THE EFFECTS OF SITE-SPECIFIC IRRIGATION MANAGEMENT ON SOIL MOISTURE AND POTATO PRODUCTION IN SOUTHERN ALBERTA

Abstract

Site-specific water management can increase water use efficiency by up to 30% but determining whether adopting the technology for site-specific irrigation will be beneficial enough to consider the additional cost is still an open question. The objectives of this study are to determine the effect of site-specific water management has on soil moisture at a field scale and to determine whether site-specific water management can reduce yield variability. Additionally, the heterogeneity of soil apparent electrical conductivity and elevation was explored as driving factors in soil moisture differences between management zones delineated using these variables. Russet Burbank potatoes were grown in Southern Alberta in a field divided into three management zones. In a two-year study conducted in the growing seasons of 2018 and 2019, plots were delineated from each of the management zones and treated with site-specific irrigation prescriptions, while uniform irrigation was used for the rest of the study area. The effect of site-specific irrigation was monitored using soil moisture sensors installed in each of the plots. The effect of uniform irrigation was also monitored using soil moisture sensors installed in the management zones in areas under uniform irrigation prescriptions. The site-specific irrigation schedule was based on an 80% maximum allowable depletion of available soil moisture. Soil moisture depletion was calculated from soil moisture sensor data for each plot. Soil moisture sensors were also used to assess soil water movement in the rootzone. Soil moisture surveys were conducted at 15 cm and 30 cm depths and were used to spatially assess soil moisture by co-kriging soil moisture surveys with soil apparent electrical conductivity and elevation. Yield variability was not improved under site-specific irrigation, but in some areas, a 10-30% reduction in total irrigation did not negatively impact yield. Hydrological differences were determined between the management zones, but relationships between soil moisture and the management zones could not be confirmed due to a lack of soil moisture sensor data. The reliance on soil moisture sensors to inform the irrigation prescriptions may have led to a moisture deficit which resulted in lower potato yields. This effect could be mitigated by installing additional soil moisture sensors in each of the management zones to provide a method to corroborate soil moisture observations. Assessing field properties for variability is a prudent step before determining whether a management zone derived site-specific irrigation management strategy informed by soil moisture sensor data as some fields may show more benefits using observational experience.