Grazing canola – agronomic and feed considerations

Take home messages

• At current livestock prices, gross margin returns in excess of $2000/ha have been achieved with irrigated grain and grazed canola.
• A better understanding of the agronomy of winter canola and how it fits into the livestock program has been established and are critical to success.
• Further work needs to be undertaken on the issues which are currently barriers to adoption.

Background

Winter canola is increasing in popularity as a dual purpose crop – offering grazing opportunities followed by grain production. The ‘winter’ habit is due to the requirement from the crop of a period of cold (vernalisation) to initiate flowering. Access to rrrigation provides growers with the opportunity to sow early to provide biomass for grazing and then lock the crop up (i.e. remove livestock) for grain production. Unfortunately, the vernalisation requirement sees the currently available winter canola varieties flower later than the ‘grain’ types which is an issue for the Northern Victoria/Southern NSW irrigation regions as delayed flowering increases the risk of high temperature stress during flowering and grain fill, leading to poorer grain yields.

Some irrigators have tested winter canola crops and preliminary results suggest that rather than a true grain and graze crop, a significant portion of the gross margin returns are from the grazing value of the crop and the grain crop could be regarded as a bonus rather than the driver of profitability. This paper summarises a number of irrigators’ experiences and poses questions for further adoption of winter canola in the irrigation region.

Method

Several growers across the western Murray Valley provided summaries of their agronomic practices, productivity and thoughts on their experience of growing irrigated winter canola (Table 1). Additional data was obtained from trials conducted by the Irrigated Cropping Council.

Results and discussion

Table 1 summarises the irrigator's agronomic practices, productivity and experiences.

Table 1. Irrigator’s data at a glance

Paddock selection

It’s important to match paddock size with the number of sheep to stop preferential grazing given a biomass of approximately 2t/ha.

Select a paddock that is preferably well drained with minimal weed seedbank (especially no broadleaf problems) and good soil structure that produces a fine seedbed. It is recommended that gypsum is applied at approximately 2.5t/ha, both as a source of sulphur and to aid plant establishment.

Variety selection

The 2018 Victorian Winter Crop Summary lists three long season winter canola varieties – SF Brazzil (conventional), SF Edimax CL and Hyola® 970CL (the latter both Clearfield® varieties). The herbicide tolerant varieties (SF Edimax CL and Hyola® 970CL) offer greater opportunity to control in-crop weeds, particularly where Group A resistance problems already occur. In the authors’ opinion, because of the extra season length and opening up of the canopy after grazing that is offered by the CL varieties that they should be the only varieties that are grown. Additionally, it would be a difficult task to achieve effective weed control with the conventional canola herbicide options.

The two Clearfield varieties are hybrids, meaning that any retained seed will not be true to type.

If contemplating summer sowing, a Clearfield® variety is essential.

Sowing rate

Sowing rates should be sufficient to establish at least 40 plants/m2. The actual rate is reflected in the irrigators’ data where those using overhead irrigation are using rates around 2kg/ha and up to 5kg/ha where watered up (Table 1). ICC trial data suggests that there is no extra dry matter produced from higher sowing rates but the individual plants are smaller which may be of benefit at windrowing/harvest. Some loss of plant numbers can also be expected by grazing.

Sowing date

The irrigators surveyed for this paper all sowed in late February to early March. The general feeling was to wait for the drop in temperature that signals the start of pasture irrigation. This timing has a few other benefits; cooler temperatures allow the soil to stay moist for a longer period during germination and weeds such as ryegrass also start germinating which allows for an early kill. Generally, a knock down herbicide is required even if weed numbers seem small. Experienced operators on good layouts can successfully water the crop up, or alternatively sowing into moisture is fine, but attention must be paid to the correct sowing depth. Sowing at this date results in rapid growth and the crop is ready for grazing in approximately 8 to 10 weeks. This sowing date has seen the required autumn irrigation vary from 1.0 to 2.5ML/ha.

Winter canola growers in the southwest of Victoria are sowing in the preceding spring and are achieving good summer plant survival. Limited attempts have been made to do this in the irrigation zone and possibly this is because this system may not be as successful in the north as in the south. Lower success rate is due to less summer rain in the north compared with the south, and therefore, the crop would most likely have to be irrigated over the summer and produce little growth. The upside would be the existence of established plants that rapidly respond to irrigation in the autumn, and therefore, early production of feed. Where this system may have a place is where a summer rainfall event is large enough to allow germination and establishment of the canola to occur.

