The potential role of companion and intercropping systems in Australian grain farming. Should we be considering them?

Key messages

• There is increasing grower interest in the use of companion and intercropping systems in Australia.
• While there are real and recognised yield benefits from intercropping, farmers experimenting with these multispecies mixtures are seeking other system benefits.
• Potential system benefits include rotational benefits, risk management, soil improvement and reduced input costs.
• Overseas experience suggests that most of the challenges can be met with perseverance and innovation.

Aims

The aims of this study were to examine the potential role of mixed-species cropping systems in Australia, including intercrops and companion crops. We examined the potential benefits and limitations of these systems, the current use of these systems in Australia and discussed the research and adoption in Europe and Canada and the potential learnings that could be applied in Australia.

Introduction

Modern agricultural cropping systems are generally based on large areas of single species monocultures. Crop rotation (between seasons) is used to obtain diversity in these farm systems.

Monocultures are grown due to the reduced complexity and ease of management on large farms where labour is scarce and expensive. However, recently there has been increasing interest in the use of intercrop and companion crop systems in large-scale mechanised cropping.

The idea of growing more than one crop/species on the same land in a mixture is not new - these systems are often used in small holder and subsistence agricultural systems in the developing world and in organic systems. There is ample evidence that these intercrop and companion crop mixtures can give yield benefits in mechanised systems both in Australia, (e.g. Fletcher et al 2016) and overseas, (e.g. Lithourgidis et al 2011; Pelzer et al 2014). However, in addition to these yield benefits there may be a range of farming system benefits that are important but less easy to quantify. These could include rotational benefits, reduced inputs and soil quality benefits.

In this paper we review the potential use of both intercrops and companion crops in Australian farming systems. There are several reasons why it is timely to revisit these systems and their potential in Australian farming systems. There are potential farming systems benefits that need to be evaluated including rotational benefits; disease and weed suppression; improved harvestability; reduced erosion risk; improved soil fertility; and reduced production risk. There are several emerging technologies, (e.g. precision agriculture, robotics, herbicide tolerant crops) that could help to remove some of the barriers to adoption. Here, we collate and analyse historical and recent small plot experiments looking at the yield and potential profitability benefits of intercrops. We evaluate the production risks of these systems. We report the broad findings of case studies we have developed with Australian farmers who are currently experimenting with intercrops and companion crops and report on the overseas (Canada and Europe) research, development and farmer uptake of these systems.

In this paper we use the following definitions:

Intercrop: where two or more species are sown and harvested together with the objective of harvesting grain of both species.

Companion crop: Where two or more species are sown together with the objective of harvesting grain of a single species. The other species are either grazed out or terminated using herbicides.

Land equivalent ratio (LER): A measure of the yield-benefit and land-saving achieved by sowing an intercrop. A LER >1.0 indicates that the intercrop is more productive than the monocultures and less land area is needed to achieve the same grain yield of the two component species as an intercrop compared to two sole crops. The LER takes account of the relative yield of the component species.

Methods

Historical Australian research data

We undertook a literature search of experimental research that had occurred with intercropping in Australia. This built on an earlier review (Fletcher et al 2016). There was a significant amount of unpublished historical research on intercropping across Australia. Much of the research was in WA due to the ease of searching the DPIRD research database (https://researchlibrary.agric.wa.gov.au/). Not every trial had yield data available. The yields from these reports and papers were collated and analysed using the LER. This analysis only included those trials where grain was separated into the component crops. In contrast, there had been very little research with companion crops.

We also compared the risk of intercrops and monoculture crops. To do this we used the mean yield of each sole crop and the combined yield of the intercrop in each experiment. We then calculated the median yield and the 10^th percentile yield. The median yield represented the typical expected combined yield across experiments and the 10^th percentile yield represented the yield in the worst seasons.

Australia farmer case studies

We undertook 20 case studies from selected farm businesses across Australia that were currently trying or have previously tried intercropping or companion crop mixtures at commercial scale. This involved consultant-led deep interviews intended to establish the types of intercrops and companion crops being tried by farmers, and their motivation and barriers to adoption. We have not identified individual farmers but rather summarised the results across the 20 farmers in Australia.

