Impact of soil spatial variability on young almond trees: A case study on heavy clay soils

The viability of modern horticulture heavily relies on adopting sustainable practices. Understanding soil spatial variability on heavy clay soils and its impact on young trees is crucial to design suitable soil and water management strategies that guarantee the sustainability of orchards. The objective of this study was to assess in an orchard with heavy clay soils of the Riverine Plain, NSW, the impact of soil spatial variability on the development of young almond (Prunus dulcis (Mill.) D. A. Webb) trees and evaluate the use of remote and proximal sensing tools for identifying threatening factors for the sustainability of the crop. Soil and aerial surveys were used to assess the soil and crop spatial variability in an 8.3-ha irrigation block. The site was divided into five areas based on apparent electrical conductivity (EC_a) measurements where soil samples were collected. Tree growth, soil, and plant water status were monitored in two contrasting areas in EC_a. In the first year of study, a significant and positive correlation was found between EC_a and percentage of ground canopy cover. Soil analysis and soil moisture monitoring revealed that high values of exchangeable sodium percentage, which are indicative of sodic soils prone to dispersion, and limited water infiltration were the cause of the reduced tree growth in areas with low EC_a. The impact of soil spatial variability on tree growth decreased in the second growing season due to weather and water management factors that influenced soil water content. This study showcases the usefulness of remote and proximal sensing in assessing potential soil-spatial-related issues in newly established orchards as well as the impact soil spatial variability can have on tree development in the first years after planting.