• There were significant increases in dry matter (DM) accumulation, nitrogen (N) uptake and crop canopy greenness where barley was established following cultivation with one pass of the multidisc, which was most evident where additional nitrogen was added at sowing.
• Although there was a trend for cultivated stubble with additional sowing nitrogen to yield more than burning, there were no significant yield differences in the trial.
• Growing a faba bean crop instead of a second wheat crop increased the yield of the following wheat by 0.34–0.47t/ha in 2016 compared with a 2t/ha advantage in the following wheat crop in 2015.
• Adequate nitrogen availability in the third wheat crop, combined with higher yield potential, and poor nodulation in the faba beans, appears to be partly the reason for the smaller yield benefit in 2016.
• Across three years of field trials, none of the different stubble management treatments have been superior to the no-till stubble retention (NTSR) control, despite differences in DM production.

• There were significant increases in dry matter (DM) accumulation, nitrogen (N) uptake and crop canopy greenness where second wheat was established following cultivation with additional nitrogen, however there was no yield benefit.
• Over four years of research (2014–17) at the Coreen focus farm there has been no benefit to either cultivating, burning or additional nitrogen at sowing with cultivation over the no-till stubble retention (NTSR) control.
• Growing a faba bean crop instead of a second wheat crop increased the yield of the following wheat by 0.34–0.47t/ha in 2016 and an average of 2t/ha in 2015, however there was no evidence that the legume benefit of the faba beans influenced canola sown two years later (in 2017).
• Burning first wheat stubbles before establishing second wheat has offered no yield benefit, despite indications of better tillering, higher DM and superior yellow leaf spot (YLS) control.

• Investigation of weed seedbank decline in nine chaff-lining systems of South Australia demonstrated that growers are achieving high concentration of weed seeds and crop residue at harvest.
• Assessment of the viable weed seed fraction after crop harvest suggests that large residual annual ryegrass, brome grass and Indian hedge mustard seedbanks have been established in cropping field because these species did not decay over the summer-autumn period in chaff-lines.
• Evaluation of chaff-tramlining systems showed that annual ryegrass seedbank decline is independent of chaff-line configuration and chaff density.
• The stability in the weed seedbanks in chaff-lines were consistent with the dry conditions over the summer-autumn period.
• Growers should be cautious of the magnitude of viable weed seeds in chaff-lines before the cropping season and expect variability in the effectiveness of this tactic between seasons.

• Cereal stubble contributes only a small percentage of the nitrogen requirement for a following cereal crop (2 to 11% of N from 2014 wheat stubble was taken up by 2015 and 2016 crops).
• Urea fertiliser nitrogen use efficiency of the 2014 wheat crop was 35%.
• The 2015 drought reduced the influence of stubble management treatments on nitrogen cycling, yield and carry over effects on microbial activity.

This research highlights how important a tactical approach to STNB management is in the medium rainfall zone.  In dry seasons there is lower disease pressure, resulting in a potentially expensive fungicide strategy which can be marginal in returns.  Conversely, where there is high disease pressure usually from wet conditions early in the season, then a double spray strategy can improve grain quality, yield and returns to the grower.

Where growing barley on barley, growers should budget for a fungicide spray at Flag-1 every year to protect the top 3 leaves in the canopy.  Where conditions are wet early post emergent (especially if stubble is retained) allowing early disease pressure and high yield potential then a fungicide spray at Z31-Z32 can reduce disease pressure and protect the canopy until the Flag-1 spray is applied.

Under high disease pressure situations (wet conditions early post emergent) removing stubble prior to sowing barley on barley can reduce inoculum levels and the build up of early disease pressure.  This will also help to reduce the selection pressure for fungicide resistance.

Where there is a dry start to the season and a slow build up of disease then stubble management has minimal impact on the buildup of STNB levels.

Burning barley stubble prior to planting barley on barley has shown to increase yield buy between 325 and 400kg in 2017 and 2015. While removing stubble can reduce early disease pressure, not all the yield increase can be accounted for by disease.  Other factors are involved that may require additional work to understand (N mineralization, allelopathic impacts of stubble or improved seed bed).  Where erosion risk is low growers should consider burning to remove barley stubble if planting consecutive barley crops.

We feel that there is no further work required to investigate the hypothesized link between STNB levels and pre-harvest head loss.

Growers, advisors and the wider barley industry are the key beneficiaries of this research.  Being able to manage disease to maintain grain quality, yield and economic returns to the grower is critical for a competitive barley industry.

