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Nitrogen fix worth the inoculant investment

James and John Davey conduct nodulation checks on their Yorke Peninsula property every season to check on the success of legume inoculation at sowing time and potential nitrogen fixation benefits for their soil.
Photo: John Davey


Grower: John, Matthew and James Davey

Farm name: Kalimar Ag

Location: Clinton Centre, South Australia

Crops grown: Wheat, lentils, beans, canola and barley

Property size: 1600 hectares

Soil types: calcareous grey loam, red loam and sandy over clay

Soil pH: 7 to 8.6

Average annual rainfall: 380 to 470 millimetres

For Yorke Peninsula grower John Davey and sons Matthew and James, nitrogen fixation from pulse crops represents an important strategy on their 1600-hectare enterprise at Clinton Centre.

John says they had previously grown a straightforward wheat/lentil rotation, but in the past two seasons have changed to wheat, lentils, beans, canola and barley.

“That’s probably where we’re going to stay for the next few years depending on the global grain trade and prices,” he says.

As well as the financial benefit of implementing pulses into their rotation, John says they have reaped many agronomic advantages over the years, including weed and disease control and nitrogen fixation.

He says while they have experienced no major issues growing pulses, they were conscious of the effects frost can have on these crops and the likelihood of decreased performance compared to other cash crops during dry years.

Inoculation is one of the most cost-effective ways to improve pulse performance, particularly if that particular pulse has not been previously grown in a paddock, or if soil conditions are not optimal. Nitrogen fixation is dependent on an adequate number of rhizobia bacteria being present in the soil and the most effective way of achieving this is through inoculating pulse seeds at sowing.

The Daveys’ inoculation strategy varies depending on several factors, including nodulation history, their knowledge of the paddock and where they are situated within their cropping rotation. “Generally, if we take on any new land with an uncertain history then we specifically plan to inoculate,” John says.

“On our own farm – the land we’ve had for many years that we know has a good nodulation history – we probably only worry about inoculating every second pulse crop in the rotation. More often than not, we just inoculate because it is easier to get it right than trying to rectify poor nodulation after it occurs.”

John estimates he has used granular inoculant for about 14 years, after making the change from a traditional peat inoculant. Granular inoculants usually contain fewer rhizobia than moist peat inoculants and their quality standard remains the responsibility of the manufacturer. In contrast, peat slurry is known for high quality, which is independently checked but it can be inconvenient to apply to seed.

“Although it is more expensive, we find granular inoculants are an easier and more viable way to get the bacteria into the soil,” he says.

“We also made the change because applying the peat inoculant was problematic in terms of seeding logistics and getting inoculated seed into the ground while the bacteria was still alive.”

The Daveys moved from granules to a liquid inoculant in 2019, which proved effective with good nodulation evident on their faba beans. They apply their liquid inoculant directly to the seed prior to sowing.

While John says the economic benefit of inoculation can sometimes be difficult to quantify, it is a ‘must-do’ for them because poor nodulation can result in a crop failure with little or no benefit to following crops.

“On land we know, it’s usually one of those things that’s a break-even. The actual dollar quantification from inoculation is a bit hard to show, but if you dig up your lentils, beans or peas and you haven’t got nodules, it’s too late to do anything for that year.

“We’re definitely getting a return on investment from that inoculant when we’re taking on new ground. Inoculation is worthwhile to keep up with a high-yielding crop rotation and fix as much nitrogen as much as possible. Also, new strains of bacteria which are more effective are always being developed so it doesn’t hurt to keep up to date with them.”

The Daveys conduct nodulation assessments 10 to 12 weeks after sowing, as recommended, using the opportunity to observe whether their inoculation strategy has been a success. When it comes to doing nodulation assessments, they take random samples from across a paddock.

“We check the roots and nodule numbers and split the nodules open to make sure they’re a nice red colour, which indicates they’re producing plenty of nitrogen,” he says.

“Then, if we’re not happy with the results in any one paddock, we’ll look closer at the possible causes and make plans to fix these for the next rotation.”

John says they often go to the GRDC website when looking for more information on inoculation, nodulation and nitrogen fixation.

They also keep an eye out for technical papers, bulletins and publications on the topic, as well as attending information days and nodulation workshops to keep up to date with best practice and research.

A GRDC investment led by Mallee Sustainable Farming, in collaboration with the South Australian Research and Development Institute, AgCommunicators and other grower groups, is aiming to improve nitrogen fixation in pulses through development of improved rhizobial strains, inoculation and crop management practices.

The nitrogen fixation process in pulses and legumes has a national benefit of close to $4 billion annually in Australian cropping systems.

More information: John Davey, 0407 791 372,

Useful resources

GRDC GroundCover TV nodulation playlist

GRDC Tips and Tactics: Legume and Nitrogen Fixation

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