Soils at crossroads: legumes or low protein
Author: Rachel Bowman | Date: 22 Apr 2013
Lower than expected protein levels in last year’s winter crop should prompt growers across the northern grains region to reconsider soil nitrogen strategies for 2013.
Matthew Gardner, NSW Department of Primary Industries (NSW DPI) research agronomist says wheat protein levels have dropped over the last three seasons due to high yields, flooding and under-use of legumes and nitrogen fertilisers.
“Receivals of low protein wheat grades (less than 11.5 per cent protein) were greater than high protein grades for GrainCorp’s Dubbo Zone for the harvest of 2012/13, with low protein grades representing 60pc of total receivals,” Mr Gardner said.
The Dubbo Zone spans from Nyngan and Tottenham in the west, Coonamble in the north and to Birriwa in the east.
“The effect of legumes and fertiliser are the two most important factors in nitrogen management for grain protein; however there does appear to be some difference among common wheat varieties for grain protein concentration for a given yield level,” Mr Gardner said.
He says Grains Research and Development Corporation (GRDC)-supported research shows there may be a small protein advantage in planting varieties that achieve higher grain protein concentrations for a given yield level in the northern region – such as has been shown with Longreach Spitfire – however variety choice only plays a small part in long term management of soil nitrogen.
“There has been a reduction in the number of paddocks tested for nitrogen in recent seasons and this may be contributing to poor nitrogen decisions.”
Mr Gardner says the 2010, 2011 and 2012 wheat crops recorded low protein, much to the frustration of growers.
“These low protein concentrations have occurred in conjunction with declining soil mineral nitrogen contents and in north-central NSW in 2012 nearly two thirds of soil had a mineral nitrogen content less than 60 kilograms of nitrogen per hectare in the 0-60 centimetre depth interval.
“This trend of low soil mineral nitrogen contents extends to the entire eastern grains belt where the number of soil tests with less than 30kg N/ha in the 0-60 cm zone has increased from 20 to 40pc.
“The most sustainable and low risk way of increasing soil nitrogen appears to be through planting leguminous crops and pastures.”
Fertiliser N will still be required to ensure that yield and protein targets can be met more reliably but it is far too costly to fully support total crop production.
Mr Gardner says the trials show the impact of crown rot on grain protein concentrations is negligible.
Video Caption: NSW DPI research agronomist Matthew Gardner discusses the role of soil testing leading up to this year's winter crop.
Photo Caption: Matthew Gardner, NSW DPI research agronomist, Tamworth says growers aiming for high protein levels need to pay careful attention to sources of soil nitrogen including fertiliser and legumes.
Audio Caption: Matthew Gardner, NSW DPI research agronomist discusses nitrogen status and its importance for winter croppers this year following the recent wet years and resulting high yields.
Audio Download: Click here to download audio.
For interviews contact:
Matthew Gardner, NSW DPI research agronomist
02) 6763 1138
0400 153 556
Rachel Bowman, Cox Inall Communications
07 3846 4380
0412 290 673
GRDC Project Code DAN00169, DAN00138