Conservation farming practices in winter wheat–summer maize cropping reduce GHG emissions and maintain high yields

Abstract

No-till (NT), straw incorporation (SI) and optimized N fertilization are important mitigation options for reducing greenhouse gas (GHG) emissions from agroecosystems. These measures may also help to maintain high crop production and are frequently recommended for use in northern China. Few studies, however, have addressed the interactive effects of these conservation and fertilization practices with respect to GHG emissions and crop yields. We report on a field experiment conducted in two consecutive dry years (2013–2015) when precipitation was much lower than the long-term average. We examined the effects of three different N fertilizer application rates, tillage practice and straw management on crop yields, GHG, area-scaled GHG (in global warming potential) and net ecosystem economic budget (NEEB) of a winter wheat-summer maize rotation system in northern China. Results showed that reducing N fertilizer significantly decreased soil N2O emissions without affecting annual crop yields. Compared with the average of all other fertilization treatments, the no-till × straw incorporation (NT × SI) practice increased both wheat and maize yields. However, in the maize season, NT also increased cumulative N2O emissions compared with conventional tillage (CT). The practices of combining N fertilization with straw management conferred an additional effect on N2O emissions when compared with single practices (i.e. fertilization or straw management). Compared with straw removal (SR) treatments, SI increased annual cumulative N2O emissions by 37% for the conventional N fertilization, but decreased them by 13% at the optimized N fertilization. Neither single practice nor integrated practices had a significant effect on cumulative CH4 uptake. The highest NEEB values were obtained in NT × SI × optimal N fertilization (OPT) and NT × SR × OPT in the 1st and 2nd cropping years, respectively. We conclude that, when considering the additional benefits of SI for improving soil fertility and C sequestration, the NT × SI × OPT practice would be a viable strategy to achieve high crop yields, while simultaneously reducing GHG emissions.