Catch crop planting and residue incorporation to reduce nitrogen leaching in intensive vegetable greenhouse field

Summer catch crop planting is commonly adapted to increase soil biodiversity and effectively reduce N leaching in intensively managed vegetable fields with double-cropping systems (winter-spring season and autumn-winter season) in China. However, little has been reported on the combined effects of summer catch crops (i.e., sweet corn [Zea mays L.]) and the incorporation of their shoot residue on N transformation and mobility in the soil profile. Here, we quantified dissolved organic N (DON) leaching, N release from the incorporated residue of sweet corn, and N movement in the rootzone using the N-15 isotopic labeling technique and a lysimeter in a vegetable greenhouse field. The results showed that catch crop planting in addition to shoot incorporation significantly increased DON by 127 and 158% in the leachate at a depth of 0.6 m, accounting for 40% of the total leached dissolved N at the first season, whereas catch crop planting without shoot incorporation resulted in the lowest N surplus. Approximately 46 and 69% of the total N in the root residue and shoot residue of sweet corn was measured in the collected leachates during the succeeding cucumber (Cucumis sativus L. 'Zhongnong No. 26') season, accounting for 8 and 62% of the total leached N, respectively. Hence, catch crop planting is feasible for removing legacy N from soil during summer fallow; however, residue incorporation should be assessed due to the increase in N leaching derived from the shoots of the catch crop in the following season.