长期保护性耕作对农田土壤水分和呼吸的影响

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

以保护性耕作长期定位试验为平台,从2011至2016年采用动态气室法(Li-cor8100)野外原位监测免耕与秋翻在轮作与连作两种不同种植模式下的土壤呼吸速率,解析了耕作方式对东北黑土碳循环过程的影响。研究结果显示,土壤呼吸速率表现出与土壤温度相同的季节性变化。玉米连作条件下,秋翻5-7月份土壤呼吸速率平均值显著比免耕分别高出20. 9%、14. 8%和6. 7%,而7-10月份,秋翻土壤呼吸速率平均值与免耕无显著性差异。在玉米大豆轮作的条件下,整个生长季节内秋翻与免耕处理的土壤呼吸速率无显著性差异。无论是在秋翻还是免耕处理下,轮作7月和8月的土壤呼吸速率均小于连作,但无显著差异。轮作土壤CO_2年释放量比连作高,其中秋翻高出3. 4%,免耕高出5. 9%。耕作处理对土壤水分含量的影响因种植模式而异。连作下免耕增加了土壤含水量,生长季节平均比秋翻增加14. 6%;轮作下免耕的含水量较秋翻高,但是差异不显著。土壤温度、土壤含水量与土壤呼吸速率混合模型分析表明,土壤温度、土壤含水量与土壤呼吸速率混合模型可解释土壤呼吸速率变异的52. 4%,且表明土壤呼吸与土壤温度呈明显的正相关关系。从土壤碳释放的角度出发,玉米免耕连作减少了作物生长前半期的土壤呼吸速率,并且增加了土壤水分含量,是有利于农田土壤有机碳固定的耕作措施。

Based on a long-term conservation tillage experiment and using LI-8100 automated soil CO 2 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.