Murrumbidgee Landcare Inc

The South-West Slopes region in the Murrumbidgee catchment, has been regarded as a relatively safe mixed farming region with growers incorporating livestock, cereals, legumes and canola in their systems. However, after 7 years of drought, the cropping component of the system was under increasing pressure and the farming community was urgently looking for innovative ways to improve sustainability and profitability of their enterprises.

Conventional farming of cereal crops in the South-west Slopes region has involved cultivation, often multiple times, prior to sowing the crop. The removal of ground cover in the form of stubble has lead to soil degradation, soil erosion and a decline in soil structure over time. Whilst cultivating does have advantages, for example as a form of weed control, conventional farming practices are not sustainable in the long term. Soil structure decline has resulted in a decline of soil water holding capacity. This in turn has reduced the capacity of farms to withstand the effects of drought. During drought, every drop of water counts.

Stubble retention and direct drilling are proven solutions to some of the degradation effects of conventional cultivation. Ground cover, in the form of stubble, reduces problems such as soil and water erosion, and can help with building soil structure by returning organic matter to the system. Stubble retention also improves both the water holding capacity of soil. Other advantages of stubble retention include:
•Improved water infiltration
•Reduced soil evaporation
•Improved levels of organic matter
•Increased numbers of soil fauna
•Increased water availability to crops.

A majority of farmers in the region are either already moving away from, or are interested in moving away from, conventional cultivation practices to conservation farming systems based on stubble retention and direct drilling. Conservation farming involves abandoning traditional practices; embarking on a significant learning curve; confronting a series of new issues including weed, disease and pest control, and dealing with the practical and financial implications of conventional cropping machinery struggling to handle high stubble loads.

In conservation farming systems weed management using cultivation is replaced by herbicides. Problems with weed management are a major constraint to adoption of conservation farming. Resistance in annual ryegrass is now a major problem, and is an emerging problem in wild oats and wild radish weeds. Other ‘difficult-to -control weeds’ become more dominant under conservation farming systems, including brome grass, vulpia, and mallow. The development of integrated weed management strategies with farmers and advisers is essential to provide long-term and sustainable weed management.

For farmers to adopt new practices it was recognized that the project be structured around the following key elements:
1.access to scientific analysis and advice
2.local, specific, on-ground demonstrations providing direct and relevant evidence for regional farmers on the advantages (and costs) of conservation farming
3.access to specialists to assist with developing management strategies to deal with the new problems arising from stubble retention systems, such as weed control
4.a community structure to share information, knowledge and learning whilst providing support for change

The overall project was co-ordinated through Murrumbidgee Landcare Inc.

The project generated valuable data on different stubble management options. The project groups were strongly involved in all activities. A new Mirrool Creek Landcare Group with farmers from Ardlethan and Ariah Park, formed to also participate in the project and was co-ordinated by the local Elders agronomist.The results have been communicated to growers though a series of valuable case studies compiled in the publication “Cereal Stubble Management Case Studies 2009”. Examples of the case studies include the following:

Derek Ingold farms with his wife Susan, his parents John and Beverley and son Alex. They manage a mixed farming operation at Dirnaseer, north of Junee, dominated by annual winter cropping and a prime lamb enterprise supported by perennial (lucerne) and annual (sub clover and annual grasses) pastures. Derek and his family are in the process of moving to a cropping system where they can inter-row sow using 2 cm autosteer on there sowing tractor. One of the key aims is to retain cereal crop residues without the challenges of clocking machinery at seeding time.

Stubble management The Ingolds are grazing stubbles less and less, last year only grazing some of their cereal stubbles very lightly. In the future it would be ideal to avoid grazing stubbles at all, and in 2010 this is the plan. The move to no stubble grazing is probably more of a change in mind-set rather than a large practical or management issue. To maintain current livestock levels a containment area for summer and autumn feeding will be implemented.

Derek has observed a number of issues with running sheep on stubbles over summer, even at low rates for relatively short periods of time. Derek has seen an increase in water run-off, and he believes it is associated with degradation of the surface soil structure. Grazing sheep also knock stubble down causing problems with trash flow at seeding.

