Stubble mulching no joke on South Coast

25 Feb, 2015 10:00 PM


STUBBLE mulch farming could be in for a renaissance in WA.

Small signs are emerging throughout the Wheatbelt as inquiring farmers continue experiments with lying down straw rather than leaving it standing after harvest.

The latter evolved from the 1980s with the escalation of no-till farming and the need to get the seeding bar through crop stubbles that protected paddocks against wind erosion.

To lay stubble down seemed self-defeating even though there were good reasons to do so.

Such surface cover (mulch) minimised run-off and erosion from summer storms and improved the conditions for plant establishment and growth.

The stubble reduced soil temperatures and conserved moisture while breaking down to increase organic matter levels and improve soil structure and fertility.

These attributes are ticking boxes with farmers wanting to renovate and ameliorate soils that were on God's to-do list to fix but somehow got lost in the creation of man.

WA soils particularly, are rated by geologists as among the oldest in the world and have become a constant income earner for anybody with an interest to research or teach the subject.

Farmers, of course, are keen to derive more income from the poisonous sands, clays and duplex soils that characterise WA's Wheatbelt (If you have some loamy soil, consider yourself lucky).

Ratten and Slater Esperance salesman Mark Bratten also is seeing positive signs of a fledgling return to the practice with promising trial results using the German-made Horsch Joker RT which has impressed several South Coast farmers discing-in four or five tonnes a hectare of straw after summer rains and watching it break down before seeding.

Beaumont (east Esperance) farmer Phil Longmire used a 12.8m (42ft) two row disc Joker after listening to Horsch owner Michael Horsch, who visited the Esperance district last year.

"I did 200ha of wheat stubble that had been ripped and spaded and it was going into canola," he said.

"The bar did a good job of levelling the soil while working the stubble into the soil.

"It also was done in March in dry conditions and broke down all the cloddy clay caused by the ripping and spading.

"We worked to about 50mm (2in) and used our DBS knife points for depth but it could have gone twice as deep. We will continue to work at 50mm but would prefer a moist profile for soil-stubble contact and aim to use the Joker over 900ha this season."

What also is appealing to Mr Longmire, apart from setting up his seeding program, is the re-incorporation of lateral roots to provide a more porous or structured environment that may reduce non-wetting issues.

"I worked it at 12.5km/h and the straw tended to float to the top with the packers crimping it and it didn't blow," Mr Longmire said.

"That incorporation or mulching gave us a good canola germination which I would rate as one of our best with good seed-soil contact and strong lateral root growth.

"I would probably use the Joker in rotation after about four years of no-till so I would be doing different paddocks every year on a one-in-five basis.

"While visiting Michael in Germany and Czech we were impressed by his prototype tramline renovator which has tynes positioned on the front of the bar that work the edge of the tramlines with curved plates guiding soil back into the tramlines and being levelled by the discs and following roller. The tynes lift up on low traffic runs.

"This could be cost-effective in avoiding trenching in our tramlines removing the need to renovate our high traffic passes.

"I also like a bit of shallow steel in our no-till system just to re-balance that top 50mm that has been subject to 20 years of no-till and lateral root growth that have created matting which we feel contributes to non-wetting and are currently researching if surface acidity is being created in stubble breakdown zone affecting residual chemical effectiveness.

"We got good early plant vigour and while we didn't get a significant yield gain we didn't get a yield negative and it was only one year so you can't go on one set of results.

"I know some guys like to mulch earlier but March is my preferred month as I don't want to re-invigorate weeds early in the year and have to do more spraying.

"In our trials we achieved less in-crop weeds from areas where we used the Joker.

"That was the result of an even germination after the working and we got a very good kill from the knockdown before seeding.

"We will continue to assess its economic performance and may continue to hire it until its proven itself as part of our system."

According to Mr Bratten, using the Joker is part of a process and will be a different tool for different farmers.

"The object will be the same but the

timing may be different for different guys," he said.

"For example some guys will want to lay down stubble at harvest or after a summer storm to get that mulching and decaying effect going over summer and have it broken down before seeding.

"Other guys will assess the timing according to how they are planning rotations and managing weeds."

According to Mr Bratten, Horsch recommends using the Joker after rain and preferably at least four months out from seeding to allow a good breakdown of straw.

"It can complement spading or claying by levelling the soil, with the bonus of incorporating stubble from the crop that has been spaded or clayed," he said.

"The rear packers also crack the clay so you're enhancing moisture penetration.

"In some instances the Joker might be used to incorporate clay, depending on the quality of the clay, the timing and whether the soil has been spaded or delved.

"There is still a place for spading and delving, or even ripping, to get into the subsoil then using the Joker to smooth the soil while incorporating the stubble.

"But its best job is incorporating stubble."

Mr Bratten said one South Coast farmer, ameliorating a sandy ridge on his property, had ripped the sand, delved, spread clay and then used the Joker to smooth the topsoil.

He has then seeded an opportunity crop of millet after harvest in late November, mainly as a cover crop and is waiting for rain to incorporate the crop before seeding.

Another farmer had used the Joker in October after ripping and spading and sowing millet, which was subsequently sprayed off.

"He used the Joker two or three times on rain and levelled it all off ready for this season's seeding," Mr Bratten said. "The Joker smashed the clay and promoted a better soil tilth."

Interestingly in comparing conventionally-harvested crop stubbles with the stubble incorporation achieved by the Joker, it was readily apparent the presence of "straw mats" between the rows of conventionally-harvested stubbles and the relatively clean finish of incorporation by the Joker.

"The straw mats are hot beds for weeds, mice, snails and other pests so that's another benefit of incorporating the stubble," Mr Bratten said.

According to Muddy River WA sales manager Roy Thurston, the Joker RT is ideal for shallow stubble cultivation for a germination stimulation of volunteer crops, to interrupt capillarity, to mix in harvest residues and for a shallow seedbed preparation with large working widths.

Despite its working width the Joker RT folds to a transport width of 3m (10ft) by means of a special folding system.

"The DiscSystem, with 52cm (21in) serrated discs, is particularly suited for aggressive working and good penetration into the soil," Mr Thurston said.

"The discs which are arranged in pairs on the suspension system guarantee a large free space and clearance for harvest residues.

"Due to the middle chassis the distance between the disc rows and the packer has increased too.

"Thus, the flow of soil has enough time to settle and is not thrown into the packer by the DiscSystem.

"This improves levelling and operational reliability."

Contour-following and stone protection of the Joker RT are carried out via a solid rubber bearing while each disc is equipped with a maintenance-free and low-wear bearing with oil filling.

Ken Wilson

Ken Wilson

is Farm Weekly's machinery writer


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