我国三种种植制度下农田土壤有机碳、氮关系的演变特征

Changes in soil organic carbon and total nitrogen and its relationship under three typical cropping systems in China

对34个国家级耕地质量监测点20余年连续监测数据进行了统计分析,旨在探讨常规施肥下我国旱作、水旱轮作和稻田系统土壤碳、氮关系的演变特征。结果表明,1985-2006年,我国常规施肥方式下旱地、水旱轮作和稻田系统表层土壤有机碳和全氮均显著增加,三种种植制度下土壤C/N演变存在一定差异。土壤C/N均值从1985-1990年的9.87上升至2001-2006年的10.32。20年期间,土壤C/N分布在9-11的区间范围内的频率为45%-48%;土壤C/N在7-9区间的分布频率从27.5%减少到14.5%,但在11-13区间的分布频率从15.6%增加到27%,且30%以上的旱地连续监测点土壤C/N呈显著增加趋势。进一步分析表明,土壤C/N与土壤速效磷、速效钾以及磷肥和有机肥的投入量呈显著正相关关系,而与土壤pH值呈显著的负相关关系。表明常规施肥方式中,磷肥和有机肥投入促进了土壤中有机碳和全氮的积累,且对旱地土壤有机碳积累的贡献大于对氮素积累的贡献,是土壤碳、氮关系演变的重要影响因子。

Based on data of 20-year continuous observation from 34 sites around the country,we analyzed the characteristics of changes in SOC,TN and the relationship between SOC and TN in dry cropland,wheat-rice system and paddy fields under conventional fertilization.The results showed that SOC and TN contents in topsoil increased significantly in dry cropland,wheat-rice system and paddy fields,while the changes in the soil C/N ratio varied among the three typical agro-ecosystems during the last 20 years of conventional fertilizations.The average of soil C/N ratio in these three types of agro-ecosystems changed from 9.87 in 1985-1990 to 10.32 in 2001-2006.The frequency of soil C/N ratio at the range of 9-11 were about 45% to 48% during the last 20 years.However,the frequency of soil C/N ratio at the range of 7-9 decreased from 27.5% to14.5%,whereas the frequency of soil C/N ratio at the range of 11-13 increased from 15.6% to 27% from 1985 to 2006.Moreover,soil C/N ratio at more than 30% of contentious long-term observation sites in dry cropland increased in the last 20 years.Further analysis indicated that there were significantly positive correlations between soil C/N ratio and the content of available P,available K,and the input amount of phosphorus fertilizer and organic nitrogen in manure,while there was a significantly negative correlation between soil C/N ratio and soil pH.Overall,conventional fertilization accompanied with phosphorus fertilizer and organic manure promoted the accumulations of SOC and TN,and the effect on SOC accumulation exceeded the effect on TN.All these results indicated that application of phosphorus fertilizer and organic manure was the most important factor that affected the relationship between soil organic carbon and nitrogen.