Top Crop Manager

Features Research Soil
Water availability and crop outcomes in Prairie cropping systems

Building resilience into water-limited cropping systems on the Prairies.

March 8, 2024  By Donna Fleury


Research shows that hydrology, snowfall accumulation, snowmelt, spring and fall rains and their interactions are all very important factors driving crop growth. All photos courtesy of Phillip Harder, Cropmistic Technology Inc.

Several factors drive crop growth and production in Prairie dryland agriculture systems, including year-round hydrology and seasonal water balance. Researchers are interested in understanding the interactions of various hydrological factors and cropping practices that impact water availability and crop water use in water-limited cropping systems.

“There is a long-running interest in how we can better manage crop water availability with improved management practices,” says Phillip Harder, former research associate with the Centre for Hydrology at the University of Saskatchewan. Harder is now research director and hydrological scientist with Croptimistic Technology Inc., an agtech company specializing in SWAT MAPS for precision agriculture and variable rate mapping.

“There has been a lot of previous research focused on individual practices such as conservation tillage, stubble and residue management and other practices that impact crop outcomes,” he says. “However, we also recognize that crop water use in Prairie dryland agriculture systems depends on hydrology throughout all seasons, which requires a better understanding of complex snow-soil-energy-water interactions to describe the impact of changing management practices. With the recent developments in field-scale sensor technologies and more comprehensive modeling platforms, we are better able to evaluate the complex interactions of these individual management practices and hydrological processes, and ultimately quantify water availability and crop use.”

Advertisement

Water is limited on the Prairies, making water conservation an ongoing objective that requires consideration of the seasonal water balance and long-term water storage. “In a recent research project [as part of the USask-led Global Water Futures Program] at a site near Saskatoon, our objectives were to quantify the crop water use and the water balance in the field,” explains Harder. “We implemented very intensive field-scale observation trials on various crops grown in commercial fields to determine whether the water balance was coming from rainfall during the growing season, snowfall accumulation and snowmelt or other factors outside of the growing season. We also wanted to understand how stubble and residue management influences crop available water and if it can be manipulated with stubble and residue management. The project included significant efforts to quantify those terms and describe the processes, as well as to develop modeling capacity so we could predict or simulate impacts of crop production practices on the water balance.”

The results showed that hydrology, snowfall accumulation, snowmelt, spring and fall rains and their interactions are all important factors driving crop growth. Water is generally limited, and even in dry years like 2022, many growers saw good yields despite hardly any rainfall. 

“This shows that crop growth wasn’t just a result of rainfall; a significant amount of snowfall and snowmelt infiltration played a role,” adds Harder. “To understand crop potential, it is important to understand the long-term storage of water in the soil across the entire profile, not just in the top 10 cm. These are long-term cycles, but there can potentially be a lot more water available than expected.”

“There are some good examples from our research. In 2015 and 2016, field conditions were on the wetter side and overall rainfall matched crop water use. However, in 2017 rainfall did not match crop water use, with canola using 220 mm of water while in-season rainfall was 67 mm. Our observations demonstrated that winter processes tended to provide the most consistent water input, on average about 50 mm, whereas summer precipitation tends to be at a deficit of 104 mm on average. Therefore, understanding where that available water is coming from over the long term and the impact of moisture accumulation from previous years is really important.”

Although growers can’t control the weather or the amount of snowfall or rainfall they receive, there are good practices that can impact crop water availability and build resilience into cropping systems. Long-term practices such as minimum and zero-till cropping systems, stubble and residue management have proven to be very important. Stubble heights and crop residues impact water availability and can be manipulated to improve crop available soil water. The continued implementation of these best practices and using those principles to maximize crop water availability is necessary. Growers can also expect significant hydrological benefits for particular technologies such as stripper headers, disc drills and others, although they may not be applicable to individual cropping systems.

“Our research projects, including 15 years of water balance observations, show stubble residue management impacts the complex interactions of snow-soil-energy-water,” explains Harder. “Increasing stubble height increases water input and increasing residue cover increases water retention. From a water balance perspective, optimization of stubble to increase snow retention and crop residues to reduce soil evaporation has the potential to increase growing season water availability by up to 20 or 30 per cent. Stubble height management for snow trapping continues to be one tool that can very effectively change the amount of water coming in or out of cropping systems. In earlier research comparing the impact of stubble heights on snow collected in fields in both Swift Current and Saskatoon, the results showed that on average, one millimetre of water is retained for every additional centimetre of stubble left behind. This is in addition to what other moisture may be collected, depending, of course, on the snowfall in that year with greater potential in heavy snow years. Under drought conditions, there may not be a lot of extra stubble or residue to manage in that particular season, but over the long term, those many benefits will be realized.”

“There are also new technologies, sensors, tools and services available to help understand soil moisture conditions; however, the challenge remains in interpreting all of the data collected into usable information,” says Harder. “Some technologies are not yet available, such as satellite remote sensing to predict root zone moisture at management scales. Growers can look to information, including soil moisture conditions, from the many weather stations located across the Prairies. However, the challenge of using soil moisture to try and make a decision is you can’t just use a regional number. Every single field will be different, depending on crop type, the stubble from last year, the crop residue status and other factors. Every field has a legacy of decisions on it that make it unique in trying to understand the actual soil moisture in individual field profiles.”

Harder emphasizes that hydrology, snowfall accumulation and snowmelt, spring and fall rains, and their interactions are all very important factors driving crop growth in water-limited dryland areas, particularly the southerly parts of the province. Minimizing disturbance and implementing practices to reduce soil evaporation and capture as much moisture as possible through the seasons should be built into planning decisions. Although the weather can’t be changed, building more resilience into cropping systems to manage the impacts of increasingly variable weather conditions and optimizing crop water availability in water-limited dryland agriculture in the Prairies is imperative. 

Advertisement

Stories continue below