The effect of soil and pasture attributes on rangeland infiltration rates in northern Australia

Abstract

Surface runoff is an important factor affecting rangeland pasture productivity and off-site sediment transportation. The application of rangeland biophysical models including sub-models of runoff and erosion provides one method to assess how management and climate variability affect the frequency and quantity of surface runoff events. However, there is often limited confidence in extrapolating runoff models developed from site-specific, hillslope field experiments to other locations due to variation in soil types and land condition states. To improve rangeland runoff models, we investigated three potentially important components at 18 paired land condition sites: (1) the importance of a variety of pasture attributes such as biomass and cover on infiltration rates; (2) the impact of surface soil texture on infiltration rates; and (3) whether soil carbon and/or soil bulk density provide valuable indicators of a site’s infiltration rates. The study found that surface soil texture was important when aboveground biomass was low and was found to have a ‘broken-stick’ relationship with infiltration rates (i.e. lowest infiltration occurred at the pivot point of 64% sand). Aboveground biomass, (which included standing grass, grass litter and tree litter) was the best soil or pasture attribute for predicting a plot’s infiltration capacity accounting for 68% of the variability. Plots with surface soil sand content greater than 60% and which had been exclosed for between 4 and 24 years had higher average surface soil carbon mass and concentration (~10%) than adjacent grazed plots. The exclosed plots also had higher surface soil porosity, which was associated with very high infiltration rates.

Sustainability of beef production from brigalow lands after cultivation and mining. 1. Sown pasture growth and carrying capacity

“…The RUEs of the Mountain Coolibah and Brigalow Uplands land types were similar to the 4.5 kg/ha.mm RUE of native black spear grass (Heteropogon contortus) pastures in the Burnett (McKeon et al1990). Sites with low TSDM and very low RUE (2.9 kg/ha.mm) were also pastures in poor condition, such as BMK 11, that would likely have lower infiltration rates (Fraser and Stone 2016). It is surprising that productivity of the Brigalow Uplands land type was lower than that of the Mountain Coolibah, as the current estimate of median annual pasture growth for Brigalow Uplands at Bowenville (~23 km from the trial site) is 5640 kg/ha, whereas Mountain Coolibah for the same climate centre has been given as 4660 kg/ha (State of Queensland 2014) on the basis of field observations throughout northern Australia and modelled estimates of pasture growth Stone et al 2019).…”

Do regenerative grazing management practices improve vegetation and soil health in grazed rangelands? Preliminary insights from a space-for-time study in the Great Barrier Reef catchments, Australia

“…Plant basal area is considered a useful metric for explaining long-term land-condition changes that happen slowly (Northup et al 2005;Searle et al 2009), and can be a good indicator of historical longer-term impacts and landscape condition. There is evidence for higher basal area leading to better soil moisture (Northup et al 2005;Searle et al 2009), and others have found that there is a strong link between higher basal area and biomass, and biomass and infiltration (Fraser and Stone 2016). The R2 and R3 treatment sites are showing statistically significant improvements in many of the vegetation attributes, including biomass, cover, litter cover and species diversity, yet percentage basal area has not changed at these sites (Fig.…”

“…The Meadowvale Station site was home to one of the original Queensland Department of Primary Industry (QDPI) exclosure sites, and a complete description of the site is given in Scanlan et al (1996) and Hawdon et al (2008). Fraser and Stone (2016) and Searle et al (2009) have also published soil attribute and vegetation data from this site. Data from the nearby Department of Defence Townsville Field Training Area (TFTA), from here on represented as R6, that had very low to no grazing, but military training activities and increased fire frequency, were also included in the study (see Koci et al 2020 for more details from the area).…”

Implications of retaining woody regrowth for carbon sequestration for an extensive grazing beef business: a bio-economic modelling case study

“…Pasture C stocks are not included in the current ERF methodologies, however, the substantial C stocks in forage and (Fraser and Stone 2016). An unexpected but important outcome of this study is that a conservative stocking strategy that maintains the condition of land is able to achieve positive GHG outcomes along with sustainable economic and productivity outcomes.…”