Length densities, occupancies and weights of apple root systems

Abstract

The root systems of apple trees from five orchards ranging in age from 1.5-y to 14-y were sampled to depths of between one and two metres using soil cores. Although trees came from orchards which differed in soil-type, tree spacings and management, consistent patterns were found in root systems. In orchards of 4-y and older, roots of adjacent trees met so that soil volumes within the planting grids (i.e, tree spacings of approximately 5 m inter-row x 4 m intra-row distances) were completely explored, although not completely occupied by roots. Mean root-length densities declined with depth for these orchards. In the 1.5-y orchard, roots from adjacent trees did not meet and root-length densities declined with radial distance from the stern as well as with depth.Root-length densities in the top i m ranged from zero to about 1.0 cm.cm -3 in all orchards and were highly variable. The proportions of core samples having zero values for root-length density were used to subdivide the root zone into volumes in which all samples contained roots, and volumes in which some samples had no roots.Results suggest that roots in an 'average' tree penetrate to at least one metre depth in all but very young orchards so that soil in this volume is fully explored. Volumes filled by roots and volumes occupied at any particular root-length density appear to reach a maximum at about 4 years. Volumes of soil occupied at any particular root-length density were equal in all orchards older than 4 years. This suggests that root growth was balanced by root death. In contrast woody roots continue to accumulate with time.

Spatial and temporal patterns of root distribution in developing stands of four woody crop species grown with drip irrigation and fertilization

“…In most reports that consider root development, stumps and large roots are excavated in time series with individual trees showing remarkably consistent relationship between above and belowground biomass that varies little among taxa and environment (cf Enquist and Niklas 2002). In a smaller number of studies, rooting density has been used to monitor site occupation by forest tree root system (Adegbidi et al 2004;Bouillet et al 2002;Hughes and Gandar 1993;Luxrnoore et al 1993;Misra et al 1998;Narnbiar 1983;O'Grady et al 2005;Zutter et al 1999). As in our work (Figs.…”

“…Temporal responses are equally important to define. For instance, root systems proliferate during forest stand establishment in proportion to plant production (Adegbidi et al 2004;Hughes and Gandar 1993;Misra et al 1998;O'Grady et al 2005), indicating increased root system capacity for nutrient and water acquisition. Defining spatial and temporal variation is essential to determining the relative magnitude of genetic and environmental fictors.…”

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

“…Furthermore, extensive soil coring in mature apple and kiwifruit orchards has shown that mean RLDs do not vary with distance from tree stems. (Gandar and Hughes, 1988;Hughes and Gandar, 1993). This does not mean that tree roots do not intermingle by intruding into empty space outside their allocated area.…”

“…However Hughes and Gandar (1993) noted that apples appear to explore available soil volumes substantially faster than kiwifruit. Because our five sampled species have different mean ages (Table 3) it is possible that some of the differences between mean exploitation indices (Table 2) could be attributed to differences in rootstock age.…”

“…Using this approach, they showed that kiwifruit (Gandar and Hughes, 1988) and apples (Hughes and Gandar, 1993), explored similar sized rooting volumes but took markedly different time periods to do it, and reached different mean RLD.…”