The Murray Plains is a cropping region located in South Australia, situated in the low rainfall zone (LRZ). The region extends from Murray Bridge to Truro and encompasses all the land between the Mount Lofty Ranges and the River Murray. Rainfall is variable throughout the region and decreases dramatically heading east of the Mount Lofty Ranges. A late break experienced in 2021 meant that canola was left out of the rotation for farmers due to the risk of poor establishment in dry conditions. Soil types are also variable throughout the region, ranging from heavy clays to sandy rises. Therefore, there is an opportunity for farmers to gain insight into better canola establishment in dry conditions on sandy soil. This project aims to provide local knowledge on dry sowing strategies to improve canola establishment, including time and rate of sowing, and examine the agronomic fit of LRZ varieties in the Murray Plains.

Project description: 

2022 trial

A trial in 2022 was developed with aims to improve management of canola in dry conditions, particularly focused on dry seeding, as well as understanding agronomic practices that can maximise return on investment with higher input costs. The trial focused on the following objectives:

• To investigate dry sowing strategies which improve canola establishment in the Murray plains, including time of sowing, fertiliser strategy and sowing rate.
• To examine the agronomic fit of specific LRZ canola varieties to the Murray Plains and the advantages of any of them in dry conditions, including GM, open pollinated and stacked trait varieties.
• To undertake gross margin analysis to determine which options will yield the highest return on investment.

The trial concept originated through the MPF Committee – consisting of a group of local farmers in the region – after it was noted the varying responses to inclusion of canola in a rotation during a dry start to the year. Some felt confident to include it, while others opted for less risky options, and canola was left out of their rotation for the year. For those who were confident to establish canola in their soil type dry and early in the season, it enabled them to consider forward contracting prices at $1000-$1100/t, plus oil bonifications, compared with the regular seasonal price of $600-$700/t. This trial concept was tested with other farmers in the region prior to the application being submitted and received a favourable response.

The 2022 trial was delayed and therefore, sowing times were behind what would be considered industry best practice and what would reflect practical risk management in a growers’ enterprise. Therefore, this project continued into 2023 to better analyse the project aim.

2023 Trial

The objective of this trial was to investigate the effect time of sowing, seeding rate, and seed variety has on maximising gross margins in the Murray Plains region of South Australia in 2023. The first time of sowing occurred on 2 May, second time of sowing on 17 May, and the final time of sowing on 29 May.

Below average rainfall in April was recorded at the Sedan weather station (BOM station number 024531) approximately 4 km from the trial site, before the season broke in early June when 40 mm of rainfall was recorded in the first week. The site received 1.5 mm of rain in the 7 days prior to seeding, and 5 mm in the 10 days after the first time of sowing on May 2. Due to limited rain falling prior to and in the week following time of sowing (TOS) 1, canola germination was uneven and staggered across the trial site. Above average rain in June resulted in the germination of remaining seed from all 3 times of sowing, but below average rain from July through October placed the canola under stress for much of the growing season.

Maximum grain yields were recorded when canola was sown at the time of sowing 2, due to soil moisture levels at and directly after sowing.

Time of sowing 1 was more effected by false and staggered germinations than the other sowing windows.

Nuseed Emu, InVigor R4022P, and 44Y94 were consistently the highest yielding varieties across the three times of sowing, whilst open pollinated varieties Stingray and Bandit TT were the two lowest yielding varieties.

As the seeding rate increased from 1kg/ha to 2.5kg/ha, 44Y94 grain yield also increased.

Key achievements and results: 

From the trials conducted at Sedan in 2023, maximum grain yields were recorded when canola was sown at time of sowing 2 (17 May). With less than 5 mm of rainfall recorded either side of time of sowing 1, many varieties were affected by false and staggered germinations, resulting in time of sowing 1 being most affected by the dry conditions recorded until the end of May and start of June. Nuseed Emu, InVigor R4022P, and 44Y94 were consistently the highest yielding varieties across the three times of sowing, whilst open pollinated varieties Stingray and Bandit TT were the two lowest yielding varieties. Bandit TT, Retained 44Y94, and Trident recorded their highest yield when sown early. Stingray, 43Y92, 44Y94, InVigor T4510, Nuseed Emu, 44Y27 RR, and InVigor R4022P all recorded their highest yield when sown mid.

All canola varieties yielded lowest when sown at the late time of sowing window. As the seeding rate increased from 1kg/ha to 2.5kg/ha, 44Y94 grain yield also increased. Differences in grain oil content as sowing rate increased were insignificant, and Protein was least effected by seeding rate.