Difference in vertical root distribution of sugar beet (Beta vulgaris L.) and its relationship to soil properties in four typical soil profiles in Hokkaido, Japan

Abstract

Vertical distribution of the root abundance of sugar beet (Beta vulgaris L.) down to a depth of 1.8 m and its relationship with soil properties were examined in four typical soils, Andosol, Brown Forest soil, Gray Upland soil and Gray Lowland soil, found in Hokkaido, Japan. The depth of the root distribution was in the following order: Andosol (150 cm) > Brown Forest soil (120 cm) > Gray Upland soil (90 cm) > Gray Lowland soil (60 cm). Andosol had no marked soil physical limitations. Both Brown Forest soil and Gray Upland soil had firm layers with a penetration resistance of more than 2.5 MPa measured using a cone penetrometer below a depth of 30 cm. However, the Brown Forest soil had a relatively higher air-filled porosity (>0.1 m3 m−3), and both Brown Forest soil and Gray Upland soil had visible cracks, which could provide space for the elongation of plant roots. Thus, roots in these two soils could elongate until they reached a deeper layer, irrespective of the hard subsoil. The Gray Lowland soil not only had a lower air-filled porosity, but also a gley layer below a depth of 66 cm. This anaerobic condition might restrict root elongation. Root distribution patterns in the four soil types were quite different and these differences were reasonably interpreted using soil physical properties (e.g. hardness, air-filled porosity, macropores and the existence of a gley layer). The order of sugar beet yields at harvest corresponded to the difference in root distribution patterns.