Canola stubbles could boost soil

Canola stubbles could be boosting soil nitrogen levels by up to 18kg/ha, according to trials held by CSBP at WANTFA's Cunderdin site.

The CSBP trial, held by the company's field research manager, James Easton, used randomised plots which were last year sown with either wheat or canola.

This year, the plots were sown with wheat and received either zero, 17, 34, 51 or 68kg of nitrogen.

Mr Easton said the wheat sown into canola stubble with no nitrogen appeared to be performing similarly to the wheat on wheat with 17kg of nitrogen.

"It's similar with 17kg of nitrogen on canola stubble to 34kg after wheat - it just steps up consistently all the way up," he said.

"Plant tests in early August showed we were getting 40 per cent better nitrogen recovery after canola.

"The soil tests going back to April show we basically found an extra 18kg of nitrogen in the top 10cm (of soil) and when you look at the plots it looks like we're seeing that canola crop last year we're getting about a 17 to18kg nitrogen benefit from last year's canola crop."

Researchers aren't entirely sure why this occurs - whether there are shifts in the soil's microbial community or whether canola roots have different compounds that could influence the amount of nitrogen that's mineralised.

Either way, Mr Easton said it's something growers should bare in mind when growing wheat after canola.

"You can't read too much into one trial... but really all we're saying is maybe there is an opportunity to vary your nitrogen rates," he said.