Canola yield sensitivity to climate indicators and passive microwave-derived soil moisture estimates in Saskatchewan, Canada

© 2019 Canola production is primarily attributed to variations in precipitation and temperature, however the direct relationship between soil moisture and canola yield has yet to be fully evaluated. Recent advancements in microwave remote sensing offer the potential for timely and accurate acquisitions of large-scale soil moisture data; however, the short temporal record of these data sets presents a challenge for defining extreme soil moisture events, and satellite limitations surrounding the detection of surface conditions prevents a direct agronomic link between satellite soil moisture and plant available water. This study examines the potential of passive microwave surface soil moisture observations from the Soil Moisture Ocean Salinity (SMOS) mission satellite as an indicator of canola yields across Saskatchewan over a 6-year period from 2010–2015. An iterative chi-square analysis was employed to investigate the association between SMOS soil moisture and canola yield data from Saskatchewan's 20 Census Agricultural Regions (CARs). Associations between canola yield and traditionally used climate indicators (temperature and rainfall) were compared to assess the relative effectiveness of SMOS soil moisture as an indicator of yield. Cooler-than-average temperatures (T max ≤ 26 °C and T min ≤ 12 °C) at the beginning of August were shown to have a positive impact on canola yield, while high nocturnal temperatures (T min ≥ 15 °C) in mid-July had a negative effect. Precipitation was found to have a minimal impact on canola production due to greater-than-average rainfall that was observed during the period of study. The strongest associations were observed between soil moisture and canola yield, particularly in low-yielding years with excess soil moisture exhibiting significant associations (p < 0.01, df = 1) throughout the growing season. The beginning of June, coinciding with the stand establishment stage, was identified as a critical time period in which excess soil moisture (≥26.6%) resulted in yield losses. The findings of this study suggest that soil moisture observations obtained by passive microwave satellites, such as SMOS, may provide an effective indicator of crop yields, particularly in areas experiencing excess soil moisture conditions.