A Proof-of-Concept Study on the Soil Ecosystem Effects of Holistic Planned Grazing for the Development of a Manual for Simple and Cost-Effective Soil Health Testing

Abstract

With almost three quarters of all grazed land being degraded, there is a need for more biodiverse and resilient ecosystems in today’s grasslands. With the right management practices, grazing animals can play an important role in reversing this environmental damage. Holistic Planned Grazing management has demonstrated the potential to result in improved soil health and ecosystem service provisioning. In this study we assess the soil ecosystem effects of Holistic Planned Grazing compared to fixed grazing, rotational grazing and no management, in a tropical climate on red volcanic heavy clay soil populated with the non-native grass Brachiaria decumbens. Simultaneously, we use this research as a proof-of-concept study for the development of a set of soil ecosystem indicators for use in a soil health assessment guide. Grazing management had been constant in each field for at least 4 years. Positive results for HPG included lesser soil compaction (P< 0.03), higher soil worm counts (P< 0.001), higher soil moisture levels (P< 0.001), faster soil water infiltration (P< 0.007), thicker organic horizons (P< 0.001) and observably more vegetative groundcover, suggesting increased soil water cycling and biological activity. Current results for HPG also point towards increased soil nutrient and carbon cycling with Holistic Planned Grazing, however less conclusively. Relative to the unmanaged field, HPG often displayed similar results. However, for soil water content, worm count and cotton cloth breakdown, HPG displayed markedly higher values. Although not significantly different, trends show faster water infiltration and higher soil biodiversity for the unmanaged field, possibly due to the observed lesser soil compaction in this field. Unexpectedly, aggregate stability and soil organic matter did not show any significant differences between fields. The rotational grazing paddock provided intermediate results. Each soil ecosystem function indicator that was used in this study has an ecological relevance and ties to one or multiple soil ecosystem functions. Because the soil ecosystem indicators used in this study seemed promising, a soil health guide was written, with promising use for citizen science (see appendix). This study indicated improved ecological outcomes with HPG management compared to fixed and rotational grazing.