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ACTIVAT: How genomics research and crop rotations could reduce GHGs

Crop Rotations, Genomics and Reducing the Costs of Crop Production

It’s a real quandary. Food producers are feeling increasing pressures to deliver high crop yields to meet increasing public demand, while at the same time, facing pressures to reduce greenhouse gas emissions on the farm. Now, researchers are looking at crop rotations and new crop varieties as a possible solution to a very difficult problem.

By Genome Prairie staff

Food producers across Canada, particularly in the prairie region, face multiple future crop growth challenges. The spread of diseases like Fusarium head blight and increasing drought events from climate change are impacting annual yields. With the battles fighting disease and lack of moisture ongoing, demands for greater annual yields are growing.

While the demand for greater crop yields is rising, pressures are also increasing on producers to scale back greenhouse gas emissions (GHGs) from crop production, including reducing synthetic fertilizers. In 2021, the Government of Canada unveiled a strategy to reduce greenhouse gas emissions by 40% of 2005 levels. According to a 2021 Agriculture and Agri-Food Canada study, agriculture (crops and livestock) accounts for just under 10 percent of Canada’s total GHG output. That’s slightly less than what’s emitted yearly from driving cars and trucks.

It’s a difficult juggling act, to say the least, for producers needing to increase their yields while scaling back their GHG emissions.

The drive to produce more while emitting less has resulted in great interest within the research community to find near and long-term solutions. At the University of Saskatchewan’s Crop Development Centre (CDC), researchers are focusing on crop rotation as a possible strategy to achieve these goals.

In late September 2023, Genome Canada and Genome Prairie announced funding of ACTIVAT, a genomics-based research project focused on strategies to enhance yields while reducing GHG emissions. The ACTIVAT project (short for “Accelerate Climate-Smart Crop Delivery”) is led by Dr. Kirstin Bett from the College of Agriculture and Bioresources at the University of Saskatchewan and Dr. Curtis Pozniak, Director of the Crop Development Centre (also at the U of S).

During the scheduled four-year project, ACTIVAT will develop new varieties (specifically lentils and wheat) that are expected to flourish while being used in crop rotation and simultaneously reduce overall GHG emissions.

“There’s lots of potential in crop rotations,” said Bett. “We’re working on developing new varieties that will help make every year, not just one year, of a rotation profitable.”

“One of our biggest project goals is to help producers to increase their bottom line. To help farmers make more money.”

The Nitrogen Challenge

In addition to finding ways of enhancing year-by-year crop production, Canadian farmers face the ongoing challenge of implementing strategies toward reducing the emission of greenhouse gases.

“One of the big contributors towards GHGs is the application of nitrogen fertilizers,” said Bett. “The problem is crops don’t absorb a portion of these synthetic fertilizers, and so they make their way into groundwater supplies and eventually are released into the atmosphere.”

Nitrogen plays a critical role in the success of any crop. Nitrogen is a central component of amino acids which, in turn, are required for constructing proteins. Proteins themselves play a critical role in the way plants collect energy and develop, and are essential to optimize growth and yield (proteins are absolutely necessary for living cells and tissues, including those in plants, to operate).

In other words, a living organism that lacks a reliable nitrogen supply will have great difficulty growing and reproducing. For crop plants, this means they are less able to tolerate stresses like disease and drought and usually don’t grow as well. Nitrogen-deficient crops perform sub-optimally, with substantially lower yields

Enter the use of fertilizers – specifically, nitrogen-based fertilizers of which nitrogen is a major component. Producers have long used nitrogen fertilizers to supply their crops with sufficient nitrogen. In the past (roughly up to the 1960s), animal manures were mainly used. The production of synthetic nitrogen-containing fertilizers is extremely energy intensive. Today, most fertilizers are mass-produced, using fossil fuels to drive the process, and their production and use is responsible for 5% of all greenhouse gases produced globally.

While invaluable for the efficient production of high yielding crops, the widespread use of nitrogen fertilizers can have environmental drawbacks—particularly with GHG emissions. The primary mechanisms through which nitrogen fertilizers contribute to GHG is through their production, application, and subsequent transformations in the soil if not used by plants.

“When nitrogen fertilizers are used in the field, crops may not efficiently take up a significant portion of the nitrogen. Some of what isn’t taken up can undergo various transformations, leading to GHGs, including the potent greenhouse gas nitrous oxide.” said Bett.

“One big strategy in addressing this inefficiency in nitrogen utilization is modifying crop rotations,” said Bett. “We think this could lead to good yields for farmers and a reduction of GHGs. A best-of-both-worlds scenario is what the ACTIVAT project is working to develop fully.”

The Practice of Crop Rotations

As a farming practice, crop rotation is a planned sequence of different crops on the same land. Crop rotations help enhance soil fertility, reduce the risk of pests and diseases, and optimize overall agricultural productivity. Instead of continuously cultivating the same crop in a particular field year after year, farmers practice annual crop rotation plantings in a specific order based on each crop’s characteristics and nutrient needs.

