Laboratory Lysimeter Analysis of NH3 and N2O Emissions and Leaching Losses of Nitrogen in a Rice-Wheat Rotation System Irrigated With Nitrogen-Rich Wastewater

TLDR: In this paper, the authors used repacked lysimeters with 90 cm height and 25 cm inner diameter for comprehensively determining ammonia (NH3) and nitrousoxide (N2O) emissions and N leachinglosses in a rice-wheat cropping system irrigated with N-rich wastewater from a live stock pond.

Abstract: Sewage effluents are increasingly used for farmland irrigation worldwide. This practice makes N losses via gaseous forms and leaching process more complex. Twelve repacked lysimeters with 90 cm height and 25 cm inner diameter were used for comprehensively determining am- monia (NH3) and nitrousoxide(N2O) emissionsand N leachinglossesina rice-wheat cropping system irrigated with N-rich wastewater from a live- stock pond. There were four irrigation treatments with three replications: wastewater with high N concentration (HW), wastewater with medium N concentration (MW, one-half dilution of wastewater of HW), wastewater with low N concentration (LW, one-fourth dilution of wastewater of HW), and ultrapure water control (CK). All treatments received equal amounts of total N (225 kg N ha �1 in the riceseasonand 150kgNha �1 in thewheat season) by balancing with commercial N fertilizer. The wastewater was provento be as effective ascommercialN fertilizer to achieve the optimum crop yields when applied in an appropriate amount. The NH3 emission, N leaching, and N2O emission losses accounted for 16.2 to 19.8%, 4.6 to 6.4%, and 0.26 to 0.35% of the total N applied in the rice season, respec- tively, whereas they were 2.7 to 3.3%, 2.2 to 2.8%, and 0.77 to 1.0% in the wheat season. Irrigating with wastewater did not change the NH3 emission flux pattern after N fertilizer (urea) was applied, but it boosted the NH3 emission flux to a certain extent in the rice season, especially for the MW treatment, which was mainly attributed to the high ammonium con- tent and pH of the flood surface water resulting from a combined effect of wastewater and urea-N application. In addition, N-rich wastewater irri- gation did not significantly increase N2O emission and N leaching when the total N inputs and the amount of irrigation were the same.