This research highlights how important a tactical approach to STNB management is in the medium rainfall zone.  In dry seasons there is lower disease pressure, resulting in a potentially expensive fungicide strategy which can be marginal in returns.  Conversely, where there is high disease pressure usually from wet conditions early in the season, then a double spray strategy can improve grain quality, yield and returns to the grower.

Where growing barley on barley, growers should budget for a fungicide spray at Flag-1 every year to protect the top 3 leaves in the canopy.  Where conditions are wet early post emergent (especially if stubble is retained) allowing early disease pressure and high yield potential then a fungicide spray at Z31-Z32 can reduce disease pressure and protect the canopy until the Flag-1 spray is applied.

Under high disease pressure situations (wet conditions early post emergent) removing stubble prior to sowing barley on barley can reduce inoculum levels and the build up of early disease pressure.  This will also help to reduce the selection pressure for fungicide resistance.

Where there is a dry start to the season and a slow build up of disease then stubble management has minimal impact on the buildup of STNB levels.

Burning barley stubble prior to planting barley on barley has shown to increase yield buy between 325 and 400kg in 2017 and 2015. While removing stubble can reduce early disease pressure, not all the yield increase can be accounted for by disease.  Other factors are involved that may require additional work to understand (N mineralization, allelopathic impacts of stubble or improved seed bed).  Where erosion risk is low growers should consider burning to remove barley stubble if planting consecutive barley crops.

We feel that there is no further work required to investigate the hypothesized link between STNB levels and pre-harvest head loss.

Growers, advisors and the wider barley industry are the key beneficiaries of this research.  Being able to manage disease to maintain grain quality, yield and economic returns to the grower is critical for a competitive barley industry.

• Cereal windrow burning achieved temperatures in excess of those required to achieve high levels of weed seed mortality, except in paddocks which had 11mm of rainfall the week before.'
• The open paddock burn with a high stubble load had a quicker, faster burn but still achieved the necessary temperatures of 450 degrees Celsius for longer than 60 seconds.

• Eight trial sites were established across South Eastern Australia to investigate whether soil organic carbon levels can be increased in no-till farming systems, inclusive of adding nutrients to aid the biological breakdown of stubble into soil organic matter.
• After three or five years of treatment, no increase in soil organic carbon could be confirmed across four trial sites. However, it is well known that no-till and stubble retention protects the soil from wind and water erosion and over a longer time-frame soil organic carbon levels may increase. But, based on these results it is likely that any potential increase in soil organic carbon will be small.

Establishment was highest where stubble was removed, however sufficient plants were established for a commercial crop where stubble remained standing rather than laying on the ground.

Conditions post spreading of the seed were perfect for establishment - seed spread onto moist soil, 30 mm of rain and cool temperates post rainfall - and a similar level of success may not be achievable evry season.

• Favourable climatic conditions in 2021 resulted in the increased prevalence of a range of cereal diseases across NSW, especially the wheat leaf diseases stripe rust, septoria tritici blotch (STB) and yellow leaf spot (YLS).
• In combination with increased cereal stubble loads produced in 2021, pathogen levels are likely to be elevated again in 2022.
• Predicted La Niña conditions over summer will maintain or increase the risk of stripe rust in 2022.
• Multiple stripe rust pathotypes were prevalent across NSW in 2021. Keep up to date with the latest varietal resistance ratings.
• Minimise disease impacts in 2022 by using an integrated approach to management.
• NSW DPI plant pathologists can assist with correct diagnosis and advice on appropriate management options.

• Burning or cultivating 2015 stubbles tended to produce higher yields, however this was only significant at Ungarie.
• High rainfall and a soft finish removed the benefit of stored soil moisture that stubble retained systems may have provided.
• Nitrogen was the limiting factor for both yield and protein for 2016.
• Growers cannot let stubble negatively impact on weed control and timely sowing.
• Growers should use crop rotation to their advantage by aiming to sow the right crop into the least antagonistic stubble.
• Stubble retained systems can require more nitrogen due to increased nitrogen tie-up.

• Grazing stubble with sheep speeds up N cycling and reduces N tie-up by the stubble. When yield is N limited, this can increase grain yield and quality.
• Over the seven year experiment, grazing and retaining stubble has been the most profitable treatment, with an annual Gross Income 172 higher than un-grazed, stubble retain (assuming a grazing value of the stubble) or $55 higher if no grazing value assumed.
• Over the seven years, there was on average a 0.5 t/ha reduction in wheat grain yield in the 2nd wheat crop where stubble was retained and not burnt – mostly related to N tie-up.

