Comparison of Integrated Crop Rotation Systems in Western Canada

Yield and Yield Stability

Canola Equivalent Yield (CEY) allows for yield comparisons between different crop rotations by standardizing the crop rotation’s yield based on the price ratio of different crop types relative to canola (Liu et al., 2019). It is calculated as follows: 

CEY = P _{non − canola}/P _canola × Y _{non − canola} 

where P non − canola is the price of non‐canola crops, P _canola is the price of canola, and Y _{non − canola} is the yield of non‐canola crops. The average price of each crop from 2017 to 2021 was used in CEY calculation. Based on the calculation, the CEY for a canola crop is the same as the canola grain yield.

Yield stability helps determine which rotations were consistently high or low yielding during the study period. This was based on the coefficient of variation (CV) of the rotation treatments across 27 site years. Rotations with a high CV and a low CEY are least favorable while rotations with a low CV and a high CEY are more favorable across diverse growing conditions (Figure 2).

In the Northern and Southern Prairies, there was rarely one rotation that was highest yielding (Table 2). In these ecozones, the high‐risk rotation had lower CEY in part due to the unsuitability of some crop species to these environments (such as soybean or durum in the Northern Prairies or faba bean in the Southern Prairies). In most Northern and Southern Prairie locations, rotations with three crop species and/or pulse species, were better‐performing rotations.

In the Red River Valley, higher CEYs in the high‐risk and market‐driven rotations were mainly driven by the inclusion of corn in those rotations. Corn was favored in these rotations during the drier and hotter 2019–2022 study period.

When assessing trends from all site‐years, the intensified rotation had relatively high yields combined with a low CV, giving it some of the most consistent yields over time and growing environments.

Note. The initial multi-year ANOVA indicated a significant location x rotation treatment interaction; as such, ANOVA was conducted separately for each location. Within each site, CEYs followed by different letters are significantly different based on a Tukey mean separation at p = 0.05.

Nitrogen Use Efficiency

Nitrogen use efficiency (NUE) was calculated as the ratio of grain yield (expressed as canola equivalent yield, CEY) to available N (soil mineral N + applied N fertilizer). The method to determine the N fertilizer rates varied by crop rotation. They were based on soil test recommendations for target yields in each location, for each crop species, except for the market‐driven rotation treatment which received 1.2 times the recommended N fertilizer rate to maximize yield.

The diversified rotation had some of the highest NUE in the Northern and Southern Prairies (Table 3). In the Northern Prairies, this is likely attributed to having pulse crops in the rotation for two of four years and winter wheat, which is able to make use of available nitrogen late in the fall and early in the spring. In the Southern Prairies, the high NUE is likely attributed to having pulse crops in rotation for two of four years.

In the Red River Valley, the high risk rotation had the highest NUE, which is attributed to the high corn and sunflower yields in the rotation for two of four years.

In all ecozones, the soil health rotation significantly reduced the amount of N fertilizer applied compared with the control rotation. However, the soil health rotation did not have a high NUE because of its low yield (Table 2).

Note. Within each site, NUE values followed by different letters are significantly different based on a Tukey mean separation at p = 0.05, except for
Lethbridge, which used a p = 0.01.

Net Economic Returns

Net revenue was calculated by determining the total value of the yield (based on average crop prices from 2012–2021) from each crop and subtracting total costs. Total costs include seed cost, fertilizer costs, pesticide costs, other variable costs (oil and fuel, machinery repair, transportation, labor, and interest), and fixed costs (land, machinery, and storage). Machinery costs were based on the average Saskatchewan farm size in 2021 of 1,766 acres (Saskatchewan Agriculture, 2021).

The average input costs of the six rotations were ranked in the order of soil health ($264/acre), diversified ($301/acre), control ($304/acre), high risk ($307/acre), intensified ($320/acre), and market driven ($338/acre).

In the Southern Prairies, the 2018–2021 growing seasons were drier than normal, and growth was unusually poor, resulting in most rotations producing negative net returns (Table 4). In environments with tendencies for harsh growing conditions, growers should focus on minimizing risk by selecting rotations with lower total costs. The intensified rotation (lentil–durum–chickpea–durum) seemed to perform better compared with other rotations and reflects common crop types grown in these areas.

Note. Within each site, net economic returns followed by different letters are significantly different based on a Tukey mean separation at p = 0.05.

In the Northern Prairies, the higher net returns often associated with the market‐driven rotation are attributed to the high frequency of canola in the rotation and the high canola crop prices. It is important to note that the market‐driven rotation often has canola being grown in three of four years, which is an agronomically risky practice that is not recommended due to the long‐term impacts of canola disease buildup in short rotations. The soil health rotation consistently has some of the lowest net returns due to the lack of yield in the green manure year of the rotation, resulting in no saleable grain in one of four years.

In the Red River Valley, the market‐driven and high‐risk rotations have the most profitable net returns. This was attributed to high corn yields in these rotations. From a risk management perspective, it is important to note that the market‐driven rotation also has the highest input costs. Field seasons at Carman were drier than average; if growing conditions were more typical for the region, the other rotations may have had more competitive net returns.

Summary

Depending on a producer’s goal, there are different optimum rotations. In most Northern and Southern Prairie locations, rotations with three crop species and/or pulse species, were better–performing rotations. However, it is important to select species well adapted to the growing area with high yield potential.

The canola–wheat intensified rotation in the Northern Prairies and the pulse–wheat intensified rotation in the Southern Prairies are very reflective of farmer practice in these areas and are also some of the most consistently high‐yielding rotations year over year.

If NUE is the ultimate goal, rotations with pulse crops being grown in two years of a four‐year rotation are ideal choices for the Northern and Southern Prairies. Inclusion of winter wheat, which makes use of nitrogen late in the fall and early in the spring, can also help improve NUE.

Although rotations with three of four years in canola were economically favorable, there is risk associated with the long‐term impacts of canola disease buildup in short rotations. However, these findings explain why many areas in the Northern Prairies have tight canola rotations.

Net economic returns were negative for most rotations when precipitation was well below average in the Southern Prairies. In these challenging ecozones, 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 highest CEY, NUE, and net economic returns for the high‐risk and market‐driven rotations. Having well‐adapted crop species that yield well under a range of precipitation regimes is important to maximize rotation performance.

The poor performance of the soil health rotation, as assessed by all metrics, was driven by the lack of saleable yield in one of the four years of the rotation. For increased adoption of the soil health rotation, other positive metrics, or other means of financial compensation, will be required. These results are based on the first four years of the study. More robust results are expected if a second four‐year cycle of the study is completed. Funding for a second four‐year cycle will be confirmed in 2023.

Acknowledgments

This research is supported by funding from Western Grains Research Foundation, Alberta Wheat, Sask Wheat, Alberta Pulse Growers, SaskCanola, Manitoba Crop Alliance, and Agriculture and Agri‐Food Canada through the Canadian Agricultural Partnership—a provincial‐federal‐territorial initiative.