Drip irrigation and application of straw reducing nitrogen leaching loss in tomato greenhouse

The excess fertilizers and irrigation water had resulted in low resource use efficiency, soil degradation, and ecosystem environment problems in greenhouse production system in China. How to maintain the good yield, and improve the resource use efficiency, reduce the environmental impacts of fertilizer, especially the N fertilizer, has become the problem that needs to be solved urgently. A long-term field experiment was conducted from 2008 to 2016 to evaluate the effect of different irrigation modes (drip irrigation and flood irrigation) and application of chicken manure combined with or without wheat straw or maize straw on tomato yield, recovery rate of added N, N leaching in the form of mineral N and dissolve organic N in solar greenhouse using a percolation pond. The percolation pond is 2 m long, 1 m wide and 0.9 m deep. At the second day after irrigation, the water leakage was sampled to measure the mineral N and total dissolved N content. Amounts of irrigation water under the drip and flood irrigation modes, which were 1173 and 1205 mm, respectively. The results showed that the yield of tomato was 105.8-127.4 and 70.6-95.9 t/hm2 in winter-spring and autumn-winter seasons, respectively. Compared with traditional flood irrigation mode, drip irrigation mode significantly increased tomato yield by 11.4% in winter-spring season, and by 21.7% in autumn-winter season. Nitrogen utilization (nitrogen uptake/nitrogen input) was 33.7% and 29.4% in winter-spring and autumn-winter seasons, respectively. The N utilization under drip irrigation mode was higher by 10 percent point in winter-spring season, and by 14.2 percent point in autumn-winter season than flood irrigation mode. Under the flood irrigation mode, the leached total dissolved N was as high as 114.3 and 281.1 kg/hm2, and accounted for 12.5% and 29.3% of the total applied N in winter-spring and autumn-winter seasons, respectively. Leached mineral N under the flood irrigation mode was 85.6 and 207.0 kg/hm2 in winter-spring and autumn-winter season, respectively. The irrigation amount of drip irrigation and flood irrigation had little difference for the whole year, but the amount of water leakage was significantly higher under the drip irrigation mode, the content of mineral N under the drip irrigation mode was lower by 51.1% than that of the flood irrigation mode, thus, the accumulated leached mineral N decrease by 80.1 kg/hm2 (38.7%), and the accumulated leached dissolved organic N decreased by 48.9 kg/hm2 (53.7%) in autumn-winter season. Application of wheat or maize straw had no effect on tomato yield, but significantly reduced annual irrigation water leakage by 24.3%, annual mineral N by 26.6% and annual dissolved organic N leaching loss by 33.7%. In general, the amount of dissolved organic N leaching loss should be considerable, drip irrigation mode decreased the N content in the water leakage and long-term addition of straw reduced the amount of water leakage, then additional application the straw under the drip irrigation mode is an useful field management to decreased the leach N.