Assessing the soil health of farmers’ conservation agriculture fields using the Biofunctool® index in South Africa

Abstract

The conservation agricultural system offers distinct benefits compared to conventional agricultural management systems. Its capacity to lower input expenses, enhance soil's physical, chemical, and biological characteristics, and boost yields is known, with the potential to support sustainable intensification in numerous cases. However, due to the rising interest in managing agricultural fields for soil health and the profound reliance of humans on these ecosystem services, it is necessary to concentrate more on assessing the soil health condition of conservation agriculture fields to assure the applicability of field-level management strategies. To produce a robust interpretation of soil health, a mix of chemical, physical, and biological factors is commonly used. However, testing the major soil health indices is costly and time-consuming. As a result, the Biological Soil Functioning Assessment Tool, known as Biofunctool®, was created to assess total soil health by combining soil biota and physico chemical parameters. The tool contains a collection of field indicators of three primary soil functions: soil nutrient cycling, carbon transformation, and structural maintenance, providing a holistic analysis of soil health status. Research has recognized that different soil organisms supported by soils play a significant role in the functioning of ecosystems. Therefore, researchers use soil enzyme analysis as a measure of soil health due to their close link to biological and physio-chemical features of the soil. The study took place in two contrasting agroecosystem regions, namely the North-West and Free-State provinces of South Africa, over a period of 4 seasons, namely, August 2021, March 2022, August 2022, and February 2023. The Biofunctool® parameters were only tested in August 2022 and February 2023. The aim of this study was to assess the soil health of farmers' conservation agriculture systems in different agroecosystem regions, the Free-state province and North-West province of South Africa, using the Biofunctool® index and the activity of selected soil enzymes. The specific objectives were to (i) determine the effect of farming systems on ecosystem functions (i.e., soil carbon transformation, nutrient cycling, and structural maintenance) using the Biofunctool® soil health index (ii) determine the effect of farming systems on the activities of Fluorescein Diacetate (FDA) and β-glucosidase soil enzymes and (iii) to identify the relationship between parameters used in the calculation of Biofunctool® indices and selected soil enzymes. The findings in our studies, for both the Biofunctool® and enzymes, highlighted a discernible gradient of soil disturbance, ranging from the conventional system to the conservation system and finally to an uncultivated field characterised by minimal disturbance. The study highlighted the impact of various farming practices and seasons on soil functions. The soil quality index revealed that structural maintenance had the most significant influence on the overall outcomes. All the tested indicators improved under a CA system, with uncultivated fields having the highest results. By incorporating functional indicators, the Biofunctool® index effectively captures the intricate nature of the soil system and its reactions to various farming practices. The study of enzymes, SOC, and active carbon also revealed a clear continuum of soil disturbance, spanning from the conventional system to the conservation system and ultimately to an uncultivated field characterised by minimal disruption.