Soils across the northern region are sending a clear message to growers – good seasons and flood events have depleted soil fertility and exhausted soil mineral nitrogen reserves built up during dry seasons of the mid-2000s.
Chris Dowling, Back Paddock Company technical services manager told the recent Grains Research and Development Corporation (GRDC) Research Update at Goondiwindi, Queensland the loss of soil elasticity is the most concerning cause of lower than expected protein levels last year.
Dr Dowling says so far the summer of 2013 has done little to improve soil mineral nitrogen reserves and the northern region is lining up for a similar scenario that existed prior to the 2012 winter crop.
“We’ve lost the soil’s ability to give a bit more in a good season because we’ve lost soil organic matter,” Dr Dowling said.
“That’s where nitrogen mineralises from; when it rains it releases the nutrient.”
He said the rich nitrogen levels and organic matter of the brigalow scrub and belah landscapes had given growers a leg up in achieving high protein levels and prime hard quality in the past.
“That’s now running down and the soil is telling us: ‘I can’t give anymore in a good season’ and what goes first is protein.”
Dr Dowling says long term declines in soil fertility came together with short term seasonal conditions to take growers by surprise last year when protein levels came in lower than expected.
He said growers had relied on the soil’s ability to release nitrogen either in the fallow or crop and a healthy buffer of soil fertility had allowed them to regularly produce crops of 13 per cent protein or more.
“With the rundown of that naturally occurring organic matter from vegetation that was pre-existing on the land, we’re getting to the point now we are struggling to meet 11.5pc grain protein in wheat.
“This is an indication that the soils aren’t able to give and this makes nitrogen management even more critical.”
Dr Dowling said contributing factors to the 2012 crop results included:
- Long term loss of soil nitrogen supply elasticity as a result of organic matter decline
- General lack of legumes in rotations
- Record wet summers prior to the 2012 winter cropHigh yields in crop preceding 2012 winter crop
- Summer 2011/12 denitrification events
- Fertiliser nitrogen management strategies – quantity and timing
- Dry spring – moisture and available nitrogen dislocation
Dr Dowling says the “set and forget” nitrogen strategy may need to be reviewed as the season progresses to ensure the crop has enough nitrogen to finish well.
He says legumes remain a key part of soil nitrogen management within the northern farming systems but would like to see more area planted to nitrogen-fixing crops.
“There’s been some hint that growers are thinking about planting more legumes this year but in reality the area needs to be up around 30 or 40pc of the wheat area on an annual basis to make a difference and we’re not getting anywhere near that at this stage.”
He says soil nitrogen fertility is an ongoing issue so without help from legumes growers need to consider crop management and fertiliser strategies that provide more influence over wheat grain protein.
“The ongoing discussion is the concept of applying nitrogen very late in the crop to try and influence protein without affecting yield where the seasonal conditions are favourable."
Video Caption: Chris Dowling, Back Paddock Company technical services manager discusses why nutrition is crucial to protein and yield this winter crop season.
Audio Download: Click the link below to download an audio grab for this media release.
Audio Caption: Chris Dowling, Back Paddock Company technical services manager says growers need to pay particular attention to nutrition this winter crop season.
Photo Caption: Good seasons and flood events have depleted soil fertility and exhausted soil mineral nitrogen reserves.
For interviews contact:
Chris Dowling, Technical Services Manager
Back Paddock Company
0407 692 251
Rachel Bowman, Cox Inall Communications
07 3846 4380 / 0412 290 673