Responses of Agronomic Benefit and Soil Quality to Better Management of Nitrogen Fertilizer Application in Greenhouse Vegetable Land

As a result of intensive greenhouse vegetable production in northern China, the potential risk of nitrogen (N) fertilizer over-applied is increasingly apparent and is threatening ecosystem and the sustainability of food production. An experiment was carried out in Shouguang, Shangdong Province, China to evaluate agronomic benefit and soil quality under different N applications, including the conventional chemical N rate (1000 kg N ha−1 season−1, N1), 70% of N1 (N2), 70% of N1 + maize straw (N3), 50% of N1 + maize straw + drip irrigation (N4), and 0% of N1 (N0), during two successive growing seasons of autumn-winter (AW) and winter-spring (WS). The maximum yields for N4 were 1.1 and 1.0 times greater than those for N1 in the AW and WS seasons, respectively. N agronomic efficiency (AEN) and apparent N recovery efficiency (REN) were greatest with the N4. A significant relationship was found between soil NO−3-N content and electrical conductivity (EC) (R2 = 0.61 in the AW season and R2 = 0.29 in the WS season). Reducing N fertilizer decreased soil NO−3-N accumulation (20.9%37.8% reduction in the AW season and 11.7%20.1% reduction in the WS season) relative to the accumulation observed for N1 within the 0100 cm soil layer. Soil urease and invertase activities were not significantly different among N treatments. The N4 treatment would be practical for reducing excess N input and maintaining the sustainability of greenhouse-based intensive vegetable systems in Shouguang.