Top Crop Manager

Features
Long-term agroecosystem experiments on the Canadian Prairies

For more than 100 years, agroecosystem experiments have provided unique and valuable insights into modern cropping systems.

July 2, 2024  By Donna Fleury


Image courtesy of Darcy Schott

Long-term agroecosystem experiments (LTAEs) have been in place on the Canadian Prairies for more than a century. Currently, Agriculture and Agri-Food Canada (AAFC) manages about 24 ongoing LTAEs across the Prairies, providing invaluable long-term, multi-decadal experimental systems for testing new research questions. The first AAFC LTAEs were designed and inspired by the famous Rothamsted Classical Experiments established in 1843 in England, with the oldest and longest-running experiments started at the Lethbridge Research and Development Centre in 1911. These experiments provide a wealth of information and understanding of agroecosystems and the complex interactions impacting agricultural production on the Canadian Prairies.

“These LTAEs were generally established to help farmers determine the types of crops they could grow in different regions and how to grow them during the early farming expansion on the Prairies,” says Charles Geddes, research scientist with AAFC in Lethbridge, Alta. “At Lethbridge, we have the oldest and longest-running agroecosystem experiments in Canada that have been ongoing since the native prairie was broken in 1910, and certain data has been collected annually from these plots for more than a century. Across the Prairies, other long-term AAFC experiments continue in Saskatchewan including at Scott, Indian Head and Swift Current. A smaller number of long-term experiments are managed by universities such as the University of Alberta Breton Plots that are over 90 years old, and the University of Manitoba’s Glenlea long-term rotation plots, to name a few. We now have over a century of information collected from these experiments that provides immense value for research purposes and understanding the agroecosystems we operate in.”

Lethbridge
The LTAEs in Lethbridge continue today with about 18 different long-term experiments focusing on crop production and agroecosystems. One of the first and longest experiments, known as Rotation ABC and located next to the Lethbridge Research and Development Centre, was part of a larger experiment started in 1911 trying to determine which crops would grow best and the most optimum and economic crop sequences in southern Alberta. Three of the several dryland rotations continue today and include A (continuous wheat), B (fallow-wheat) and C (fallow-wheat-wheat). Rotation ABC has continued to be used as a check or benchmark for various other experiments over the years. Another experiment known as Rotation U, established in 1911, focused on irrigated crops, originally under surface flood irrigation, transitioning to high-pressure sprinkler irrigation in 1973, and in 2024 evolved to a new efficient low-pressure, lateral move irrigation system.

“This long-term history provides a very unique timeline of consistent data collection over a century and a timeline of changes and adoption of new technologies and farming practices,” Geddes says. “The original plots were managed using horse-drawn farm equipment and tillage and have evolved over the years to no-till systems, chemical pest management, and modern cultivars. Over time, the research has shown an improvement in crop productivity, mainly due to the adoption of new practices, technologies, and varieties introduced over the last century. This knowledge is now being used to address emerging issues such as climate change, sustainable cropping systems, carbon sequestration, and nutrient cycling.

“We are also looking at opportunities to integrate the various historical datasets such as yield and quality data, soil samples, weather, and precipitation together in a more systems-based approach,” Geddes says. “We have statistical techniques that didn’t really exist in the past and new modeling approaches to help answer questions. We can look at variables such as changes in yield stability over time rather than just yields. This can help evaluate how stable yields were over time and how resilient they are under different management scenarios, especially under changing climate. Historical soil samples can help answer questions around changes in microbial communities, for example, with the earliest soil samples that date back even before synthetic fertilizer or pesticides were used in crop production. The continuous and multiple decades of research are even more valuable today as we address big questions around carbon sequestration, climate change, productivity risk, sustainability and long-term economic viability.”

Geddes adds that LTAEs can help address a range of management issues including weeds. For example, weed surveys are showing widespread glyphosate resistance of kochia and, more recently, a new type of resistance to Group 14 herbicides. Some producers are considering strategic tillage to manage herbicide-resistant kochia populations. In a recent study, a long-term no-till experiment from the 1960s has been revamped to focus more on strategic tillage, comparing no-till, conventional tillage, and occasional tillage of about one in every four years. This study, now in its 10th year, will help understand if soil health can be maintained even with strategic tillage and includes sampling of both soil health and the weed seedbank. Hopefully, the results will show that using tillage sparingly for weed management might be done without negative impacts on soil health.