The trial establishment was variable early due to some non-wetting soil and the crop was sown too deeply due to furrow fill from significant rain after sowing. Early crop vigour as a result was low with blackleg further reducing plant establishment; this coupled with high levels of Vegetable beetle damage also reduced the evenness of the plots.

According to the DAFWA sporacle model spore maturity occurred on approximately the 22nd May which meant this trial was at very high risk of significant disease risk as emergence coincided with high spore levels being released from last year’s stubble.

• Cover cropping did not improve cotton yields in this experiment.
• High stubble loads from spraying out the cover crop after the cereals reached growth stage Z39 negatively affected established cotton plant numbers and consequently lint yield.
• Cover crops terminated at growth stage Z39 had no yield penalty, but stored more soil water than the fallow treatment.

• Crop establishment was not improved by on-row seeding or by increasing seeding rate in 2016.
• Higher seeding rate increased early dry matter but this effect declined during the growing season.
• In 2016 row placement or seeding rate did not affect grain yield or grain quality.
• Sowing on-row may be an advantage on non-wetting soils with low moisture at seeding.

Neither crop establishment, grain yield nor quality were changed by on-row seeding or by increased seeding rate in 2017, similar to results in 2016.

Crop establishment in the non-wetting soil was poor in 2017.

In 2015, with low moisture at seeding, improved crop establishment from on-row seeding in the non-wetting soil increased crop competition and lowered brome grass weed seed set.

The 2017 season was significantly colder than average with about 500 hours below zero.

While stubble management may influence in-canopy temperatures, the differences between management practices were minimal during 2017.

Differences in frost damage of grains were significant between treatments at both the Coreen and Yarrawonga sites, with the burnt treatment showing the greatest frost damage at Coreen, while the no-till stubble retained (NTSR) treatments showed the greatest damage at Yarrawonga.

Stubble management per se did not influence frost damage in wheat during 2017, with frost damage not necessarily related to in-canopy temperatures.

Stubble management practices can influence the rate of crop development and may lead to changes in flowering time. This change in rate of development can influence crop susceptibility to frost at different times throughout the growing season.

 

• Stubble management can influence in-canopy temperatures.
• The in-canopy temperature of long stubble was colder than short stubble.
• All trial sites experienced fewer temperature extremes during 2016 than in previous years of this trial.
• There were no measured frosts during flowering in 2016. Further research is needed to determine the physiological significance of the observed temperature differences.

• Four wheat trials sown during mid-April 2014 and 2015 showed no difference in grain yield or qualityas a result of being grown on 22.5cm, 30cm and 37.5cm row spacings, when averaged across four varieties (Bolac/Kiora, Lancer, Trojan and EGA Wedgetail).
• The 2016 trial sown during mid-April again showed no difference in yield between 22.5cm and 30cm row spacings, however yields were significantly less with the widest row spacing (37.5cm).
• Trial yields in 2016 were 1.5t/ha higher than 2014 and 2015 (3–4.25t/ha), with the higher yield potential likely to be a key factor in the poor performance of the widest row spacing (37.5cm).
• The Riverine Plains Water Use Efficiency (WUE) project (2009–13) showed that when crops weresown in the traditional sowing window, the 22.5cm spacing was more successful than the 30cm spacing, except in drier years with lower yield potential (2.5–3.0t/ha).
• In the three years (2014–16) of trialling row spacing on early-sown crops, crops grown on a 22.5cm row spacing produced more dry matter (DM) than crops grown on wider rows. However, the 2016 trial was the first to show a yield disadvantage to the widest
row spacing (37.5cm) when sown early.
• As a result of lower yields, the 37.5cm row spacing gave significantly poorer water use efficiency (WUE) than 30cm row spacing, with a greater proportion of calculated water losses (soil evaporation, drainage or unused water).
• A barley row spacing trial, sown at the same time alongside the wheat, provided some usefulcomparative observations during 2016, with La Trobe barley producing higher DM and yields thanwheat with a harvest index (HI) of approximately 50% compared with wheat at 40%.

A combination of fertiliser inputs and irrigation can rapidly breakdownincorporated cereal stubble and allow sowing 4 weeks later. Getting the balance of fertiliser, in particular N rates, to ensure rapid breakdown, but creating neither N deficiency or excessive N remains elusive.

