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Getting pastures back on track at Baynton
By Jane Court, Pastoria, Vic.
More than 100 people turned out for the Baynton paddock walk held on the 11th March 2009; the Baynton district is in central Victoria, about 20 km north east of Kyneton.
The theme for the day was “Getting pastures back on track” as their persistence and yields were struggling after the run of dry years; for some locals, this issue took on the added perspective of the effects of the
recent Redesdale fire on their pastures.
The day started at Gerard and Belinda Ryan’s farm in Baynton, on which they run Coopworth ewes, a self-replacing wool flock, and some trading cattle. Gerard provided some background information about their farm to put into context one of their key goals of maintaining stocking rates through the dry times using
grazing practices and fertiliser to help lift pasture production.
The better soils on the flats at Baynton can grow ryegrass and phalaris successfully, and Gerard’s
preference is to get phalaris into much of this country. The tougher hill country at Pyalong has been mostly destocked to reduce the pressure on the ground cover on these hills. Gerard is still convinced that
fertiliser is a good investment, despite the higher prices.
Newly-sown phalaris
The first paddock we inspected was a new phalaris pasture that had been sown in late August
2008 with 2 kg/ha of Landmaster phalaris, 1 kg/ha of Australian phalaris and 3 kg/ha of Trikkala sub clover. The paddock was an impressive stand of dry phalaris. Plant sizes and densities across the paddock were good, indicating that a successful sowing and grazing regime had put this pasture in excellent condition to be a good performing paddock in the future. Gerard’s main concern was its low clover content, as the spring sowing of phalaris, which works best for this district, was after a couple of years of cropping which had
reduced the clover seed bank.
Lisa Warn from the Mackinnon Project spoke about renovating and re-sowing bare paddocks.
She highlighted the importance of letting newly-sown phalaris run to head and flower in the first spring, and to use rotational grazing over the first autumn and winter to allow the plants to achieve good crown sizes.
Establishing sub clover in spring-sown pastures can be a challenge, because as an annual, it needs at least 100-140 days of growing season rainfall (depending on the maturity type of the clover) to germinate, grow and set seed before the season ends. Thus, even for earlymaturing cultivars of sub clover, sowing them later than mid-July increases the risk that they will not set any seed. Many pasture paddocks, however, may still have good clover seed banks (you can check by counting the seeds),
although if you have concerns that the clover seed bank has been run down by the dry seasons, an
option to consider is to broadcast or drill some clover seed in with
the fertiliser in the autumn.
Ryegrass-based pasture
The second paddock we ‘walked’ was a ryegrass-based pasture that had been set stocked for a considerable amount of time with good ground cover but not a lot of feed. Although there were
plenty of ryegrass plants in this paddock (estimated to be more than 40 plants/m2), many other
paddocks in the district have much lower densities. In addition, this paddock still had its organic matter layer and top soil intact. The run of failed springs has had the effect of reducing the seed set of annual grasses, such that the density and total dry matter production of this pasture in the following year will be reduced.
Bare paddocks?
Lisa urged attendees not to jump into an immediate pasture renovation program simply because many of their paddocks look bare. It is important to assess each paddock individually as some may recover with rain,
fertiliser and good grazing management practices over time.
Lisa commented that many people are often pleasantly surprised to find more perennial plants have persisted than they had expected, and that in many situations, management options are far better and less expensive than re-sowing.
Nevertheless, paddocks that have clearly lost their surface layer of organic matter, top soil
and seed banks of annual species will struggle to achieve satisfactory pasture densities and production, and would be higher priorities for re-sowing.
The best technique to help assess the recovery potential of bare paddocks is to wait for some rain and use a quadrant in a transect across each paddock to count the number of desirable plants and estimate average
ground cover.
Lisa provided the following critical values to help you decide if you should re-sow
or not:
· at least 5-7 phalaris plants/m2,
· at least 8-10 perennial ryegrass
plants/m2,
· 70% ground cover/ dead feed
left.
Phalaris cultivars
Participants asked about the value of newer winter-active cultivars of phalaris compared
with the ‘tough as old boots’ Australian cultivar. Lisa’s recommendation was that if you
are running a fairly intensive production system, using a winter-active phalaris is preferable as the improvement in winter feed supply is significant (around 40% more dry matter). There is no reason why these cultivars, with good grazing management, will not last as long as Australian.
Weeds
The major weed issues identified by participants in the two paddocks were silver grass
and barley grass, with some bent grass and capeweed. Silver grass can be controlled with winter
cleaning but the downside is the severe loss of winter feed. This has been Gerard’s experience in
the past, with his winter feed supply really ‘hammered’, although he felt that it was probably worth revisiting, as silver grass was a likely contributor to the low clover contents of his pastures.
Barley grass has been very dominant this year, because it is an opportunity grass, and the dry
spring of last year favoured it because of its ability to seed early. Options to control this annual grass weed include spray-topping the pasture this coming season, or in the longer-term, increasing the competitiveness of the perennial species through improved grazing management.
Lime
Liming was also discussed, as many people are putting out lime due to the high fertiliser prices. Lisa explained that the decision to apply lime should be based on soil tests, with aluminium levels being the problem rather than the pH itself, especially for sensitive species like phalaris and lucerne. Four to five years after lime had been applied, Gerard’s paddock had had only a minimal change in pH (0.1 unit decrease) but the aluminium level had remained much lower.
