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Site Selection

Managing K concentration in perennial grass forage is very site-specific, owing to the tremendous variation in available K among soil types. Most soils contain large quantities of K, but very little of it is available to plants. Physical, chemical and biological processes in the soil result in release of mineral K over time. Most soil K is found in fine-grained clays, and clay content is a good indicator of the potential K-supplying power of a soil. There is a wide range in K-supplying power of soils in most regions. Organic soils, as well as sandy soils, are typically low in available K.

Soils with relatively high K-supplying power may never need any K fertilizer applied to maintain sufficient K available for grass growth and persistence. On the other hand, soils with low K-supplying power will require additional K fertilizer to avoid K deficiency in grass and reduce the risk of winter damage caused by low plant K. The amount of K released by the soil each year and made available for plant uptake varies with climatic conditions. Soil testing will identify fields with lowest soil K. These fields are prime candidates for dry cow grass management.