Effects of different models of applying nitrogen fertilizer on yield and quality of tomato and soil fertility in greenhouse

Continuously excessive nitrogen (N) input in greenhouse is one of the major problems in China, especially in Shouguang, Shandong province，a famous vegetable production base, and this led to deteriorate fertilization profit, product quality and soil quality, etc. Aiming at those problems, a field experiment was conducted to study the effects of different models of applying N fertilizer on yield and quality of tomato and soil fertility in greenhouse in Shouguang to provide better approaches and models to develop the sustainable utilization of soil. Compared with the local farmer's conventional model of applying N fertilizer (N1), the treatments of reducing 26% chemical N fertilizer (N2), reducing 26% chemical N fertilizer combined to adjust soil C/N ratio (N3), reducing 26% chemical N fertilizer combined to adjust soil C/N ratio and adopting drip irrigation measure (N4) and reducing 45% chemical N fertilizer combined to adjust soil C/N ratio and adopting drip irrigation measure (N5) respectively, could ensure the yield and quality of tomato. Total N uptake by plant, N use efficiency and N agronomic efficiency of the models to reduce N fertilizer application were higher than those of local farmer's, N5 treatment was significant higher in N use efficiency and N agronomic efficiency than N1（P<0.05）. The results showed that reducing N fertilizer combined with soil C/N ratio adjustment and/or drip irrigation can reduce chemical N application, increase the yield and quality of tomato. The nitrate accumulation of the treatment of N3, N4 and N5 were lower than that of N1. During winter-spring season, there were no significant difference in the contents of soil alkali-hydrolysable N, available phosphorus (P) and available potassium (K) and in soil urease activity and invertase activity, however, soil bacterium/fungi (B/F) ratio was higher under the integration models of N3 and N5. The results of all the above-mentioned indicated that reducing N fertilizer combined with agronomic measures can reduce the waste of fertilizer resource and remit degeneration of the soil quality, without loss of yield and quality compared to farmer's conventional fertilization approach. Above all the results showed that the integration models of N3 and N5 have a promising future and can provide the basis of the theory for studying the reduction of N fertilizer application, ensuring high grade and yield of the vegetable and soil sustainable utilization.