The benefit of leafy vegetable as catch crop to mitigate N and P leaching losses in intensive plastic-shed production system

Significant leaching losses of nitrogen (N) and phosphorus (P) from soil occurred during the summer fallow period of intensive plastic-shed vegetable production systems, which could be resolved by catch crops. We firstly estimated the economic profits and then evaluated the efficiencies of six catch leafy vegetables on reducing N and P leaching losses. Meanwhile, responses of soil nutrient contents and the yield as well as the quality of subsequent lettuce were observed under plot-scale experiment. The six leafy vegetables as catch crops can bring approximately 23, 000–43, 000 yuan RMB hm–2 extra economic profits to farmers. There were five catch treatments that reduced the NO3–-N leaching losses from 22.7 kg hm–2 under the control treatment to 4.6–15.8 kg hm–2. The total P leaching losses were lower under all six catch crop treatments (with 10.5–22.3 kg hm–2) than that under the control treatment (with 39.2 kg hm–2). The mitigation efficiency of catch crops on N and P leaching losses was dependent on the vegetable variety. Overall, vegetable crops did not exhaust soil available N but increased soil available P by 42.1% and organic matter content by 16.8%. The catch crop-based vegetable plantation did not influence yield and N and P uptake capacities of subsequent lettuce. As such, the qualities of lettuce (including the soluble protein, sugar, vitamin, and nitrate contents) were also not influenced following the plantation of catch crops. Leafy vegetable as catch crop during the fallow season increased farmer’s income while reducing N and P leaching losses. Moreover, there were no negative effects on subsequent vegetable production and qualities. We can also attempt to reduce the input of N and P chemical fertilizers to subsequent vegetable, as increased available P and organic matter were found in the catch crop treatments.