Managing pasture - is burning necessary?

by Liz Beavis
This time of year (spring) we don’t get much rain.  The tropical grass species in our pasture have dried out over winter due to the low temperatures and low rainfall.  They are in a fully mature state, with relatively low protein and mineral content.  The stock feeding on this pasture tend to lose or maintain weight, but rarely gain significant weight. 
Now that the temperatures are starting to increase, we are waiting for rain so that the pasture will re-enter its leafy growth stage and provide good quality fodder for the cattle to start getting fat for market. In Queensland, late winter and spring tend to be our dry period, with rain coming in summer.


Growth stages of perinneal grasses and legumes (image source),
note that protein and mineral content decrease with maturity
There are several ways to accelerate this process.  Certainly if you leave the dry dead bushes of grass in the pasture, the amount of leafy growth will be sub-optimal, even when it rains.  New leaves tend to grow from the outside of the bush, so the bigger the bush, the high proportion of old dead leaves on the inside.
If you can remove most of the dry grass, the leafy growth will start early, from all around the plant, particularly if there is still good soil moisture from winter rains (ha!).  The dry grass can be removed by:


  • Controlled burning


  • Slashing


  • Managed grazing



Controlled burning is very popular in our area at this time of year, and we can often see plumes of smoke on the horizon.  When we haven’t had any rain for months, I get very nervous about the capability to control these fires (when is a fire truly controlled!?).  This anecdote gives a good explanation of the why farmers burn their pastures in Australia:



“The a'bos did it. Grandad did it. Everyone does it. You must burn the grass to make it grow. (A pretty silly reason.) It gets rid of regrowth and fallen timber. The ash fertilizes the soil. You must get rid of the old grass to allow fresh grass to grow. Cattle "do" better on fresh feed. I have this primitive urge to light a fire, it makes me feel good. Plus a few others that I have forgotten.”


That article also explains that the writer stopped burning on their property and the cattle and pasture “did better” than the neighbours who continued burning.  And then this more scientific study from a QLD government department explains that even though burning the grass does release nitrogen, so that the grass initially has high protein content, the cattle actually have better weight gain overall if the pasture is not burnt, as the dry material helps with muscle formation.
Many farmers claim that they need to burn to control woody weeds and saplings, however this research (and my observations of properties belonging to neighbours who burn paddocks) shows that those are the plants more likely to survive fire, while the perennial and annual grasses that you want to promote are most likely to be damaged!  Not just the plants, but also the seeds in the soil.


In terms of soil mineral management, carbon in the form of organic matter can help to balance deficiencies and excesses.  It feeds the microbes and improves water holding capacity.  Soil carbon is the very thing that you want to increase in order to improve pasture.  Burning the pasture destroys all that carbon in the dead grass, turning it into climate-change inducing carbon dioxide.  Over the longer term, this has the effect of preventing soil-building and degrading the pasture (more information here).


For this reason, this article recommends:


Slash/mulch a pasture, rather than burn it.
Slashing/mulching promotes green pick. Slashing is preferable to burning, as the cut pasture material will break down and add valuable organic matter tothe soil. Much of the organic matter is lost when a pasture is burnt.”



 More on slashing vs burning here.  


Obviously slashing pasture is not always practical over large areas.  We have certainly seen the improvements on our eight acres since we started slashing (as per Peter Andrews’ recommendations in his books Back from the Brink and Beyond the Brink). 
We have seen improved pasture coverage (ie fewer bare patches) and better growth in general.  Even though it is claimed that the heaps of dry grass can kill the grass, we have never seen that happen, in fact I will often kick the dry grass away to find lush green grass below, and the cattle will do the same. 
At our 258 acre Cheslyn Rise property, we (I mean Pete, with me supervising) have slashed certain areas of the pasture that we know are free of stumps and logs etc.  At Eight Acres, our strategy was to fence off a paddock of about an acre, let the cattle eat as much as possible, then we could see what to avoid on the slasher. 
On the larger property this is not possible as we currently have no way to provide water to small paddocks, and there are a lot of stumps cut off just below grass height by the previous owner, so we have to be very careful with slashing in new areas! 


for example, some very dry grass before slashing
The ideal solution would be an even more intensive grazing pattern (if/when we have the water set up) as practiced by Joel Salatin (Polyface farm) and my other favourite farmer – Matron of Husbandry (of the blog Throwback from Trapper Creek).  They move their cattle every day, with the theory being that the cattle trample any grass or weeds that they don’t eat.  This prevents woody weed growth, and builds soil carbon. 


At Cheslyn Rise we have another good reason to keep the grass short – we have found out that we have a good population of paralysis ticks, which can kill small calves.  These ticks live in the long grass and one way to manage the tick population is to keep the grass short.  This is a little complicated as we have about 100 acres of forested area, some of which has grass growing under the trees.  More here and here.


One way that we could manage the grass that we can’t slash and that the cattle won’t eat, is to burn it.  It would have to be a very controlled burn, as you wouldn’t want the 100 acres of forest area to catch alight, and we have some very good fencing that we wouldn’t want to have to rebuild either!  We are currently considering our options.


General information about pasture management:


Any advice from your experience with managing pasture?

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