长期机械耕作压实对绿洲农田土壤优先流的影响

Effects of long-term mechanical compaction on preferential flow in oasis cropland

长期机械耕作压实会对土壤的物理性质和水力特性产生显著影响,进而影响土壤优先流强度,但机械耕作压实对土壤优先流强度的影响仍存在较大争议。本研究在临泽绿洲农田边缘持续压实区(CC)和正常耕作区(对照,CK)分别设置3个样方,利用亮蓝溶液进行原位染色试验,测定土壤容重、土壤孔隙度和土壤饱和导水率等指标,分析长期机械压实对土壤优先流的影响。结果表明:长期机械耕作压实对耕作层(0～20 cm)的土壤物理和水力特性无显著影响,而对犁底层20～60 cm的土壤物理和水力特性影响显著(P<0.05)。其中,持续压实区土壤剖面20～60 cm土壤容重增加了10.8%,土壤总孔隙度减少了11.9%,土壤饱和导水率减少了32.3%。长期机械耕作压实显著改变了土壤优先流特征及强度。持续压实区的土壤优先流呈现明显的横向流,显著区别于正常耕作区的大孔隙流;并且持续压实区的土壤优先流显著大于正常耕作区的土壤优先流(P<0.05),主要体现在最大入渗深度(P<0.05)。本研究结果表明,长期机械耕作压实显著改变了耕作层以下的土壤物理和水力特性,并加强了土壤优先流强度。

Long-term mechanical compaction could affect soil physical and hydraulic properties.These changes have further influence on the strength of soil preferential flow,but there is no consensus on such effect.To investigate the effects of long-term mechanical compaction on soil preferential flow,we set three plots in each of the margin area(continuous compaction area,CC)and normal farming area(CK)in the Linze oasis croplands,and carried out a dye tracer experiment using the brilliant blue FCF solution.We measured soil bulk density,total soil porosity,and soil saturated hydraulic conductivity.Our results showed that long-term mechanical compaction had no effects on soil physical and hydraulic properties in the plow layer(0-20 cm),but had significant effects in the plow pan(20-60 cm)(P<0.05).Mechanical compaction increased soil bulk density by 10.8%,and decreased total soil porosity and soil saturated hydraulic conductivity separately by 11.9%and 32.3%at the 20-60 cm depth.Long-term mechanical compaction significantly affected the characteristics and strength of soil preferential flow.Lateral flow in continuous compaction area was significantly different from the macropore flow in normal farming area.The strength of soil preferential flow in continuous compaction area was also significantly greater than that in normal farming area(P<0.05),which was mainly related to the maximum infiltration depth(P<0.05).Our results indicated that long-term mechanical compaction significantly affected the soil physical and hydraulic properties in the plow pan and enhanced the strength of soil preferential flow.