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

<p><b>Purpose</b> 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.<br/><b>Materials and methods</b> 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.</br><br/><b>Results and discussion</b> 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.</br><br/><b>Conclusions</b> 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.</br></p>