Summary

This project evaluated key agronomic practices for super high oleic (SHO) safflower in South Australia to improve yield reliability and profitability. Safflower has historically been sown in late winter or early spring, but this project demonstrated suitability for autumn and early winter sowing across a range of environments. Establishment was critical to success and fertiliser responses were generally low, confirming safflower as a relatively low input crop. Safflower was highly effective at extracting deep soil water which supports yield in dry seasons but potentially reduces stored moisture for following crops. Managing excessive biomass remains a challenge, particularly in higher rainfall seasons, and further work is required to improve harvest index and crop architecture.

Background

Interest in SHO safflower has increased due to strong grain prices and its suitability for low to medium rainfall environments. However, current cultivars have slow early growth, a long growing season, and a late reproductive phase which has resulted in growers being uncertain about when to sow, input requirements and rotational fit. Historically, safflower has been grown as a spring-sown opportunity crop, often following winter waterlogging, to avoid frost or utilise soil water associated with sandhill seeps. This project investigated whether alternative agronomic strategies could increase yield reliability and broaden adoption of SHO safflower across South Australian cropping regions.

Research Aims

The core objectives of the project were to:

• Define agronomic practices that improve the likelihood of successful SHO safflower production in South Australia
• Evaluate sowing time, establishment and nutrition responses across representative environments
• Assess water use patterns and implications for crop rotations
• Investigate options to manage excessive vegetative growth and improve harvest index.

In The Field

Field trials were conducted over two seasons at Balaklava, Merildin and Farrell Flat. Treatments examined sowing time, sowing rate, and responses to nitrogen, phosphorus, sulphur and zinc fertiliser. Crop growth, biomass production, lodging risk and grain yield was assessed. Additional work investigated canopy modification techniques, including apex removal and the use of plant growth regulators to limit vegetative growth. Weed management was not investigated, but some observations on problematic weeds, crop competitiveness and weed control options were made in trials. Observations on pests and foliar disease risks were also made.

Results

SHO safflower was grown successfully across a range of environments, typical of winter cropping in South Australia. Earlier sowing consistently delivered higher grain yields than later sowing as long as frost damage was avoided.

Successful establishment of safflower was critical. Under ideal conditions, sowing rates of 12kg/ha were sufficient to maximise yield. Higher sowing rates (20 kg/ha) improved plant density but only increased yield reliability where emergence or germination was compromised.

Across all trial sites, safflower recorded minimal grain yield responses to applied nitrogen, phosphorus, sulphur or zinc. This indicates that either soil reserves were adequate, or safflower is able to access nutrients deeper in the soil profile compared to cereals and pulses. As a result, SHO safflower can be considered a relatively low input crop.

Safflower demonstrated a strong capacity to extract soil water, including from deeper layers not readily accessed by cereals and pulses. This trait supported grain yields even in very dry seasons, with yields of 2.5t/ha achieved in 2024 at Farrell Flat – the driest year on record. However, high water use means substantial soil moisture depletion, which may negatively affect following crops. This impact may last for more than one year if soil water is not replenished by rainfall.

Safflower competed poorly with weeds up until mid stem elongation and late maturity of safflower restricts crop topping for weed seed set control. Trial sites were selected based on low broadleaf weed burden, which normally might be a restriction on where the crop can be grown. The limited number of registered post-emergent herbicides means pre-seeding and early post-emergent weed control is critical.

Safflower continues to accumulate biomass while sufficient soil water is available, rather than filling grain. This can mean excess vegetative growth, increased lodging risk and low harvest index in seasons with adequate or abundant rainfall. Modifying canopies with apex removal and plant growth regulators (PGRs) temporarily reduced growth, but the long growing season meant regrowth occurred. Repeated PGR applications would be needed to achieve lasting effects, which reduces practicality. Genetic improvements or alternative agronomic strategies are needed to control vegetative growth and improve efficiency of converting biomass into grain.

Establishment pests are particularly damaging as early vigour of safflower is very poor. Recovery from pest damage is also poor meaning proactive pest management is key. No foliar diseases were recorded during the project. Feeding damage from Rutherglen bug was evident and the late maturity of safflower may be problematic as bugs migrate from maturing field crops and weeds to invade and reproduce.

While safflower is low input there is substantial removal of key nutrients, often from depth. Following crops could be subject to both low soil water availability and low nitrogen availability.