Soil Fertility Guide

Potassium (K)

Most Manitoba soils contain adequate amounts of available potassium (K) for crop production. Soils likely to be low in K are coarse-textured sands, sandy loams and organic soils. Potassium may be required on about 6% of arable Manitoba soils for maximum production of commonly grown annual crops such as cereals, canola and flax. About one-third of Manitoba soils require additional K for the production of special crops such as corn, potatoes and small fruit or vegetable crops.

Potassium enhances winter hardiness and spring growth of forages. Further information regarding fertilizing forage stands, consult the MAFRI publication, Fertilizing Alfalfa Forage .

Like phosphorus, K levels do not change significantly from year to year in response to climatic conditions or crop management practices. An exception would be when high yields of forage are repeatedly removed from coarse textured soils ( Table 1).

Where required, applied potash (KCI) can increase crop yield and quality. Depending on the type of crop, it may also increase frost and disease resistance, palatability, storage quality and other characteristics.

For most efficient use by cereal crops, K fertilizer should be placed with the seed. For most row crops, potash should be side-banded to the side and/or below the seed. The efficiency of broadcast and incorporated potash is about 50% that of potash banded with the seed or side-banded 35 . If potash is broadcast, the recommended rate for seed placement or side banding should be doubled to obtain equal crop response. Broadcast K fertilizer should also be incorporated into the soil.

For further information, contact your Manitoba Agriculture Representative.