长期培肥下红壤有机碳组成与团聚体稳定性的关系

Composition of organic carbon and their relationship with aggregate stability in red soil under different fertilizer application

为研究培肥措施对红壤有机碳组成和团聚体稳定性的影响,以及有机碳与团聚体稳定性的关系,通过长期定位实验,选取不同施肥措施（未培肥CK、化肥NPK、化肥＋秸秆NPKS和粪肥AM）下的典型红壤为研究对象,分析土壤有机碳组成和团聚体稳定性差异,揭示3种施肥措施下不同层次的有机碳组成和团聚体稳定性的变化规律。结果表明,3种施肥措施均可以提高土壤表层（0-25 cm）有机碳质量分数（尤其是颗粒有机碳）,其中AM效果最显著,NPKS次之。不同施肥措施下红壤不同层次的团聚体稳定性顺序为AM〉NPKS〉NPK〉CK。与CK相比,AM处理对表下层（5-15 cm）土壤的总有机碳和团聚体稳定性的提高效果最显著。回归分析表明,颗粒有机碳（POC）与湿筛法平均质量直径以及快速湿润（FW）、慢速湿润（SW）、预湿润震荡（WS）3种处理的平均质量直径的相关性最好（R^2=0.79、0.80、0.66、0.81）,说明相对于其他组分,颗粒有机碳更有利于降低消散作用以及抵抗机械破碎进而增强团聚体稳定性,是间接评价土壤团聚体稳定性的良好指标。

[ Background ] The study was order to investigate the effects of fertilizer application on composition of organic carbon and their relationship with aggregate stability in red soil. [ Methods] The composition of soil organic carbon and aggregate stability were determined and analyzed to explore their differences and changing pattern at different soil layers under different treatments （no fertilization as a control , CK; chemical fertilization, NPK; chemical fertilization plus straw, NPKS; pig manure fertilization, AM） in 16 years＇ fertilizer experiment. [ Results] Results showed thatorganic carbon （especially particulate organic carbon （POC） ） in the topsoil （0 - 25 cm） increased under three treatments, as well as the rate of POC/TOC （total organic carbon） ; among these three treatments, the effect of AM was the most significant, followed by NPKS and NPK. Compared with CK, TOC, POC and MOC by AM increased respectively in0-5 cm by 120%, 257% and 62%, in 5-15 cm by 126%,134% and 79% , in 15 -25 cm by 78% , 228% and 52%. Soil organic carbon was mainly present in the MOC （mineral-associated organic carbon）. Different fertilizer application significantly improved the aggregate stability of surface soil （0 - 15 cm） , but the effect of them for the underlying soil was not obvious. Aggregate stability of red soil under different fertilizer application ranked in the order of AM 〉 NPKS 〉 NPK 〉 CK. Compared with CK, mean weight diameter obtained by wet sieving method of AM, NPKS and NPK increased respectively in 0 -5 cm by 44% , 32% and 6% , in 5 - 15 cm by 138% , 76% and 46%. Mean weight diameter （MWD） obtained by LB （Le Bissonnais） method at different pretreatment was generally in the sequence of fast wetting （FW） 〈 wet stirring （WS） 〈 slow wetting （SW） , and relative slaking index （RSI） was greater than relative mechanical crushing index （RMI） at the same level with all the treatments, indicating that the main breakdown mechanism of the soil aggregates was slaking. Soil aggregate stability was positively correlated with organic carbon. Regression analysis showed that determination coefficient of organic carbon and MWD obtained by wet sieving method, FW and WS of LB method was higher than that of organic carbon and MWD obtained by SW of LB method and the correlation of POC and MWD was the best （R^2 =0.79, 0.80, 0.66, 0.81）, indicating that soil organic carbon especially particulate organic carbon content could reduce slaking to enhance aggregate stability, and POC was a good indicator to evaluate the performance of soil aggregate stability indirectly. [ Conclusions] These results provide a basis for research of soil structure and soil fertility, and have a valuable reference for soil improvement, soil conservation and sustainable utilization of cultivated land in the Southern Red Zone.