Summary of international experiences (France and Canada)

In July 2019, we undertook a study tour to Canada to visit farmers who are currently using intercrops on broadacre farms and researchers currently experimenting with intercrops. This tour was organised by Western Ag Innovations and Farmlink. This tour also included several interested farmers from southern NSW.

The insights into recent intercropping research and adoption in Europe by the scoping team emerged from a recent CSIRO-INRA Exchange Programin 2017-2018 which supported exchange visits in July-August 2017 (French in Australia) and June 2018 (Australians to France).

We describe the experiences and insights from these trips along with other information we were able to obtain from our colleagues.

Results

Historical Australian experimental results

In total there were 19 experiments that investigated cereal-legume intercrops and 15 of these had yield data available. The main experimental crop combinations of cereal and legume examined were: oats and lupin (six experiments), oats and field pea (four experiments), wheat and field pea (five experiments), barley and lupin (three experiments). All other combinations were trialled in one or two experiments only.

For the cereal legume intercrops, the mean LER was 1.12 (Fig 1a) and the LER was greater than 1 for 49 of the 72 individual comparisons. This indicates a yield benefit from intercropping with 12% more land required to grow the same amount of grain in monocultures compared to intercrops. These are consistent with a range of cereal-legume experiments in Europe (Pelzer et al 2014).

Figure 1. Summary of previous intercropping experiments in Australia (filled points) for wheat-legume (a) and brassica-legume (b) mixtures comparing the relative yields of each component species. Data from European and Canadian experiments are provided for comparison. Each data point is a separate experimental treatment. The total LER are indicated by the shaded areas in the background. The solid diagonal line is y = x for comparison of the competitive abilities of each component crop in the mixture.

In total there were 22 experiments that investigated canola-legume intercrops but only 13 of these had yield data available. The LER was greater than 1 for all but one treatment. The mean overall LER was 1.49 (Figure 1b) which indicates 49% more land would be required to grow the same amount of grain in monocultures compared to intercrops. The LER’s found here were consistent with a range of recent oilseed brassica-legume intercrop experiments in Canada.

Figure 2. Box plot summarising the total yield of intercrops and component crops across a range of cereal legume (a) and canola-legume (b) intercropping experiments in Australia. To avoid biasing the result the means of each experiment were used in the analysis. The analysis thus represents the site to site variation rather than the within experiment variation. The boundaries of the box are 25th and 75th percentiles, the horizontal line in the box marks the median. The error bars represent the 90th and 10th percentiles and the data points represent the outliers.

There was reduced yield risk in the intercrops compared with the monocultures (Figure 2). In the cereal-legume intercrops the median yield was 2.3t/ha for cereal, 1.5t/ha for legumes and 1.9t/ha for intercrops. The 10th percentile yield was 1.4t/ha for cereals, 0.41t/ha for legumes and 1.1t/ha for intercrops. In the canola-legume intercrops the median yield was 0.9t/ha for canola, 1.2t/ha for legumes and 1.6t/ha for intercrops. The 10th percentile yield was 0.27t/ha for canola, 0.71t/ha for the legume crops and 0.89t/ha for the intercrops. This highlights that the overall risk is reduced because the other crop will still be able to produce some yield. This may help with the adoption of some crops that are perceived to have higher risk, such as the pulses.

As an example of the potential economic advantage of intercrops we re-analysed the data of Walton (1980). We calculated the gross return from each component of an oat-lupin intercrop assuming grain prices of $320/t for lupins and $390/t for oats. This showed that the intercrop always had a higher gross return than the mean of the two sole crops. Averaged across all sowing combinations the gross return was $191/ha greater in the intercrop. If the proportion of oats in the intercrop was greater than 50% there was greater economic return from the intercrop compared to the most valuable monoculture (Oats) (Figure 3). Of course, this will depend on the relative prices and yields of the two component crops. The economic advantage will be greatest when the two crops have similar prices and large amounts of overyielding. When one crop has a much higher return than the other the economics will show that this crop will be more profitable than the intercrop. However, prices vary from year to year and intercrops could help to reduce this economic risk as well as yield risk.

