Intercropping provides pulse productivity gains

Clare-based SARDI pulse agronomy senior research scientist Penny Roberts said while research into the science of intercropping remained scarce, trials in the Mid North, Eyre Peninsula and South East were showing it had potential to bring benefits to a range of cropping systems.

She says intercropping has been used for a number of years in smallholder systems overseas, or in instances in Australia, when a grower might combine two species for a hay crop.

But there was also growing interest within Australia and internationally, such as Canada, in more traditional grain or oilseed systems.

Dr Roberts said intercropping could be a more complex system than a monoculture, and also required some adaption of seeding machines, but its possible benefits included greater yields, reduced input costs, greater rotational benefits when using pulses or oilseeds, better risk management and improved environmental or soil health.

Existing trials address three main applications - low rainfall zones to enable successful and economical pulse crops; frost-prone areas to reduce damage to plants; and medium rainfall zones to lower input costs of chickpeas.

She said they were into the fifth year of field research in low rainfall zones with positive results.

"We can achieve productivity gains with oilseeds and pulses," she said.

Dr Roberts said using a land equivalent ratio, they found a 30pc to 80pc increase in productivity with a lentil/canola combination, compared to being grown as a solo crop, while vetch/canola productivity lifted 30-40pc. This year they are trialling dual pulse combinations, such as faba beans/lentils and faba beans/vetch.

She said the crops could be harvested at the same time and put through a seed cleaner to access conventional markets, with the economics showing even with the cost of seed cleaning, intercrops were still ahead for profitability.

Among the other applications is the reduction of some of the disease, weed control and even desiccation input costs involved with growing chickpeas.

"We're asking, can we reduce input costs by taking advantage of mixed species systems?" Dr Roberts said.

"In this work we're focused on reducing input costs rather than increasing yields."

She said the disease risk tended to be lower due to the physical distance between rows and having a barrier of another crop variety, while the weed burden also lowered.

Data on the third potential use for intercropping - managing frost risk - is expected to be available within months.

Dr Roberts said there were trials under way using two to three species combinations of cereals, oilseeds and pulses, which could increase the range of pulses grown in frost-prone environments.

"The question is, can we use multiple crop combinations as a frost mitigation strategy?" she said.

She said crop canopies had a different structure in an intercropping environment, which could change the way frost interacted with plants.

"We're hoping it may mean more air movement through the canopy," she said. "In the worst case scenario, you'll end up with a very useful forage option for grazing or hay."

Dr Roberts said there were 672 temperature sensors operating at the trial site at Farrell Flat to capture the differences within the control and treatment plots. She said there were more than 20 frosts since sowing in April, with the area also prone to spring frosts, providing lots of data.

RELATED READING: Innovative methods help drive up profit

Resilience shines in dry

She said this was an exciting area as it could provide new options to some traditional challenges growers faced each year.

"There is a need to look at more adaptive, innovative systems that have the potential to address some of the environmental constraints we're battling with every year, like frost, the need for ground cover or the potential for soil erosion," she said.

She said one reason why intercropping was able to take on an increasing role in operations was improved technology for in-crop herbicide treatments that allowed Group B tolerant wheat, canola, bean or lentil crops to be grown together.

Dr Roberts said intercropping was still a largely unresearched field and more work needed to be done to best understand how to adapt it to a wider range of operations and regions.