Long-term conservation tillage effects on soil respiration and soil water content

Based on a long-term conservation tillage experiment and using LI-8100 automated soil CO₂ flux system (LI-COR Inc., Lincoln, NE, USA), we measured soil respiration biweekly from 2011 to 2016, and assessed the effects of conservation tillage (no-till:NT) on soil carbon cycling in a Black soil agro-ecosystem in northeast China.We found that soil respiration showed a significant seasonal pattern which was similar to soil temperature and water content (SWC).The highest rate occurred in summer (July or August), followed by spring and fall.From May to July, soil respiration rates under mouldboard plough (MP) were 20.9%, 14.8% and 6.7% higher than those under NT in the monoculture maize, while there were no significant difference between MP and NT from August to October.There was no significant difference between MP and NT with the soybean-maize rotation.Rotation increased soil respiration rate in July and August by 3.4% and 5.9% compared with monoculture maize, respectively.The effect of tillage treatment on soil water content varied.Compared with MP, NT significantly increased soil water content by 14.6% under monoculture maize during the growing season; while the increase under rotation was not significant.The combined exponential model indicated that soil temperature and SWC could jointly explain 52.4% of variation in respiration showed that soil respiration had a positive correlation with soil temperature.These results suggested that NT under monoculture would be beneficial to soil carbon sequestration by decreasing soil respiration rate during the early period of growing season, and increasing soil water content.