soil-crop-climate interactions, emphasizing on nitrogen fertilization and water use, was used to predict nitrogen emissions to the environment in relation to the following scenarios for a cauliflower-leek rotation in Belgium. The reference system included 4 N-dose fertilization rates, were dose 3 is matching standard commercial cropping conditions. The following potential reduction strategies were carried out for the 4 N-doses in a factorial design: 1. FF: a fractionated (by 4) weekly fertilizer application of each N-dose rate (with cumulatively the same amount). 2. SC: a soil cover or plastic mulch during winter fallow period preventing water infiltration and N-leaching between the harvest of leek and the start of cauliflower of the next rotation cycle. 3. FFSC: a combination of the two reduction strategies above. Overall, the crop yield showed benefits from one or both the reduction strategies under the lower N-dose rates compared to the higher. This was especially the case for the cauliflower cultivation from March to June. Regarding crop cultivations per year, under the lower N-dose rates, yield increased due to fractionated fertilizer application (FF and thus FFSC),which seems to correspond better with the daily N-demand of the crop over its entire cultivation period. N-stress is reduced, especially at the later stages of crop growth. Overall, a reduction in field nitrogen emissions to the environment is expectedimplementing one or both the reduction strategies. Whereas the FF system benefits the environment regarding ammonia volatilization (NH3) and nitric oxide (NOx) emissions, the SC system and even more the combined FFSC system reduce the nitrogen losses themost, regarding nitrate leaching (N03) and nitrous oxide (NzO) emissions. Nevertheless, as a result of the full Life Cycle Assessment, the environmental impact of the reduction strategy systems would be higher as compared to that of the reference system. Main reason is the extra material (plastic cover) and energy input needed by the reduction strategy, which is not compensated (enough) by the expected yield increase and/or reduced field nitrogen emissions to benefit the environment.