李 婕， 杨学云， 孙本华， 张树兰

(西北农林科技大学，农业部西北植物营养与农业环境重点实验室， 陕西杨凌 712100)

1 材料与方法

1.1 试验地概况

1.2 试验设计

1.3 样品采集与分析

2011年冬小麦收获后，将各小区划分为3部分，每个处理采集3个重复。采取0—10，10—20，20—30 cm土层的原状土。将采集的原状土样在室内沿自然结构轻轻掰成小土块，过10 mm筛，自然风干，备用。

1.4 数据处理

各大小机械稳定性或水稳性团聚体的含量(%)=各大小机械稳定或水稳性团聚体质量(g)/土壤样品总质量(g)×100，土壤团聚体稳定性以团聚体破坏率(PAD)衡量，参照陈山[16]的方法计算，公式如下：

PAD(%) =(Wd-Ww)/Wd×100

式中：Wd为机械稳定团聚体中>0.25 mm团聚体所占的比例；Ww为水稳性团聚体中>0.25 mm团聚体所占的比例。

不同土壤管理措施对团聚体的影响采用单变量方差分析，当方差分析结果显著时，采用LSD法进行处理间平均值的多重比较，所有数据采用SPSS 16.0进行分析。

2 结果与分析

2.1 不同土壤管理措施对土团聚体分布的影响

表1 不同土壤管理措施下机械稳定团聚体的组成(%)Table 1 The composition of dry aggregates under different soil management practices

注(Note): 同列数据后不同字母表示同一层土壤不同管理模式间差异达5%显著水平 Values followed by different letters in a column are significant among management practices in the same soil layer at the 5% level.

表2 不同土壤管理措施下水稳性团聚体的组成(%)Table 2 The composition of water stable aggregates under different soil management practices

注(Note): 同列数据后不同字母表示同一层土壤不同管理模式间差异达5%显著水平 Values followed by different letters in a column are significant among management practices in the same soil layer at the 5% level.

2.2 长期施肥对土团聚体分布的影响

表3 长期不同施肥下不同土层土壤机械稳定团聚体的组成(%)Table 3 The composition of dry aggregates of different soil layer under different fertilizations

注(Note): 同列数据后不同字母表示同一层土壤不同处理间差异达5%显著水平 Values followed by different letters in a column are significant among treatments in the same soil layer at the 5% level.

2.3 不同土壤管理措施团聚体破坏率差异

表5显示，长期不同土壤管理措施对团聚体破坏率有很大的影响。在0—10 cm土层，与作物体系相比，休闲和撂荒显著降低了团聚体破坏率，并且休闲和撂荒之间没有显著差异。10—20 cm土层，撂荒措施的团聚体破坏率显著低于作物体系和休闲， 休闲与作物体系相似。20—30 cm土层，休闲、 撂荒与作物体系相比，团聚体破坏率均没有显著差异。

从表6可以看出，长期不同施肥对土壤团聚体破坏率有一定影响。0—10 cm土层，与CK处理相比，M1NPK显著降低了团聚体破坏率，而其它处理团聚体破坏率没有明显变化。10—20 cm土层，除NPK处理较CK的团聚体破坏率显著提高外，其它处理的团聚体破坏率也没有显著变化。20—30 cm土层，除NK、 NP较CK处理显著增加团聚体破坏率外，其它处理的团聚体破坏率也没有明显的变化。

3 讨论

3.1 不同土壤管理措施对团聚体分布的影响

不同土壤管理措施对土壤机械稳定性或水稳性团聚体分布的影响主要限于表层和亚表层(0—10，10—20 cm)(表1，表2)，这可能主要与耕作扰动以及植物根系主要集中在该区域有关。

表4 长期不同施肥下不同土层土壤水稳性团聚体的组成(%)Table 4 The composition of water stable aggregates of different soil layer under different fertilizations

注(Note): 同列数据后不同字母表示同一层土壤不同处理间差异达5%显著水平 Values followed by different letters in a column are significant among treatments in the same soil layer at the 5% level.

表5 不同土壤管理措施下土壤团聚体破坏率(%)Table 5 The values of PAD under different soil management practices

注(Note): PAD—Percentage of soil aggregate disruption. 同列数据后不同字母表示同一层土壤不同管理模式间差异达5%显著水平 Values followed by different letters in a column are significant among management practices in the same soil layer at the 5% level.

表6 长期不同施肥处理下土壤团聚体破坏率(%)Table 6 The values of PAD under different fertilizations

注(Note): PAD—Percentage of soil aggregate disruption. 同列数据后不同字母表示同一层土壤不同处理间差异达5%显著水平 Values followed by different letters in a column are significant among treatments in the same soil layer at the 5% level.

3.2 长期施肥对团聚体分布的影响

4 结论

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