ABSTRACT

A potential method of growing canola in the high rainfall zone of south-eastern Australia, where farmers have been unable to adopt the crop because of winter waterlogging, is described. The effects of the method, known as Controlled Traffic Raised Bed Cropping, and the likely impact on canola production if it is widely adopted in the high rainfall zone, are discussed.

INTRODUCTION

In Victoria, canola is grown mainly in the regions known as the Wimmera, (annual rainfall 375 – 450 mm), the North-central and North-eastern Regions (typically in districts with 500 mm annual rainfall) and the southern part of the Mallee, (down to annual rainfall 350 mm). In these regions canola crops are generally sown in May and harvested in November.

This paper discusses the development of a canola industry in the high rainfall South-west Region of Victoria and similar high rainfall areas in south-eastern Australia. Mean annual rainfall in SW Victoria ranges from 500 to 800 mm, with much of the region receiving over 600 mm. Crops of canola can be sown in April and are harvested in December.

The Western Plains, one of the largest basaltic plains in the world (Blainey, 1984) occupies a large part of the region. On this plain and in other districts of South-west Victoria, very high yields of canola can currently only be produced in fields that are unusually free draining, or where annual rainfall is below 550 mm. In most of the region, canola production is prevented by severe winter waterlogging caused by the high, winter dominant rainfall, the duplex soils with poorly permeable clay subsoils (Conley, 1984) and the fact that the drainage of the whole area is not well developed (Joyce, 1984).

Because waterlogging often destroys crops or lowers yields, grazing, particularly wool production, has dominated the agriculture of the Western Plains for well over a century. This dependence on grazing enterprises creates wealth when wool and meat prices are high but causes severe economic problems when they are low. A period of low beef and wool prices in the 1990s led to renewed interest in crops, and to the attempt to alleviate waterlogging that is described below.

POTENTIAL FOR CANOLA IN SW VICTORIA

The region has a high, but largely unrealised, potential to grow cereal, pulse and oilseed crops. This is illustrated by a comparison of the yields of the winning crops from the canola competition run from 1990 to 1996 with the SW Victorian regional average.

Table 1. Meadow Lea Canola Awards South-west Victoria winning crops.

Year	Location of winning crop	Yield t/ha	SW Victoria, average canola yield t/ha.
1990	Lake Bolac *	2.60	1.0
1991	Lake Bolac	3.48	1.4
1992	Lethbridge	2.05	0.6
1993	Lethbridge *	3.61	1.0
1994	Lake Bolac	3.10	1.3
1995	Lake Bolac *	4.35	1.5
1996	Lake Bolac *	3.89	NA

* Victorian State Winner

The potential to grow canola if waterlogging can be prevented is further illustrated by the trend towards higher yields over that time. The average yield of the 1990-92 winning crops was 2.72 t/ha, for the whole seven years 3.3 t/ha and for the last three years 1994-96 it was 3.87 t/ha.

LAND DRAINAGE IN SW VICTORIA

History

In South-west Victoria, draining agricultural land to grow crops has not been common. Although grazing farmers have often tried to switch to crop growing when grazing returns have been low, poor results caused mainly by waterlogging have led to rapid changes back to traditional grazing enterprises when prices recover. This has not encouraged research into pipe and mole drainage, and its high cost and doubtful effectiveness has meant there has been little adoption of the technique.

Drainage work in the 1990s

In 1995 a group of high rainfall grazing farmers seeking greater investment in high rainfall cropping research formed an organisation called Southern Farming Systems (SFS), with the aim of developing new high rainfall mixed farming systems. They were supported by agronomists working for the Department of Natural Resources and Environment (DNRE), Victoria. It was not long before realisation of the potential economic and social benefits of a profitable high rainfall grains industry led to support for SFS from government and industry.

Recognising that waterlogging is the major constraint to cropping in the high rainfall areas, SFS began immediately to concentrate on finding solutions to the problem by reviewing a number of possible drainage methods.

Pipe and mole drainage was considered but, while it is common in many countries in the world, installation costs up to $A1200 per hectare and is not affordable for most farmers in Victoria. Forming the land into “wide raised beds”, 20 – 30 m wide, which some Victorian farmers have tried in the past, was another possible method.

