Exploration and exploitation of soil by apple, kiwifruit, peach, Asian pear and grape roots

Measurements of root-length density (RLD) in a range of 31 apple, kiwifruit, peach, Asian pear and grape orchards were used to derive indices to describe the exploration and exploitation of rooting volumes. Orchards were of various ages and located on a range of soil types, geographic regions, management systems etc. Data were obtained from core samples of volume 1.66×10-4 m3 randomly taken within a “standard volume”, determined by average planting grids, of 2 m radius centred on tree stems, and 1 m depth. Root systems were described using an exploitation index, E(ϕ), and an exploration index, E(0). E(ϕ) is defined as the proportion of the soil volume which contains roots at RLD greater than or equal to some specified value, ϕ. E(0) is defined as the proportion of the soil volume which contains roots at any RLD greater than zero. These indices are dependent on sample size, as are all volumetric or soil-coring data.