Turning sowing times on their head with winter habit canola and wheat

GRDC project code: SFS00020, SFS00028

Keywords: spring sown canola, spring sown wheat, vernalisation, grazing, cover crops.

Take home messages:

• Winter habit canola has been successfully sown in spring, grazed over summer and harvested for grain in 2012, 2013 and 2014.
• Establishing canola in spring means larger, more resilient plants in autumn with less impact from slugs and waterlogging.
• Forage value is comparable to commercially available dedicated forage rapes over summer and autumn with added benefit of oil seed production.
• Grazing management and timing of stock removal is proving to have an impact on grain yield.
• Vernalisation means winter wheats have the potential to be used in the same way.

The spring sown canola story

Grazing cereals has proven to be a major opportunity for mixed livestock and cropping farmers in southern Victoria. If managed correctly, the crop can provide ample amounts of forage over winter and go on to produce grain without a penalty on yield. With more and more land sown to canola in the high rainfall zone (HRZ), finding the fit of canola in a mixed farming system has been the focus of more recent research. Over the last four years, Southern Farming Systems (SFS) trials have shown that grazing canola over winter has not supplied much feed and has usually been at the expense of yield.

Conventional grazing of canola in the HRZ provides valuable winter fodder, yet often at the expense of grain yield come harvest. With the introduction of varieties with a vernalisation requirement, such as CB™ Taurus and Hyola®971CL, spring sowing and grazing over the summer/autumn period can fill the feed gap with potentially little impact on subsequent grain yield. Additionally, they can provide other management options for problem paddocks.

Sowing in October or November means that the crop is in the ground for over 12 months. The vernalisation requirement of winter canola varieties dictates that a plant will not flower until it has endured a certain period of cold weather, over winter. To test this theory, in 2010 some Hyola®50 (spring canola variety) was sown alongside CB™ Taurus, and attempted to flower over summer.

What have we learnt in the last 12 months?

The earlier you sow, the better

Paddocks sown mid-late September 2014 were ready for grazing at the start of November, establishing on very little rainfall. Having the seed in the ground, rather than waiting for a big rain and sowing afterward, would be the best approach but could also be considered more risky. Establishing on a few separate rainfall events is not going to hurt the crop provided the youngest plants are established well enough before the first grazing. There is very little risk of vernalisation requirement being fulfilled in the late spring, however sowing before mid-September would be pushing it.

Refining grazing management

Deciding how hard to push the crop is going to depend on the preference of the grower and the seasonal opportunities such as sheep prices, weather conditions and so on. Grazing the plants hard is not an issue, but set-stocking a paddock and grazing lightly for an extended time seems to result in poorer recovery than a short, heavy graze with high stocking numbers. Smaller paddocks or strip grazing if stock numbers are low may be a way to manage this better.

Remove stock when sowing canola in autumn

The timing of locking the paddock up for grain seems to be crucial and needs to be stressed to growers grazing spring sown canola. As a rule of thumb, for optimal grain yield animals should be taken off the crop around the same time canola is being sown in the autumn. The later this ‘lock up’ date is pushed back, the harder the crop has to work to recover from grazing before cold and wet conditions in late autumn and winter cause stress to the crop.

Do not be scared by low plant numbers

We yearn for good, even germination in a canola crop, aiming for around 60 to 70 plants per square metre in an autumn grain crop. While aiming for these numbers in spring (around 3 kg/ha sowing rate), we have often failed to get even half that due to weather conditions. It is daunting, but soon goes unnoticed once the plants start growing and covering ground. Plant numbers in the autumn after summer of grazing seem to be closer to the 15 plants/m² mark, yielding the same if not better than an autumn sown crop with a plant stand over 50 plants/m². Plants numbers have dropped over summer whether grazed or not.

Sheep prefer the taste of canola over rape

Using real sheep to graze trial areas gives us this insight into the preference for canola over rape. In February 2014, the rape plots were left virtually untouched by the sheep, with the rest of the trial area eaten down to bare earth. This is thought to be due to the higher glucosinolates in rape which ward off pest damage over the summer, but have been bred out of canola and seem to make the taste less bitter. In 2014, SF Brazzil was the preferred canola variety over any others, with four plots clearly bared out in the trial area before any of the others were touched. Other industry research suggests grazing ewe lambs on spring sown canola compared to other traditional pasture or forage crops increases conception rates.

