Tillage does not increase nitrous oxide emissions under dryland canola in a semiarid environment of south-eastern Australia

CSIRO - NSW Department of Primary Industries, Graham Centre for Agricultural Innovation

Type: Research
Knowledge level: Advanced

Farm Table says:

This study looked at the emission data collected over 365 days under dryland canola to test whether tillage increases nitrous oxide (N2O) emission and whether N application improves productivity without increasing N2O emission.

What is the problem?

Dryland cereal production systems of south-eastern Australia require viable options for reducing nitrous
oxide (N2O) emissions without compromising productivity and profitability.

The objectives of the experiment were to investigate whether

  • tillage increases N2O emissions and
  •  nitrogen (N) application can improve productivity without increasing N2O emissions

What did the research involve?

A 4-year rotational experiment with wheat–canola –grain legumes–wheat in sequence was established at Wagga Wagga, in a semiarid Mediterranean-type environment where long-term average annual rainfall is 541mm and
the incidence of summer rainfall is episodic and unreliable.

The base experimental design for each crop phase was a split-plot design with tillage treatment (tilled versus
no-till) as the whole plot, and N fertiliser rate (0, 25, 50 and 100 kg N/ha) as the subplot, replicated three times

What were the key findings?

This paper reports high resolution N2O emission data under a canola crop.

There was no evidence to support the first hypothesis that tillage increases N2O emissions, a result which may give farmers more confidence to use tillage strategically to manage weeds and diseases where necessary.

However, increasing N fertiliser rate tended to increase N2O emissions, but did not increase crop production at this site

Final comment

Activities that affect  soil microbial processes could have a significant impact on N2O emissions.

No-till farming has been widely adopted for dryland grain production in Australia due to benefits including improved soil structure with better water infiltration and water retention, increased ground cover with less soil erosion and increased soil fertility with more soil organic carbon sequestered

In addition, the adoption of no-till farming reduces energy, machinery and labour inputs, hence increasing on-farm
profitability.

The challenge is to find a balance between the negative impacts of tillage on soil structure by tillage and the maintenance of optimum crop agricultural production. In recent years, several field experiments were conducted across northern and southern grain regions in Australia to investigate how much damage is done to soil by occasional tillage, strategically applied, in an otherwise no-till system

2016 - CSIRO - NSW Department of Primary Industries, Graham Centre for Agricultural Innovation
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