Author: Lee Menhenett, IPF Technical Agronomist, Pasture – Agronomy & Ideation

Twelve major bushfires across Victoria have caused extensive damage to the rural countryside.  Over 400,000ha of land has been burnt, destroying more than 250 homes and killing more than 40,000 head of livestock. The recovery period will be long, with a key component of that recovery being re-establishing pastures.

Image 1: Paddock at Dropmore burnt from Longwood fire. Source: Lee Menhenett, IPF Technical Agronomist, January 2026

Key pasture considerations following fire

There are many components to consider for assessing recovery options across fire-affected paddocks, and this article is designed to logically work through the key issues:

  • Burn intensity and variability across paddocks
  • Survival of perennial species and annual seed reserves
  • Soil fertility status and potential nutrient losses
  • Timing and reliability of the autumn break and follow-up rainfall
  • Weed pressure relative to pre-fire pasture condition
  • Likely reduction in carrying capacity and grazing flexibility.

Most fires have a drastic effect on a pasture. Fire changes the botanical composition and will retard the pasture leading to a reduction in the growth and carrying capacity of the pasture in the following season. Fire changes pastures in different ways according to several different factors: the intensity of the fire, the pasture species present, the fertility of the soil, the time of the autumn break and follow up rains.

Fire intensity

The intensity, or how hot the fire is in a particular paddock has a major effect on the recovery of the pasture. Three categories of burns can be defined by considering what was burnt and destroyed during a fire – and what was left.

Cool-moderate burn (50-150C) – Most dead plant material is burnt. Some seed and perennial grasses and clovers survive. Small amounts of unburnt residue usually remain.

Hot burn (100-250C) – Typically occurs where heavy pasture or stubble fuel loads exist. Most dead plant material, many seeds and weaker perennial plants are destroyed. Topsoil often appears charred and bare. Pastures may recover with careful grazing management where at least 5–8 perennial plants/m² survive.

Very hot burn (>250C) – Soil surface organic layers are burnt. Common under hay bales, windrows, sheep camps or where intense fires move from bushland into pasture. Almost all plant material and seed is destroyed.

Image 2: Phalaris pasture Ruffy. Surface organic material remaining following cool-moderate fire burn. Cow pat (centre right) is an area of Hot burn where organic matter has been turned to ash. Source: Lee Menhenett, IPF Technical Agronomist, January 2026

CSIRO researchers have observed that while temperatures at the soil surface can reach up to 600°C during a fire, soil temperatures below 15 mm depth typically increase by no more than 10°C and return to their original levels within five minutes. This indicates that plants with seeds buried in the soil, or with growing points located below the surface, are more likely to survive fire events.

Effects on annual species

Grasses

Most annual grasses produce very little dormant seed. Usually, 80-90% of the seed in one season will germinate in the following autumn. This means that any factor, such as fire which destroys annual grass seed will cause a drastic reduction in the annual grass component in the pasture.  Any seed remaining in the head, above the ground, when the fire occurred will suffer high losses.

All the seed of the major volunteer grass species in our pastures such as barley grass, brome grass and silver grass remain on or very close to the soil surface. This makes the seed vulnerable to either being destroyed or the effects of high temperature as the fire passes.

Observations after three fires near Melbourne in 1968-69 showed that on average 53% of the annual grass seed was destroyed. The germination of the surviving seed was also reduced by 66%. Therefore, there was only about one fifth of the original number of viable seed able to germinate in these pastures after the fires.

In addition, the annual grass seed that survives the fire is very vulnerable to removal by wind. After the Minhamite (southwestern Victoria, north of Warrnambool) fire of 1982, there were large areas of moderate to hot burn where most of the protecting old plant stubble was destroyed. This allowed the surviving annual grass seed to be blown away before the autumn break, denuding whole areas of annual grass.

