| The cultivation of vegetables is an important utilization of agricultural farmland in China, and the issue of nitrogen (N) non-point source pollution due to improper N fertilizer application has become increasingly prominent. This study examined the results of field experiments conducted in 3 years, in which seven different fertilizer treatments (no fertilizer, CK; organic fertilizer, OF; conventional fertilizer, CF; organic-inorganic compound fertilizer, OIF; sulfur-coated urea, SCU; biological carbon power urea, BCU; and bulk-blend controlled release fertilizer, BBCRF) were applied to Chinese cabbage crop in an intensive vegetable cultivation base located in Taihu Lake basin. The research examined the features and influence mechanism of ammonia (NH3) volatilization, N runoff loss and leaching loss of the vegetable field, as well as the effects of different fertilization treatments on the yield, quality, and nitrogen utilization efficiency of Chinese cabbage. In addition, this research developed an effective ecological interception system, performed project demonstration and running effect analysis. This study has provided a theoretical basis for the vegetable producing industry to choose environmentally-friendly and effective application of N fertilizers, as well as technical support and project demonstrations for the control of non-point source pollution of vegetable agriculture. The main findings are as follows:(1) NH3 volatilization rate was significantly and positively correlated to topsoil pH and NH4+ concentration. In the OF, CF and OIF treatments, NH3 volatilization occured mainly in the 7 days after fertilization, peaked at 3-4 days after fertilization, and reduced to near control level within 14 days after fertilization. Application of the three slow-release fertilizers were found to be able to extend NH3 volatilization process, where the peak of volatilization was observed 7-9 days after fertilization, and the volatilization slowly reduced to control level in approximately 20 days after fertilization. Compared to CF treatment, OF treatment promoted NH3 volatilization by 11.77%-18.46%, while OIF treatment reduced the process to some extent, by 9.09%?13.16%. slow-release fertilizers had significantly positive effects on controlling NH3 volatilization, and BBCRF treatment achieved the best reduction of NH3 volatilization by 79.44%?84.77%.(2) NO3--N was the main runoff component, accounting for 49.32%?71.82% of the total N runoff losses. NO3--N concentration was significantly and positively related to total N (TN) concentration in the runoff. Significant differences in N runoff loss were observed between N fertilizer treatments. N runoff losses from CF treatment were 10.43?22.68 kg·ha-1, significantly higher than that from other treatments, and the TN net runoff loss rates for CF treatment were 3.48%-7.56%. Compared to CF treatment, OF and OIF treatments could reduce N runoff losses to some extent, with a reduction rate of 15.70%-18.14% and 27.37%-36.27%, respectively. Applications of the 3 slow-release fertilizers could significantly reduced N runoff loss in vegetable field, of which BBCRF had the best reduction effect, with a reduction rate of 59.79%-63.59%.(3) Application of N fertilizer significantly reduced leachate volume in vegetable field. NO3--N is the main form of N leaching in vegetable field, accounting for 53.99%?78.59% of the total N leaching losses and there is an extremely significant positive linear correlation between NO3--N and TN concentration in leachate. Application of N fertilizer could significantly increase N leaching losses in vegetable field. TN leaching losses in CF treatment was significantly higher than that in other treatments. Compared with CF treatment, OF and OIF treatments showed certain reducing effect on nitrogen leaching loss in vegetable field, with reduction rates of 16.68%?23.58% and 25.83%?31.40%, respectively. However, the applications of the 3 slow-release fertilizers (SCU, BCU and BBCRF) showed highly significant effects on reducing N leaching losses, and the reduction rates were 50.45%?63.03%, 49.43%?55.71% and 52.40%?60.90%, respectively. N leaching severely affected groundwater quality in vegetable field, and there was a significant linear positive correlation between the groundwater and leachate NO3--N concentration in each treatment. Compared to CF, the reduction effect of NO3--N contamination risk was most prominent in the applications of slow-release fertilizers.(4) Different N fertilizer treatments was the main factor affecting Chinese cabbage yield, quality and N utilization rate. Compared with CF, OF application significantly reduced the yield and nitrogen utilization efficiency of Chinese cabbage, while the applications of OIF and slow-release fertilizers could improve yield and nitrogen use efficiency of Chinese cabbage. The quality of Chinese cabbage was decreased by N fertilizer application comparing with no fertilizer application, but when comparing with CF treatment, the Chinese cabbage quality improved in different degrees when OF, OIF and slow-release fertilizers were applied.(5) N and P concentration in farmland drainage were significantly reduced by implementing demonstration project of ecological interception system in typical intensive vegetable cultivation lands. After two years effective operation, the TN concentration of the main outlet was 1.56?3.41 mg·L-1, the removal rate was 47.24%?66.84%; and the TP concentration was 1.12?0.28 mg·L-1 of the main outlet, the removal rate reached 43.43%-81.58%. This ecological interception system could effectively control non-point source pollution of vegetable field, reduce the risk of eutrophication, and produce a good ecological landscape in the demonstration area, as well as achieve cyclic utilization of regional water bodies. |
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