不同轮作模式对土壤团聚体有机碳与电导率的调控效应

Regulatory Effects of Different Rotation Patterns on Soil Aggregate Organic Carbon and Electrical Conductivity

摘要:

合理的轮作模式是提升土壤结构稳定性与维持土壤养分的有效措施。为探究河西走廊地区不同轮作模式对不同粒径团聚体土壤团聚体稳定性、有机碳与可溶性盐分(以电导率表征)分布规律的影响,本研究选取该地区3种典型长期轮作模式:2 a玉米+ 1 a茴香轮作(ZZF)、1 a葵花+ 1 a茴香轮作(SF)与2 a甜瓜+ 2 a茴香轮作(CCFF),以荒地(WL)作为对照,测定了0 ~ 40 cm土层不同粒径(大于2. 00 mm、0. 25 ~ 2. 00 mm及0 ~ 0. 25 mm)团聚体的有机碳(SOC)含量与电导率(EC)。结果表明:轮作模式显著提高粒径大于2. 00 mm团聚体比例(P < 0. 05),CCFF轮作模式下土壤平均质量直径(MWD)与几何平均直径(GMD)最高。0 ~ 20 cm土层,轮作模式下粒径0. 25 ~ 2. 00 mm与0 ~ 0. 25 mm团聚体的SOC含量显著高于WL(P < 0. 05),且轮作模式可以降低该土层土壤各粒径团聚体的EC。该土层粒径0. 25 ~ 2. 00 mm团聚体SOC含量分别与粒径0. 25 ~ 2. 00 mm、0 ~ 0. 25 mm团聚体EC呈显著负相关关系(R2分别为0. 68、0. 65)。20 ~ 40 cm土层,轮作模式下粒径大于2. 00 mm与0 ~ 0. 25 mm团聚体SOC含量显著高于WL(P < 0. 05),ZZF与SF轮作模式较WL显著提高土壤各粒径团聚体EC,CCFF轮作模式显著降低土壤各粒径团聚体EC,该土层各粒径团聚体SOC含量与EC呈显著正相关关系(P < 0. 05)。研究结果表明,长期的轮作模式显著影响了土壤有机碳与电导率在不同粒径团聚体中的分布规律,且这种调控效应因土层深度而异,CCFF轮作模式对促进土壤大团聚体比例提升与团聚体EC降低的效果最佳。

Abstract:

Crop rotation is an important management strategy for improving soil structure and sustaining soil fertility. The long-term rotation patterns influences on soil aggregate stability and distribution of soil organic carbon (SOC) and soluble salts represented by electrical conductivity (EC), among aggregate-size fractions in the Hexi Corridor of Northwestern China were investigated. Three typical long-term rotation patterns were examined: 2-year maize + 1-year fennel (ZZF), 1-year sunflower + 1-year fennel (SF), and 2-year melon + 2-year fennel (CCFF), with fallow land (WL) as the control. Soil samples were collected from the 0 ~ 40 cm profile, and SOC content and EC were determined in three aggregate fractions ( particle size r > 2. 00 mm, r = 0. 25 ~ 2. 00 mm, and r < 0. 25 mm). Crop rotation significantly increased the proportion of r > 2. 00 mm aggregates (P < 0. 05), with CCFF showing the highest mean weight diameter and geometric mean diameter. In the 0 ~ 20 cm layer, SOC content in the 0. 25 ~ 2. 00 mm and r < 0. 25 mm fractions was significantly higher under rotation than that under WL, whereas EC was lower in all aggregate fractions. SOC content in the 0. 25 ~ 2. 00 mm fraction was negatively correlated with EC in the 0. 25 ~ 2. 00 mm and r < 0. 25 mm fractions ( R2 = 0. 68 and R2 = 0. 65, respectively). In the 20 ~ 40 cm layer, SOC content in the r > 2. 00 mm and r < 0. 25 mm fractions was significantly higher under rotation than that under WL. Relatively to WL, ZZF and SF increased EC in all aggregate fractions, whereas CCFF reduced EC. In this layer, SOC content was positively correlated with EC across aggregate fractions (P < 0. 05). Overall, long-term crop rotation reshaped the distribution of SOC content and EC among aggregate fractions in a depth-dependent manner. Of the three systems, CCFF showed the greatest potential to improve aggregate structure and reduce salt accumulation as indicated by lower EC.