Author: Lee Menhenett, Senior Technical Agronomist, Incitec Pivot

Key messages

  • Upper canopy Blackleg infection and Sclerotinia stem rot are two of the main fungal diseases associated with canola that can have a significant negative impact on yield.
  • Fungicide applications during flowering are the only in-crop control tool for the diseases.
  • Canola dry matter accumulation and nitrogen demand peaks through branching, flowering and podding.
  • EASY N is a high analysis liquid nitrogen fertiliser suitable for boomspray applications.
  • Combining both fungicide and EASY N provides a one pass solution for nitrogen application and disease control.

Foliar diseases

Sclerotinia stem rot is a foliar disease affecting canola, which is seasonal dependent, favoured by prolonged humid or wet conditions during flowering. The pathogen remains viable in the soil for up to four years and can survive for up to 10 years if buried deeper.

Crop rotation is the key management option to reduce spore loading and subsequent infections. Approximately 10 days of wet soil in mid- to late winter with temperatures 11°C to 15°C will stimulate apothecia (mushroom like appearance) growth which produce spores over a five-to-six-week period. These spores infect the flower petals, which then drop into the canopy and lodge on leaves, branches and leaf axils where the disease enters the plant. Extended wet periods during petal fall with temperatures 15°C to 25°C allow greatest disease development. Where main stems are infected yield losses can be greater (GRDC, 2014).

Blackleg disease in canola is caused by a fungus that survives on old canola stubble and releases spores that infect new season crops. The greater the canola stubble load and closeness in distance (<500m) and the younger the stubble is, the greater the spore release causing greater new season canola infection.

Infection can be as crown canker (early infection) or upper canopy. Typically, early flowering canola is more prone to upper canopy infection and yield loss, due to cool moist growing conditions at flowering and a longer period of pathogen development to cause tissue damage (GRDC, 2022).

Both Sclerotinia and Blackleg diseases develop independently, however there are some common factors that influence the development of both. While a fungicide application maybe targeted at one disease, it may also control other disease(s) – which would add to the economic response. For either or both diseases an application timed at 20-30% flower is considered best practice. For sclerotinia a second application maybe warranted at 40-50% flower.

Canola nitrogen requirements

Timing of nitrogen applications in canola is of less consequence to yield compared to nitrogen rate.

Nitrogen supply should not be limited during vegetative growth stages, to support crop growth that rapidly provides ground cover (outcompete weeds and pests and moving moisture through the plant rather than losses through evaporation) and supporting plant size to provide a base for reproductive growth.

Figure 1 shows both percentage of dry matter accumulation and nitrogen uptake over time. While the crop is vegetative, and up to the growth stage of stem elongation, less than 10% of the total dry matter and nitrogen has been accumulated. Once stem elongation begins, with subsequent branching, flowering and podding, there is a rapid draw on nitrogen requirements to support dry matter accumulation. It is critical that nitrogen supply during this period of growth is not limited. Any stresses during this time will have a negative impact on yield.

Figure 1: Generalized dry matter accumulation and distribution and nitrogen uptake patterns for canola. Source: Koenig et al, 2011

Review nitrogen budgets

Total nitrogen demand will depend on the yield target. A yield target for dryland cropping systems needs to be constantly adjusted through the growing season based on stored and growing season moisture.

As water limited yield is adjusted so too is nitrogen demand (from soil mineral N, mineralisation and fertiliser applications). Adjusting nitrogen budgets during the reproductive growth stage (when there is also rapid demand for nitrogen) maybe warranted. Additional nitrogen demand can be supplied using EASY N.

EASY N

EASY N is high analysis liquid nitrogen solution applied through boomsprays. The product contains 42.5% N (w/v) and is comprised of three nitrogen forms:

  • Nitrate (25%) – immediately plant available through the roots and leaves. Non-volatile.
  • Ammonium (25%) – taken up through leaves and roots. Conversion to nitrate will take weeks. Volatile in presence of calcium carbonate.
  • Urea (50%) – taken up through leaves and roots. Conversion to ammonium takes days, conversion to nitrate takes weeks. Volatile.

EASY N has a solution pH of 6-7 – an important product attribute which helps reduce volatilisation losses. The slightly acidic to neutral pH drives less ammonia production coupled with half of the nitrogen in nitrate and ammonium forms, which have lower volatility.

Figure 2 shows the lower volatilisation losses of EASY N compared to urea in volatilisation trials conducted in 2024 and 2025. Reduction in ammonia losses between EASY N and urea ranged from 4% to 54% with the average loss from all trial data being 38%.

Figure 2: Volatilisation losses of EASY N compared to urea at various locations. Source: Incitec Pivot Volatilisation Trials, 2024 and 2025

In addition to the agronomic benefits there are also operational benefits in using EASY N:

  • Use of the same wheel tracks
  • Even application across the boom with <5% variation between nozzles
  • Mixing with fungicide for a one pass operation
  • Less wind influence on application evenness compared to granules

One pass operation

Where both fungal disease management and additional nitrogen is required, there is an opportunity to combine both fungicide and EASY N. This offers time savings, operational efficiencies and agronomic benefits.

Figure 3 shows a canola trial at Dookie where a basal application of 80 kgN/ha was banded at sowing followed by a topdress application of 40 kgN/ha (94 L/ha EASY N) at 30% flower. This topdress application was applied as different treatments:

  • Urea
  • EASY N
  • EASY N + fungicide
  • EASY N 1 pass plus fungicide 2nd pass.

The urea topdress treatment did not provide a yield benefit over the control; however, all the EASY N treatments were significantly higher to the control. There was no yield penalty to applying EASY N independently; combining with a fungicide; or applying separately (two passes). Canola oil % significantly increased with the two-pass treatment compared to EASY N and EASY N + fungicide treatments. Canola yield was also significantly greater compared to the urea topdress treatment.

Figure 3: Nitrogen rate and product trial, combining fungicide application. Source: Incitec Pivot Dookie Nitrogen Trials, 2014

There are no known incompatibilities of fungicides with EASY N, however, it is always prudent to do a jar test combining products in the correct ratios to assess. The correct order of mixing is:

  1. Water (at least 20% of spray volume) 2
  2. Fungicide 3
  3. Wetter (if required)
  4. EASY N – maintain agitation and apply within several hours

Rates of EASY N inclusion can be up to 100 L/ha; however, fungicide products that have high loading of wetters/emulsifiers (e.g. Aviator) should be applied at lower rates of EASY N <50 L/ha. These fungicides when applied with EASY N can cause additional leaf burn.

Summary

If fungicides in canola are required for yield protection there is a great opportunity to include EASY N to supply additional nitrogen to the crop. Combining agronomic and operational benefits makes a compelling case to have EASY N storage on farm.

Further information

For more information on EASY N, please contact Lee Menhenett, at: lee.menhenett@incitecpivot.com.au.

References

Grains Research and Development Corporation (GRDC) (2014) Managing Sclerotinia Stem Rot in Canola. Fact Sheet.

GRDC (2022) Managing upper canopy blackleg infection (UCI) in medium and high rainfall regions. GRDC Update Papers.

Koenig RT, Hammac WA and Pan WL (2011) Canola growth, development and fertility. Washington Oilseed Cropping Systems Series. Washington State University Extension.