Polyhalite as a potassium and multinutrient source for plant nutrition

Polyhalite, a source of potassium (K) and other nutrients, has been suggested as an alternative to fertilizer in Brazil. Two greenhouse pot experiments were carried out to evaluate the agronomic efficiency of polyhalite as a K and multinutrient source. Soil samples were collected from the Brazilian Cerrado. Pots were filled with 2 kg of soil. Treatments were composed of muriate of potash (MOP) and polyhalite was applied at rates of 20, 40, 80, 120, 160, and 200 mg K kg(-1) soil in experiment I. A mix of soluble sources of K, sulfur (S), calcium (Ca), and magnesium (Mg) was compared to polyhalite at the same rates of 0.33, 0.66, 1.33, 2.00, 2.66, and 3.33 g pot(-1) in experiment II. After 45 days of vegetative corn growth, plants and soil were collected. In experiment I, rates of K influenced yield of corn dry matter, but not the source of K. Corn dry matter yield in experiment II was higher with polyhalite. Polyhalite was similar or superior to conventional sources and was highly efficient at supplying K, Ca, Mg, and S to plants.