Drip fertigation with reduced fertilizer and water inputs has been widely used in greenhouse vegetable production in China. However, farmers usually do not apply additional organic material with a high carbon content, although soil organic carbon (SOC) concentrations are mostly below the optimum level for vegetable production. Returning straw or biochar to fields is an effective strategy for sustainability and environmental friendliness. We tested whether drip fertigation, (DIF) combined with maize straw (DIF+S) or biochar (DIF+BC), is a suitable option to improve SOC sequestration over eight growing seasons, and how these options affect soil N2O emissions and yields or partial factor productivity of applied N (PFPN) of crops over three growing seasons. During the winter–spring growing season, DIF+BC significantly reduced soil N2O emission by 61.2% and yield-scaled N2O emission by 62.4%, while increasing the tomato yield and PFPN compared with DIF. Straw incorporation had similar trends but without significant effects. Conversely, straw and biochar incorporation increased N2O emission during the autumn–winter season. The structural equation model indicated N2O emission was dominantly driven by soil NH4+-N concentration, temperature and moisture. The N2O emission factor decreased significantly with increased PFPN. Moreover, the contribution of biochar to the increased SOC was approximately 78%, which was four times higher than that of straw incorporation. Overall, the results highlighted the potential of drip fertigation with biochar incorporation to mitigate N2O emissions, improve PFPN and significantly increase SOC storage, which could all contribute to maintaining environmental sustainability and soil quality of greenhouse vegetable production.

<p>Vegetable production in solar greenhouses in Eastern China generally suffers from over-fertilization and unreasonable irrigation, which result in severe soil degradation and soil-borne pathogens occurrence. Anaerobic soil disinfestation (ASD), as a newly developed economic technique, can combat pathogens in greenhouse vegetable soils. The ASD can create strong reductive conditions through the decomposition of added fresh C sources (crop residues or livestock manure) under saturated irrigation and warm conditions induced by plastic coverage to kill soil pathogens. However, ASD-induced organic matters application may increase N leaching and greenhouse gas (GHG) emissions, which remains unknown. Here, we investigated the effects of combined application of two crop residues (rice shells/maize straw) with different amounts of dry chicken manure (0, 300, 600, 1200 kg N ha<sup>-1</sup>) on N leaching and GHG emissions losses in greenhouse vegetable production systems adopting ASD technique in Eastern China. Our results showed that seasonal N leaching and N<sub>2</sub>O emissions ranged from 144-306 kg N ha<sup>-1</sup> and 3-44 kg N ha<sup>-1</sup>, respectively, which both significantly increased with manure application rate. Approximately 56-91% of seasonal N<sub>2</sub>O emissions occurred during the ASD period (5 weeks before vegetable transplantation), whereas 75-100% of total N leaching occurred in the following vegetable-growing season after ASD. The incorporation of crop residues significantly increased N<sub>2</sub>O emissions by 33-47% while decreasing N leaching by 26-27% compared with CK treatment. The application rate of chicken manure did not affect vegetable yield while significantly increasing the greenhouse gas intensity (GHGI) and reactive N losses intensity (NrI), with reducing 75% manure application significantly decreased 40-45% and 33-38% in GHGI and NrI, respectively. Our results demonstrate that overfertilization with conventional irrigation will not benefit the yield but at a high cost in environment N losses. Overall, current ASD schemes combined with additional manure and irrigation schemes need to be adapted to avoid GHG emissions and N leaching for reducing environmental pollution and improving the sustainability of greenhouse vegetable production systems.</p>