Monitoring the behaviour of Australian Vertosols in response to the shrink–swell characteristic and cotton picker traffic

Abstract

Vertosols are widely used for cotton production globally. One main advantage of this soil type is its capacity to improve its structure gradually due to natural processes over time. However, Vertosols are highly susceptible to compaction, especially under wet soil conditions. This study investigated the change in characteristics of Australian Vertosols due to the impact of rainfall, seasonal variability, and John Deere 7760 cotton picker traffic. Soil cores were collected between October 2016 and May 2017. Measurements of soil physical properties (soil water content, dry bulk density, and soil penetration resistance) were carried out in the 0–80 cm depth profile during the study period. Increasing soil water content due to rainfall caused the Vertosol to swell, providing some degree of natural compaction alleviation and decreasing the dry bulk density and soil penetration resistance. Increased temperatures from October 2016 to January 2017 resulted in increased moisture evapotranspiration. This led to shrinkage of the Vertosol and resulted in increased dry bulk density and soil penetration resistance, particularly in the top 0–30 cm of soil. Traffic from the JD7760 cotton picker induced significant compaction throughout the depth profile. These findings have important implications for farmers intending to grow crops in Vertosols and managing the issue of soil compaction.