Subterranean clover

Subterranean clover can bury its seed. This substantially reduces the damage to the seed caused by fire. Unlike annual grasses, subterranean clover also has large reserves of dormant seed in its seed bank in the soil.

Despite this, after the 1968-69 Melbourne fires, 54% of the subterranean clover seed was burnt and the germination of what survived was reduced by 56%.

This means that there was still a significant reduction in the number of viable seed remaining. The timing of the autumn break and follow up rains has a major effect on the recovery of subterranean clover after fire.

Following a good, early autumn break after the 1983 Cudgee (Southwest Victoria) fires, subterranean clover regenerated well on the cool-moderate burn areas. By May, subterranean clover provided between 25% and 80% of groundcover on the burnt pastures. Where there was a good regeneration of perennial grass, subterranean clover contributed less to the groundcover. Where there was little grass to regenerate, subterranean clover quickly dominated the recovering pasture.

Poor subterranean clover recovery after fire however was observed at Maldon (between Ballarat and Bendigo) in 1969 and parts of the western district in 1977 following late autumn breaks. The survival and growth of subterranean clover and the annual grasses is also highly dependent on follow up rains after the break. After what appears to be a reasonable germination, many plants may still fail to survive because the soil dries out faster where there is no surface litter, and growth of surviving plants can be stunted following the initial set back. If a false break occurs, then act quickly prior to mid autumn and re-sow annual pasture or direct drill in a fodder crop (such as oats) if soil temperatures are rapidly falling in late autumn.

Image 3: Variability of fire heat. Cool-moderate burn (top of photo) to areas of hot burn where less organic material remains on the surface. This may cause sub clover seed viability to be variable across paddocks. Source: Lee Menhenett, IPF Technical Agronomist, January 2026

Effect on perennial species

Grasses

Recently resown perennial grass pastures can be seriously damaged by fire. The young perennial plants without well-established root systems and reserves are more vulnerable to fire damage, especially if the pasture was sown with a cover crop.

Almost all well-established perennial grasses survive a cool-moderate burn. The ability to survive a hot burn varies between species: grasses with growing points below the soil surface survive best. The grasses that were observed following the 1977 and 1983 fires, in decreasing resistance to destruction by fire, were: bent grass, phalaris, tall fescue, cocksfoot and perennial ryegrass. A very hot fire will usually kill all perennial grasses.

Near Hamilton, the density of surviving perennial ryegrass plants on burnt areas of pasture was compared with adjoining unburnt pasture. If the density of perennial ryegrass plants in the unburnt areas is called 100%, the comparative densities on the burnt areas were:

Cool-moderate burn – 79% to 98%
Hot burn – 44% and 38% (separate situations)
Very hot burn – 0%

These figures agree with the observations from other fires that the hotter the burn, the poorer is the survival of perennial ryegrass plants.

Image 4: Phalaris crown burnt, due to cool-moderate burn should re-shoot. Cut crown open and check shoots/lower stems are moist and pliable. Source: Lee Menhenett, IPF Technical Agronomist, January 2026

Legumes

Observations of burnt white clover-based pasture following the 1983 Cudgee fires indicated that the survival of white clover is very similar to the survival of perennial ryegrass.

The surface stolons (runners) of white clover can be destroyed in hot and very hot fires but will largely survive cool-moderate burns well. Strawberry clover was observed to survive better than white clover, with the only severe damage occurring in the very hot burn areas.

Established lucerne survives even a very hot burn well, despite the tops of the crowns being burnt. Newly sown plants (less than six months old) can be killed by a moderate burn, particularly if there are a lot of weeds mixed through the stand to fuel the fire.

Effects on weeds

Perennial weeds with well established, deep root systems survive fire very well. Weeds such as flatweed, docks, sorrel and onion grass are the first plants to recover and are often prominent after fires.

Following the 1983 Cudgee fires, strong perennial pastures which had little or no weed burden prior to the fire had very little if any weed problem when recovering.

