Cumulative transformation characteristics and application reduction potential of soil nitrogen in continuous cropping greenhouse

Abstract

ABSTRACT Based on the continuous watermelon greenhouses in Daxing District, Beijing, this paper investigated the dynamic transformation characteristics and surplus risk of soil nitrogen in greenhouses of different cropping years and proposed a reasonable nitrogen fertilizer reduction potential for greenhouses of different continuous cropping years. Based on the results, (1) The total nitrogen inputs gradually decreased with the increase of cropping years. The soil nitrogen was accumulated mainly in the 0∼30 cm tillage layer. The nitrogen supply capacity of the soil gradually increased over 20 years (a) of continuous cropping and declined after >20a. (2) The environmental risk levels of soil nitrogen surpluses with different cropping years in the study area had all reached heavy levels and above. The nitrogen fertilizer reduction potential was large, in which the lowest recommended nitrogen application rate was for the greenhouses with 1∼5a of continuous cropping, and the highest was for the greenhouses with 11∼20a of continuous cropping. For watermelon greenhouses with different continuous cropping years, the range of the highest reasonable nitrogen fertilizer reduction potential to ensure the economic benefits of farmers was 74.18% to 87.28%, and the lowest environmentally safe nitrogen fertilizer reduction potential to safeguard environmentally safe conditions was 69.22 to 78.11%.