Use grazing as an IPM strategy

Loss of leaf due to grubs over the summer is something we have seen each year, in varying degrees depending on location. While an early spray for grubs may be inevitable in some situations, the integrated pest management (IPM) approach suggests that the damage caused by the grubs to the plant is going to be superseded by the impact of stock grazing. Manage pest burdens by grazing as soon as possible to remove the green leaf and feed source, but consider high nitrate levels if grazing early. Slug pressure in autumn has not been a problem for established spring sown plants.

Dry matter production and yield 2012

In spring 2011, we set out to answer some key questions relating to grazing spring sown canola.

• How many times can it be grazed before a yield penalty is suffered?
• Should I graze it lightly or can I graze it as heavily as my cereals?
• Does nitrogen application following grazing enable better recovery?

Quality of feed on offer was high throughout the grazing period. Metabolisable energy (ME) averaged 13.5 MJ/kg DM and protein was up around 22 per cent. Nitrate poisoning was not of concern, with levels well under the toxic threshold of 1000 mg/kg for lambs. In saying that, introducing stock to forage brassicas needs to be done gradually. It is important that stock are not put out on canola with an empty stomach and they should be supplied with some roughage when grazing.

Table 1. Dry matter production and grain yield for spring sown CB™ Taurus canola at Dunkeld, Victoria in 2012.

In 2012, grazing over summer increased grain yield compared to no grazing (ungrazed) as shown in Table 1. Spring sown and ungrazed yielded 1.9 t/ha with optimal grazing going 2.7 t/ha. CB™ Taurus sown at the conventional time in April yielded 2.3 t/ha. Observations were that grazed plants had branched more and produced a denser canopy with stems producing pods for grain.

The number of times the crop was grazed had a small effect on yield. Grazing twice produced the best result, yielding 0.1 t/ha more than grazing once and 0.2 t/ha more than grazing three times. Although there was a yield penalty by grazing three times compared to two times, the third grazing supplied an additional 1 t/ha of high quality feed at the beginning of May.

Heavy grazing reduced yield compared to light grazing irrespective of the number of times it was grazed. However the reduction in yield was small and the heavy grazing produced 4 t/ha of feed compared to 1.4 t/ha when lightly grazed. When deciding on stocking rate and grazing intensity, it can be a trade-off between the value of the feed over summer and autumn and final grain yield, suggesting that attitude and preference will vary between growers.

Applying nitrogen over summer had no yield benefit, except for multiple (three) heavy grazings.  In this case yield increased from 2.0 t/ha to 2.7 t/ha when 150 kg/ha of urea was spread after each grazing. This would suggest that an application of fertiliser purely to boost crop performance is not necessary.

Dry matter production and yield 2013

The 2013 season was almost completely opposite to 2012, with extremely dry and hot conditions from sowing until the break in May 2013. Table 2 shows that dry matter production was down on 2012, over a tonne less feed, however the value of the green feed in 2013 would most likely outweigh the extra tonne in the favourable 2012 season. It is difficult to put a price on almost three tonne of high quality green feed when there is nothing else around.

Resilience of the canola was well and truly tested, with three very heavy grazings occurring between the end of January and the end of April. There were plants lost and for a while it looked like nothing was going to grow back, however the thick starchy stem and root system of the established canola allowed the plants to hang on and begin to grow leaves back once the break finally came. The recovery of the plants was just astounding – in winter 2013 you would not have believed what the area looked like only three months before.

Table 2. Dry matter production and grain yield for several winter canola varieties sown in spring 2012 and harvested in December 2013, Inverleigh Victoria.

Dry matter production and yield 2014

The 2013/2014 season provided a fairly tough start for the canola with another dry and hot summer looking to threaten the success of this relatively new rotation. However, as seen the previous summer, once the autumn broke plants came back and quickly covered the ground, recovering well to yield. An unfortunately late application of clethodim saw the loss of many flowers/pods across the trial, with some varieties compromised more than others depending on flowering time.

In terms of any differences, over the last three years dry matter production has been comparable, as has grain yield. Decisions need to be made on seed costs (OP v hybrid) and herbicide tolerance (conventional v Clearfield) rather than looking at the 2014 results too closely. The autumn sown plots were the hardest hit as they flowered a little later and were in full flower at the time of the clethodim application.