“The Lethbridge LTAEs comprise a very precious resource and are really a research platform that can be used to assess various cropping system factors,” says Ben Ellert, AAFC research scientist – biogeochemistry. “The experiments are not museum pieces but rather have evolved as technologies have advanced in equipment, genetics, inputs, and other factors. We no longer use horses or stationary threshing machines or the Noble blade. The experiments continue to test our understanding, whether we are looking at long-term trends or developing computer simulations and predictions that can be tested against the real data. We are able to deploy scientific technologies, such as accelerator mass spectrometry to trace radiocarbon, that those who first established the studies couldn’t even envision. But such advanced tools help us evaluate and understand factors such as nitrogen use efficiency, greenhouse gas emissions and soil carbon changes over the century.”

One other long-term experiment of note is at Onefour Research Station, originally established in 1927 as a Dominion Range Experiment Station in the southeast corner of Alberta. In 1930, a range productivity monitoring study was established in the northwestern portion of the experimental station. The Smoliak-Willms site, as it is locally known, had comparatively poor soils that were representative of large areas of native rangeland in that region. The site was, and still is today, valued for its intact native grasslands, rare plants and animals, diversity of soil and rangeland types and unspoiled wildlife habitat.

“The amount of forage dry matter produced in annually re-positioned cages to prevent loss to grazing has been monitored since 1930,” explains Ellert. “The trend in long-term precipitation changes was small; however, starting in about 1990, there was a clear increasing trend in forage production per cm precipitation. There were no changes to grazing intensity or cattle distribution or anything else, but forage yields were increasing. It appears that the increases are related to increasing atmospheric CO2 concentrations that measured 360 ppm in the 1990s but have increased to 420 ppm today. The early rangeland ecologists who established the study in 1930 would not have anticipated that we would be contemplating the possible influence of atmospheric CO2 on productivity.”

Now that almost 100 years of data have accumulated for this native rangeland at Onefour, researchers are able to ask new questions of the data and test their understanding of how such systems respond to climatic and other challenges, now and likely to be encountered in the future. The site is now run as a rangeland research ranch by the Province of Alberta in conjunction with the University of Alberta and local ranchers after being divested by the Government of Canada to the province in 2015.

Indian Head
The LTAE in Indian Head has been in place since 1958 to address the decreasing soil organic matter content and wind erosion concerns, and continues today. “We have always maintained the traditional continuous wheat, fallow-wheat, fallow-wheat-wheat and comparisons of unfertilized and fertilized plots from the beginning,” explains Bill May, crop management agronomist with AAFC in Indian Head. “There have also been various experiments conducted to analyze the productivity of wheat crops when they are treated with variables such as fertilizers, green manure legumes and reduced fallow frequencies. Some other rotations have included fallow-wheat-wheat with about 30 per cent of the straw baled off the field and a fallow-wheat-wheat followed by three years of alfalfa. In 1990, the experiments were converted from conventional to no-till cropping systems. Most recently we added modern rotations to compare to the LTAE including wheat-canola-soybean and wheat-canola-oat-soybean, adding an agronomy focus to the more soil health focused experiments.”

May adds that although the traditional LTAE experiments have been maintained, when new agronomic practices are incorporated by farmers in the region, those inputs are incorporated in the LTAE cropping systems as well.

“We want to try to model what is actually happening on the farm as opposed to a static system based on 1958 production practices, such as trends towards increasing fertilizer rates. When comparing the long-term unfertilized to fertilized experiments and the move to no-till, the first impacts to the unfertilized plots tended to be stability of production; however, over time, we are seeing yields increase. Soil organic carbon has increased from the increasing fertilizer rates and the transition to no-till. The long-term plots that included three years of hay in rotation had the greatest amounts of soil carbon. In a recent study, we also compared the soil organic carbon and nitrogen content between these crops thirty, forty and fifty years into the study, and concluded that straw removal had no significant effect on the soil or grain yields. Over the years, the results show that the appropriate application of fertilizers, the inclusion of green manure and forage crops, reducing tillage, and converting to no-till farming practices all increased grain productivity and enhanced soil organic matter content.”

The long-term experiments at Indian Head will continue, along with the collection of crop production data, weather and precipitation and soil samples. May notes that they regularly publish papers on various aspects of the LTAE to make the data and information more accessible. The papers usually include trends since the beginning of the experiments, rather than just a short five or 10-year snapshot. This provides the opportunity to evaluate how the last 10 years, for example, is adding on to the whole rotation or contributing to changes as a whole. By incorporating new practices and advancements that could be adopted by farmers in the region, the experiments provide unique and valuable insights into modern cropping systems.

