不同施肥措施及复垦年限下土壤团聚体的大小分布及其稳定性

土壤团聚体的数量和质量直接影响着土壤性质和有机碳固存。研究长期不同施肥措施及复垦年限对采煤塌陷区土壤团聚体的重量分布比例及其稳定性的影响,为该区域的农业生产和土壤质量提升提供科学依据。采集复垦6年和11年定位试验不同施肥处理耕层土样,选取不施肥(CK)、平衡施氮磷钾肥(NPK)、单施有机肥(M)、有机无机肥配施(MNPK)4个处理,利用干筛法和湿筛法获得4种粒径的团聚体/粉黏粒组分(> 2 mm、0.25-2 mm、0.053-0.25 mm和< 0.053 mm),用> 0.25 mm团聚体含量(R_0.25)、平均重量直径(MWD)、团聚体破坏率(PAD)和土壤不稳定团粒指数(E_LT)表示团聚体的稳定性,并测定了土壤有机碳含量。结果表明：复垦年限对土壤团聚体的含量及稳定性影响产生了显著影响。干筛条件下,复垦6年和11年均显著降低了各处理0.053-0.25 mm团聚体和< 0.053 mm组分的含量,降幅分别为68.39%-87.37%、69.63%-78.32%(6年)和90.01%-93.68%、78.29%-83.93%(11年)；湿筛条件下,复垦11年显著提高了各处理> 2 mm团聚体的含量,增幅达473.35%-645.16%,但是显著降低了0.053-0.25 mm团聚体的含量,降幅为43.67%-57.54%。土壤团聚体的稳定性也随着复垦年限的增加而逐渐增强,表现为DR_0.25、WR_0.25和MWD值呈增加趋势,而PAD和E_LT值呈降低趋势。土壤有机碳含量与DR_0.25、WR_0.25、MWD_水稳性呈极显著正相关关系,而它与PAD和E_LT呈极显著负相关关系。本研究表明,该区域连续复垦11年提高了土壤大团聚体的含量而伴随着微团聚体含量的显著减少,导致土壤结构越来越稳定。它对提高采煤塌陷区复垦土壤肥力、改善土壤结构效果最佳。

Effects of Different Fertilization Regimes and Reclamation Age on Distribution and Stability of Aggregates in Reclaimed Soil

The quantity and quality of soil aggregates directly affect soil properties and soil organic carbon (SOC) sequestration. This study investigated effects of various fertilization regimes and reclamation age on the distribution and stability of dry aggregates and water-stable aggregates, aiming at providing a scientific basis for improving agricultural production and soil quality in long-term reclaimed areas, Shanxi Province, China. Surface soil samples of 0-20 cm horizons under different fertilization regimes were collected from a 6-year and 11-year reclaimed area, respectively. There are 4 different fertilization treatments [no fertilizer (CK), chemical fertilizer with nitrogen, phosphorus and potassium (NPK), organic manure alone (M), chemical fertilizer combined with manure (MNPK)]. All samples were separated into four aggregate-size fractions (> 2 mm, 0.25-2 mm, 0.053-0.25 mm and < 0.053 mm) by dry sieving and wet sieving methods. The > 0.25 mm aggregate content (R_0.25), mean weight diameter (MWD), proportion of aggregate destruction (PAD) and unstable soil aggregate index (E_LT) were used to indicate the stability of aggregates. The SOC content in the bulk soil was determined. The reclamation age had a significant effect on the distribution and stability of soil aggregates. Under the dry sieving condition, the distribution of 0.053-0.25 mm and < 0.053 mm fractions in each treatment was reduced significantly at both reclamation age, with a decrease of 68.39%-87.37%, 69.63%-78.32% (6-year) and 90.01%-93.68%, 78.29%-83.93% (11-year); under the wet sieving condition, the distribution of > 2 mm fraction increased significantly by 473.35%-645.16%, but the distribution of 0.053-0.25 mm fraction was significantly decreased by 43.67%-57.54% after 11-year reclamation. The stability of soil aggregates was also gradually enhanced with the increase of reclamation age, showing that the distribution of DR_0.25, WR_0.25 and MWD had an increasing trend, but the PAD and E_LT had a decreasing trend. After analyzing the sensitivity of the stability indexes of water-stable aggregates, PAD value was found to be the best indicator to describe the stability characteristics of water-stable aggregates in the plough layer. SOC content showed an extremely significant positive correlation with the DR_0.25, WR_0.25 and MWD_water-stable, but an extremely significant negative correlation with PAD and E_LT. It was concluded that the SOC content in the study area increased significantly after 11 years of consecutive reclamation, resulting in a more and more stable soil structure. It was conducive to improve stability of aggregates in this reclaimed area.