Table 3 outlines the results in 2014, though compromised by herbicide damage, which paired up a fairly harsh summer with a very hard spring finish. The root system on the plants was not comparable to any autumn sown crops around. The roots established deep over the summer and autumn, getting through the winter and more than likely accessing a lot more resource in the dry spring than the shallow roots on the autumn sown plants.

Table 3. Dry matter production and grain yield for several spring sown canola varieties sown in spring 2013 and harvested in December 2014, Lake Bolac Victoria.

What about weeds?

Planting a conventional variety can limit weed control from the beginning. Sowing into a paddock that has an existing broadleaf weed burden is likely to exacerbate the problem due to the long rotation and limited control options throughout this time. In 2012, there was no observed difference in weeds when grazed compared to ungrazed, nor were there fewer weeds in the April sown crop. Throughout both years of trialling, weed numbers have been of no concern as it appears the rapid closure of the canopy following grazing easily out competed any early weeds and is noticeable throughout the season.

In 2014, different herbicide regimes were trialled under spring sown and grazed conditions as well as autumn sown conditions. Some of the grazed plots were sprayed with Spray.Seed® at 1.2 L/ha or Roundup® at 1 L/ha a few weeks after the sheep were removed (onto green leaf) and grew back to yield grain. The autumn sown plots had an autumn knock prior to sowing. Weed counts in spring showed no significance. Yield results are below in Table 4. Plant numbers in autumn sown were much higher than spring sown but this did not seem to add to yield of the crop.

Table 4. Grain yield and plant numbers spring vs autumn sowing with different herbicide regimes.

Can we do the same with winter wheat?

What started as a crazy idea in November 2013 turned into a valuable learning experience as well as perhaps an accidental discovery into the potential of long season crops in the southern HRZ. Winter wheat was sown at the Lake Bolac SFS trial site on the 11th November 2013 to see if it would behave like a winter canola, establish and allow summer and autumn grazing before being locked up for grain harvest at the end of 2014.

Disease, weeds, hot temperatures and lack of rain were all flagged as potential risks, as well as the suggestion that the vernalisation may not hold up over the summer and the crop could run to head early. The plants jumped out of the ground well, relishing the soil moisture that was available and the warm temperatures. Things were looking pretty exciting; as the spring wheat 'control' ran up to head by Christmas, the winter wheats were tillering well and coping with the summer. So far, so good!

On Australia Day 2014, after five days over 40 ^oC and no real rain since the crop germinated in November, the wheat was pronounced dead. It was literally turning to powder under foot, it looked like it had been accidentally hit with a knockdown spray - that is how dead it was! Research can be like that sometimes, you hold hope in a crazy idea, and sometimes, well, it just is not meant to work. After seeing what spring sown canola can deal with, we were quietly disappointed in the wheat but admitted defeat, at least now we knew!

Fast forward to the end of March, a bit of rain, and the trial started to green up again. The wheat was grazed, with 800 kg/ha of dry matter eaten by sheep in early April. Management of the crop was very minimal, no in-crop fungicide was applied, fertiliser inputs were low, and weeds were left to do their thing (we still weren’t convinced it was going to eventuate!). As expected, the crop followed the normal growth pattern for the year, flowering about three weeks before autumn sown winter wheat. Root growth over the long growing season allowed the crop to finish surprisingly well in what ended up being a very dry spring. Compared to nearby autumn sown wheat, the root mass would have easily been four times greater. These observations have really made us think about what plants can cope with, and actually that some less than ideal weather conditions at key stages may actually cause the plant to 'try' a little harder.

Table 5. Grain yield, protein and dry matter of spring sown wheat varieties at Lake Bolac, Victoria.

At harvest, grain yields of the spring sown wheat averaged 3.2 t/ha. Grazing value, summer cover and low inputs in a marginal finish seems to have paid off and we continued this work by sowing more in December 2014 at Inverleigh and Lake Bolac. So far they have established and are tillering very well. Sometimes, crazy trial ideas can lead to huge lessons. We have seen canola and wheat withstand some of our hottest, driest summers and still perform well. Given these crops can sometimes struggle to establish and grow well in the HRZ wet, cool autumns, spring sowing has shown me just how tough they can be.

Acknowledgements

Host farmers Neil Vallance and Rowan Peel; and resident sheep wranglers, Gina Kreeck and Aaron Vague.

Contact details

Annieka Paridaen
Southern Farming Systems
23 High St, Inverleigh VIC 3321
(03) 5265 1666
0439 339 433
aparidaen@sfs.org.au
@AParidaen