Measuring soil organic carbon following incorporation is giving mixed results as to the ability to increase soil OC via incorporation with fertiliser

Burning the stubble gave greater yield and oil content

• In 2017 the removal of a high barley stubble load resulted in better medic plant numbers late in the season (September), and increased (but still very low) dry matter production.
• Heavy barley stubbles from harvesting either high or low resulted in similar medic regeneration.
• Treating heavy barley stubbles with either rolling, a light tickle or left standing did not change medic establishment or dry matter production in 2017.

Of the seven frost events that showed significant differences, all showed that the reduced stubble treatment (2t/ha) reached colder minimum temperatures than the removed stubble treatment (1.6t/ha). Across the seven events, the retained stubble treatment (2.5t/ha) also remained warmer than the reduced stubble treatment. The removed stubble treatment spent significantly less time at -2⁰C temperature threshold compared to the reduced stubble treatment. The retained stubble treatment was not significantly different to either of these.

These results suggest that removing stubble decreases the severity and duration of frost, however as discussed, there was variability in the results between the retained and reduced stubble treatments. This suggests, that in seasons where frost events are so severe, stubble management does not have a large effect on the severity of events.

The interim temperature results suggest that retaining 4t/ha of stubble significantly increases the severity and duration of frosts when compared to 0t/ha. On all occasions, reducing stubble loads to 0t/ha reduced the severity and duration.

• Over nine seasons, incorporating livestock into the rotation improved overall system outcomes in this trial, including; increased nitrogen cycling and water use efficiency, reduction in weed and pest populations and no negative effects on cereal performance or soil health, while value adding to stubble and pastures by grazing.
• The high input grazed farming system had a gross margin of over $100/ha/year more than lower input and ungrazed treatments over the nine-year trial period.

• A two year pasture break has been more beneficial in the first cereal year than a one year break, resulting in lower grass weed numbers, higher soil reserves of N and low disease levels.
• The impact of pasture management and pre-seeding tillage on grain yield and quality was greater following a medic pasture in 2015 than in 2016.

• Hay cutting in 2013 resulted in lower medic dry matter in 2017.
• Grass weed numbers were very low in 2017 due to low opening rains and poor germination.
• Two years of wheat increased Rhizoctonia, Yellow leaf spot and Pratylenchus.
• A two year pasture break was beneficial to the following cereal because of lower grass weed numbers, higher soil reserves of N and lower disease levels.

• The ability to capture barley grass seeds at harvest is limited.
• If seed can be captured and placed in windrows, windrow burning can reduce grass weeds.
• Seed capture at harvest is higher with annual ryegrass than with barley grass.
• Burnt narrow windrows sustained temperatures above 400oC for longer than 10 seconds, which is sufficient to sterilise annual ryegrass seed.
• Snail numbers were reduced with windrow burning.
• Barley grass germinates later in Minnipa Agricultural Centre cropped paddocks than in non-cropped areas.

• Harvest weed seed collection showed barley grass is harder to capture using harvest weed seed collection techniques due to its habit of shedding seed early.
• Burning windrows decreased the number of weed seeds present in the soil seedbank at Minnipa in 2017.
• Harvest weed seed collection allows for the capture of ryegrass weed seed and cereal screenings, potentially increasing feed utilisation for stock when placed in chaff dumps or rows.

Knowing your initial soil nitrogen levels will assist in determining if there is likely to be a benefit of including nitrogen and other nutrients for humification when incorporating stubble. If initial soil nitrogen levels (0-60cms) are adequate i.e. above 70kg N/ha in the high rainfall zone, and above 50 kg N/ha in the medium rainfall zone, then the addition of nitrogen may not provide immediate responses – depending on the stubble nutrient levels.

• Herbicides which may be influenced by high stubble loads include trifluralin, triallate, pyroxasulfone, prosulfocarb and metalochor products. If grass weeds are an issue in paddocks with high stubble loads (greater than 50% stubble cover), removal of some stubble may maximize the herbicide activity and grass weed control.
• In-crop germination patterns are later for barley grass than for other grass weeds in MAC paddocks, which is limiting early control with pre-emergence herbicides.
• If you expect most of your grass weeds to emerge straight after sowing maybe 2 L/ha trifluralin (plus an added herbicide depending on cost and risk factors such as seasonal conditions, soil type, rotation etc.) is the best value for your system.
• If you have a later germinating population, and aim to reduce the seed bank, you may be better investing in some of the more expensive herbicide mixes even though they may cost more in the first season.

