Managing Global Resources for a Secure Future

Irrigation with reclaimed water has become an important agricultural practice due to potentially alleviating the scarcity of fresh water resources. Reclaimed water contains a great amount of organic materials and inorganic N, these nutrient materials via reclaimed water irrigation could alter the soil fertility status and C/N cycling, and thus affect greenhouse gas emissions. A 2 years field plot experiments irrigation with reclaimed water and ground water during summer maize-winter wheat crop rotation was conducted in Beijing, and C/N mineralization incubation experiments were also carried out at the same time. The field experiments showed that reclaimed water irrigation did not significantly increased soil CO₂ and N₂O emissions. N fertilization had no significant effect on soil CO₂ emissions. But N fertilization significantly increased soil N₂O emissions, the emissions of N₂O in urea and ammonium sulfate fertilization treatments were significantly higher than that in slow-release urea fertilization treatment. Compared with furrow irrigation, drip irrigation did not significantly increased the emissions of CO₂ and N₂O. Reclaimed water irrigation had no significant influence on crop yields and quality of summer maize and winter wheat, N fertilization significantly increased the crop yields of summer maize and winter wheat, but no significant difference among different N fertilizer types. Soil C and N mineralization experiments showed that N fertilization significantly increased DOC, DON, soil organic carbon and soil organic nitrogen, N fertilization significantly enhanced the mineralization of C and N, reclaimed water did not increase the mineralization of C and N. N fertilization and DOM are the two important factors for C and N mineralization. These results showed that irrigation with reclaimed water, using drip irrigation, and fertilization with slow-release urea can not only maintain crop yields, but also save fresh water resources and decrease greenhouse gas emissions.