Release Rates of Controlled-Release and Soluble Magnesium Fertilizers

Abstract

Release rates at 21 °C were determined in sand columns for 12 commercially available soluble and controlled-release Mg fertilizers. Lutz Mg spikes, K2SO4, MgSO4, MgSO4·H2O, and MgSO4·7H2O released their Mg within 2 to 3 weeks. Within the first 6 weeks, MgO·MgSO4 released its soluble Mg fraction, but little release occurred thereafter. Dolomite and MgO released <5% of their Mg over 2 years while MagAmp released <20% of its Mg. Florikan 1N-0P-26K-4Mg types 100 and 180 exhibited typical controlled-release fertilizer characteristics, with most of their Mg release occurring during the first 15 weeks.