Vegetation & Soils Monitoring on ‘Lana’

Christine Jones & Judi Earl - Balala-Brushgrove Landcare Group

Pinrush & Grazing Management Trials

Cell grazing was adopted over the entire property, ‘Lana’, in 1993. Monitoring commenced in the same year to determine whether cell grazing had a positive, neutral or detrimental effect on groundcover, botanical composition, or soil physical and chemical properties.

Three sites were established to monitor changes over time. At each site were paired comparison paddocks, one of which remained under conventional grazing management (the ‘control’) and one which was part of a ‘cell’. Annual assessments were made of soil strength, bulk density, water infiltration rate, the relative contribution to the total biomass of the plant species present, species richness, diversity indices, and the undesirable indicator pasture components. All of these measurements were taken at fixed points on fixed transects.

Water Cycle

Higher levels of groundcover equate to more effective use of rainfall, particularly in droughts. During the extremely dry conditions experienced over the monitoring period, the basal cover of plants remained significantly higher in cell grazed paddocks than the conventionally grazed paddocks (range: 12% to 42% higher).

The strategy at ‘Lana’ included leaving 30% of the available forage, not only to protect soil, but also to provide habitat for soil biota. Infiltration rate at the higher tensions was significantly greater under the cell grazing regime, indicating a relative increase on the presence of larger soil pores, which are the result of biological activity.

The improvements in soil structure under cell grazing were most likely the result of increased root growth, a greater diversity of plant species with different root characteristics, and an increase in the biomass and diversity of soil biota.

Tim Wright, “Lana”, Uralla, beside Roumalla Creek on his farm, where planned grazing has improved his pastures.

Photo courtesy of the Singleton Argus. 

Mineral Cycle

Soil cannot function effectively as a living biological system unless it is permanently covered with living pants or plant litter. From 70-90% of living things are underground. Groundcover provides a protected habitat and food supply for soil biota. Higher levels of organic matter and biological activity result in improved nutrient cycling, and improved aeration and aggregate stability on soils.

Soil chemical tests (0-15cm) revealed that available phosphorus and calcium levels, under planned cell grazing, had become double those in the conventionally grazed treatments after two years. Organic carbon levels increased by 35% under cell grazing while declining under continuous grazing. In two years, soil strength significantly decreased, (that is, soil condition was better, and roots could grow more easily).

Plant Community Dynamics

The percentage of desirable plant species such as broader-leaved, more digestible grasses and cool-season grasses increased in the cell grazed paddocks, while the relatively undesirable pasture species declined markedly under the cell grazing regime.

When paddocks are grazed conventionally, relatively unpalatable species have a competitive advantage, particularly in dry years, in obtaining water and nutrients, because the more palatable and potentially more competitive plants are suppressed by selective grazing. The resting regime of cell grazing enables faster growing and more palatable pasture components to outcompete.

The emergence of more desirable native perennial grasses and native legumes is enhanced by the presence of surface litter whereas the emergence of annual weeds is facilitated by bare ground.

Energy Flow

In the cell grazed paddocks, the dominance of warm-season species declined over time, while the percentage of cool season and year-long green species increased, which increased overall productivity. In the southern and south-western parts of Australia the converse would be true, though at ‘Lana’, the planned cell grazing regime moved the potential growing season from predominantly summer/autumn towards year-round production.

Changes in energy flow and product conversion are reflected in the carrying capacity of the land. The stocking rate at ‘Lana’ has increased by 4,000 DSE since planned cell grazing commenced.

Competitive Interactions Between Species

In order for more desirable pasture components to produce vigorous top growth, and therefore vigorous roots, we need to allow sufficient plant growth between graze periods. Plant community dynamics will do the rest. Competition below ground is the most effective way to reduce the vigour of established weeds. To reduce the germination of new weed seedlings, groundcover needs to be maintained at 100% (plants plus plant litter), for 100% of the time. This again depends on grazing management.

Conclusion

There are probably many paths to regenerative agriculture, but it is hard to escape the fact that most of them will require radical departures from current thinking. Traditional thinking has got us where we are now, and more of the same can only make things worse. New technologies embracing a much broader view of ecosystem function must become an integral part of agricultural production.

Changes to grazing management such as those implemented on ‘Lana’, which improve biodiversity and groundcover, can move us beyond destructive agriculture, beyond the bandaid measures of sustainability and on to a new era where things are continually getting better rather than continually getting worse.

Many cumulative benefits are likely to accrue to improved grazing management. These are not confined to on-site physical, chemical and biological improvements in soil and vegetation. Far-reaching benefits include positive outcomes for human health and well-being, the possibility of marketable carbon credits for organic matter increases in soil and the enhancement of water quality in aquifers and rivers.

Living soils and healthy aquifers were taken for granted when natural resources were abundant. In the next millennium, fresh water will become one of the world’s most coveted resources. Many aquifers, even in Australia, have become polluted, saline or dysfunctional, due to inappropriate land management practices.

Regenerative agriculture requires new approaches to learning about the natural world. In the past we have strived to increase yield, by minimising variation within the system. It has been part of our cultural heritage, encouraged by government provisions, to remove entire communities of native plants and replace them with introduced trees, crops and pastures. In response to the ensuing environmental and fertility stresses, we have tried to maintain production through the use of non-renewable resources such as fertilisers, pesticides and fossil fuel, rather than exploring ways to rebuild natural capital through improvements in ecosystem function.

Let’s change attitudes, think creatively, and practice regenerative agriculture in biodiverse landscapes.