有机肥施用量对土壤有机碳组分和团聚体稳定性的影响

为探明有机肥施用量对塿土有机碳组分和团聚体稳定性的影响,通过培养试验,在有机肥不同施用量(0%、1%、2%和4%,分别表示为T0、T1、T2和T4)和不同培养时间(120、180、240、300和360 d)下研究了土壤有机碳(SOC)组成如轻组有机碳(LFOC)、多糖、纤维素、水溶性有机碳(WSS)、富里酸碳(FAC)、胡敏酸碳(HAC)含量以及团聚体稳定性的动态变化.结果表明,施用有机肥增加了土壤有机碳及其组分,且随有机肥用量的增加而增加,与T0处理相比,培养至360 d时,T1～T4处理SOC、LFOC、多糖、纤维素、WSS、FAC、HAC含量和HAC/FAC比值分别增加了15. 3%～83. 2%、6. 8～15. 9倍、8. 5%～46. 4%、39. 3%～122. 6%、35. 7%～112. 9%、3. 3%～46. 9%、42. 5%～88. 3%和28. 5%～38. 6%;随着培养时间的延长,SOC和HAC含量呈降低趋势,LFOC先增加后降低,FAC和HAC/FAC比值呈现波动变化,多糖含量呈增加趋势.施用有机肥,降低了土壤中 2 mm力稳性团聚体的含量,增加了土壤中 0. 25 mm水稳性团聚体的含量,培养至360 d时,与T0处理相比,T4处理使水稳性团聚体平均重量直径(WMWD)增加了58. 6%,使团聚体的破坏率(PAD)降低了22. 2%.相关分析表明,有机碳及其组分间多数具有显著的相关关系,有机碳组分(除多糖外)与团聚体稳定性间也具有显著相关性.通径分析表明,土壤HAC含量和 2 mm力稳性团聚体的含量对力稳定性团聚体的平均重量直径(DMWD)具有显著的直接作用(P 0. 05); 2 mm和0. 25 mm水稳性团聚体的含量对WMWD具有极显著直接作用(P 0. 01);0. 25 mm水稳性团聚体的含量直接影响到团聚体PAD,SOC和WSS通过影响0. 25 mm水稳性团聚体的含量而间接影响到PAD.

Effects of Manure Application Rates on the Soil Carbon Fractions and Aggregate Stability

An incubated study was conducted to explore the effect of different manure application dosages (0%, 1%, 2%, and 4%, referred to as T0, T1, T2, and T4, respectively) on dynamic changes in the organic carbon fraction and aggregate stability of soil under different incubation times (120, 180, 240, 300, and 360 days). Soil organic carbon (SOC) and its fractions, such as light fraction organic carbon (LFOC), and polysaccharides, cellulose, water-soluble substance (WSS), fulvic acid carbon (FAC), humic acid carbon (HAC) content, and aggregate stability were measured. The results showed that SOC and its fractions were increased with increasing manure application rates. The SOC, LFOC, polysaccharides, cellulose, WSS, FAC, HAC contents and the HAC/FAC ratio increased by 15.3%-83.2%, 6.8-15.9 times, 8.5%-46.4%, 39.3%-122.6%, 35.7%-112.9%, 3.3%-46.9%, 42.5%-88.3%, and 28.5%-38.6% under T1-T4 treatments, respectively, compared to the T0 treatment at the end of the incubation period. With a longer period of incubation, the contents of SOC and HAC showed a decreasing trend, the LFOC increased first and decreased. The FAC content and the HAC/FAC ratio showed a fluctuation trend, but the content of polysaccharides showed an increasing trend. The application of manure decreased the content of >2 mm mechanically stable aggregates but increased the content of > 0.25 mm water stable aggregates in the soil. The mean weight diameter of water stable aggregate (WMWD) increased by 58.6%, while by the end of the incubation period, the percentage aggregate destruction rate (PAD) decreased by 22.2% under the T4 treatment compared to the T0 treatment. Correlation analysis showed that there was a significant correlation between SOC and its fractions, and between organic carbon fractions (except polysaccharides) and aggregate stability. Path analysis showed that the content of HAC and > 2 mm mechanically stable aggregate had a significant direct impact on the mean weight diameter of mechanically stable aggregate (DMWD) (P<0.05). Furthermore, the content of > 2 mm and < 0.25 mm water stable aggregates had a significant direct impact on the WMWD (P<0.01). The content of<0.25 mm water stable aggregates had a significant direct impact on the PAD (P<0.01), while the content of SOC and WSS had a significant indirect impact on the PAD via a direct effect on the content of<0.25 mm water stable aggregate (P<0.05).