A third method considered was to form whole fields into “narrow raised beds” between 1.5 and 2.0 metres from centre to centre, a method already used for vegetable and flower production and for irrigated crops. This system allows most or all of the machinery wheels to run in the furrows between the beds, so the method also prevents soil structure damage by compaction.

Broad acre cropping on permanent raised beds was developed, principally at The Institute for Sustainable Irrigated Agriculture at Tatura, Victoria, Australia, as an irrigation method. Irrigation water runs down the furrows and wets the soil through to the centre of the bed. Agronomists working with Southern Farming Systems thought the technique might also be useful to remove excess water from fields and to prevent the soil surface from becoming inundated.

In 1995 SFS commenced the set up of a drainage demonstration, on a site that was very prone to waterlogging, to show what might be possible if that constraint could be removed. The area was surrounded by a surface drain to prevent water running onto it and a single 0.5 hectare block of the three methods described above was installed, along with an undrained control area.

The site was sown to canola in May 1996. The winter was wet enough to test the drainage systems, with 303 mm of rain falling between May and October. For much of that time, water flowed freely from the pipes and furrows of the drainage systems while parts of the undrained area remained under water for several weeks. Canola plant growth was good on the narrow beds and on the pipe and mole drained area, poor on the undrained control and on the wide beds growth varied from good on the crowns to poor in the furrows.

The tap root growth of the plants provided the most striking difference between the systems. Plants from the undrained area had short, fibrous root systems, which when pulled out, always had mud adhering to them. Plants from the pipe and mole drained block had better root development, but still pulled up muddy. On the wide raised beds, there were again big differences between the crowns, slopes and furrows of the beds. However, on the narrow raised beds, long canola tap roots, white and free of soil, could be pulled easily from the tops of the beds at all times during the growing season.

Grain yield assessment showed all three drainage blocks yielding approximately 3.5 t/ha while yield on the undrained area was approximately 2.2 t/ha. On the wide raised beds, yield was high on the crowns, reducing on the slopes down to very poor yield in the drains. Also, the canola ripened earlier on the slopes than on the crowns, so choosing windrowing (swathing) time was difficult.

In 1997 malting barley was direct drilled into the same beds and in 1998 winter wheat. Both seasons had exceptionally dry winters and springs but some waterlogging occurred in 1997 after spring storms. Malting barley yields were high on raised beds in 1997 but the winter wheat on beds in 1998 did not yield as well as the other drainage methods. This was due probably to seed placement and crop establishment difficulties on the beds, and the fact that after two dry seasons the beds may have dried out more than areas cropped on the flat.

There are indications that in the second and subsequent years the soil structure on raised beds starts to improve. Measurements on the drainage demonstration site indicate improvements on the beds in penetrometer reading, bulk density and water infiltration rate. This is consistent with long term observations and measurements on many soil types in SE Australia that show the deleterious effects on soil structure of both waterlogging and compaction. The soil on top of the raised beds does not appear to become waterlogged or compacted. Sheep, which can cause compaction when grazing stubbles, are generally kept off the beds between harvest and sowing.

Farmer adoption of raised bed cropping

After that first successful year Southern Farming Systems decided to concentrate on the narrow raised bed cropping system, using bed widths of 1.7 m or 2.0 m centre to centre, because of its apparent potential to reduce waterlogging damage to crops and to improve soil structure by controlling traffic. Installation costs for the method were calculated to range from $A100 - $A300 per hectare, and this was likely to be affordable, on a broad acre scale, for high rainfall farmers.

The system was becoming known as Controlled Traffic Raised Bed Cropping and in 1997 a group of 8 SFS members agreed to each install an area of about 40 hectares of raised beds on their farms, and a total of 300 hectares, mostly canola, were cropped by the method. Winter in 1997 was much drier than average but several sites received heavy spring rainstorms and the crop damage evident on surrounding paddocks seemed not to occur on the beds.

Despite the dry winter, enthusiasm remained high and, following the 1997 harvest, interest in the system spread to other high rainfall areas of SE Australia. Bed forming machines were developed and constructed, seed drills were modified, and several contractors began forming and sowing beds for farmers. In the 1998 season an estimated 5000 hectares of raised bed crops were grown in South-eastern Australia. The winter was again dry in most of Victoria, but some high rainfall districts experienced wet conditions and the raised beds appeared to improve crop growth and yield.

