Reasonable Water Governance When Cultivating Lowbush Blueberry in a Variable and Changing Climate

Quebec is the largest producer of lowbush blueberries in Canada, generating 35% of the overall market production. The production is processed and sold on the Canadian market (15%) or exported (85%).

In 2012, the value of exports from Quebec plants amounted to nearly $90 million. However, the sector is subject to significant fluctuations of the production and export volumes due to the damage caused by frost and drought.

This variability in the production and the offer for exportation is posing a challenge. Irrigation against frost or to avoid water stress is a potential solution to stabilize yields. However, the use of this type of measure remains marginal in Quebec given the scale of investment and the required volumes of water, and the lack of knowledge about its implementation and profitability.

This measure thus warrants further examination, in particular in the current climate and by taking climate change into account.

• Develop an approach to optimize water management in the production of lowbush blueberries and verify the robustness of this approach in the context of a variable and changing climate.

• Development of knowledge and tools for irrigating according to the risk of frost and water stress, based on data resulting from experiments in blueberry fields and a bioclimatic model of the phenological development of lowbush blueberry;

• Assessment of the impact of climate change on the risk of frost and water stress in major production regions of Quebec by combining the phenology model and a water balance-based approach to climate scenarios for 2050;

• Analysis of financial profitability scenarios and irrigation systems in current and future climates.

Statistical analysis of the results did not reveal any significant relationships between the four water regimes studied and the yields measured in the plots. The highest yields, as well as the lowest, were measured in both irrigated and non-irrigated plots. The high variability of yields observed in the plots, linked to factors other than the water regime, could explain these results

In the context of the study (climate and crop management), the water extraction of a blueberry field is low when compared to other crops, which gives it greater autonomy between irrigations. As a result, the risk of the crop becoming water stressed is low. In the context of the study, a soil reserve of 20 mm of readily available water (RAW) could be depleted on 4.6 to 9.0 days per season in the current climate in the production area around Lac Saint-Jean (1981-2010).

This risk could increase due to climate change in these low-RAW soils. Thus, for the period 2041-2070, 20 mm of RAW could be depleted on 4.6 to 13.5 days (low-change scenario) and 9.1 to 22.5 days (high-change scenario) per season (Figure 1). However, the risk of water stress must always be evaluated individually for each operation.

Meanwhile water extraction, which was measured on a continuous basis, suggests that the potential yield of the monitored blueberry fields is quite likely higher. Currently, water extraction is generally 50% below the potential evapotranspiration demand.

Most crops reach 100% of potential evapotranspiration at some point in the season. If this assumption proves to be true and yields were to increase and become more homogeneous within plots, the risk of water stress could increase.

The analysis carried out under this project showed that the risk of frost damage to flowers will not change significantly for the period 2041-2070 compared to 1981-2010. This risk is currently quite low but can, in some cases, be higher depending on the location and layout of the blueberry field.

Figure 1: Number of days of zero water balance in lowbush blueberry (RAW=20 mm, crop coefficient Kc=0.45), from shoot emergence to October 31: a) 1981-2010 period, b) high change scenario (2041-2070).

In the current context (cost of crop insurance, blueberry selling price, cost of irrigation systems, climate), investing in an irrigation system does not appear to be advantageous compared to crop insurance, if the purpose of the system is primarily or solely to manage climate risk.

If irrigation is considered, it is recommended that producers use decision support tools—both for managing irrigation and for assessing its appropriateness—, conduct small-scale trials, select an irrigation system that is appropriate for the intended purpose, prioritize the most productive fields, and ensure that the water supply is sufficient in quantity and quality

• Agriculture and Agri-Food Canada (AAC)

• Bleuetière des Blanc Ferme forestière Paul Grenon & fils

• Ministère de l’Agriculture, des Pêcheries et de l’Alimentation (MAPAQ)

• Université du Québec à Chicoutimi (UQAC)