Effects of combined application of organic manure and chemical fertilizerson N2O emission from greenhouse vegetable soil

The application of organic manure and chemical fertilizers is identified as significant sources of greenhouse gases in vegetable production. Less information is available on the effect of different fertilization patterns on nitrous oxide (N2O) fluxes from greenhouse vegetable soils. This study was conducted to determine the effect of combined application of organic manure and chemical fertilizers on N2O emission using the static chambergas chromatograph method under celerytomato rotation system in Tianjin from September 2010 to June 2011 The field experiment consisted of six treatments of 1 (no N), 2 (4/4 CN+0/4 PN, all nitrogen in chemical fertilizer, CN donotes N in chemical fertilizer and PN donotes N in pig manure), 3 (3/4 CN+1/4 PN), 4 (2/4 CN+2/4 PN), 5 (2/4 CN+2/4 SN, SN denotes nitrogen in straw), and 6 (CF, conventional fertilization). Equal NPK was designed for treatments 2, 3, 4, and 5 Rates of P2O5 and K2O application were respectively equal for each of treatments 1, 2, 3, 4 and 5 The results showed that: 1) the peak of N2O emission flux occurred within 5-7 days after basal fertilization (1-3 days after irrigation), whereas within 1 day after fertilizer topdressing (fertilization and irrigation were carried out simultaneously) during the celery and tomato growth period. 40%-65% of total N2O emissions during celery or tomato growth period were from over the first 20 days after basal fertilization. 2) The N2O emission fluxes gradually decreased after basal fertilization, then rapidly increased after irrigation. Significant correlations between the N2O emission fluxes for all treatments and soil moistures were observed, with correlation coefficients ranging from 0.43 to 0.72. 3) Distinct total N2O emission during tomato growth period was found, with the total amounts for all treatments being 3.1 times as high as that of the celery growth period. Significant correlations between the N2O emission fluxes for different treatments and soil temperatures in 5 cm layer during the celery and tomato growth period were generally observed, with correlation coefficients ranging from 0.40 to 0.58. 4) Compared with the conventional fertilization with much higher rates of N fertilizer, the combined application patterns of organic manure and chemical fertilizers significantly decreased the total N2O emissions by 66.3% and 85.1% as well as loss ratio of N fertilizer by 45.2% and 74.9% during the celery and tomato growth period, respectively. 5) Straw application compared with pig manure application with the same N rate respectively decreased the N2O emission by 43.4% and 74.2% during the growth period of celery and tomato under this experimental condition.