Using Woody Perennials to Achieve Sustainable Broadacre Cropping Systems

摘要

Drainage of soil water below the rooting zone mostly in winter is a major threat to the long-term sustainability of agricultural land-use in much of the broadacre cropping areas of southern Australia. In this study we compared water-use of a mixture of three woody perennials, lucerne and continuous annual crops, and how they modified the capacity of the soil to store winter rainfall within the root zone, thereby minimising drainage. Water-use over the 20-month study period (October 1995 to May 1997) was in the order: woody species (1178mm) > lucerne (1067mm) > annual crops (984mm). The amount of water that drained below 2m depths, which was reduced by 44% under woody species and by 8% under lucerne compared to under annual crops. Excavation of the soil 2 years after the removal of the woody species found that significantly more biopores were formed in the subsoil, than under continuous annual crops. The initial water availability after the removal of woody species was low and inhibited the yield of the following annual crops for two seasons. This water deficit was overcome by the time of the third crop following woody perennials, when yield increased by 22% compared to continuous annual crops.