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Top Crop Summit speaker series: Getting the most out of crop rotations

Sheri Strydhorst is the principal of Sheri’s Ag Consulting Inc. She has over 20 years of experience in research and the agricultural industry. Her career has focused on enhancing the profitability of Canadian crop producers. She discussed the Integrated Crop Agronomy Cluster’s ‘Resilient Rotations’ research project at the Top Crop Summit, Feb. 22.

The elements of a successful, sustainable crop rotation include fertility building with legumes and fertility exploitative crops; crops with different root systems; crops with varied pest and disease susceptibility; mix of weed susceptible and weed suppressing crops; and a winter soil cover. 

The struggle is that today, agronomic recommendations for disease management include canola one-in-three or one-in-four for blackleg and clubroot management. And, one-in-six for Aphanomyces disease management in pea or lentil.

The reality, though, is farmers have very tight rotations. According to Statistic Canada, canola, soybean and spring wheat account for 81 per cent of seeded acres in Manitoba. Similar trends were seen in Alberta with data from Alberta Farm Services Corporation, and data analysis is in progress from the Saskatchewan Crop Insurance Corporation.

A February survey confirmed that 60 per cent of farmers thought the dominant crop rotation on the Prairies was a two-year rotation of canola-wheat, or durum-pulse, or a three-year rotation of soybean-wheat-canola. At the same time, 59 per cent agreed or strongly agreed there was a need to diversify their current crop rotation. The major barrier, though, was finding a crop rotation with better net economic returns than they currently had. But, there are many other challenges to diversifying rotations, as well.

To address these issues, research was conducted by the Integrated Crop Agronomy Cluster to help determine what rotations can have the most productive, resilient and profitable cropping system while improving nutrient use efficiency and long term soil health, enhancing system resiliency to abiotic and biotic stress, reducing the carbon footprint and improving farm profitability. 

The ‘Resilient Rotations’ research was carried out over four years at four locations in the northern Prairies, two locations in the southern Prairies and one location in Red River Valley. Six different rotations were compared and the crops grown in each rotation reflected the ones grown in the different geographical areas:

• the control rotation represents the traditionally recommended rotation in each ecozone 
• the pulse or oilseed intensified rotation is the typical rotation being grown in each ecozone
• the diversified rotation includes multiple pulse species and/or winter cereals
• the market driven rotation has crop types selected based on the highest commodity prices prior to planting
• the high risk rotation includes new crop species that may require more or new resources in the form of genetics, agronomy and equipment, but could potentially result in high economic rewards
• the soil health rotation includes green manure and/or intercrops and/or winter cereals

Cropping system performance was assessed by measuring yield and yield stability, N use efficiency and net economic returns. Yield was based on Canola Equivalent Yield (CEY) and took into consideration the price of canola, price of non-canola crops and the yield of non-canola crops.

Looking at yield and yield stability, the results varied by geographical zone. In the northern Prairies, several rotations had high yield, but the high-risk rotation had lower CEY, partly because some of the crops were not well suited to the environment they were grown.

In the southern Prairies, there was rarely one rotation that was the highest yielding at individual sites. When choosing between multiple, high-yield rotations, the research suggests to select a rotation with more than two crop species, and select for more pulse crops in the rotation. The high-risk rotation had lower CEY. 

In the Red River Valley, the high-risk rotation of corn-dry bean-canola-sunflower had the highest CEY that was 22 to 57 per cent greater than the CEY of other rotations. 

Yield stability analysis found that the intensified rotation was the most stable, while the market drive and high-risk rotations were least stable across the Prairies.

Rotations with pulse crops consistently had the highest Nitrogen Use Efficiency in the northern and southern Prairies, since N fertilizer was applied less frequently in those rotations. In the Red River Valley, the high-risk rotation had the highest NUE attributed to the high corn and sunflower yields in the rotation for two of four years. 

Looking at net economic returns, on the northern Prairies, rotations with three or four years in canola were most economically favourable, but there is risk associated with the long-term impacts of canola disease build up. This high return explains the tight canola rotations in many areas of the northern Prairies.

On the southern Prairies, net economic returns were negative for most rotations when precipitation was well below average during the research. The intensified rotation (lentil-durum-chickpea-durum) seemed to perform better compared with other rotations and reflects common crop types grown in these areas.

In the Red River Valley, the high yields of corn, relative to other crop species, resulted in the rotations with corn having the highest net economic returns.

Overall, depending on a farmer’s goal, there were different optimum rotations. Regardless of area, it was important to grow crops well suited to the growing area.

The poor performance of the soil health rotation, as assessed by all measurements, was driven by the lack of saleable yield in one of four years. For increased adoption, other positive metrics or means of financial compensation, will be required.

The complete report can be found at wgrf.ca/resilient-rotations-factsheet.