Lisa also pointed out that putting out lime is no substitute for applying maintenance rates of phosphorus fertiliser. If excess aluminium is a problem, liming will alleviate its toxic effects and allow better establishment and root growth of sensitive species, which in turn enables them to take up more nutrients and water. Victorian trials that looked at the impact of topdressing lime on established pastures have shown few economic responses. Where there was a quick plant response, it was usually due to an increase
in the availability of molybdenum.
Key messages
· Don’t rush into re-sowing paddocks; assess paddocks individually to assess the chance of the pasture
recovering.
· Rotational grazing practices will allow plants to recover from dry seasons; they need time to increase their size, dry matter production and root growth.
· Destock paddocks when ground cover falls below target levels (70-80% ground cover, or800-1000 kg DM/ha) to reduce the risk of losing valuable top soil, pasture species, organic matter and nutrients, through
wind or water erosion.
· A soil test is essential to make informed economic decisions about the fertiliser applications needed to optimise pasture production.
· For beef and sheep farmers, a good, well-managed perennial pasture should last a lifetime!
Another key component of the day was looking at pastures that were burnt in the recent fires, and
how to deal with pastures burnt to different degrees. The main issues discussed were the intensities of the burns and the implications for pasture recovery. The information provided on the day was based on Lisa’s comments and a DPI AgNote written by Graeme Ward, and are summarised below.
Cool to moderate intensity burns
For paddocks with low fuel loads, for example, a well-grazed pasture or a drought-affected paddock with little cover to burn, the intensity of the burn is described as ‘cool-to-moderate’.
What this looks like is that most of the dead pasture is burnt with some unburnt patches. These
pastures should recover well, with all perennial species and sub clover re-establishing after the
autumn rains.
However, the seeds of annual grasses could be affected. As explained in the DPI AgNote “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, that destroys annual grass seeds will cause a
drastic reduction in the annual grass component of next season’s pasture. 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 affected by high
temperatures as the fire passes”. A key comment from Lisa was that pastures affected by cool burns should recover to their original density over the next year and the best strategy was to take a wait-and-see approach.
Hot intensity burns
For paddocks with greater fuel loads, for example, a tall standing dead pasture or stubble, where all the pasture is burnt and the soil surface charred and bare, the intensity of these burns is described as ‘hot’. In this situation, you could expect the loss of annual grass species and damage to weaker perennials such
as established perennial ryegrass or newly-sown perennial species.
Phalaris, lucerne and native grasses are more likely to survive a hot burn than tall fescue, cocksfoot and perennial ryegrass. In this situation, Lisa explained that re-sowing can be an option; however, it would be wise to wait and see what re-grows after the autumn break before deciding on re-sowing.
Very hot intensity burns.
For paddocks or treed areas with high fuel loads, such as bush paddocks or pastures along the edges of tree belts, or where round bales have been burnt, the intensity of these burns are described as ‘very hot’. Very hot burns leave the soil virtually sterilised, with all plant material and seed destroyed as the fire
burns into the surface organic matter layer of the soil. With burns of this intensity, re-sowing is warranted.
Graeme Ward reiterates in his DPI AgNote that “Recently-sown 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 “coolmoderate” burns well. The ability
to survive a “hot” burn varies between species: grasses with growing points below the soil surface survive best. It was observed following the 1977 and 1983 fires that the ‘fire resistance’ of grasses were, from most- to least-resistant; bent grass, phalaris, tall fescue, cocksfoot and perennial ryegrass. A “very hot” fire will usually kill all perennial grass plants.”
Helping your pastures recover from fire
What can be done to help pastures to recover after fires is best described in the information provided in the DPI AgNote and is summarised below. There are several possible courses of action after a fire. The
appropriate one will depend on the intensity of the burn. Their general aim is to speed up the return of the pasture to its original density and productivity.Low densities of surviving, desirable pasture species has more impact on lost production over the first 12 months after fire than the types of pasture species surviving. You should consider the following management
practices to improve the recovery of your pasture after fire.
Adding new pasture seed.
New seed can be added in a variety of ways, including direct drilling or chisel seeding. It is usually best to wait until there is a germination of annuals after the autumn break. If the weeds are dense, chemical
control may be necessary before sowing the seed.
Heavy harrowing.
Heavy harrowing can unearth buried seed and improve their germination, especially of sub clover. However, this may cause further damage to surviving perennial species.
Autumn saving.
Leaving stock off the burnt pastures for six or more weeks after the autumn break improves the vigour and
growth of surviving plants.
Fertiliser.
Where there is an adequate density of regenerating plants, or pasture seed has been sown, fertiliser applications will speed the growth and recovery of the pasture.
Broadleaf weed control.
Where broadleaf weeds start to dominate the recovering pasture, control measures such as the use of herbicides or spray-grazing are recommended.
Seed set.
The pasture plants should be encouraged to set seed in the spring following the fire. To assist greater seed set, avoid heavy grazing pressure in mid-late spring and do not cut the pasture for hay. The DPI AgNote referred to above, ‘Pasture recovery after fire’ (AG0203), can be downloaded from DPI’s website
Finally, the organisers of the farm walk wish to thank the sponsors of the day, ‘Making
more from sheep’ and ‘Rural Finance’, because with their generous support, the day was
free for participants.
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