Development of Magnesium Fertilizer Replacing Kieserite from Bio-Physico-Chemical Activated Dolomite

All plants, especially cocoa and oil palm, require magnesium (Mg) along with other macro- micro-nutrients. Kieserite as the most common Mg-supplying fertilizer for crops is still imported Indonesia due to lack of natural deposits in country. On hand, dolomites (CaMgCO3) are found abundantly mostly used liming material low MgO content solubility well. Many efforts have been carried out since a century ago convert dolomite into Mg substituting kieserite. However, there no efficient processes available yet therefore it objective this study develop potentially process by employing bio-physico-chemical activation approach converting kieserite-like product. A series experiments were conducted using calcinated from Sidayu, Gresik, East Java, reacting H2SO4, inoculating Mg-solubilizing microbes. An 80-mesh calcined powder was reacted water at 1:3 ratio (% w/v) after one hour stirring added technical grade H2SO4 improving 27.7% 18% 23%. The formula then tested its effectiveness palm seedlings greenhouse three six months, respectively. By combining NPK standard dosage Mg-fertilizer 75% kieserite rate yielded highest performances six-month-old experiment. To obtain conclusive results under field conditions, immature mature trees. At 0.9 kg/tree/year dosage, superior conventional 1.6 supporting vegetative growth palm. From trial, can be concluded that use new formulated 50% (2 kg/tree/year) resulted an insignificant different yield fresh fruit bunches (FFB) compared dosage.