Solonetzic soils, often called burnout or gumbo soils, are characterized by a tough, impermeable hardpan that may vary from 5 to 30 cm (2 to 12 in.) or more below the surface. This hardpan severely restricts root and water penetration of the subsoil. Variation in the hardpan causes crops to have a wavy growth pattern during periods of moisture stress. Deep plowing and, more recently, subsoiling have been developed as methods for improving some of these soils. More than 160 deep tillage trials have been established to identify the Solonetzic soils with the greatest potential for improvement and to determine crop responses. This factsheet presents the results obtained from these trials.