Dry seeding conditions and lack of rainfall at the start of the 2017 season resulted in challenging conditions for both establishing crops and weed control.

Stubble residues reduced plant establishment and weed numbers; standing stubble in dry conditions had higher wheat germination than chained stubble.

April dry sowing had lower wheat numbers than later sowings, which reduced grass weed competition during the season. Grass weed numbers were also higher and set more seed in the April sowing.

No pre-emergent herbicide provided total barley grass weed control and keeping the weed seed bank low through other methods is important.

Under the production regimes of upper EP, stubble management is unlikely to impact negatively on performance of pre-emergence herbicides targeting grass weed control, providing adequate water rates and best practice application techniques are used.

1. Barley and wheat crops led to increases in P. neglectus, while mungbeans, wheat and chickpea led to increases in P. thornei.
2. The non-host summer crops (cotton, maize, mungbean and sorghum) provided the greatest reduction in crown rot inoculum while most non-host winter crops had virtually no impact.
3. There was little impact from most species on common root rot levels with wheat the worst crop option, while common root rot declined under the moderately resistant barley variety CompassP.

Having an indication of the stubble load present at harvest in cereals and canola (based on grain yield harvested) will help with future decisions around harvest management and management of stubble loads during the fallow period.

• Barley sown into standing stubble yielded higher (between 0.15-0.33 t/ha) than cultivated or removed stubble in 2016.
• Standing stubble cut low (15-17 cm) resulted in the highest level of stubble being maintained into the following season.
• Maintaining standing stubbles may be the best option for yield and stubble carry over, but adequate nitrogen must be maintained.
• In 2014 and 2015 stubble management and seeding position did not impact strongly on weeds, disease or pests with relatively high stubble loads in a low rainfall farming system at Minnipa.

Standing stubble cut low (15-17 cm) resulted in the highest level of stubble being maintained into the following season.

Stubble management and seeding position had little effect on grass weeds.

Snail numbers were higher in standing stubble cut high (30 cm) and stubble removed had the lowest numbers.

Stubbles can be estimated using 1.3-2.8 times the grain yield, but it may underestimate the stubble in an average season following a good year, or after a very poor season.

In many low rainfall farming systems livestock are still a very important part of the farming system and the level of stubble carryover is reduced after grazing.

Stubble management and seeding position have not impacted greatly on crop production, weeds, disease and pests over three years with relatively high stubble loads for low rainfall farming systems.

While water volume and droplet size were the focus of this study there are further measures that can be taken by the spray operator to increase herbicide penetration in stubble. In a recent paper by Gordon (2017) some of the strategies highlighted were:

• Reducing spraying travel speeds can generally improve the penetration into stubble and improve the evenness of the application.
• Narrower nozzle spacings can also be of benefit, provided the spray quality and boom height are suitable. 
• Alternately, many operators have plumbed machines with nozzle spacings to match the crop row width. Where nozzles are positioned in the centre of the inter-row gap between standing stubble lines, the nozzle height may be lowered to obtain an overlap close to the base of the stubble. This may improve soil contact and reduce interception by the stubble, provided spraying speeds and wind speeds do not excessive.

• Electromagnetic (EM) zoning was strongly related to differences in pH at 10–30cm depth in two out of three paddocks.
• All three paddocks showed variability in chemical properties, with the EM zoning showing good separation of chemical properties between zones. This provides confidence that the zoning was suitable.
• Variability in plant growth needs to be examined ‘holistically’ rather than just focussing on one variable. While a paddock may show variation in plant available water (PAW), it may be that sodicity or subsoil acidity is the key limiter in plant performance, not water availability per se.
• Existing precision agriculture (PA) datasets, in conjunction with selected chemistry sampling, can be used to indicate relative change in PAW across paddocks, but not the actual volume of water storage.

Take Home Messages

Whilst the trial didn’t go according to plan there were still some key messages that arose:

• Maximising seed-soil contact is the aim at sowing especially for the larger seeds that require more moisture to imbibe and germinate compared to small seeds.

• Unseasonably low June rainfall hindered establishment of partially sown beans due to a drying topsoil. These may have been

OK under normal June rainfall conditions.

• Hair pinning can be a serious issue when using a disc seeder especially when sowing into wet/ moist lodged stubble.

• Solutions to avoid hair pinning – sow when stubble is dry (good in theory), keep stubble standing, use sharp discs and ensure bar

has sufficient down force to cut through tough stubble.

