| Nitrogen input has been more than actual needs of crop since ever, which resulted increasingly serious problems of resources waste, environmental pollution and soil quality degradation. Excessive nitrogen input may result from flooding irrigation. Optimized nitrogen management, under conventional flooding irrigation conditions, failed to significantly decrease nitrogen input in greenhouse vegetable production and increase risking of nitrogen leaching losses. As a combination of the fertilization and irrigation, fertigation technique can have precise control of the amount of irrigation and fertilization, which has applied in Europe and other developed countries. However, due to inadequate reference of vegetable nutrition needs and other basic information, the study of irrigation and fertilization regime is insufficient, the application of fertigation in greenhouse vegetable production has not yet universal in our country. The greenhouse tomato double-cropping system at Shouguang, Shandong were studied to compare the tomato yield, the inter-annual variation of yield, water and nitrogen use efficiency, soil nitrate leaching and economic benefic under conventional flooding irrigation system (CI) and drip irrigation system (DI), so that provide a theoretical basis for achieving sustainable development greenhouse vegetables. A long-term field experiment was conducted in Vegetable Research Institute of China Agricultural University in Shouguang, Shandong from2008to2013, which included two main treatments (drip fertigation, conventional flooding irrigation and fertilization) and three vice treatments (without straw, with wheat straw and with corn straw). Tomato yield, apparent N balance, soil nitrate residues and leaching, soil respiration, soil organic carbon and soil total nitrogen and the natural abundance were investigated to study the productivity, environmental and economic effect of systems on these traits. The results are as following:1) Compared with CI, fertilizer N and water inputs were reduced by78%and46%under DI, respectively, while nitrogen partial productivity and irrigation water use efficiency were significantly increased. Tomato yield and economic benefits were increased by6%and22%with DI. Total number of tomato fruits was significantly increased in DI, increasing of planting density was the main reason of yield improvement. Straw application was helpful to increase tomato yield in two cultivation systems.2) In autumn-winter growing season, the root length density of new developed roots in0-50cm soil layer was significantly higher in DI, and the inter-annual variation of yield was significantly lower than CI. No significant differences were found among two cultivation systems for the root length density of new developed roots and the inter-annual variation of yield in winter-spring growing season. Comparatively speaking, drip irrigation and fertilization was a relatively stable production system.3) The average seasonal apparent nitrogen loss was398kg N/ha in CI, while it was only70kg N/ha in DI. The average seasonal nitrate residue was819kg N/ha at the depth of0-90cm in CI, while it was only412kg N/ha in DI.4) Total nitrate leaching loss reached240kg N/ha in CI, while it was only17kg N/ha in DI. One to two days after flooding irrigation was the main period of nitrate leaching in CI. Conventional flooding irrigation was a major contributor to excessive N inputs in greenhouse vegetable production. Straw application was helpful to reduce nitrate leaching.5) No significant differences were found among two cultivation systems for soil organic carbon and soil total nitrogen. However, the application of straw was helpful to improve soil organic matter accumulation in greenhouses. Straw application significantly increased soil respiration rate, while there no significant differences were found among two cultivation systems for accumulated CO2emission. |
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