Nitrous oxide emissions affected by tillage measures in winter wheat under a rice-wheat rotation system

Abstract

It is well documented that nitrous oxide (N2O) emissions from agricultural soils are the result of complex interactions between climatic parameters and the physical, chemical, and biological properties of soils. Adopting no tillage or reduced tillage may therefore potentially affect N2O emissions from croplands through effects on soil properties; however, net effects are inconsistent and not well quantified globally. We used static chamber and gas chromatography techniques to examine the effects of different tillage measures (no tillage, rotary tillage, plow tillage) on N2O emission fluxes during the winter wheat season over 3 years (2008-2011) under a rice-wheat rotation system, in the lower reaches of the Yangtze River. The characteristic seasonal variation in N2O emissions during the winter wheat season under different tillage measures was defined as the peak in N2O flux observed within one month of basic fertilizer application, and/or from mid-April to the maturity stage of wheat after booting fertilizer application. Total N2O emissions were significantly influenced by year and tillage measures (P<0.01). Total N2O emissions were: no tillage > plow tillage > rotary tillage, averaging 2.50, 2.05 and 1.66 kg/hm2, respectively. Total N2O emissions for no tillage were 22.0% higher than for plow tillage (P<0.05), and rotary tillage was 19.0% lower than plow tillage (P<0.05). Correlation analysis showed that the relationship between N2O emission flux, soil water-filled pore space (WFPS), and soil temperature at 10 cm depth within a month of fertilization, varied with year and fertilization time. In 2009-2010, there was a significantly negative correlation between the N2O emissions flux and WFPS within a month of basic fertilizer application (P<0.05). In 2008-2011, significantly positive correlations between the N2O emissions flux and WFPS, and soil temperature at 10 cm depth within the month after booting fertilizer application were also found (P<0.05 or P<0.01). This illustrated that rotary tillage can effectively decrease total N2O emissions during the winter wheat season in a rice-wheat rotation system; this is thus the best tillage measure to reduce the greenhouse effect in the lower reaches of the Yangtze River.