In weaker, more run down pastures that received cool-moderate burns, weeds such as capeweed, erodium (corkscrew), onion grass and thistles that were present before the fire were very prominent after the fires. Their prominence was most likely to be due to lack of competition from preferred pasture species.

Effect on soil fertility

A grassfire can change the fertility of the soil in the short term. Elements such as potassium may become temporarily more available to the recovering pasture. Soil phosphorus and sulphur are not affected unless it is a very hot burn (>250C) and the change is only temporary.

Burning of the surface stubble cover, pasture residues and accumulated trash obviously is a loss of nutrients to the system, particularly organic matter, nitrogen (N), phosphorus (P), sulphur (S) and potassium (K). When cereal stubble is burnt, 80% of its nitrogen and sulphur and 40% of its phosphorus and potassium can be lost in gaseous forms to the atmosphere.

In hot fires or after the fire, some of the surviving N, P, K and S can be lost off-site in windblown ash. Losses of 80% of the carbon from the stubble have also been measured.

The amount of N available to the recovering pasture is generally reduced as the fire may burn some of the organic matter near the soil surface. As a result, many burnt pastures show symptoms typical of N deficiency (pale to yellow older leaves) during the following winter. N application following a break in autumn may be of benefit. Targeting winter active grass species or fodder crops, with good plant densities and low weed burdens, will improve N responses.

During the recovery of pastures after the 1983 Cudgee fires (Southwest Victoria), it was very evident that pastures with a good fertiliser history responded much faster and to a greater degree than those with a poor history.

Omitting the annual PKS fertiliser application in the autumn following the fire, especially on cool-moderate burn pastures with low-moderate soil fertility can retard the recovery of these pastures.

Effects of fire on the chemical properties of soil organic matter

Heating soil organic matter produces rapid losses of carbohydrates and proteins and eventually produces residues rich in aromatic compounds. The aromatic compounds formed include aromatic forms of N, which may be responsible for the reduced N availability observed in some burned areas.

Fire-induced soil water repellence can occur when heating of the surface and near-surface soil causes the vaporisation of organic compounds, which move downwards through the soil profile in response to temperature gradients, and subsequently condense and form a hydrophobic layer or coating around soil particles. This reduces water infiltration, increasing runoff and erosion risks and also reducing water availability to plants/crops. Organic matter also slows surface movement of water allowing for greater soil moisture infiltration. Where fire has removed this organic material water penetration rates will decrease. During intense rainfall events on hill country, soil erosion is a high risk.

Water repellency effects have been shown to be not universal and can be variable in different fires and soil types. Simple field “water droplet” tests can be used (see information sources below) to assess this.

Effects of fire on soil physical properties

Fire may alter several physical soil properties, such as soil structure, texture, porosity, wettability, infiltration rates, and water holding capacity. The extent of fire effects on these soil physical properties depends on fire intensity, fire severity, and fire frequency. Low intensity fires do not cause enough soil heating to produce significant changes to soil physical properties.

Effects on carrying capacity

Factors that affect the paddock carrying capacity:

  1. Intensity of the burn that influences the degree of annual seed recruitment/survival and degree of perennial grass survival
  2. Summer rainfall and timing of the autumn break
  3. Soil fertility
  4. Residual dry matter left unburnt
  5. Weed management
  6. Grazing management flexibility

Fire impacted pastures are going to have reduced carry capacities over the next 12 months. Planning for this scenario will ease supplementary feeding, protect soils from over grazing and allow quicker pasture regeneration.

