Maximising rainfall infiltration for production
Improved infiltration through grazing management
On a number of our case study grazing properties, time-controlled planned grazing has been implemented (many based on Allan Savory’s Holistic Management techniques). A key component of this form of grazing management is increased mob sizes. By using higher density stocking, regrowth of unpalatable mature grasses is knocked down and this, plus any other plant litter, is trampled into the soil enabling it to break down more rapidly. This strongly contributes to the generation of soil organic matter and ultimately soil organic carbon level improvements. (Remember – 1 gram of soil organic carbon can hold up to 8 grams of water!)
Planned grazing also provides sufficient rest and recovery for pastures and triggers succession from low order species to more palatable and productive plants, particularly perennial species, increasing ground cover.
It is these processes that give Shane and Shan Joyce of Dukes Plain in the Southern QLD Brigalow Belt and Charlie and Anne Maslin of Gunningrah on the NSW Southern Tablelands (amongst others), the capacity to manage production in periods of low rainfall. The improved soil structures and increased ground cover aid the:
- infiltration, retention, availability and sustained supply of water from such soils;
- aeration and capacity of roots to proliferate and penetrate deep into soils;
- capacity for water to recharge and irrigate soils from below to limit loss due to evaporation; and
- restoration of in-soil reservoirs and aquifer recharge.
The Joyces produce organic beef on Dukes Plain and manage their stock to
help improve their soil and pasture to maximise rainfall infiltration
The Joyces monitor post rain events to observe how deep moisture has penetrated and have found that rain infiltration in the soil has improved over the years since they implemented planned grazing. Rainfall events of less than 10mm were traditionally seen in the area as ineffective, however with the conditioned land and high levels of soil organic matter this moisture is now being absorbed into the Duke Plains soil. With around 70% of their rainfall events comprising less than 10mm rainfall, the Joyces are now able to harness this resource that previously had been lost.
Both the Joyces and the Maslins have increased production time on their properties, even with variable rainfalls, due to the improved hydrological function ensuring maximum infiltration and extending the growing season of pastures.
Reducing run off with humus-rich soils
Bill and Rhonda Daly’s mixed grazing/cropping enterprise Milgadaraon the NSW South West Slopes has seen a significant improvement in soil structure to a tilthy, well aggregated soil with higher humus levels. Rainfall that is received penetrates further into the soil profile and is retained in the soil for longer. Any excess now flows through the profile without taking nutrients with it, reducing the amount lost to run off or evaporation. As a result, water is best conserved and used by plants and animals where it falls.
The key innovation implemented on Milgadara was to restore humus and the natural biological balance back into the soils. To build productive soils the Daly’s developed a humus compost designed to influence all three aspects of soil: chemical, physical, and microbiological. For broadacre farming the humus compost is applied at around 500kg a hectare. The improvement in soil structure and plant health does not come from the quantity of compost applied, but rather, it is a catalyst that supports natural system functioning – including hydrological processes.
Increasing available productive land
And as a final example, on Talaheni in the NSW Southern Tablelands, John and Robyn Ive have invested heavily in revegetation to capture rainfall higher in their property. This increased retention at higher levels has reduced the water table on the lower salt-affected flats and subsequently reduced salinity problems.
Together with additional manual planting, the Ives estimate they have established more than 200,000 trees on their property.
Data from regular monitoring over 20 years shows a significant decline in watertable levels and salinity levels of groundwater. John has estimated that each hectare of ridge top that has been revegetated has led to a beneficial lowering of the watertable in over 50 hectares of nearby adjoining flats, much of which is on neighbouring properties, increasing land available for production.
Left: Bare soils and visible saline seeps previously affected productivity on Talaheni.
Right: The same paddock, with increased vegetation. Through active water management the Ives have restored pastures to productivity
Read more in the Talaheni case study and watch Michael Jeffery interview John Ive on our case study page.
If you take action, it’s amazing what can be achieved to manage your water for efficiency in use and productivity outcomes!
Check in next week to read about a great case study in waterway management.
The Soils for Life team.