Evaluation of Polyhalite As a Potassium Fertilizer in Comparison to Muriate of Potash at Major Maize Mega-Environments of the World.

Being a natural mineral containing four out of the six essential macro nutrients, polyhalite (K₂SO₄.MgSO₄.2CaSO₄.2H₂O) offers an alternative potassium fertilizer option to farmers. The objective of the current exercise is to compare polyhalite as a fertilizer with Muriate of Potash (MOP) in major maize mega environments (MME) as defined by CIMMYT and developed by Grains research Development Corporation. Data was collected from six corn environments at : 1) MME-8, dry temperate north western China; 2) MME-7, wet temperate US- Corn belt; 3) again at MME-7, wet temperate UK; 4) MME-6, dry low land tropical Brazil and;5) MME-4 dry mid-altitude subtropical Tanzania. Treatments; 1) control, supplied with nitrogen and phosphorus; 2) MOP, applied at different K₂O rates in addition to N and P; and 3) Polyhalite applied at similar K₂O rates as in treatment 2 were compared as a straight fertilizer at four environments and as a part of popular blends in dry low-land tropical Brazil. Single degree freedom linear contrasts were used to compare the treatments of interest. Polyhalite significantly outperformed MOP at all locations except in Brazil, where both treatments were on par with each other. These results could be attributed to the supply of additional nutrients such as S and Mg from polyhalite. Depending on K₂O application levels and price comparisons, farmers can consider polyhalite as an alternative to MOP.