Fertiliser

The phosphorus (P) requirement of the crop needs to be applied at sowing, typically 100 to 120kg DAP or MAP/ha. Nitrogen (urea or sulphate of ammonia) has been used where the paddock N levels are low to encourage early growth. The danger is too much N early which results in high nitrate levels in the plant and subsequent health issues for the grazing stock, particularly young or pregnant stock.

Once stock are removed, the crop is top-dressed with 150 to 200kg urea/ha depending on the initial soil nitrate levels and the target yield.

Herbicides

If the crop is sown prior to autumn, it is highly likely that summer weeds will be an issue and the Clearfield® system offers the best opportunity for weed management. However, this does present an issue for subsequent weed control as applying a second Clearfield herbicide application is not permitted according to label recommendations. Care also needs to be taken to adhere to the labelled crop growth stage at application and the grazing withhold period for products registered for use in Clearfield canola production systems.

Group A herbicides are an option, but application only adds to the development of resistance in cropping paddocks. They should only be used early in the crop’s development if grasses pose a competition risk to the canola. Some weeds present in the crop may be an advantage when stock are introduced as it gives the stock something to graze on that they are familiar with and allows the rumen to gradually adapt to the canola.

Generally, trifluralin cannot be used if watering up by flood irrigation, but can reduce grass problems under a pivot or lateral irrigation system.

Current best management systems employ an early autumn sowing, then use the Clearfield® system plus a grass selective, plus clopyralid after grazing.

Grazing

Sheep can be introduced when there is at least 1.5t DM/ha; i.e. when the crop is approximately 250mm in height.

The irrigators surveyed generally have introduced sheep approximately 8 to 10 weeks after sowing, with dry matter on offer being between 1.5 and 2.6t/ha, with the higher amounts being from earlier sowings. Sheep have been set-stocked, with the removal of stock determined by the lack of feed, generally around mid to late June. Stocking rates have been as high as 35 cross-bred lambs/ha, while others have started with ewes and lambs (40 head/ha) and tapered the stocking rate off as the lambs have matured and have been drafted off to market.

All irrigators report that they have used the same common-sense approach when introducing stock to any new feed; i.e. introduce the sheep when they are not hungry and slowly introduce them into the canola over a few days. Post this, they reported no palatability or health issues.

An advantage of having winter canola for grazing is that it takes the pressure off the pasture paddocks, allowing them to get away and have sufficient feed available once the canola is finished.

Theoretically, sheep could graze later in the season via rotational grazing, as the plant will not start to bolt until late August. This late grazing could potentially compromise grain yield as the crop must have time to recover biomass before flowering. But if the principal reason for growing winter canola is in the feed value, then reduced grain yield may not be such an issue.

Feed quality and supplemental feeding

Average feed quality data is presented in Table 2. This data is from six test results taken prior to sheep entering the paddock.

Table 2. Average feed quality (Dry matter basis).

While most results are in the upper range of what is regarded as quality feed, two components do stand out as potential issues. The level of neutral detergent fibre in many cases is lower than the recommended 30% (from ‘A producer’s guide to production feeding for lamb growth’, MLA) which can be addressed by having a source of roughage available such as hay or straw.

The nitrate level can be relatively high depending on soil N and applied fertiliser. The highest level was from canola planted into an old lucerne paddock with 100kg MAP/ha and 150kg Stimulus/ha, adding up to 55kg N/ha applied at sowing. The resulting nitrate level just prior to grazing of the crop was 2200ppm. According to information supplied by FeedTest, nitrate levels less than 1500ppm are regarded as safe, nitrate levels between 1500ppm and 4500ppm prompt a warning – ‘CAUTION: Problems have occurred at this level. Mix, dilute, limit feed forages in this level’.

This can also be addressed by having straw or hay on offer in the paddock. The set-stocking approach does make for challenging early N management as you want to make sure enough N is present to ensure high growth rates but not too much that creates nitrate issues, with little ability to change the N status in-crop unless stock are removed for at least 2 to 3 weeks post topdressing.

Irrigators surveyed for this paper have had supplemental feeds on offer, ranging from straw to barley grain and oaten hay. At this stage it is likely that the straw is required whereas the grain and hay components are more of an insurance system than a necessity.

