Optimising crop nutrition in canola

WHY THIS PROJECT WAS IMPORTANT

The project was designed in response to farmers in southern NSW who were questioning the accepted requirements of in-season sulphur (S) in canola.

Traditionally, up to 20-24kg S/ha is applied prior to, or onto a canola crop. However, given canola-wheat is now a key cropping rotation and many paddocks have good history of sulphur application, and there is also evidence of sulphur accumulation at depth, growers have been questioning if that amount is actually required for each canola crop.

In short: This project addressed grower concerns about sulphur requirements in canola in southern NSW. Field trials at Howlong and Yarrawonga in 2017 and Howlong and Coreen in 2018 aimed to evaluate nitrogen-sulphur interactions and provide an economic analysis of the crops response. 

Project focus

As part of the project, two field trials were conducted at Howlong and Yarrawonga during 2017 and at Howlong and Coreen during 2018. The trials aimed to generate local information about the interactions between nitrogen supply and sulphur uptake, to ensure sulphur uptake is not inhibited by sub-optimal nitrogen levels. and to provide an economic analysis of the response.

Replicated trials were sown at Howlong and Coreen during 2018, involving different combinations of nitrogen and sulphur treatments. The sulphur treatments were: 0, 10, 20, 30, 40 kg S/ha (applied as ammonium sulphate, while nitrogen was applied at 0, 40, 80, 160 or 240 kg N/ha (as urea).

Soil sampling, dry matter (DM) sampling, tissue analysis, NDVI and harvest yield data was collected for plots at, enabling gross margin analysis to be undertaken for both 2017 and 2018. 

Project outcomes

Key outcomes from the 2018 trials were:

• The Coreen trial was not harvested due to dry conditions
• While harvest results at Howlong were compromised due to dry conditions, early dry matter and tissue nitrogen and sulphur results indicate an interaction between nitrogen and sulphur
• While early DM production increased with added nitrogen, there was a trend for further early biomass production when sulphur was also added
• As tissue nitrogen concentrations increased, sulphur concentrations also increased, as measured at harvest
• There were no differences in yield due to applied nitrogen or sulphur treatments, likely due to the dry conditions
• Protein levels increased with added nitrogen, while oil levels decreased.

Two years of trial results from this project were published in Research for the Riverine Plains, 2019. Please note that the 2019 report contains an amendment to the data and analyses in the report previously published in Research for the Riverine Plains, 2018.