Crop sequences reduce disease risk

Author: Rachel Bowman | Date: 07 May 2013

Key Points

  • Sow break crops between standing wheat rows which need to be kept intact.
  • Sow the following wheat crop directly over the row of the previous year’s break crop.
  • This ensures four years occur between wheat crops being sown in the same row space and can reduce the incidence of crown rot in wheat crops.
  • Improved germination of break crops, especially canola, not hindered by stubble.
  • Chickpeas will benefit from standing stubble reducing the impact of virus.
  • Standing wheat stubble gives better protection to break crop seedlings.

New crop sequencing strategies for cereals and break crops are helping grain growers battle diseases like the costly pathogen, crown rot.

Dr Andrew Verrell, NSW Department of Primary Industries (NSW DPI) research agronomist says inter-row sowing has also been shown to reduce the impact of crown rot and increase yield by up to nine per cent in a wheat wheat sequence.

Dr Verrell says research supported by the Grains Research and Development Corporation (GRDC) is tackling crown rot head on with the current focus on crop rotation.

“Crop rotation reduces the incidence and severity of crown rot, resulting in yield gains of 17-23pc over continuous wheat,” Dr Verrell said.

“We’ve now taken a closer look at whether row placement strategies coupled with a break crop-wheat rotation would result in differences in grain yield over a five year crop sequence.”

Dr Verrell told the recent GRDC Adviser Update at Coonabarabran, NSW massive yield advantages could be gained for growers moving away from continuous wheat, particularly where a legume was grown.

“After five years, the mustard-wheat and chickpea-wheat break crop systems showed grain yield advantages over continuous wheat of 40pc and 44pc in 2012.”

He urges growers to follow two simple rules:

  1.  Sow break crops between standing wheat rows, which need to be kept intact.
  2. Sow the following wheat crop directly over the row of the previous year’s break crop.

“By following these two rules it ensures four years occur between wheat crops being sown in the same row space and reduces the incidence of crown rot in wheat crops,” Dr Verrell said.

“It also improves germination of break crops, especially canola, as they are not hindered by stubble and chickpeas will benefit from standing stubble reducing the impact of virus.

“Standing wheat stubble gives better protection to break crop seedlings.”

He says the experiment shows simply alternating row placement in consecutive years will not result in yield gains but a yield loss and increased crown rot.

“In one sequence the break crop was sown between standing cereal stubble which was kept intact.

“The following wheat crop was sown between the previous year’s (break crop) rows but this put it directly over the old 2010 wheat row.

“The consequence of this sequence was that the wheat crop was sown into old infected wheat stubble hence the higher level of crown rot infection resulting in high whitehead counts.”

He says the benefit of the break crop in breaking any disease cycle was not realised in this case.

“Even the traditional on row system had a better yield and crown rot outcome because the break crop was sown directly over the old wheat stubble row excavating the residue out of the row (tyne with spear points) and providing a direct break to the crown rot fungus.

“This may not be the case however if a low disturbance disc system is used.”

Dr Verrell says following a wheat crop, the break crop (pulse or oilseed) should be sown between the standing stubble rows.

“In the next year, the wheat crop should be sown directly over the previous season’s break crop row.

“Then in the next year of the rotation the break crop should shift back and be sown between the standing wheat rows.

“Finally, in the fifth year, the wheat crop again should be sown directly over the previous year’s break crop row.”

ENDS

Contact Details

For Interviews
Dr Andrew Verrell
NSW Department of Primary Industries
0429 422 150
andrew.verrell@dpi.nsw.gov.au

Contact
Rachel Bowman, Senior Consultant, Cox Inall Communications
07 3846 4380, 0412 290 673
rachelb@coxinall.com.au

GRDC Project Code DAN00116 Integrated disease management in northern no-tillage systems using precision agriculture

Region North