How-to use LandMapper and consumer-grade GPS data-logger to quickly map salinity on farm fields

Task on hand: estimate salinity level on fields planned for rice next year. Six fields with total area of 322 acres were selected by farmer.

Equipment on hand: two LandMappers with different size probes attached (measuring electrical conductivity (EC) down to ~ 8” and 18”), Columbus GPS data-logger, all-road vehicle or “Mule”. Three people: farmer driving a '”mule” and recording data on paper, one person measuring with Landmapper at 18” depth, other person measuring EC with LandMapper to 8” depth and recording POI or way points with GPS. Results: 30 points recorded in less than 1.5 hour (including about 45 min break to wait out the rain). EC in the field varied from 5 mS/m to 106 mS/m on surface; and from 19 mS/m to 400 mS/m in deeper layer.

Problems encountered: pouring rain, all electronics got wet, one LandMapper refused to store data (so it is always a good idea to write measurements on paper as a backup :), we did small repair of probe banana-plug contact with pocket knife.

To see what type of soils are on the farm and where we measured EC, download and install Google Earth from http://earth.google.com . Then go to Google Earth Interface and download soilweb.kmz plugin. Save it to your harddrive. In Google Earth program go to File/Open and open attached .kml and KMZ files. You will see locations of our measurements, satellite imagery of the fields and outlines of soil map units. Clicking on yellow abbreviations bring quick reference about soil series name and profile. Clicking on soil name brings you a lot of detail information about soil properties, scientific soil name, typical native plant (with hyperlinks to plant database) and recommended soil usage. This database is maintained by UC Davis.

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