Potassium considerations for southern Idaho soils

Potato tuber yields of over 500 cwt/A are being achieved by many of Idaho's potato growers. At this production level, tubers can remove over 200 lbs K/A. A recent study (Westermann and Tindall, 1995) showed that many southern Idaho fields responded to a K fertilizer application when the soil test K concentration was less than 175 ppm K in top 12 inches of soil. That study also showed that the K fertilization rate necessary to achieve maximum yields at a given soil test K concentration was significantly higher than that presently recommended in the fertilizer guide for potatoes (McDole et at., 1987)