Diversified Crop Rotations Can Offset Drought-Induced Yield Losses
In a recent cropping systems study across the prairies, results showed that precipitation and N-management are primary factors affecting yield performance. Precipitation explained 25% of the yield variations while N management explained 21% of the yield variations. Diversified rotations tended to increase yield performance faster and also demonstrated greater resource use efficiency, achieving higher yields with lower N inputs. Adopting diversified rotations suited to local conditions and enhancing N management through fertilizers and pulse crops can help mitigate yield loss and optimize crop productivity and resiliency, particularly under drought and heat stress conditions.
Optimizing cropping system productivity and resiliency can be challenging under increasingly variable climate conditions. Particularly in the low precipitation semi-arid regions in the Prairies, developing targeted management strategies to improve productivity under drought and heat stress conditions are key to maximizing cropping system performance and economic returns.
As part of a larger cropping systems project across the prairies, the goal of this study was to evaluate how rotations could offset drought-induced yield losses and improve cropping system productivity and resiliency. This five-year study conducted at six sites in western Canada from 2018 to 2022 compared six rotation systems including: conventional, intensified, diversified, market driven, high risk-high reward and a soil health-focused systems. The objectives of the study were to assess protein-based yield performance across the six rotation systems, identify key factors affecting productivity, and evaluate how rotations, precipitation and N-management impact yield performance.
The experiments evaluated cropping systems across various ecosites including at Beaverlodge, Lethbridge, and Lacombe, Alberta; and Scott, Swift Current, and Melfort, Saskatchewan. The no-till cropping sequences at each site were tailored to local soil attributes, climatic conditions, and farming practices. In the year prior to the study, all fields were seeded with cereals, followed by a four-year-based rotation.
The N fertilizer applications were adjusted based on soil test recommendations and target yield, with urea (46-0-0) applied as the N source at all sites except Lethbridge where ammonium nitrate (34.5-0-0) was used. No N fertilizers were applied to pulse and intercrops between 2018 and 2021, except for minor N input from compound fertilizer. In 2022, intercrops received N at 25% of the recommended monocrop N rate for the non-pulse monocrop component. Based on soil test recommendations, phosphorus (P) fertilizer rates were determined based on soil test recommendations, with a minimum application rate of 15 lbs P2O5/ac (17 kg/ha). For each crop, precipitation and air temperature from planting to physiological maturity were recorded.
Diversified crops stabilized yields
Overall, the results from this study showed that precipitation and N management are the primary factors affecting cropping system productivity. Precipitation explained 25% of the yield variations while N management explained 21% of the yield variations. Precipitation also had a significant indirect effect on protein-based yield by affecting biological N fixation of pulse crops. Across the study sites, almost all of the site years experienced some level of drought, with 36% of those site years reporting precipitation levels less than half the 30-year average. A 10% reduction in precipitation showed substantial decreases in grain yield, as did even a 10% increase in air temperature and slight to moderate heat stress.
The study concluded that more diverse crop rotations showed significant advantages over traditional cropping systems. This benefit became more pronounced over time due to enhanced resilience to drought and heat stresses. The results showed that increasing pulse frequency and rotation complexity during low rainfall seasons mitigated yield loss by 10 to 24%. Overall, all rotations compared to the control showed an increasing trend in protein-based yield over time. The diversified rotations increased 13 to 28% faster than market-driven and intensified rotations, and also demonstrated greater resource use efficiency, achieving higher yields with lower N inputs.
Since the most important factors affecting cropping system performance are shown to be precipitation and N management, growers will need to develop site-specific cropping systems by selecting crops that best suit their local conditions. Adopting diversified rotations and enhancing N management through fertilizers and pulse crops can help improve crop productivity and resiliency.
Overall, developing target management strategies suited to local conditions to improve cropping system productivity, particularly under drought and heat stress conditions will help mitigate yield loss and improve profitability particularly in the low precipitation semi-arid regions in the prairies.
Funding for the study was provided by the Western Grains Research Foundation, Alberta Pulse Growers, Sask Wheat, Sask Canola, Alberta Wheat Commission, Manitoba Crop Alliance and Agriculture and Agri-food Canada (AAFC) through the Integrated Crop Agronomy Cluster as part of the Canadian Agricultural Partnership AgriScience program.
Guoqi Wen, Kui Liu, Hiroshi Kubota, Gary Peng, Greg Semach, Prabhath Lokuruge, Henry Wai Chau, and Mohammad Khakbazan. 2024. Precipitation and nitrogen management are key drivers of cropping system productivity in the Canadian prairies. Canadian Journal of Plant Science. 00: 1-12. https://dx.doi.org/10.1139/cjps-2024-0114
Photo courtesy Kui Lui, AAFC
