NITROGEN trials conducted by the Hart Field-Site Group have shown higher yields and lower nitrous oxide emissions when wheat is planted after lentils instead of canola.
The group's research and extension manager Sarah Noack presented key findings of the trials during the Getting the Crop In seminar in Clare, including wheat time-of-sowing results and harvest weed seed control options, focusing on narrow windrow burning in canola.
The nitrogen trial, which studied management strategies for improved productivity and reduced nitrogen losses, focused on nitrous oxide emissions - one of four main nitrogen gases that could be lost from soil and fertiliser applications.
"Nitrous oxide is the easiest one to measure," Mr Noack said.
"We could also make reasonable assumptions because of the strong relationship between how much nitrous oxide we lose and those other nitrogen gases."
The trial crop was sown on May 13, and harvested December 5.
Gas chambers were used to measure nitrous oxide emissions during the growing season.
The trial compared Mace wheat grown after a lentil crop and a canola crop.
Before sowing, there was a difference of 10 kilograms a hectare more of available N under the lentil plots.
There were six different nitrogen management strategies studied to see which improved productivity and reduced nitrous oxide emissions:
* nil nitrogen treatment
* 40kg N/ha at first node stage (or GS31)
* 80kg N/ha at GS31
* 80kg N/ha incorporated by sowing
* 5. 80kg N/ha Entec urea (nitrification inhibitor) at GS31 - a product designed to slow the release of fertiliser nitrogen
* Greenseeker used and at GS31 we used 25kg N/ha on the ex-lentil ground and 51kgN/ha on the ex-canola ground.
Across the six different nitrogen strategies in productivity, Ms Noack said wheat yields after lentils was generally higher than after canola, regardless of application.
When it came to nitrous oxide emissions, it was found that there were higher levels when wheat was sown after canola compared to a legume.
"This contradicted what we originally thought, as legumes leave more N in the soil compared to canola," Ms Noack said.
In wheat sown after canola, she said emissions peaked in mid-June though to mid-July, when N was applied upfront.
Ms Noack said at peak levels, when N was incorporated at seeding, nitrous oxide emissions, were 0.4kg/ha.
"So the assumptions we made, with other gases included, what that about 8-12kg N/ha was lost over the growing season," she said.
"This is about 10-15 per cent of the N applied at the incorporated at sowing treatment."
In the CSIRO-conducted trial on wheat time of sowing, Rosella, Trojan, Wedgetail, Mace and RAC1843 varieties were studied at sites in Hart, Minnipa, Cummins, Port Germein and Tarlee.
"These trials were looking at the requirements the different varieties needed to trigger flowering across a range of sowing dates," Ms Noack said.
At Hart, Trojan wheat was the standout performer, she said, compared to Mace grown in its optimal sowing time, of early to mid-May.
"It out-yielded Mace by 0.6-1t/ha," she said.
"While these trials are only in their first year, we observed from the 2014 data that Trojan can be seen to be a complement to Mace in a cropping program."
The results from all three trials, including the narrow windrow burning trial, can be downloaded for free online. A limited number of hard copies are available for purchase.
Details: www.hartfieldsite.org.au
Alisha Fogden
Cropping editor of Stock Journal.
Cropping editor of Stock Journal.