Weed management Derek and Alex have most weeds are under control with no real problem weeds; however they are always focused in reducing the risk of weeds developing resistance to herbicides. Many of their weed management decisions are based around managing that risk as well as reducing weed numbers.

The current move to increasing the levels of stubble retained is likely to cause a reduction in the effectiveness of soil-incorporated residual herbicides such as trifluralin.

Implications of stubble retention on crop health and the soilDerek sees that stubble retention will bring more benefits than challenges. Insect numbers may increase, however the increase may be in beneficial species resulting in a more environmentally friendly cropping system. The reduction of stubble grazing should result in increased infiltration of water into the soil due to improvements in structure of the soil surface. More of the high-intensity summer rains will be stored in the soil profile and the stubble cover will reduce evaporation. Derek hope the increase in soil water will not only result

One of the challenges Derek sees with the cropping system he is moving to (controlled traffic and inter-row sowing) is the inability of the header to effectively spread crop residues across the width of the header. Both Derek and Alex would like to have a header or system in place within five years that can properly spread straw.

Some of the other challenges facing the new cropping system are ‘unknowns’:What will happen to crop diseases in the new system? Will the cereal stubble increase the pressure of foliar diseases in particular? Will our current varieties stand up in the new system?How will the seeding equipment and inter-row sowing work when high yielding seasons return? Will it be effective in high stubble loads?How will soil incorporated residual herbicides be used effectively? Perhaps a strategic burn will have to be used to enable use of these herbicide tools. Will the weed spectrum change?

Geoff Dale manages ‘Englefield Plains’, Illabo.The property is primarily focused on annual winter cropping with 25% perennial pastures.

The cropping program is driven by yield, which in turn depends on crop disease, weed management and matching crop and variety to sowing time or season length. Managing crop residues is rapidly becoming one the biggest challenges facing Geoff and David. Dealing with stubble at planting time is a key area of the cropping system where improvements are required. Issues with hair-pinning and blockages of the seeding cultivator need to be addressed.

Stubble management Stubble management at ‘Englefield Plains’ begins at harvest cutting the crop at the lowest practical height. Then in late summer the heaviest cereal stubbles are mulched using a flail mulcher with the aim of chopping straw into short lengths.

Geoff and David have trialed inter-row sowing as a solution to effectively sowing into stubble, however they run into problems when sowing across hillsides. The cultivator has a tendency to fall back into the previous year’s furrows resulting in sowing back into the previous year’s row of stubble, resulting in residue blockages.

Grazing stubbles is not part of stubble management on ‘Englefield Plains’. Geoff sees no real benefit in grazing stubbles but a number of associated problems including:Compaction of the topsoil, andRemoval of groundcover, especially if grazing occurs soon after harvest and groundcover is reduced for a long period of time. Both of these factors then lead to reduced water conservation—reduced infiltration and increased surface evaporation.

Weed management One of the major challenges David faces with managing weeds in annual winter crops is controlling grasses in cereal crops, especially annual ryegrass (Lolium rigidum) and annual brome (Bromus sp.). However with attention to detail when it comes to boom setup and herbicide application technology, and the use of crop sequence and an occasional stubble burn, these weeds can be managed effectively.

Implications of stubble retention on crop health and the soil Retaining stubble may or may not impact on crop disease. The main concern is foliar diseases which can pass from the stubble of the previous crop to the current crop. Yellow leaf spot is one disease to be watched, but its impact is as yet unknown. Rarely has the disease been reported to cause yield loss in southern NSW however this may change with increased adoption of full stubble retention.

Geoff says, “I think we can work around these *seeding and disease+ issues for the potential benefits of healthier soils with greater water holding capacity.”

Future opportunities and challenges Geoff and David plan to improve their current seeding cultivator, the Conservapac, to work more consistently in thick stubble. At this stage they are not convinced that a disc seeder is the answer for their operation. They aim to trial some form of coulter in front of each sowing tyne.