Insights from farmer cases studies - Australia.

There were several key insights from the farmer case studies that were undertaken. These insights were consistent across Australia. For most farmers the yield benefits of intercrops and companion crops were secondary motivations compared to the farming system benefits they were trying to achieve, (e.g. rotational, risk management, soil improvement and reduced input costs). The farmers identified improving the logistics and agronomy of sowing, managing and harvesting the intercrops and companion crops to achieve the systems benefits as priority areas. These farmers were experimenting with a wide range of intercrops and companion planting systems, many of which have not been studied in formal experiments by researchers.

Overall there was a wide range of intercrops and companion crop systems planted. There was a range of canola-legume intercrops (including canola-pea, canola-faba beans, canola-vetch, and canola-lentil); many farmers were trialling companion crop mixtures where companion crops were either grazed-out or terminated to harvest a cereal crop; and at least three farmers had tried chickpea-linseed intercrops. In contrast, there was only a few that had trialled cereal-legume intercrops.

Insights from international experiences- Canada and Europe

There has been a recent resurgence in the adoption and research of intercrops in Canada. Despite important previous plot-scale research on intercrops this resurgence has largely been driven by farmers. Most farmers reported significant overyielding (5-40%) from intercrops compared with sole crops. This is consistent with most of the small plot research (Figure 1b). However, this overyielding was not necessarily a driver for adoption; it was a bonus. The key motivations for adoption have been reduced input use and costs, improved soil health and higher profit. Reducing risk on variable soils at the landscape scale due to the adaptation of different crops to different conditions was another driver. Risk associated with price and yield variations was also offset in intercrops.

Table 1. Area and type of intercrops insured in 2018 and 2019 in Canada.

The area of intercrops has increased rapidly in the prairie provinces of Canada. For example, the area has doubled in Saskatchewan from 2018 to 2019 (from 15,600 to 29,300ha). In 2019 there were a total of 140 growers with insured intercrops, indicating that this was more than a few growers with large areas. One farmer that we visited had more than half his 2500ha cropping farm planted to intercrops.

The permanent adopters of intercropping that we visited in Canada took time (~10 years) to develop successful systems, overcoming practical and logistical barriers and innovating as necessary (with machinery, agronomy and markets). All of them identified seed separation at harvest as a major hurdle to adoption at scale. Due to differences in seed moisture, mixed species cannot be stored together. Furthermore, the speed of harvest cannot be compromised. For this reason, peaola (pea and canola intercrops) was often an entry point to intercrops (Table 1). The large differences in seed size meant that they could be separated at harvest using a rotary screen. Chickpea-linseed intercrops were also emerging as a popular combination because of reduced disease in the chickpea component and the ease of separation.

There has been renewed interest in intercropping in Europe. However, there is very little information on the actual area of intercrops and species mixtures being grown. Europe has been the centre of significant intercropping research for decades and the detailed crop physiological understanding on species mixtures is well published and reviewed (Pelzer et al 2014; Brooker et al 2015). Previous research has been “researcher-led” and “policy-driven” (EU agricultural policies), i.e. focus on crop diversification, biodiversity, soil health, ecosystem services; less by farmer demand. Higher support and adoption of organic farming systems in Europe, along with subsidies have made some aspects of crop mixtures feasible in certain cases, (e.g. higher prices for organic cereals-legume mixtures can offset lower yields). A recent large investment in intercropping ReMIX project (https://www.remix-intercrops.eu/) has initially focussed on better understanding of farmer decision making towards intercropping and the barriers to adoption.

Conclusion

There is increasing interest in the use of mixed species systems (both intercrops and companion crops) in both Australia and overseas. There are potentially large yield benefits from growing mixtures of two species. However, any future adoption of these approaches is likely to be driven by the farming systems benefits associated with intercrops and companion crops.

