Wheat and chickpeas can be grown together as companion crops without incurring a yield penalty and, in some cases, could yield higher than a monoculture crop.

Queensland Department of Agriculture and Fisheries (DAF) research agronomist Andrew Erbacher says that with only two seasons of data, he does not want to draw strong conclusions, but the results are positive. “In northern farming systems where we are reliant on stored soil water, companion crops can be grown and not incur yield penalties.”

Mr Erbacher, who presented his findings at GRDC Grains Research Updates earlier this year, says that – in some instances – they can perform better than monocultures.

For example, at Emerald in 2021, the companion crops yielded 115 per cent on a land equivalent ratio (LER) – showing the crops performed better together.

In this case, the LER is calculated by dividing the sum of the intercrop yield by the sum of the monoculture yield to produce a ratio. A number greater than one indicates a higher benefit from intercropping compared with monoculture cropping.

Calculations

The DAF team used LER– to compare yields. Mr Erbacher says the combined yield in the intercropping was expected to be somewhere between the two monoculture crops, which could make it difficult to assess whether planting together was beneficial or not.

“So, the crop yields were converted to a ratio where the intercrop yield is divided by the monoculture yield.”

He explains that, for example, an LER of one, that is 60 per cent wheat plus 40 per cent chickpeas, indicates the same grain yield would have been achieved by intercropping and monoculture cropping. When LER was higher than one, it shows that the crops performed better as a mix (intercropping).

The latest research by the DAF agronomy team is an extension of previous work. That research showed that growing cover crops in the fallow can help improve ground cover and available soil water for the next crop.

Wheat and chickpeas planted in alternate rows. Photo: Andrew Erbacher

“The companion cropping concept extends the opportunity to grow a cover crop alongside our chickpeas,” he says.

“Chickpeas are well-suited to northern growing conditions and generate significant gross margins, but their popularity can be stymied by their sparse residual stubble, which leaves bare soil. In turn, this can reduce fallow efficiency, a significant issue in an area reliant on stored soil water.”

Mr Erbacher says the concept is not new. “What is novel is applying this concept on a broadacre scale and with mechanically harvested crops.”

A review of Australian intercropping research showed its potential to increase crop productivity. The question for the DAF team was whether it had potential in a subtropical environment and a farming system reliant on stored soil water for yield stability.

The answer is yes. In research trials at Emerald and Goondiwindi, companion cropping yields were on par or better than monoculture yields.

Did it increase fallow efficiency after chickpeas? That is trickier to answer given the past two seasons, he says. “With a wet fallow over 2021-22, there were no differences in plant-available water (PAW) from companion crops versus the low-cover chickpea stubble or high-cover wheat stubble. An average (drier) fallow may produce bigger differences in the fallow efficiency, but this was not the case in these experiments.”

Grower interest

The team at Toowoomba-based Farm Agronomy and Resource Management (FARM) has been working with clients on companion cropping, including at Kioma, where some of the DAF research took place.

FARM founder and director Ian Moss says growers have been doing this with forage crops for some time. “Now some are moving to try it with grain crops.”

His team has tried companion cropping in various combinations. This includes chickpeas with wheat, faba beans with barley, and linseed with chickpeas.

With three main ways to go about companion cropping – through grazing, crop termination, or crop integration and taking it to grain – whole-farm considerations need to be thought about.

FARM agronomist Claudia Benn says the question is: “What are you trying to achieve? If it’s money, do interrow sowing; if it’s soil health, that might drive you in a different direction.

“Then get down to the practicalities. What about machinery and agronomics? That will all impact the species you can use – and then what suits each paddock.”

Mr Moss says that, historically, many northern grain growers would also have grown medic and lucerne. “Many of the considerations needed today for companion cropping were not needed when growing for forage.”

With that in mind, he says he would love to see more research on it, as part of a systems-wide approach. “We’re good at looking at what will be good to grow now, but what’s good for the next five years – we need to get better at that as an industry.”

Future

Mr Erbacher agrees that more research is needed in manipulating crop configuration to get the best mix. “However, these results suggest that reducing the more-competitive crop’s planting rates – in this case, wheat – or using wider row spacings in alternate row companion crops, will increase chickpea grain yield and improve the likelihood of achieving an LER above one.”

Companion cropping can also provide the opportunity to reduce insect and disease pressure.

“For example, our 2022 wheat crop following companion crops (in 2021) also showed evidence of reduced crown rot in treatments where chickpeas provided breaks in the wheat stubble, and there is strong anecdotal evidence in southern Australia that fungicide applications can be reduced by one to two for Ascochyta blight in chickpeas.”

In one of the best-yielding treatments of the season at Kioma in 2022, wheat and chickpeas were mixed together at a low wheat population. Photo: Andrew Erbacher

Weed control needs to be considered and selecting paddocks with low weed pressure and/or species with herbicide options compatible for both crops is critical. “Mixtures of crops can limit in-crop herbicide options, residual herbicides can provide other options and the growing range of Clearfield® crops is providing further opportunities.

“Critical to all pesticides used is that the products need to be registered (or covered by a current permit) for all crops being sprayed, to ensure chemical residues comply with MRLs of the intended market.”

Mr Erbacher says that economics also need to be considered, especially grading and contamination costs.

“Separating the grain after harvest may add additional cost requiring a positive LER to maintain an overall gross margin of companion cropping versus monoculture.

“The other risk is the contamination of one species with the damaged seeds of the other after screening, which may affect the value of each crop. For example, wheat contaminated with chickpea splits may only be able to be sold into a feed market.”

The trials in Emerald were grown at the Emerald Research Facility in both 2021 and 2022. Goondiwindi trials were near Billa Billa in 2021 and near Kioma in 2022.

More information: Andrew Erbacher, andrew.erbacher@daf.qld.gov.au; Ian Moss, ian@farmagronomy.com.au