长期不同轮作模式对黄壤团聚体组成及有机碳的影响

依托23年的黄壤长期定位田间试验,对比研究玉米单作(MM)、小麦||绿肥–玉米轮作(WMR)和油菜–玉米轮作(RMR)对土壤团聚体组成及有机碳的影响。结果表明:各处理机械稳定性团聚体和水稳性团聚体均以大团聚体(>0.25 mm的团聚体)为优势团聚体,占比高达93.04%和74.59%以上;WMR和RMR处理较MM处理显著提高了5~2 mm和2~1 mm机械稳定性团聚体含量及>5 mm和5~2 mm水稳性团聚体含量;WMR处理的水稳性团聚体MWD(平均重量直径)较MM处理显著增加了50%;WMR、RMR处理的PAD(团聚体破坏率)和ELT(土壤团聚体不稳定团粒指数)较MM处理分别显著降低了31.32%、25.97%和35.90%、30.65%;不同粒级水稳性团聚体中均以WMR处理的有机碳含量最高,>5、1~0.5、0.5~0.25 mm粒级团聚体的有机碳含量比MM处理显著增加了17.60%、34.41%、45.67%;土壤团聚体有机碳主要集中在>0.25 mm的大团聚体中,而在微团聚体中含量较少,轮作主要提高了>5 mm水稳性团聚体中有机碳的贡献率,WMR、RMR处理较MM处理分别提高了23.18和9.16个百分点。小麦||绿肥–玉米轮作能有效改善土壤团聚体组成,提高团聚体稳定性和有机碳含量,可作为贵州黄壤旱地较佳的轮作模式。

Effects of Different Long-term Rotation Patterns on Aggregate Composition and Organic Carbon in Yellow Soil

The effects of rotation patterns on soil aggregate composition and soil organic carbon were studied in this paper in order to setup rational rotation pattern in yellow soil based on a successive 23-year field experiment, in which three treatments were chosen:maize monoculture system (MM), wheat (intercropping green manure)-maize rotation (WMR) and rape-maize rotation (RMR). The results showed that >0.25 mm aggregates were the dominant component of the mechanically stable and water stable aggregates with the proportion beyond 93.04% and 74.59% respectively. Compared with MM treatment, WMR and RMR treatments significantly improved the contents of 5-2 mm, 2-1 mm mechanical stability aggregates and the contents of >5 mm, 5-2 mm water stable aggregates; WMR treatment significantly increased MWD (mean weight diameter) of water stable aggregates by 50%; WMR and RMR treatments significantly decreased PAD (percentage of aggregate destruction) and ELT (soil aggregates unstable mass index) by 31.32%, 25.97% and 35.90%, 30.65% respectively. WMR treatment had the highest organic carbon content in different size levels of water stable aggregates, and organic carbon contents in >5, 1-0.5, 0.5-0.25 mm aggregates increased by 17.60%, 34.41% and 45.67% respectively compared with MM treatment. The contents of soil aggregate organic carbon was mainly in >0.25 mm aggregates, higher than that in microaggregate (<0.25 mm). Rotation measures mainly increased the contribution rate of organic carbon in >5 mm water stable aggregates, WMR and RMR treatments increased 23.18 and 9.16 percentage points respectively compared with MM treatment. In summary, wheat (intercropping green manure)-maize rotation can effectively improve the composition of soil aggregates, improve the stability of soil aggregates and organic carbon content, thus, is a reasonable rotation pattern in the yellow soil of Guizhou.