Linseed is not new to Western Australia or the Great Southern region as it was grown in the Boyup Brook region from the 1940’s to the 1960’s. It was grown for fibre and milled at the Boyup Brook Flax Mill. Linseed (flax) Linum usitatissimum is a niche product and has the potential to offer an alternative revenue steam for producers outside of the traditional crop. Demand for Linseed has recently shifted to a health food. Linseed has several uses, it can be crushed for Linseed oil which is a rich source of linolic acid and Omega 3 fatty acid and the remaining linseed meal can then be used as livestock feed or it can also be eaten as a whole seed or ground.

Linseed also has agronomic benefits as a potential break crop that provides a disease break, the opportunity for alternative weed management strategies, provides an insect pest break and can be effective in reducing some soil borne root diseases and soil borne pathogens namely root lesion nematodes. Canadian research has demonstrated that cereal yields were higher when planted on linseed stubble compared to wheat stubble.

The aim of the project is to investigate agronomic packages which support the introduction and scale up of commercial cultivation of Linseed in the Great Southern region of Western Australia.

Consistent supply with volume is imperative to develop a market that has the ability to realise the full value of Linseed produced. Also, in order for growers to take up production it is important they have a full agronomic package available to grow the crop successfully. Finally, Linseed needs to generate an equivalent return per hectare of alternative rotational crops such as canola in order to expand into the rotation.

The key objectives of this project are:  

A: To determine if Linseed can be successfully grown under dryland farming conditions in the Great Southern region of Western Australia with the potential to scale up to commercial cultivation.

B: To determine if any investment is required into machinery and infrastructure by growers to grow linseed.

C: To develop basic agronomic guidelines to grow linseed in WA.

D: To assess the yield potential of two commercially available linseed varieties grown under dryland conditions in WA, Croxton and Bilton.

The project was conducted over two years in 2019 and 2020. In 2019 the trials were conducted in small plots across three sites. In 2020 the trials were conducted as producer demonstration sites utilising grower machinery and large-scale plots.

In 2019 three sites were located across the Great Southern Region of Western Australia covering a variety of soil types, climates, paddock histories and growing conditions. The trials sites were in the shires of Darkan, Wagin and Kojonup. The trials involved growing two commercially available varieties Croxton and Glenelg over three times of sowing (TOS) 10 to 14 days apart at three seeding rates (SR): 35, 40 and 45 kg/ha and applying three top dressed nitrogen application rates (low, optimal and high) 40, 80 and 120 units N/ha.

Over the three trial sites, the seeding rates and nitrogen application rates trialed did not consistently result in significant differences in grain yield or oil quantity and quality. Time of sowing had the greatest impact, with the earliest time of sowing generally resulting in higher grain yields. Glenelg on average had a higher grain yield and oil quantity, with Croxton having the highest oil quality.

Trial Site

Average Site Yield

t/ha

Darkan

0.562

Wagin

0.914

Kojonup

0.998

Table 1: Average Site Yields in 2019 (Below average rainfall)

The Darkan site plant counts were the highest, however this was not reflected in the yield. Darkan was the lowest yielding of the three sites. This may be due to the below average rainfall and lack of finishing rains experienced on the non-wetting forest gravel soils at this trial site. Kojonup and Wagin on average achieved nearly double the yield of the Darkan site despite lower plant counts and early plant disease.

In 2020 four demonstration/bulk up sites were established across the Great Southern Region covering a range of soil types, rainfall, rotations and growing conditions. The four sites were located in Katanning, Wagin, Darkan and Kojonup.

The methodology in the second year of the project was to bulk up the Linseed seed for future commercial production and to also integrate high level variety comparisons between the two varieties being utilized in the project Bilton and Croxton. Two sites, Wagin and Darkan, incorporated replicated plot treatments as a variety trial with the other 2 sites being predominantly bulk up sites.

The key outcome of any variety demonstration is the final yield result. Due to operational difficulties within the demonstration some yield data is not available however the key findings from the data available was:

• Bilton yielded on average 0.95 MT/Ha and 85% of Canola
• Croxton yielded on average 0.86 MT/Ha and 72% of Canola.
• Bilton out yielded Croxton on both sites.

The seasonal conditions may have contributed to Bilton out yielding Croxton. Bilton is a slightly shorter maturing variety and the below average rainfall received in 2020 is expected to have favoured shorter season varieties.

