Sulfur (S)

For minimum sulfur requirement for potato production, irrigation water may provide some or all of the needs. The water may be tested for S content. In sandy, low organic soils as used in most potato production in the Northern States, a soil test will help determine S deficiencies. S is most available in soils with pH greater than 6.0; availability gradually decreases as pH decreases below this level. Table 1 gives S fertilizer rates to avoid deficiency based on soil S levels.

There are no market pressures on S application as there are with N, P and K fertilization. However, there may be disease pressures affecting the desired amount of S fertilization (Pavlista, A.D.  1993. Control of Common Scab with Sulfur and Ammonium Sulfate. Spudman 31(8):13,32,34). There is evidence suggesting that higher amounts of sulfur applied in-furrow can substantially decrease tuber infection by common scab and black scurf. Common scab is especially important in the table-stock and chip-stock markets and somewhat important in the other two major markets. Black scurf is especially important in the  table-stock and seed-stock markets. The best form of sulfur to apply is ammonium sulfate (AS) placed in the furrow at planting. Table 2 gives the effect of AS and the equivalent S on these two soil-borne diseases.

Nutrients: Deficiency and Excess Symptoms

The minimum sulfur requirement for potato production is usually satisfied by irrigation water. The water may be tested for S content. In sandy, low organic soils as used in most potato production in the Northern States, a soil test will help determine S deficiencies. To avoid S deficiency symptoms, 25 lb S/acre is sufficient even in the absence of S in the soil or water. S may be added in many forms (Table 3).

Sulfur deficiency is rare. There is a general yellowing of leaves and leaflets exhibit a slight upward roll. This yellowing is first observed with young leaves and is uniform on affected leaves.

There are no negative effects associated with excessive S.

Resources

Pavlista, A.D. 1995. Potato Production Stages: Scheduling Key Practices. EC95-1249. University of Nebraska Cooperative Extension, Lincoln, NE.

Pavlista, A.D. and J.C. Ojala 1997. Potatoes: Chip and French Fry Processing. In Processing Vegetables: Science and Technology, Eds. Smith, Cash, Nip and Hui. Technomics Pulb. Co. Inc., Lancaster, PA.

Pavlista, A.D. and J.M. Blumenthal. 2000. Potatoes. In Nutrient Management of Agronomic Crops in Nebraska. Eds. R.B. Ferguson and K.M. De Groot, Publ. Univ. Nebraska Cooperative Extension (EC00-155), Lincoln, NE.

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