Interest continued to increase and farmers from all the high rainfall parts of Australia began to visit Southern Farming Systems to learn about Controlled Traffic Raised Bed Cropping. Many more bed forming machines were built and in the autumn of 1999 an estimated 30,000 hectares of raised beds were sown to crops in high rainfall regions of SE Australia. Research and development work on the technique is being conducted in parallel by a group in Western Australia and adoption is also increasing in that state. Scientists and farmers from both sides of the continent have visited each other and regularly exchange information.

Raised bed cropping research

An extensive program of research on the agronomic aspects and environmental effects of raised bed cropping has recently commenced across Australia. It is likely that optimum technology for growing high rainfall crops on raised beds will be different from that required for conventional crops. Plant spatial arrangement, crop nutrition and integrated pest and disease management all require investigation to determine the best techniques for obtaining consistent high yields.

Another important focus for research is the environmental side of raised bed cropping. It is essential this new farming system be environmentally sound and sustainable. Effects on water flows from fields, effects on ground water recharge and also possible movement of nutrients out of the field or into the groundwater are being measured in detail. Soil erosion control is also a major focus of this research.

Machinery development is another important research area. Although the technique started by using commonly available equipment that required only minor modifications, specialist machines for forming and sowing beds are now being developed. Machines capable of accurately applying plant nutrients to the tops of beds but not to the furrows are also under development. These are required to avoid economic and environmentally damaging nutrient losses.

CONCLUSIONS

Continued success of raised bed cropping where grain growing is currently not an important enterprise will have profound effects on grain production in Australia. Evidence from Australia and the world shows that, in the absence of waterlogging and with sound agronomic practices, yields of high rainfall crops can be much higher than those from low rainfall regions. Average yields of 5.5 t/ha of wheat, 3.5 t/ha of canola and 5.0 t/ha of malting barley are believed to be readily achievable.

When yields are at the level of the winning canola award crops, canola is the most profitable crop in high rainfall SE Australia. While this remains the case, farmers will grow canola on their farms to the maximum extent that good crop rotation practices allow.

It has been estimated that there are 2.5 million hectares of waterlogging prone grazing land in South-eastern Australia, which could be used for grain growing if raised bed cropping is proved to alleviate the waterlogging. If a high proportion of this land were converted to mixed farming there could be at least 1 million hectares of extra crop grown each year. At a one year in four canola rotation this would be 250,000 hectares of extra canola per year.

If the average yield is 3.0 t/ha the extra production of canola would be 750,000 tonnes, worth about $A250 million in direct farm income. There is also the income from the other grain crops in the rotation. Research is being conducted into techniques that may allow high value horticultural crops such as potatoes and vegetables to be grown on the beds in rotation with grain crops. Catching run off water in dams and using it to irrigate summer crops is also under investigation.

The direct and flow on economic and social benefits of this are hard to calculate but they are likely to be high enough to ensure that the opportunity is taken up within these regions. There are already instances of city based investment funds being used in SW Victoria to develop farms for raised bed cropping, and if this continues it could affect the value of high rainfall arable farming land.

Both farmers and investors will try to grow crops by using optimum technology, to maximise returns, and this will increase the need for research into improved high rainfall crop agronomy. This may further raise average crops yields and increase production. Pressure will increase on farmers and researchers to ensure that crops are grown in an environmentally sustainable way, and a close watch will be kept for any environmental effects of the land use changes.

The marketing implications of the expanded production also need to be considered. It may be desirable to increase research to enable high rainfall regions to produce grains of different type, quality and end use to those grown in lower rainfall parts of Australia. This would expand the markets for Australian produce and reduce competition between regions in the marketplace.

It therefore seems likely that, if this new technology continues to show promise, and if adoption continues to increase at the current rate, a continual expansion of research effort will be required into the agronomic technology, the environmental sustainability and the economic implications of high rainfall cropping in Australia.

References:

1. Blayney (1984); Conley (1984); Joyce (1984). In: The Western Plains, a Natural and Social History. Ed. D Conley & C Dennis, Pub. The Australian Institute of Agricultural Science, 1984