Differentiation of potato ecosystems on the basis of relationships among physical, chemical and biological soil parameters

摘要

A study of soil physical, chemical and biological properties of five cultivated agro-ecosystems (two conventional potato, two organic potato and one cereal production systems) and two uncultivated agro-ecosystems (pasture and 20-yr abandoned potato field) was carried out at 21 field sites over 3 yr in New Brunswick, Canada. Twenty-four of the initial 42 variables chosen for their significant response to differences among farming systems were used in a principal component analysis to understand their relationships with the agro-ecosystems studied. The chemical, physical and biological soil properties considered contributed to a single dominant factor (PCI) of agricultural soil health representing soil organic matter dynamics. Conventional, uncertified organic and certified organic potato agro-ecosystems were lowest, intermediate and highest, respectively, on the PCI gradient. Conventional potato systems were characterized by high erosion, high soil bulk density, high soil test sulphur and phosphorus and high bacterial counts. Certified organic potato systems formed a separate group with the reference ecosystems (i.e., pasture and abandoned potato field under long-term rejuvenation). This group was characterized by high soil organic carbon, high soil aggregate stability, high soil water-holding capacity and high meso-and macro-fauna counts. The uncertified organic potato production system and organic barley system were characterized by average values, intermediate between conventional and certified organic potato systems. Results confirmed the strong negative impact of intensive cycles of conventional potato production on soil health. The clear separation observed between conventional, uncertified organic and organic potato ecosystems indicates that the positive impact of rotations and other management practices must be sustained over long periods for full rehabilitation of soils previously under intensive potato production. However, results also revealed that fields under organic certified potato production were retaining the properties of undisturbed reference sites such as pastures and abandoned potato fields under long-term rejuvenation.