Salinity Mapping for Precision Variable Rate Fertilizer Application

The incidence of saline-affected areas in irrigated fields restricts crop growth. 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. This can lead to a build up of excess nutrients, especially N and P. The potential outcome of the project is to use salinity level designated management zones to variable rate apply nutrients on the cropped fields. It is planned to delineate at least four variable rate fertilizer rate management zones in the mapped area. For example as follows: 1) non-saline zone, 0 to 0.5 mS/cm, receiving full rate fertilizer applications; 2) low level salinity zone, 0.5 to 2 mS/cm, receiving about a 0.75 rate of fertilizer compared to the zone 1; 3) moderate salinity zone, 2 to 4 mS/cm, receiving about 0.5 rate of fertilizer compared to zone 1; and 4) very saline zone, > 4 mS/cm, not receiving any fertilizer.

A Veris™ salinity mapping unit was used on an irrigated farm near Stavely, AB, on October 29 through to November 1, 2014. The field mapping done included 1,400 irrigated acres of the 10,000 acre farm. The farm supplied an auto-steer equipped tractor, and an operator for the project. Salinity mapping was done on 50 ft wide transects over the mapped area.

Each of the delineated salinity, or lack of salinity zones, will be soil sampled separately, by taking soil samples from 15 random points from within the zone on a 320 acre field basis. The soil sampling will be done to a depth of 4 ft as follows: 0 to 6, 6 to 12, 12 to 24, and 24 to 48 in. The farm manager will separately obtain satellite image derived Normalized Difference Vegetation Index (NDVI) crop productivity zones, based on at least 10 years of satellite images, generated by the Farmers Edge Precision Agriculture consulting group. The NDVI generated crop management zones will be compared to the Veris™ generated soil salinity management zones. A final report will be completed by the fall of 2015.