The project has successfully set in the place the ability for growers in the Great Southern region to scale up production of Linseed and demonstrated its ability to fit within the current rotations with the additional benefit of assisting in the long-term management of soil borne root pathogens.

However, for the scale up of the commercial cultivation of Linseed there is the requirement for beyond farm gate systems to be in place before producers will scale up production. An active market to determine a fair price, storage and handling facilities off farm to enable harvested grain to be stored before delivery to consumers, supply chains in place which enable efficient delivery of the grain anywhere around the world and long-term buyers/processors who will receive the grain year in year out. There is still a lot of process to be put in place before Linseed production will scale up to a considerable level.          

Grower adoption beyond the project has continued with over 60 Ha planted in southern WA in 2021 across 4 growers. Confidence in the supply chain beyond the farm gate remains as the major obstacle stopping increased uptake and requires addressing before increased production can be expected.

Irrigated durum wheat can meet DR1 specification

The nitrogen requirement is approximately 50 kg N/t 

Growing durum wheat on a pulse stubble has both disease and nitrogen management benefits

Although we reached harvest at both Kimba and Farrell Flat, multiple environmental factors coinciding with bacterial blight infection meant that data was compromised, and no sound conclusions could be drawn from this work.

• In 2017, don’t let stubble compromise the big things (weeds, disease, timeliness).

• Sowing at the earliest opportunity (which requires rainfall) is an important component of reducing the risk of canola production in low rainfall environments.
• The amount of N available to the crop is critical to productivity in a canola crop that has established well.
• Applying adequate doses of fertiliser N at seeding or early in the crop’s development have produced the highest grain yields but this was less important in a wet spring like 2016.
• Legumes can provide N to a subsequent canola crop, but in many cases, canola growing on legume residue will still respond to fertiliser N inputs.
• Analysis of the profit-risk context for optimal N inputs for canola produced in low rainfall environments is underway.

The theoretical N contribution from faba stubbles is 20 kg N/tonne of stubble. However this assumes all residue is mineralised. 

Stubble retained on the soil surface is broken down more slowly than residues present in the soil.

A 6 t/ha bean crop resulted in approximately 140 kg N/ha being released for the following season. 

• Grazing crop stubbles makes more mineral N available to crops which increases grain N uptake and is perhaps an overlooked benefit of keeping livestock in stubble-retained farming systems.

Increased rates of N resulted in increased biomass, but the relationship between stubble N content and applied N was poor.

Higher applied  N resulted in higher Harvest Index

Harvest Index ranged from 0.45 to 0.47. 

• In 2017, don’t let stubble compromise the big things (weeds, disease, timeliness)
• If the intent is to retain stubble:
◊ Pro-actively manage the stubble for your seeding system
◊ Diversify (add legumes to rotation), deep band N and manage invertebrates. Mice could also be a major problem
◊ For tined seeders, reduce stubble load by mulching, incorporation + nutrients, baling, grazing and consider sowing at 15-19 degree angle to previous sown row
• If stubbles are too thick to sow through, consider strategic late burn, especially before 2nd wheat crop or if sowing canola into large stubbles
• Early monitoring is essential to see how effective actions are to allow for re-planning

• Reducing stubble loads can reduce the severity and duration of frost events under certain conditions. However, under the situation of multiple and severe frost events the influence of stubble is less defined and stubble reduction does not reduce risk.
• In the Mallee, most stubble management practices carried out prior to seeding to increase stubble incorporation or breakdown (cultivation, slashing) did not reduce stubble loads enough to reduce frost severity and duration.
• In the Wimmera, reducing stubble loads did not consistently reduce frost severity or duration possibly due to a combined effect of greater canopy closure with higher yield potential (2014) and higher stubble break down with low stubble levels (2015).
• Stubble management in frost prone areas is not about complete removal of stubble, but reducing it to a level that minimises your risk.

• In 2017, don’t let stubble compromise the big things (weeds, disease, timeliness).
• If the intent is to retain stubble:
• Pro-actively manage the stubble for your seeding systemDiversify (add legumes to rotation), deep band N and manage invertebrates. Mice could also be a major problem.
• For tined seeders, reduce stubble load by mulching, incorporation + nutrients, baling, grazing and consider sowing at 15-19 degree angle to previous sown row.
• If stubbles are too thick to sow through, consider strategic late burn, especially before second wheat crop or if sowing canola into large stubbles.
• Early monitoring is essential to see how effective actions are to allow for re-planning.

