Phosul Rock Phosphate Potato Trial in High pH Soils

A comparitive fertilizer trial was started in Sugar City, Idaho on high pH soils seeded to potatoes by Circle P Farms. Phosul (0-16-0-4), which is a blend of Fertoz Rock Phosphate, plus other important soil amendements was compared to a standard fertilizer treatment. Two months after seeding, some initial observations show good plant above ground biomass resulting from the fall application of Phosul, as compared to standard P fertilizer applications. While the initial field observations are encouraging, we plan to assess plant biomass and yield data post harvest.


The fields seeded to potatos (May 12th, 2022) contained alkaline soils, with pH of 8.6. Nitrogen and potash fertilizer was equally applied. Application rates and timing are indicated in the table below. Both fields were seeded on the same day using the same seeding equipment, with similar settings and row spacing.


Total Nutrient Content from Fertilizer Applications (Approximate)

Initial Results

Visible differences were observed in the Phosul treated fields compared to the MAP treated fields in these photos, with the potato plants in the Phosul treated fields having larger plants with more ground cover.

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