Abstract
In many agricultural areas, nitrogen pollution of groundwater owing to the influence of surplus chemical fertilizer inputs has been reported. In this study, we examine a cultivation system for satsuma mandarin that reuses nitrogen in groundwater to retrench chemical fertilizers and reduce their environmental impact. Specifically, we conducted a field test combining groundwater use and a drip irrigation and liquid fertigation system with year-round plastic mulching, a popular and stable production system for high-quality fruit. We quantitatively evaluated the eutrophication impact using the life cycle assessment method.
Consequently, in a standard cultivation system, the nitrogen emission had a very high impact of approximately 90% of the eutrophication impact. In the drip irrigation and liquid fertigation system, the nitrogen emission was drastically decreased and the eutrophication impact dropped to approximately 15% of that of the standard cultivation system. When the nitrogen balance was evaluated for the basin on the basis of a water source well, the amount of nitrogen in groundwater used by the drip irrigation and liquid fertigation system exceeded the amount of nitrogen emission during the satsuma mandarin production stage. Moreover, according to the estimated eutrophication impact, this cultivation system could be used as a purification system.
