Sowing two harvestable crops into the same paddock, otherwise known as intercropping, could have significant economic advantages, according to a GRDC-invested study.

The CSIRO desktop study considered documented examples of intercropping from grain growing regions across Australia.

The findings point to the potential benefits of planting two crops, such as peas and canola (peaola), in the same season and the same paddock.

CSIRO farming systems scientist Andrew Fletcher undertook the desktop study along with colleagues John Kirkegaard (CSIRO) and Greg Condon (Grassroots Agronomy).

He says in most of the examples analysed in the study, intercropping out-yielded the monocultures of the two individual crops making up the mixture.

Potential systems benefits

Dr Fletcher says the study also highlighted the numerous potential systems benefits of intercropping, such as:

• rotational benefits;
• disease and weed suppression;
• improved harvestability;
• reduced erosion risk;
• improved soil fertility; and
• reduced production risk.

"When considering both the systems benefits and the yield increases from the data in this study, intercropping appears to have an economic upside and may be a tool for some growers to consider in the future," Dr Fletcher says.

His study involved a literature review of documented trial results and his experience of this emerging practice.

“One might think that two crops planted into the one paddock, with both crops competing for a limited water resource, would result in reduced yields for both crops - but in the majority of the historical examples, this was not the case,” he says.

“What we saw in all parts of this study was the potential benefits of intercropping, outweighing the obvious challenges and hurdles.”

Separating seeds a hurdle

Dr Fletcher says separating and storing two different harvested seed products could be a hurdle to adoption.

“From my observations, peaola seems to be an easy entry into intercropping, because the seed size difference between the two crops makes for easier separation at harvest time.”

Another barrier to adoption might be the introduction of complexity into a seeding and harvesting program. “Many growers rely on seasonal and often inexperienced labour during those busy times, so they may think intercropping is too complex a process to consider. There is also the challenge of understanding and optimising inputs for the dual cropping system.”

Yields and economics

The desktop literature review of previous intercropping trials investigated the value of 19 cereal/legume intercrops (oats/lupins, oats/field peas, wheat/field peas and barley/lupins).

Fifteen of these trials had documented yield results, with the majority showing positive yield increases in the intercropping trials compared to monocultures.

The cereal/legume review showed that 12 per cent less land was required in an intercropping scenario to achieve yield results equal to a monoculture rotation.

From an economic perspective, Dr Fletcher used an example of an oat/lupin intercrop and says that the combined gross return from the intercrop (assuming $320 a tonne for lupins and $390/t for oats), achieved $191/hectare more than the returns of the two monocultures.

Using data from a trial in Mount Barker, Western Australia, an oat/lupin intercrop achieved a 30 per cent increased return compared to the two crops grown separately.

Data from the analysis on canola/legume crops is even more convincing, with 49 per cent more land required to grow the same amount of grain in monocultures compared to intercrops.

For the canola/legume examples, 22 trials were identified, with 13 of those trials having documented yield data. Again, yields in the intercropping scenarios were greater than in a monoculture.

Peaola seems to be an easy entry into intercropping, because the seed size difference between the two crops makes for easier separation at harvest time.

Dr Fletcher’s findings correlate with an increased adoption rate of both intercropping and companion cropping in other parts of the world, particularly Europe and Canada.

The canadian experience

During a study tour to Canada, organised by FarmLink, Dr Fletcher visited farmers currently using intercropping in their broadacre businesses.

He says despite the clear yield benefits, grower adoption of intercropping and companion cropping in Canada was primarily based on the long-term systems benefits and reduced input costs of the practice.

“Higher yields are a bonus but are not the primary driver for adoption of this cropping system in Canada.”

Canadian growers identified many benefits of an intercropping system, including:

• Disease control (for example, planting linseed with chickpeas to reduce Ascochyta blight in chickpea crops);
• Reduced inputs (herbicides, fungicides);
• Weed control (using crop competition to reduce weed numbers);
• Reduced fertiliser requirements;
• Greater stubble retention over summer period;
• Improved yields on both crops; and
• Reduced risk of crop wipeouts due to frost and drought.

“Reduced risk is a really interesting point to note in this list of advantages,” he says. “In our Australian study, we did see there was a much lower risk of a complete crop failure with intercrops, when compared with monoculture crops.”

Canadian examples have shown it can take a number of years to develop a successful system to handle the various hurdles involved.

“Intercropping practices might not be widespread at the moment, but this study demonstrates there is potential for this type of system in Australia’s grain industry.”

He says companion cropping, a closely related practice that involves planting a crop mixture with the intent to graze and/or spray out the companion crop prior to harvesting the main crop, may also have potential in a mixed farming system.

More information: andrew.fletcher@CSIRO.au