Swift Current
At Swift Current, there are three LTAEs, including the first ‘Old Rotation’ established in 1966, the ‘0MC’ or zero-minimum tillage study in 1981 and the ‘New Rotation’ established in 1987. “Although the experiments have evolved, some systems that were in place at the inception are still currently ongoing,” explains Mervin St. Luce, research scientist with AAFC. “In some rotations, fallow was replaced by pulses and more diversified cropping systems including pulses, canola, and polycultures were added. In these continuous wheat experiments, nutrient cycling, uptake and efficiency, water use efficiency and sustainability (e.g., carbon footprint) comparisons continue. There are also sub-plots within the main experiments that are comparing unfertilized to N and P fertilization as well as investigating legacy P and P cycling. This component is led by AAFC research scientist Barbara Cade-Menun.”

The 0MC experiments compared wheat-fallow base systems under conventional, minimum-till and no-till cropping systems. Along with wheat-fallow and continuous wheat experiments, rotations including lentil, chickpea, and green manure were included. In 1997, wheat-pulse systems were established on plots that had been wheat-fallow under conventional and no-tillage, respectively. “Retired AAFC researcher Brian McConkey also led a project from 1996 to 2018 to monitor soil organic carbon across commercial farm fields in Saskatchewan,” notes St. Luce. “The Prairie Soil Carbon Balance project monitored soil organic carbon after the conversion from fallow and conventional tillage to no-till and continuous cropping from 1996, with 136 benchmark fields that were resampled four times, the final sampling in 2018 where 90 fields were sampled. We are finalizing a study comparing the on-farm results to the soil organic carbon change in the small LTAE plots. Early indications are that the results were trending in the same direction for soil carbon; however, total N was the reverse with more losses in the small plots as compared to the farm fields. We speculate that this was due to higher fertilizer rates on the farm and the higher frequency of canola in rotation. The soil organic carbon rate of change was 0.28 Mg/ha/yr in commercial fields and 0.16 Mg/ha/yr in the LTAE plots.”

The ‘New Rotation’ was established in 1987 as a comparison to the ‘Old Rotation’ under conservation tillage. The rotations have evolved, with durum wheat replacing spring wheat in a diversified rotation with canola and lentil, the inclusion of green manure, and a crested wheatgrass-meadow brome perennial system.

“The New Rotation is managed as no-till, and all of the rotations are fertilized based on soil tests for each rotation,” explains St. Luce. “This gives us the ability to look at nitrogen use efficiency, carbon footprint, and system productivity for each rotation. Almost all of the rotations are fully phased, with each phase of the rotation present each year so that each crop experiences the same conditions. Every year we collect soil samples in spring and fall for nutrient analysis and measure grain yield, grain protein, and N and P in grain and straw. The soil organic carbon levels are significantly higher in the perennial grass as compared to the annual cropping systems. In 2022, the New Rotation became fully no-till as we transitioned from termination of the green manure through shallow tillage to herbicide kill.”

St. Luce emphasizes the value of the LTAEs that provide information to better understand and address climate change, carbon sequestration, greenhouse gas emissions, NUE and crop selection, especially for the Brown soil zone where moisture is the most limiting factor. “Like other LTAEs in Canada and internationally, we have archived soil and plant samples and detailed information going back to the 1960s. We are working on developing the first soil spectral library for the Prairies using the samples and information from the various LTAEs across the Canadian Prairies. Our LTAEs are also getting national and international attention, such as the inclusion of Swift Current, Indian Head, Lethbridge and One-Four in the recent North American Project to Evaluate Soil Health Measurements (NAPESHM) project, which includes 120 long-term agricultural research sites spanning from north-central Canada to southern Mexico. More than 20 indicators were used to evaluate effective measurements for soil health and to contribute to calibrating and validating models such as carbon change models. Unlike short three- to five-year funded projects, the LTAEs and continuous experiments on the same fields undergoing so many environmental conditions over time result in a solid data set to reach conclusions and make recommendations for a wide range of areas from agronomy, economics, soils, nutrient cycling, water management to climate change, resiliency and sustainability.”

“To ensure we continue the legacy of this unique and valuable long-term agroecosystem resource that AAFC has invested in over the years, we are collectively working to integrate the resources into a more accessible database system for our researchers,” says Geddes. “We know this resource has already been very useful over the years and going forward has relevance for new work, such as new molecular technologies focused on the soil microbiome and other new technologies. This multi-decadal experimental system will remain a precious tool for testing novel research hypotheses, developing and verifying ecosystem models, providing a deeper view of agricultural sustainability and determining whether old or new production systems truly stand the ‘test of time’. This long-term agroecosystem resource will continue to be valuable for addressing other research questions into the future, some we likely haven’t even thought of yet.” 

Advertisement

Stories continue below