耕作方式与水肥组合对小麦-玉米田温室气体排放的影响

气候变化是当前人类社会面临最为严峻的全球环境问题之一。中国作为当前全球温室气体排放的第一大国家，实现碳中和是应对气候变化的最根本举措。该研究以河北省晋州市周家庄乡为研究区域，以冬小麦-夏玉米轮作体系为例，通过对不同灌溉技术、灌溉方法和灌溉制度下的冬小麦-夏玉米农田开展耕作试验，结合作物产量和土壤CO2、N2O排放通量的测定，分析在保证作物不减产的情况下不同耕作方式和水肥组合下土壤CO2、N2O排放通量变化特征及其规律。结果表明：1）在当地传统灌水量和施肥量的基础上适当增大或减小，都会显著影响作物产量、水分利用效率；2）耕作方式与灌水量、施肥量三者间存在显著的交互作用（P<0.05），共同影响土壤二氧化碳当量的排放。与深耕相比，旋耕方式下的冬小麦-夏玉米土壤N2O排放通量依次降低21.19%、16.29%（P<0.05）；土壤CO2排放通量依次降低15.33%、8.29%（P<0.05）；3）优化水肥模式，适当减少灌水量和施肥量，可以在保证作物产量不低于当地传统产量的情况下兼顾节水与减排，从而降低农业温室气体排放，为碳中和做出贡献。

Effects of the tillage and combination of water and fertilizer on the greenhouse gas emissions of wheat-maize field

Greenhouse gases are ever increasing at the great risk of climate change in recent years. Climate change adaptation has been the most fundamental measure to achieve carbon neutrality. It is a high demand to reduce the agricultural carbon and nitrogen emission for water use efficiency during irrigation. In this study, a systematic investigation was made to clarify the effects of tillage systems on greenhouse gas emission and water use efficiency in farmland fields using the winter wheat-summer maize rotation system. The farmland experimental site was selected in the plot of the ninth production team of Zhoujiazhuang Town, Jinzhou City, Hebei Province of China. The test area was about 30 000 m2 with a width and length of 91, and 330 m, respectively. A total of 54 plots were then divided into the experimental area, each with a randomly arranged area of 120 m2 (8 m×15 m). The field experiment was performed on the different tillage and irrigation systems during the winter wheat-summer corn growing season from 2017 to 2018. The influencing factors were also determined, including the irrigation quantity, fertilizer application rate, and tillage mode. Among them, the conventional irrigation and fertilizer application were set as the control group in this case. The rotary and deep tillage modes were set at the same time. A total of 18 experimental treatments were carried out, each of which was arranged in the three experimental plots for repeat. Some parameters were measured, including the soil gas emission flux, crop water use efficiency, and crop yield. The test results show that: 1) There was a very significant level in the single factor effects of irrigation amount and fertilizer application rate on the yield and water use efficiency, as well as the effect of tillage mode on the yield, except for water use efficiency. There was no significant interaction between the three factors. Since the irrigation amount in a certain range increased the yield of the winter wheat, too much irrigation amount led to a significant decrease in the grain yield. The water use efficiency was higher than before when the irrigation amount was in the middle and low level. 2) There was the highest flux of N2O emission in summer during the growing period of winter wheat, while the lowest in spring and winter. Specifically, the N2O emission flux of soil showed several peaks, most of which occurred after irrigation during the growing period of summer corn. There was a positive correlation between the soil CO2 emission flux and soil surface temperature during the growing period of winter wheat. The peak of soil CO2 emission flux during the growing period of summer maize was concentrated in the stages from the seedling emergence to the jointing and from the tasseling to the silking. 3) There was a significant level in the interaction effects of irrigation water, fertilizer application, and tillage modes on the CO2-eq emission fluxes of winter wheat and summer maize. The mean N2O and CO2 emission fluxes were 261.57 mg/m2 and 7 885.52 kg/hm2, respectively, under the rotary tillage. In the deep tillage, the mean values of N2O and CO2 emission fluxes were 331.91 mg/m2 and 9 313.69 kg/hm2, respectively. The cumulative emission fluxes of N2O and CO2 under rotary tillage were 21.19% and 15.33% lower than those under deep tillage. 4) The low to medium level of irrigation and fertilizer application under the rotational tillage greatly contributed to the improved water utilization and crop yield, while reduced CO2-eq emissions. The CO2-eq emissions decreased by 3.4%, whereas, the water utilization increased by 8.16% under the low water and medium fertilizer rototill conditions. The CO2-eq emissions decreased by 1.9%, whereas, the water utilization increased by 19.9% under the medium water and low fertilizer rototill conditions. The CO2-eq emissions decreased by 13.8%, whereas, the water use efficiency increased by 12.24% under the low water and low fertilizer rototill conditions. The findings can provide a strong reference for the water saving and emission reduction of winter wheat and summer corn.