Economic circumstances since the 1982 drought led to a reappraisal of our farming programme. The main aim has been to develop a pasture and cropping system which would maximise returns and be both agronomically desirable and sustainable.

Our property is comprised of 650 ha, 16 kilometres east of Lockhart. About 300 ha are cropped annually. The remainder carries an 800 ewe self - replacing corriedale flock. Annual rainfall is 450 mm (8 inches). Soil types vary from lighter red loams through red clay loams to heavier grey and black clays. The red clay loams have a very sodic clay subsoil. Gypsum is being applied to these soils at rates of 2.5 tonnes per hectare. Soil pH levels range from 4.5 on the light loams to 6.5 on the heavier clays. No significantly high levels of aluminium have been found.

The main weed species on the light soils are capeweed, barley grass and silver grass. Ryegrass generally does not persist, although it does tend to become dominant on the heavier clays. Barley grass and thistles are also a problem on the heavy soils whereas capeweed and silver grass normally do not persist. Wild oats are a major problem on all soil types.

Past Farming Practices

Several years ago a fairly typical rotation was employed. This comprised generally a cultivated spring fallow, three cereal crops undersown to subclover in the third year to be left as pasture for around five to six years. These pastures usually becainegrass dominant which caused problems with disease and fertility when the paddocks came back into the crop phase.

In an attempt to minimise the cost of pasture estabishment a one year in - one year out” system was tried for a short time. The clover hard seed levels were sufficient to ensure the stands persisted but it became evident that adequate grass weed control could not be achieved and cereal root diseases were a major problem. This sytem was not suitable for growing lucerne nor did it lend itself to a broader range of crops.

Controlling Weeds in Pastures

Various methods of controlling both grass and broadleaf weeds in the pasture phase have been tried and some problems have been encountered.

Spray-graze Reduced rates of 2,4 - D and MCPA followed by heavy stocking to control capeweed has given mixed results. The main problem has been a shortage of dry sheep at the right time of the year to provide sufficient grazing pressure to eliminate th~ weeds.

Diuron/MCPA This mixture has been an improvement over the spray - graze technique in our situation. However, in some treatments a lack of good surface soil moisture has given poor results.

Roundup pasture topping Although good visual results have been achieved, where heavy infestations have occurred the reductions have not been adequate and weeds have continued to be a problem in the following year. Unfortunately the effect of Roundup on subclover has been variable as the critical timing required for maximum weed control can coincide with flowering of the clover. Therefore, application in the early years of the pasture phase, before the clover has developed sufficient hard seed levels, could cause reductions in pasture density. Pasture topping also appears to cause a marked increase in the levels of summer weeds such as melons, umbrella grass and heliotrope, possibly due to a reduction in soil moisture utilisation by the pasture and therefore higher moisture levels present over the summer. However, this is a low cost technique and should be useful where weed densities are low and as a method for maximising the soil nitrogen input of the pasture.

Gramoxone winter pasture cleaning My experience with Gramoxone has been limited to the 1987 season. Despite the higher costs of this treatment, it should give better results where mixed infestation of grasses occur. It is very difficult to time Roundup applications for optimum results on two species such as barley grass and silver grass. The main drawback with Grainoxone would appear to be the effect it has in retarding clover growth and the consequent loss of grazing.

Observations and Objectives

Some observations about the productivity of pastures have been made. These include:

• good in - crop weed control and earlier sowing dates lead to better pasture establishment;

• dense clover stands are less likely to succumb to weed infestations, particularly broadleaf weeds;

• good grazing management and insect control can reduce the likelihood of infestations;

• total grass - free farming is probably not a practical reality and the removal of a reasonably useful grass species such as Wiininera ryegrass tends to lead to the ingress of undesirable species such as barley grass;

• the longer the pasture phase the more likely that grasses will become dominant. Grasses respond well to topdressing;

• chemical pasture treatments can reduce clover production considerably and usually rely on critical grazing management;

• introduction of lucerne to a pasture will provide competition for both summer and winter weeds as well as giving significant increases in livestock production.

With these points in mind we have tried to change our farming practices with the aim of maximising both our cropping and livestock enterprises.

