Comparison of various technical measures for controlling nitrogen loss from tomato-grown soil in greenhouse facilities

Tomatoes are the largest vegetable in China. The soils in which the tomato is grown experience heavy nitrogen loss owing to the application of large amounts of nitrogen fertilizer and irrigation, which aggravate nitrate pollution of the groundwater. To effectively reduce soil nitrogen loss caused by excessive nitrogen application and irrigation in tomato production facilities, we compared various control methods in this study by integrating physical barrier materials, fertilizer synergists, enzyme preparations, microbial preparations, and other products with fertilizer application technologies developed by the national key research and development plan project of China “Nitrogen and Phosphorus Pollution Load Reduction Technology and Product Development in Agricultural Facilities.” The best control technology was then developed to provide a reference for controlling soil nitrogen loss in vegetable fields. In this study, conventional fertilization (FP), optimal fertilization (OPT), physicochemical regulation (PCT), biological ecological regulation (BET), water and fertilizer regulation (WRT), and comprehensive regulation (CRT) were compared by applying physical barrier materials, fertilizer enhancers, enzyme preparations, microbial preparations, and other products that can prevent and control soil nitrogen loss. The tomato yield, soil nitrogen loss, and soil nitrogen form as well as the economic benefits of growing tomatoes with the different methods were determined. The methods were compared and screened for the best in controlling soil nitrogen loss. The results showed that OPT and FP yielded the same amount of tomatoes, whereas CRT yielded significantly higher amounts than those obtained from FP, OPT, or BET treatments (P < 0.05). The tomato yields of soils treated with PCT, BET, WRT, and CRT were respectively 4.70%, 2.05%, 7.93%, and 9.28% higher than that of the soil treated with FP. The CRT treatment resulted in the highest net income, followed by the WRT, PCT, and BET treatments, whereas the FP treatment had the lowest net income. The FP treatment furnished the highest total nitrogen content (114.8 kg∙hm⁻²) in soil leachate, which was 25.6%, 35.6%, 34.5%, 40.5%, and 40.9% higher than those of the OPT, PCT, BET, WRT, and CRT treatments, respectively. The nitrate nitrogen loss from the FP treatment was the highest (49.0 kg∙hm⁻²), being significantly higher than those from the other treatments (31.5%–49.2%), whereas that from the CRT treatment was the lowest. The FP treatment resulted in the highest organic nitrogen loss (65.8 kg∙hm⁻²), which was 21.2%, 37.7%, 31.5%, 38.0%, and 34.7% more than those from the OPT, PCT, BET, WRT, and CRT treatments, respectively. Organic nitrogen and nitrate nitrogen losses respectively accounted for 55.2%–62.9% and 36.7%–44.6% of total nitrogen losses in the different treatments, whereas ammonium nitrogen accounted for less than 0.5%. In the soil treated with FP, the nitrate nitrogen content in the 0–100 cm layer was lower than that in the soil treated with OPT, and the ammonium nitrogen content was lower than that in the soils treated with WRT and CRT. Moreover, the nitrate nitrogen content in the 20–100 cm layer was in the order of WRT > CRT > BET > PCT. In conclusion, in terms of both economic and environmental benefits, water and fertilizer regulation would be the best technology for controlling soil nitrogen loss in tomato cultivation facilities.