Abstract

Fertilizers applied pre-sowing or pre-planting at a full-season dose might cause salinity hazards to a young developing crop. The fertilizer salt index (SI) concept provides several methods to evaluate the risk of a given fertilizer to increase soil salinity and consequently cause osmotic stress. Polyhalite is a natural, organic, new emerging complementary fertilizer which contributes potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S). Polyhalite is marketed under the trade name Polysulphate^® (ICL, Israel). In the present study, we determined the SI of polyhalite, using two methods, to compare it with other commercial fertilizers (MOP, SOP, and SOPM) that donate some of the above listed nutrients. Although considerable differences occurred between the methods, polyhalite consistently obtained lower SI values, suggesting it is a safer product compared to MOP and SOP. The results are discussed and compared to previously published equivalent data.

Keywords: Gypsum; salt stress; solubility; plant nutrition.