There are no silver bullets in agriculture — agro-ecosystems are too complex for any one tool to guarantee outcomes. All the same, some tools seem to have an outsized benefit.
This holds true for pulses, according to a suite of research studies led by Agriculture and Agri-Food Canada (AAFC) research scientist Yantai Gan, whose focus is alternative crops and diversification. Over the last 15 years he has led projects funded by partners including AAFC, the Agricultural Development Fund of Saskatchewan, Western Grains Research Foundation, SaskPulse and the Canola Council of Canada. Their aims were to develop diversified cropping systems which increase productivity, soil health and sustainability while decreasing their environmental footprint.
One study which began in 2010 at Swift Current, Sask., and Brooks, Alta., looks at pulse-intensified rotations (lentil, chickpea and pea). Researchers compare a variety of rotations including continuous wheat, wheat-wheat-oilseed-pulse, and pulse-intensified systems for their impact on soil bacterial communities.
Another study which ran for four years from 2012 to 2016 at Indian Head, Sask., looked at fungal communities in cropping systems containing pea, lentil, hybrid canola, wheat and oats.
A new “Cluster” study under the Canadian Partnership Program began in 2018 and will run until 2022 on seven sites across the Prairies. This study, in which pulse- or oilseed-intensified rotations are compared with other rotation systems under a variety of management techniques in different soil zones, aims to improve system resiliency and sustainability. Gan says the study uses best management practices as a check and improves upon them in side-by-side plots to find out how to build more productive and resilient rotations.
“Our overall goal is to develop the best crop rotation systems for each of those eco-zones to increase productivity and enhance resilience and long-term soil health and sustainability,” Gan says. “Sometimes the farmer is looking for outcomes in the current year or the year after, but they may not be looking at productivity over five-year cycles. We’re trying to see which system is most productive and resilient to abiotic and biotic stressors, disturbance from market instability or disease outbreaks, or other unexpected events.”
Gan says that as pulses have been part of Canadian cropping systems for two decades, some of their benefits are well known.
Even when markets fluctuate, such as with the recent drop in lentil prices, Gan says Canadian producers recognize the longer-term payoffs from pulses.
For example, lentils and peas are shallow-rooting and don’t pick up water and nutrients below two feet. This means those nutrients remain in the soil as credits for deeper-rooted crops like corn and canola in following years.
Pulses are also efficient nitrogen fixers. Gan’s post-doctoral student Zakir Hossain recently published a study showing that lentil and pea can fix 60 to 80 pounds of nitrogen per acre each year. Chickpeas and fababeans can fix even more.
But the benefits of pulses to overall soil health, specifically soil microbial community structure and function, are not well understood, says Kui Liu, a researcher on Gan’s team who is currently working on the system resiliency study.
In a three-year rotation with nine site-years in Western Canada, the team found that adding lentils enhances the productivity of oilseed-cereal cropping systems by 24 per cent compared with conventional systems. In that study, the positive rotational effect of lentil persisted for at least two years.
Also on that team, Gan’s post-doctoral student Adriane Navarro-Borrell found that pulses had a positive legacy effect on subsequent wheat crops. Pulses, particularly peas, influenced fungal populations which benefit the following wheat crop.
Gan says his research team is not “promoting pulses per se.”
“We are looking at how the pulse-intensified systems, or higher frequencies of pulses, affect the soils,” he says. “We’re looking at how pulses can benefit systems. But if you plant too many pulses in a rotation you get a buildup of pathogens.”
Gan doesn’t like offering specific rotation advice to producers, because conditions vary too much across the Prairies for one prescription to work everywhere. For example, producers in the Indian Head area can’t get away with planting too much lentil or pea, but could in drier areas such as Swift Current or Brooks where disease pressure is lower. “We got lots of phone calls and emails from farmers asking what to put on their fields. We can only give them principles,” Gan says.
The one piece of advice he can offer is to diversify. “That you will never get wrong — diversifying pulses with oilseeds and cereals. Then you’ll be safer in terms of pathogen buildup and market risks,” he says.
Liu adds that producers should emphasize thinking of their cropping systems as “ecosystems,” assessing not just the immediate but the long-term impacts of farming practices on their crops and soils. “The research we’re doing now is focused on systems — I’d encourage farmers to think on this level,” he says.