Salinity Mapping for Precision Variable Rate Fertilizer Application

The incidence of salinity affected areas in irrigated fields results in restricted crop growth in the saline areas. If fertilizer applications are a constant rate blanket application over the field, the saline affected areas receive a greater rate of nutrients than the crop can use, because crop growth in the salt-affected areas is less and yields lower. This results in an excess application of nutrients compared to what the crop will use. The purpose of the project is to assess the levels of salinity in designated zones on the fields of the study area. This applied research project was coordinated by Mr. Dick Puurveen of the University of Alberta – Renewable Resources Department. A Veris™ salinity mapping unit was used on an irrigated farm, Clear Lake Colony, near Stavely, Alberta, on October 29 through to November 1, 2014. The field mapping included 1,400 irrigated acres of the 10,000 A farm. Using Global Position System (GPS) tagging, salinity levels were recorded in the area mapped. Salinity mapping was done on 50 ft wide transects over the mapped area.

The landscape and soils of the Clear Lake Colony farm are described as a veneer to blanket of sandy loam to loamy sand, glacial fluvial deposits overlying clay loam-textured glacial till. It is rolling to undulating in slope. The soils have been developed for irrigation for the last 15 years. The lower landscape areas have become salinized since irrigation began. In early 2015, soil samples were taken at three depths (0 to 6, 6 to 24, and 24 to 48 in.) in select transects going from map points delineated as very saline, moderately saline, slightly saline and non-saline, based on the maps generated from the previous Veris salinity mapping. The soil samples were analyzed by the Farmers Edge Laboratory, Winnipeg, Manitoba, and tested for plant-available nutrients, salinity, pH, cation exchange capacity, and base cation saturation.

The average salinity (electrical conductivity) in the 0 to 6 in. depth was respectively 4.8, 2.4, 0.8, and 0.3 dS/m, going from the high to low salinity areas, based on the map unit areas described above. The farm manager plans to work with their crop consultant to produce fertilizer rate maps to variably apply fertilizer by salinity zone, specifically reducing fertilizer rates on the severely saline, and moderately saline areas. A final project report will be completed in 2016.