Approaches to assessing soil nutrient cycling condition: A case study in the Hunter valley Wine district

Abstract

Assessing soil change is essential to understanding the impacts of management practices on the soil and for determining whether specific functionalities of soils have improved or degraded over time. This study applies the soil security assessment framework to investigate two approaches for estimating the condition dimension of the function "soil as a store and regulator of nutrients" in the Hunter Valley wine-growing region, NSW, Australia. The approaches evaluated include (i) the absolute difference and (ii) the relative difference between genosoils (reference state) and the respective phenosoils (current state) within the five main pedogenons of the study area (Stanleigh, Marrowbone, Tamburlaine, Sandalyn and Wandin). Additionally, we examined the application of these approaches at both the indicator stage and the final score stage, comparing the results using laboratory-based datasets and mid-infrared (MIR) spectroscopy-derived datasets. It was observed that the relativistic data can enhance the contrast between soil that has improved or degraded in nutrient cycling, showing more variation when mapping the average condition. The laboratory results were consistent across the approaches applied at both stages. Estimating condition from the final stage was preferred. The MIR dataset only aligned with the laboratory dataset when using the relative difference at the indicator stage. It was found that the five pedogenons had varying responses to viticulture management. The nutrient cycling condition of phenosoils improved in most of the region as the dominant pedogenon, Stanleigh had improved on average as well as Marrowbone. However, the other pedogenons were shown to be degraded in nutrient cycling condition.