There are several logistical issues that need to be overcome before the use of these systems can be widespread. These include (1) sowing, when the two crops require different sowing depths (2) the range of herbicides available for some mixtures could be limited (3) intercrops could require different harvester settings, and (4) the separation of harvested grain. Despite these issues, the evidence in Canada is that most can be resolved with persistence and innovation.

There is potential for these systems to be included in large mechanised cropping systems in Australia. This is highlighted by the Canadian experience where there has been a recent increase in adoption. In our tour we visited one farmer who was growing 2200ha of intercrops. In 2019 there were at least 30,000ha of intercropping in Canada. As in Canada, Australian growers and consultants are leading the impetus for renewed research on intercrops and calling for appropriate supporting research to explore the most promising options within Australian farming systems. The future challenge is to see whether they have a fit in Australian systems and to identify any limits to adoption.

Acknowledgments

We gratefully acknowledge the contributions of the many farmers, researchers and consultants from both Australia and internationally that generously provided their time opinions, observations and data. We especially thank Farmlink who co-organised the tour to Canada in 2019.

The research undertaken as part of this project is made possible by the significant contributions of growers through both trial cooperation and the support of the GRDC, the authors would like to thank them for their continued support.

References

Brooker, R.W., Bennett, A.E., Cong, W.F., Daniell, T.J., George, T.S., Hallett, P.D., Hawes, C., Iannetta, P.P.M., Jones, H.G., Karley, A.J., Li, L., McKenzie, B.M., Pakeman, R.J., Paterson, E., Schöb, C., Shen, J., Squire, G., Watson, C.A., Zhang, C., Zhang, F., Zhang, J., White, P.J., 2015 Improving intercropping: a synthesis of research in agronomy, plant physiology and ecology. New Phytologist 206, 107-117.

Fletcher, AL., Kirkegaard, J.A., Peoples, M.B., Robertson, M.J., Whish, J., Swan, A.D., 2016 Prospects to utilise intercrops and crop variety mixtures in mechanised, rain-fed, temperate cropping systems. Crop and Pasture Science 67, 1252-1267.

Lithourgidis, A.S., Dordas, C.A., Damalas, C.A., Vlachostergios, D.N. 2011 Annual intercrops: an alternative pathway for sustainable agriculture. Australian Journal of Crop Science 5, 396-410.

Pelzer, E., Hombert, N., Jeuffroy, M.H., Makowski, D., 2014 Meta-Analysis of the Effect of Nitrogen Fertilization on Annual Cereal–Legume Intercrop Production. Agronomy Journal 106, 1775-1786.

Walton, G.H., 1980 Lupin agronomy / Field pea agronomy / Alternative grain legume comparisons / cereal/legume mixtures. Department of Agriculture and Food, Western Australia, Perth.

Contact details

Andrew Fletcher,  CSIRO Agriculture and Food
147 Underwood Ave, Floreat, WA 6014
08 9333 6467
Andrew.L.Fletcher@csiro.au

John Kirkegaard,  CSIRO Agriculture and Food
2-40 Clunies Ross St, Acton, ACT 2601
02 6246 5080
john.kirkegaard@csiro.au

Greg Condon,  GrassRoots Agronomy
PO Box 73, Junee, NSW 2663
0428 477 348
greg@grassrootsag.com.au

Tony Swan, CSIRO Agriculture and Food
2-40 Clunies Ross St, Acton, ACT 2601
0428 145 085
tony.swan@csiro.au

Ken Greer,  Western Ag Innovations
804 Central Ave, Saskatoon, SK, Canada S7N 2G6
(1) 306 978 1777
kengreer@westernag.ca

Eric Bremer,  Western Ag Innovations
804 Central Ave, Saskatoon, SK, Canada S7N 2G6
(1) 403 394 4310
ericbremer@westernag.ca

James Holding,  Trials Agronomist- FarmLink Research
361 Trungley Hall Rd, Temora  NSW 2666
0447 198 640
James@farmlink.com.au