• Rainfall over the summer fallow period will cause nutrient leaching from stubbles.
• Stubble crop type determines initial value of stubble and what may be leached due to rainfall.
• It is important to consider other loss pathways such as microbial breakdown and volatilisation as well as leaching when calculating stubble nutrient value following the summer fallow period.

• In 2016, a Decile 10 season, stubble load had no effect on soil mineral nitrogen or soil water.
• The presence of stubble resulted in higher soil mineral nitrogen over the summer fallow period.
• Wheat yields were higher following peas or fallow than they were after wheat or canola in 2016.

• Cereal stubble should be thought of as a source of C for microbes, not as a source of N for crops. In the Mallee under no-till systems, only 1-2% of the N requirement of wheat crops is derived from the previous wheat stubble.
• N tie-up in cropping soils is only a temporary constraint as the immobilised N will be released through microbial turnover, generally later in the crop season in spring.
• N tie-up by cereal residue is not just a problem following incorporation – it also occurs in surface-retained and standing-stubble systems.
• Management of tie-up is reasonably straightforward – supply more N (5 kg N for each t/ha of cereal residue) and supply it early to avoid impacts of N tie-up on crop yield and protein.
• Deep-banding N can improve the N uptake, yield and protein of crops, especially in stubble-retained systems.

• Total number, severity and length of frosts increased as surface residues increased.
• Increasing the amount of surface residue delayed plant growth, lengthened growth phase duration, and overall time to maturity for both chickpea and lentil.
• For both chickpea and lentil, high surface residues, above 9 t/ha, significantly reduced biomass accumulation and grain yield.

• Soil mineral nitrogen (N) values were low across all sites, which was indicative of the wet seasonal conditions and high nitrogen losses.
• There were no significant differences in mineral nitrogen values between the stubble treatments due to high variability (likely due to transient waterlogging across the sites).
• The project has been extended to enable the research to be repeated during 2017.

• While significant differences in mineral nitrogen (N) values were measured between stubble treatments, these differences were small and unlikely to elicit a plant growth response.
• No consistent trends were observed between trial sites.
• Delayed plant growth and development under no-till stubble retained (NTSR) systems in the Riverine Plains region is unlikely to be due to decreased mineral nitrogen availability as a result of immobilisation.

When canola was sown into wheat stubble in an east-west direction, long stubble (42cm) significantly reduced photosynthetically active radiation (PAR) and reduced true leaf number up to mid-winter.

Although there were trends suggesting a reduction in dry matter (DM) production at the yellow bud stage (GS3.7) as a result of increasing stubble height, the differences were not statistically significant.

The average canola yield of the trial was 1.58t/ha with no significant differences in either yield or oil content due to stubble height of the previous wheat crop.

The results mirror a trial conducted at Dookie, where yields in long stubble were 3.70t/ha and 3.75t/ha in short stubble. At this site there were significant reductions in DM production early in the season in the long stubble treatment.

• Zymoseptoria tritici and Pyrenophra tritici-repentis, the disease-causing pathogens of septoria tritici blotch (STB) and yellow leaf spot (YLS), can produce ascospores on wheat stubble regardless of their resistance status.
• Any infected wheat stubble has the ability to initiate an epidemic for up to 2 years.
• Reduce harvest cut height to limit Z. tritici colonising stubble.
• Excess harvest material must be removed from the paddock to produce a net reduction of Z. tritici inoculum.
• Minimise disease impacts by using an integrated approach to management.

Windrow burning can reduce small pointed snail populations by over 90%. If there are weeds or fallen stubble that are not burnt then snails can still be present in the paddock.

Windrow burning can reduce small pointed snail populations by over 90%. If there are weeds or fallen stubble that are not burnt then snails can still be present in the paddock.

Take Home Messages

• Near perfect growing season for canola, provided ideal opportunity to assess the residual N feeding effect of the legumes.

• All legumes sown in 2016 – peas, lupins, sub clover and faba beans had similar starting soil N levels and soil water nitrate readings throughout the year which was reflected in similar grain yields inferring that all legume species were equal in terms of their N fixing capabilities.

• The average amount of N fixed by the legumes was calculated as ~86kg/ha.

• Growing adequately nodulated legumes can give rise to a ~1t/ha canola yield advantage compared with a non-legume.

• Linseed used more moisture, from a greater depth, than the faba beans in 2016. Resultantly more moisture was extracted by the canola crop sown on the faba bean stubble in 2017, and yet there is still more  residual moisture left.