Current Practices

The aim has been to develop a rotation that will minimise cereal diseases carried by grasses that may be present in the pasture phase and at the same time employ in - crop weed control that would tend to reduce our overall weed problem. A rotation utilising both rapeseed and lupins is currently being used. Heavy rates of grass herbicides can be used in these crops to provide good control. Broadleaf weed control can be obtained cheaply in the wheat crops using mixtures such as Diuron + MCPA. Since 1983 fallow commencement has been achieved by using Roundup at rates of around I litre per hectare in late September/early October which is the “traditional” fallowing time in our area. This has given better results than later applications at “topping” rates. If good grass control can be achieved in winter with Gramoxone, a spring application of Roundup may be delayed until summer or autumn to provide summer weed control.

Lucerne

All pastures are now established utilising a mixture of winter - active lucerne and subclover. While the potential of lucerne in the Lockhart area is somewhat limited by soil type and rainfall it has been shown that it can significantly increase livestock production potential.

Although the autumns of 1986 and 1987 were similar, an increased area of established lucerne this year has meant that lambs were able to be grazed continuously on green feed from weaning (August lambs weaned in October). This year lambs were ready for market 6 weeks earlier and wool cut increased 10 to 15%.

Pasture Establishment

Typical pasture seed mixtures would include:

1.5 - 2.0 kg/ha winter - active lucerne, e.g. Siriver, Cuf 101

1.5 - 2.0 kg/ha hard - seeded subclover, e.g. Dalkeith, Nungarin

1.5 - 2.0 kg/ha Seaton Park subclover

Winter wheat (typically Osprey) is used as a cover crop. This allows for an earlier sowing and broader range of herbicides than oats or barley. Early sowing (mid to late April) allows the pasture seedlings to establish before the onset of very cold weather and subsequent insect and mite hatch ings.

Pasture seed is sown through a band seeder attached to the rear of the combine so that the pasture seed is placed between the wheat rows. Wheat sowing rates are reduced to 30 kg/ha or less.

Fertiliser rates are increased throughout the rotation to reduce the necessity for pasture topdressing. Sulphur requirements are being met by the use of single superphosphate on broadleaf crops and also through the use of gypsum.

In our rainfall area, yield limits of cover crops for successful pasture establishment would appear to be 2.0 to 2.4 tonnes per hectare. While the profitability of a 2.0 tonne wheat crop may be questionable, the wheat return does offset the cost of pasture establishment which would not be significantly less if a cover crop had not been used, i.e. major costs such as spraying, fertiliser, sowing, etc, would still be incurred.

Other Factors

As shown this season, mites and insects have the potential to dramatically limit pasture production. The adoption of a strategic spraying programme would be desirable. Paddocks should be sprayed prior to the year of pasture establishment. If rapeseed is included in the rotation the paddock should be sprayed the year before. Insecticides can be mixed with the herbicide used for fallow commencement. However, where pasture topping is used instead of an earlier fallow spray, insecticide application may be too late to give earth mite control and an earlier spraying should be used.

The ingress of weeds such as capeweed from fence lines would appear to be significant. The use of chemicals to maintain firebreaks may be useful in reducing this problem.

In the long term, the development of an overall farm strategy should prove beneficial in maximising both crop and pasture production. The pasture phase is an important part of a crop rotation and should be given close attention. Weed control is very important but may possibly be achieved at lower costs by overall management practices.

Appendix 1

Fertiliser - Is Topdressing Required?

	Old Rotation			New Rotation
Crop	Fert	Units P	Crop	Fert	Units P
W	60 Double super	10	R	180 Single super	16
W	60 Double super	10	W	80 DAP	16
0	60 Double super	10	L	70 TRIFOS	12
P	110 Single super	10	W	80 DAP	16
P		-	W	8ODAP	16
P	110 Single super	10	P
P		-	P
P		-	P
			P
			P
8 years		50 units P	10 years		76 units P
Average 6.25 units per year			Average 76 units per year

Appendix 2

Cost Of Chemical Firebreaks In Crop

Assume similar preparation for both options

Option 1 - Sow and cut for hay then cultivate

Seed, wheat 50 kg/ha	$6.00
Fertiliser, DAP 80 kg/ha	$30.00
Mow and rake	$8.00
Round bale and cart, 10 bales/ha @ $7.50	$75.00
Plough	$5.00
Cost ($/ha)	$124.00

Less value of cereal hay

Option 2 - Spray

2 applications of Roundup, I L/ha	$36.00
Application	$5.00
Scarify	$5.00
Cost ($/ha)	$46.00