苜蓿对旱地土壤有机碳氮变化的驱动作用

Driving Effect of Alfalfa(Medicago sativa L.) on Dynamics of Soil Organic Carbon and Nitrogen in Dryland

根据旱地长期定位试验和分离土壤有机质中微粒有机质及矿物结合有机质的方法,研究了长期生长苜蓿对土壤有机碳、全氮变化的驱动作用。结果表明:不施肥条件下,苜蓿地土壤有机碳、全氮的含量比裸地土壤中的含量明显增加,土壤有机碳和氮库中的微粒有机碳、氮的含量没有显著增加,而增加的有机碳、氮主要分布在矿物结合有机碳、氮组分中。在施用有机肥及氮、磷化肥条件下,苜蓿地土壤有机碳和全氮的含量显著地提高,增加的有机碳、氮几乎平均地分布在微粒有机碳、氮和矿物结合有机碳、氮组分中。由此表明,保持适宜的苜蓿生产力并采用合理的施肥措施,长期生长苜蓿能够有效地驱动土壤固定有机碳和氮素,从而保持和提高土壤肥力。

Land use has a significant impact on change in soil organic carbon and nitrogen. The driving effect of alfalfa （Medicago sativa L. ） on the dynamics of soil organic carbon and nitrogen in dryland was studied based the long-term field experiment and the method for separating the soil organic matter into particulate organic matter and mineral-associated organic matter. The level of soil organic carbon （SOC） and nitrogen in the land grown alfalfa without fertilization increased compare with the bare land, the particulate organic carbon （POC） did not demonstrate significant changes whereas the mineral-associated organic carbon （MOC） and nitrogen increased. The status of SOC and N in the land grown alfalfa applied manure and N and P fertilizers showed significant increase compared with that in the land grown alfalfa without fertilizer, and the increased organic carbon and nitrogen distributed in the fraction of POC and MOC, respectively. These results suggest that applying the manure and chemical fertilizer in the alfalfa land and keeping the rational alfalfa productivity is the sustainable way to sequester organic carbon and nitrogen and to improve soil fertility in the semiarid area.