Effects of long-term fertilization modes on spatio-temporal distribution and accumulation of soil nitrate nitrogen in solar greenhouse

Continuous localization experiment was conducted for seven years to study the spatio-temporal distribution and accumulation of soil nitrate nitrogen in solar greenhouse. The study showed that nitrate nitrogen content increased through soil profile with increasing planting time. The order of annual increment in soil nitrate nitrogen in relation to fertilization mode was as follows: conventional fertilization > low-input fertilization > organic fertilization. The main nitrate nitrogen distribution soil layer was 0~40 cm. Nitrate nitrogen content in the 0~60 cm soil layer was low at the early stage, high at the middle stage and low at the late stage of crop growth. Compared with the upper soil layers, nitrate nitrogen content in soil layers below 100 cm was increased. Average nitrate nitrogen accumulation in the 0~200 cm soil layer was 33.8% and 45.9% less in organic fertilization mode than in low-input and conventional fertilization modes. It was also 18.3% less in low-input fertilization mode than in conventional fertilization mode. Nitrate nitrogen leaching tendency to soil layers below 200 cm was observed in all three fertilization modes. Compared with conventional fertilization mode, organic fertilization mode obviously reduced nitrate nitrogen content in the soil profiles and retarded downward movement of nitrogen. However, improper application of organic fertilizer induced soil nitrate nitrogen leaching which led to environmental pollution.