[Effects of Plastic Film Mulching and Nitrogen Fertilizer Application on CH₄ Emissions from a Vegetable Field]

To investigate the effects of plastic film mulching and nitrogen fertilizer application on CH₄ emissions from a vegetable field, static opaque and gas chromatography methods were applied, and in situ field observations of a chili-radish rotation system, from May 2014 to April 2016, were carried out in the Key Field Station for Monitoring of Eco-Environment of Purple Soil of the Ministry of Agriculture of China in the farm of Southwest University in Chongqing. Eight treatments were set up in the field experiment:control routine (no N application and no plastic film mulching) (NN0), control mulching (FN0), low N routine (NN1), low N mulching (FN1), conventional N routine (NN2), conventional N mulching (FN2), high N routine (NN3), and high N mulching (FN3). The characteristics and influencing factors of CH₄ emissions and the changes of soil carbon and nitrogen composition from all treatments were studied. The results showed that there was no significant difference in the CH₄ emissions from the vegetable fields between the mulching methods. From May 2014 to April 2016, the annual average cumulative absorption of CH₄ in nitrogen-free, low-nitrogen, medium-nitrogen, and high-nitrogen vegetable fields under film-mulching cultivation was 28.96, 51.90, 43.43, and 34.41 mg·m^-2, respectively. The average annual cumulative uptake of CH₄ under conventional planting was 40.76, 63.56, 62.77, and 21.92 mg·m^-2, respectively. Different nitrogen application gradients had no significant effect on CH₄ emissions from vegetable fields. There was a significant positive correlation between CH₄ uptake and soil temperature, and a significant negative correlation between CH₄ and soil water content. Plastic film coverage accelerated the mineralization of soil carbon in the pepper season, but there was no significant effect in the radish season.