“A typical rotation in Saskatchewan today is a lentil crop followed by wheat followed by a pulse crop such as beans, peas or chickpeas. Pulse crops have the added advantage in that they are able to obtain their own nitrogen compounds from the air rather than the soil.”

The number of producers who practice rotations, said Bett, is markedly better today than in past generations.

“If you look back 50 years ago, some farmers were planting wheat yearly, and that was it. Then Agriculture and Agri-Food Canada introduced canola, and the Crop Development Centre introduced pulse crops for incorporating into crop rotations, so we’ve seen a broadening of options.”

In addition to potentially growing more plentiful crops, the practice of crop rotation can also break the cycle of impactful diseases like Fusarium head blight.

“Crop rotations break disease cycles. Growing the same crop, like wheat or canola or a pulse year after year, could lead to the establishment of diseases in a field,” said Bett. “So growing different crops from year to year and preventing disease establishment has huge benefits because diseases affect yield and can be very expensive to eradicate.”

“Crop disease is an ongoing and big challenge. For example, lentils and peas share many diseases, particularly root rot, which has hurt the bottom line for many producers.”

Besides harming annual yields, managing crop diseases can be costly and energy-intensive.

“One of the incentives to grow crops in rotations is reducing the cost and time required to manage diseases. Fighting disease often means you must spray your entire field, which means driving a tractor back and forth.

“So you need to break this disease cycle. That’s where crop rotations come into play. In that case, it can reduce field spraying, which invariably means fewer GHG emissions.

Bett said in an ideal scenario a typical farm would have a larger rotation schedule with at least 5 or six, and preferably eight, different crops. However, the options currently offered are narrow.

“There is a limitation because typically only a few different crop species are grown. A model crop rotation would be eight species, but I’m unaware of many producers doing that many.”

Nonetheless, Bett is optimistic that the ACTIVAT will help push the needle towards more diverse rotation practices.

“We aim to have two pulse crops available for every acre in Western Canada. Ideally, there would be an eight-year crop rotation where you’d have two lentils, a cereal crop, a canola crop, and so on.”

“The ACTIVAT project will develop new crop varieties that will entice farmers because they will continue to deliver high yield, high quality and high disease and stress resilience. We’re trying also to make these varieties work great in crop rotations together and, as a bonus, reduce GHG emissions.”

Developing New Varieties for Crop Rotations

While aiming to fight disease, enhance yields, and lower GHG emissions, the ACTIVAT project will use genomics to develop new varieties that complement each other in crop rotations.

“Dr. Pozniak is working with a wild cereal line that reduces biological nitrification,” said Bett. “Preventing nitrification of unused nitrogen compounds in fertilizer is a major goal as this prevents the production of nitrous oxide, which is an extremely potent greenhouse gas. The CDC has identified strains that can slow down nitrification, so they’ll do genomic mapping to figure out which region of the wild cereal’s genome is responsible.

“The ACTIVAT project will be busy working on introgressing this nitrification trait from the wild species into a domesticated species [introgression is the stable introduction of gene from one species to another typically using conventional breeding techniques]. Introgressing nitrification reduction will have a huge impact on reducing major GHG emissions in wheat as less fertilizer will be required and lower amounts of nitrous oxide will be released.

“Once we’ve done the introgression, we will examine how each performs in a rotation. So it’s a double-win if you can layer better use of nitrogen by reducing nitrification and use these varieties in rotations.”

Bett said a particular curiosity and project focus are pulse crops (peas, lentils, chickpeas, among others), which appear to be very beneficial in a rotation.

“We want to have a better understanding of pulses. We know that pulses fix their own nitrogen. Farmers tell us they get a better wheat crop following after a lentil crop. They’re getting increased yield per unit area and higher quality.

“We don’t know exactly why this is happening. Part of it might be nitrogen left behind by the pulse crop. Part of it might be altered microbial communities. We’re not entirely sure.

“At least half of this project’s efforts will be focused on breeding lentils and wheat to work well in specific rotations.”

The Future of Farming

From Bett’s perspective, whether producers adopt strategies like crop rotations and genomically selected varieties will come down to “dollars and sense”.

“For rotations, it’s a mixed bag right now. It all boils down to economics. Farmers may believe it’s important to rotate crops. Still, at the end of the day, if their calculations say it’s cheaper to grow canola on canola, they’ll grow canola on canola.

“So we have to think about how can we incentivize farmers to rotate their crops. It may require government initiatives to encourage rotations. It may come from market forces like distributors who would like to label their food products as climate-smart or climate-friendly.”

Still, Bett is upbeat that the multiple beneficial outcomes from ACTIVAT, with its emphasis on farming using rotations, reducing fertilizer costs and reducing greenhouse gas emissions, will eventually win the day.

“In the short term, growing a crop on a crop works but in the long term, rotations pay off. Those who think about it long term might eat a loss in a given year, but over a few years, they’ll come out ahead.”


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