The most imprtant soil physical property is soil structure, this being the nature and stability of the bonds between soil particle, causing aggregation and large soil pores.
第一个逗号前是主句 :The most imprtant soil physical property主语 is soil structure系表结构
两个逗号中间是独立主格结构,做状语,对主句进行补充说明 this逻辑主语 being the nature and stability of the bonds between soil particle .
第二个逗号之后是现在分词作状语,表结果 causing aggregation and large soil pores.
翻译：土壤最主要的物理特性是土壤的结构,这个结构是土壤颗粒之间结合的的稳定性和本质,它造成了聚合和大的土壤孔隙.