Volume 50 highlights current areas of interest to both researchers and students of agronomy internationally. Areas covered include a thorough treatment of redox chemistry in soils, advances in agronomic improvement in oilseed brassicas, population groupings of soybean bradyrhizobia, crop responses to chloride, and plant nutrient sulfur in the tropics and subtropics. Advances in agronomic improvement in oilseed brassicas A comprehensive overview of population groupings of soybean bradyrhizobia Details on crop responses to chloride A thorough treatment of redox chemistry in soils Plant nutrient sulfur in the tropics and subtropics