Most irrigators surveyed have used mineral supplements of some kind. These supplements may act as a useful buffer when changing from one feed source to another.

Post grazing management

Once sheep are removed, the crop is top-dressed to regenerate plant biomass and subsequent yield. This is achieved with 150 to 200kg urea/ha. This is also the best window for herbicide application.

Spring water use has ranged from 1.25ML/ha to 2.5ML/ha. This water use is typically higher due to the late maturity of the winter canola. On average two flood irrigations in the spring have been necessary.

Flowering date is delayed due to the winter habit and the plant requiring a certain period of cold temperature to change from vegetative to reproductive growth. Consequently, flowering date is not altered significantly by sowing date. This results in the flowering period being delayed when compared to canola crops grown for grain. Irrigators surveyed recorded flowering dates from mid-September to early October. In the 2013 ICC canola variety trial, Hyola 971 began flowering six weeks later than the rest of the trial. This late flowering increases the risk of heat stress during flowering (prematurely ending flowering therefore limiting yield) or grain fill (lower yield through smaller grain).

Windrowing, harvest and yields

Of those surveyed, crops have been both windrowed and direct headed for harvest. In one respondent’s opinion, windrowing was essential as he had green material in the sample due to one variety continuing to grow as long as there was moisture. He also had issues with the header cutter bar and stem thickness (referred to as tree trunks) when direct harvesting.

Harvest has been generally in the mid to late December period. Yields ranged from 1.25t/ha (43% oil) to 2.0t/ha (39% oil). It should be noted that these same farmers have grown mid-season irrigated canola varieties on the same areas in other years and achieved yields in the 3.0 to 3.8t/ha range.

Gross margins

Table 3. Gross margin for the production of canola grain only.

Canola: 3.5t/ha
Price: $550/t
Income: $1950

Table 4 indicates the gross margin for a grain and graze scenario using a winter canola. One major component that needs to be included in the gross margin is the cost of the livestock that are used for grazing. This will range from a low value (if the lambs would have been produced anyway and the canola is regarded as supplemental feed) to the cost of buying stores at market specifically for grazing. The scenario will vary from grower to grower; and therefore, it’s necessary for growers to use their own figures when calculating gross margins. Another aspect not included, and difficult to put a figure on, is the extra pasture growth obtained by having stock on the canola rather than grazing the pasture.

Table 4. Gross margin for the production of canola grazing and grain.

Further issues

Clearly these are early days when it comes to establishing best management practice for grazing of canola and a number of questions still need to be answered:

• Rotational versus set-stocking. Would rotational grazing, allowing recovery periods and opportunities to top-dress between each grazing event, result in higher dry matter grown?
• Varieties need to be more suited for the north of the state and its higher autumn and spring temperatures. Maybe the answer is a ‘Wedgetail’ type canola variety that has a reduced cold temperature requirement, and therefore, flowers earlier.
• Other herbicide tolerance options, but not triazine tolerant (TT) as the vigour and yield penalty of these varieties, along with the herbicides options for watering up aren’t a good fit. However, a Roundup Ready variety of appropriate season length and a two spray option could help.

Conclusion

At current livestock prices, financial returns are possible based on the grazing value of the canola alone, and grain is the secondary commodity but still important.

Start early but not too early, aim for the autumn temperature drop off point.

If an opportunity to establish plants before autumn arises, then seriously consider it.

A true graze and grain variety for the Murray Valley is not quite here yet.

Use best management grazing practices when shifting from one feed source to another.

Useful resources

• Winter canola for grazing and grain production GRDC Update paper
• How pasture characteristics influence sheep production. NSW DPI Primefact 530

References

• A producers’ guide to production feeding for lamb growth. Meat & Livestock Australia Limited, June 2007
• Guidelines for use of feeds with known nitrate nitrogen (%DM basis) content. FeedTest

Acknowledgements

The authors would like to acknowledge the following people for their contribution to his project; Jack Eastman, Jack Hewitt, Michael Hughes, Daniel Liphuyzen, Deid and Ron Schlitz and John Fowler, MLLS

Contact details

Rob Fisher
Agronomic Results
28 Nolan St, Kerang 3579
0428545263
agresults@dragnet.com.au