Kiwifruit root systems 1. Root-length densities

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Abstract
Root-length densities (RLD; root length per unit volume of soil) were measured in core samples taken from nine North Island kiwifruit orchards. Despite differences in vine spacings, root-stock ages and types, soils, climates, and management, there was a consistent pattern to root systems. In orchards younger than 10 years, roots explored bowl-shaped soil volumes and mean RLD fell with both depth and radial distance from vines. In older orchards, root systems of adjacent plants met so that soil volumes available to plants were completely explored and mean RLD fell with depth. Roots were found at depths greater than 1 m in most orchards. In both young and old orchards, RLD ranged from 0 to 8 cm/cm3 but proportions of zero values increased towards the peripheries of root systems. These proportions were used to subdivide rooting volumes into volumes of total occupancy in which all RLD were greater than zero, and volumes of partial occupancy in which volumes containing roots were interspersed with ‘void’ volumes without roots. These results are discussed in relation to water and nutrient uptake.