What can be done

There are several possible courses of action after a fire, this will depend on the intensity of the burn, the condition of the pasture prior to the fire and the finance and time available:

  • Cool-moderate burn (50-150C) – the pasture should recover to its original density during the following year given adequate moisture. Soil test to identify any soil nutrient deficiencies before application of fertiliser and don’t topdress until there is at least 70% groundcover.
  • Hot burn (150-250C) – in most cases it is probably best to wait a season and see how the pasture recovers before considering resowing. Undertake soil testing before resowing. Starter phosphorus fertiliser (Croplift 15 or SuPerfect followed by urea) is advised for resowing pastures.
  • Very hot burn (>250C) – almost all plant material will be dead so the area should be cropped to a forage crop or resown to pasture following the fire. Undertake soil testing with enough lead time to get the results back and select the appropriate type and rate of starter fertiliser. For forage crops (such as oats/wheat/barley) it is best to apply MAP or DAP close to the seed at sowing, followed by a urea application at early crop tillering growth stage.

There are several management practices which may improve the recovery of pasture after fire:

  • Adding new pasture seed. New pasture seed can be added to the new pasture in a variety of ways such as by direct drilling or chisel seeding. Avoid cultivation where erosion risk is high and wait until there is a germination of annuals after the autumn break.
  • Grazing management. Where possible use sacrifice paddocks or containment areas to minimise the area stock have access to. Following a fire, the soil surface is more vulnerable to ash and soil loss. Excluding stock off the burnt pastures for six or more weeks after the autumn break improves the vigour and the growth of surviving plants. With most of dry plant material (roughage) burnt, stock grazing pastures should be supplied with straw or hay over autumn and winter to assist with feed conversion and animal health.
  • Soil testing. Representative burnt areas should be soil tested for major nutrients (N, P, K, S, pH) to assist pasture and crop fertiliser decisions. Comparison with previous (pre-fire) soil tests for the same paddocks, or test results from nearby unburnt areas on similar soil types, will assist interpretation and decision-making. When taking 0-10cm soil samples, retain surface ash and other organic material in the sample (do not scrape away and exclude from sample).
  • Fertiliser. Where there is an adequate density of regenerating plants, or pasture seed has been sown fertiliser application will speed the growth and the recovery of the pasture where nutrients are limiting. Phosphorus will be the priority nutrient for re-establishment, followed by N once pasture has established (preferably prior to winter). Topdress fertiliser when there is at least 70% groundcover (particularly on hilly country). This reduces the risk of fertiliser losses from the paddock.
  • Seed set. The pasture plants should be encouraged to set seed in the spring following the fire. This can be assisted by avoiding heavy grazing pressure in the mid-late spring period and not cutting the pasture for hay.
  • Weed control. Weeds will be the first plants to colonise pastures. Where broadleaf weeds start to dominate the recovering pasture, control measures such as the use of herbicides or spray-grazing are recommended. Early weed control removes pasture competition, allowing for a more vigorous and dense pasture sward. Check chemical labels to ensure correct clover and grass growth stage prior to application. Take the opportunity to spray out bent grass areas with a knockdown herbicide applied at robust rates. Depending on summer rainfall, there may be an opportunity for two sprays on these areas.

Image 5: Several Flatweeds survived fire. Weed control will be critical during pasture re-establishment. Source: Lee Menhenett, IPF Technical Agronomist, January 2026

Pasture recovery guides

Further information

For more information, contact IPF Technical Agronomist Lee Menhenett on 0412 565 176 or via email: lee.menhenett@incitecpivot.com.au

References

Egan, J. (2006). Measuring and monitoring fire effects on agricultural land. Final report for the Lower Eyre Peninsula Bushfire Re-establishment Program, SARDI.

NSW Environment & Heritage. Water repellency test – soil assessment method – https://www.environment.nsw.gov.au/resources/soils/testmethods/rep.pdf

DeBano, L.F. (1991). The effect of fire on soil properties – https://forest.moscowfsl.wsu.edu/smp/solo/documents/GTRs/INT_280/DeBano_INT-280.php

USDA Forest Service, General Technical Report INT-280.NSW DPI. Pasture recovery after bushfires – https://www.dpi.nsw.gov.au/__data/assets/pdf_file/0019/320626/Pasture-recovery-after-bushfires.pdf