Long-term pasture recovery
Managing fire-damaged pastures is a key part of recovery for a livestock business. Factors that influence pasture recovery include:
Cool to moderate burn – some residual plant material exists, including base of plant.
Hot burn – all plant material is burnt, ground is bare.
Very hot burn – soil is virtually sterilised, top organic matter layer of soil is burnt.
It is difficult to assess how well pastures will recover after being burnt initially. Assessment over the subsequent 12 months may be required.
Type of pasture
Different grass species may respond to fire differently. Species with growing points below the ground (phalaris, kikuyu, most native pastures, lucerne) will recover from hot burns much better than perennial ryegrass or annual grasses. Subterranean clover, which buries seed, often recovers well, as was widely reported in 2020.
Risk of erosion
The risk of soil erosion escalates significantly if ground cover falls below 70–90%. On hilly terrain or with light sandy soils, pasture cover should be retained over 90%. Prioritise protecting the most vulnerable paddocks.
Sheep graze closer to the ground and should be removed before cattle. Remove stock from pastures with insufficient ground cover to a securely fenced sacrifice paddock, containment area or unburned area of the farm, or to agistment.
Time before effective rainfall to stimulate pasture growth post-fire
In the medium term, burnt pastures that regrow may have decreased productivity and therefore carrying capacity for up to 12 months. One estimate from historical data in Victoria in a typical moderate rainfall location is shown in Table 1. Some years will be substantially better: in 2020, pasture recovery was very good in NSW and Gippsland due to the severe preceding drought (leading to low pasture cover and cool burns) being followed within weeks by effective rainfall in many areas and normal pasture production by mid-winter.
Undertake a full feed budget for your retained stock, factoring in reduced carrying capacity with return to normal pasture production 12 months after fire. Adjust these budgets once seasonal rains allow you to assess any reduced pasture growth.
Pasture recovery strategies
Initial options for pasture recovery (first six months):
- Retain stock in containment areas (or other non-damaged pastures) until after seasonal rains have improved pasture cover.
- Use grazing management to hasten pasture recovery of desired species and optimise pasture production.
- Apply nitrogen in autumn and winder and gibberellic acid in winter to boost pasture production.
- Apply strategic fertilisers in other nutrients will limit pasture growth.
- Control weeds; weed incursions are likely on damaged pasture with more bare ground.
- Plant fodder crop on severely damaged pastures that need preparation (weed control)before re-sowing to permanent pasture the following year.
- Over-sow weakened pastures to hasten recovery.
Long term, create a whole-farm pasture recovery plan, aiming for a cost-effective strategy for pasture recovery that returns pastures to full production over one or more years. Practicalities, seasonal constraints and cash flow are common constraints to the ideal program.
Differentiate pastures that need long-term renovation from those that can recover with effective management. Use grazing management, targeted weed control and fertiliser to recover pastures where possible, allowing time for a response before you commit to expensive work re- sowing. Pastures may recover surprisingly well. Heavily watering small ‘test’ areas can help assess the density of surviving desirable pasture species and is useful even where very hot burns appear to have sterilised the soil.
Pasture renovation, while expensive, is an investment that can result in more productive pastures than previously. Consider what species might be suited to your farm goals, including likely productivity and persistence. Don’t rush into full renovation as poor preparation will result in poor pasture establishment.