Geospatial variability and nutrient partitioning of potassium, calcium, and magnesium in Iranian wheat grains:...

Wheat is a globally significant cereal crop and constitutes a primary source of essential nutrients for human consumption. Comprehensive understanding of the mineral composition of wheat grains, including the distribution of minerals among the whole grain, bran, and germ, as well as the nutrient concentrations in various bread types, is essential for accurately evaluating its nutritional contributions. This study aimed to quantify the concentrations of three essential minerals-potassium (K), calcium (Ca), and magnesium (Mg)-in wheat grains cultivated across Iran under both irrigated and rainfed agricultural systems and mineral partitioning between the germ and bran fractions. A total of 1876 wheat samples, representing both irrigated and rainfed cultivation systems, were collected from diverse agroecological zones throughout Iran and their K, Ca, and Mg concentrations were measured. The mean concentrations of K, Ca, and Mg in the wheat grains were 4059 mg kg^-1, 394 mg kg^-1, and 1046 mg kg^-1, respectively. Notably, all three minerals exhibited significantly higher concentrations in irrigated wheat compared to rainfed wheat. Spatial analysis indicated regional variability in mineral concentrations: potassium and calcium levels were lowest in northern provinces, which may be attributed to higher precipitation, intensified cultivation practices, and resultant soil nutrient depletion. Magnesium concentrations demonstrated a contrasting pattern, with reduced levels in northern and western provinces and increased concentrations in eastern and southern regions. A weak yet positive correlation was observed between mineral concentrations (K, Ca, Mg) and wheat grain yield. Furthermore, mineral concentrations were highest in the bran fraction, followed by whole grain and germ. Among different bread types analyzed, Baguette, Taftoon, and Sangak exhibited the highest concentrations of K, Ca, and Mg. These findings underscore considerable regional variability in the mineral content of wheat grains cultivated in Iran and suggest that irrigated agricultural practices generally enhance the accumulation of essential minerals in wheat.