Ultimately the key is to move completely away from late stubble burning altogether and be able to reliably inter-row sow on hillsides—currently the seeder creeps into the previous years furrow. Lack of soil moisture or inefficient utilisation of the rain that falls is a threat to the profitability of the current cropping system. Geoff believes the issues associated with retaining stubble (potential crop disease, herbicide resistant weeds and seeding issues) can be worked through to achieve the potential benefits including healthier soil with greater water holding capacity

Tony Lehmann manages 2300 ha in the Illabo district with a focus on annual winter cropping and a significant sheep enterprise. Two thirds of the area is sown to annual winter crops based around wheat, with canola used as a break crop for weed and cereal disease management, and barley used to extend the cereal component of the rotation.
Stubbles are lightly grazed with a focus on retaining ground cover on both stubble and pasture paddocks.

Tony invested in his disc airseeder four years ago and retained his tyned airseeder, initially because he wasn’t game not to have it. After four seasons he believes there are more pros than cons with the disc seeder. Tony says, “I still like to use a tyne machine to bring new paddocks in – leveling ,busting up tight bits and I don’t like bear paddocks that blow in the summer. We work them fairly deep – six to eight inches and then take advantage of that to use a soil residual herbicide.I am sure sometime I may need a tyne machine for rhizoctinia or similar control, or maybe even cockchafer disturbance. Sowing pasture is still a bit of a concern with the disc machine, but maybe that’s just the dry seasons?”

Stubble management Currently Tony grazes his stubbles lightly over summer and when needed, applies herbicide to control summer weeds when they are small. Tony aims to retain ground cover on all his country with the aim of optimising soil moisture retention. Grazing stubbles takes the pressure off his pasture paddocks, allowing them to recover and spreading the grazing load. The stubbles enable Tony to better manage his sheep over summer, maintaining their body weight and minimising the need to contain and feed them.

As well as these benefits Tony sees many drawbacks with grazing stubbles including:Tracks formed by sheepStubble on ground causing trash-flow problems at sowingCompactionSpread of weedsNeed for sound fencesPaddock size to suit grazing compared to cropping efficiency.

In the future, Tony would like to be able to spread the crop residue evenly across the width of the header and leave all the stubble standing. He believes the best way to retain standing stubble is to inter-row sow. Currently his row space and stubble hair-pinning are limiting his ability to achieve this. He may have to move to wider row spacing and has added Aricks wheels in front of his disc seeding assemblies. The Aricks wheels have addressed the hair-pinning, although they are a bit more aggressive then the zero disturbance of the disc and will be expensive to run as they are high maintenance.

The issue of spreading crop residue across the width of the header is gradually being improved with chopper and spreader improvement made by header manufacturers but remains a challenge.

Weed management The key weed management issue facing Tony’s cropping program stems from the use of the disc seeder and the inability to incorporate residual herbicides. This places pressure on in-crop selective herbicides and increases the importance of implementing alternate weed management tactics, such as sowing some paddocks after the first weeds germinate and a knockdown herbicide can be used. This is very effective but not every season is suitable.

Implications of stubble retention on crop health and the soil

The increased level of stubble retention has reduced the weed number (both summer and winter weeds) and changed the weed spectrum. There also seems to be more cockchafers, earwigs and other pest insects. Hopefully on the plus side, there is also more worms and soil biology is greatly improved.

Future opportunities and challenges Future plans for improving stubble retention with the cropping system includes the use of wider row spacing to enable inter-row sowing and the use of both the tyne and disc system. It is unlikely we will be able to spread crop residues effectively to 12 m (40’) which is a key issue to making the inter-row cropping system work. Levelling paddocks would improve the system which may mean the rotation starts with a cultivation.

One of the challenges with the stubble retention system including light grazing is the residue that is laying on the ground when it gets wet. This can cause hair-pinning and trash-flow problems at sowing time.

Once the challenges are overcome the benefits are endless and based around the ability to utilize smaller rainfall events and retain moisture in the soil for longer than in bare ground. This has the potential to enable more timely sowing, and result in effective germination and crop establishment on small rainfall events. Timely crop establishment then directly increases potential crop yield.