THE USE OF SOIL RESOURCES IN HIGH DENSITY PLANTING SYSTEMS

The root growth, water use and mineral nutrition of trees of Golden Delicious/M.9 planted at densities from 1 700 to 111 000 trees/ha have been studied using a root observation laboratory.
Spacing modified the form of the root system as revealed by dry excavation, the predominant root orientation being horizontal at the wider spacings and vertical in the higher density plantings.
The amount of root/tree decreased while the density of roots in the soil and the proportion of roots at depth increased with increasing tree density.
Differences between the spacings in root density and distribution with depth decreased with time.
The seasonal periodicity of new root growth was similar at all spacings.

The soil water deficit in September increased with increasing density of planting although differences decreased during the life of the trial.
A similar pattern, between spacings, was shown in any one season with the higher density plantings using more of the water available to them early in the season.
The exploitation of soil water below 50 cm depth was greatest at the higher tree densities.
Although no mineral fertilizers were added during the life of the trial, concentrations of nutrients in the leaves remained adequate except for nitrogen at the highest densities where levels were marginal.
Large amounts of mineral nutrients were removed from the soil with only a small effect on the concentration of available nutrients in the soil.

Symposium on High Density Planting

D. Atkinson

https://doi.org/10.17660/ActaHortic.1978.65.12