Production agriculture: Economic and agronomic assessment of deep tillage in soybean production on Mississippi River Valley soils

Using deep tillage to alleviate the adverse effects of deleterious soil physical properties has been tried many times. Consistent economic returns have been reported for in-the-row subsoiling of loamy sand and coarser soils and for deep loamy soils where the subsoil slit bisects the water flow channel during rainfall events where there is runoff. Recent reports of yield responses on clayey soils and silt loams led to a reassessment of subsoiling of these soils in Arkansas. A randomized complete block design was conducted at four locations with tillage treatments of conventional shallow, deep chisel, subsoil dry, subsoil wet, subsoil at 45° to planting direction, and paratill. Plots were harvested for grain. Economic analysis was performed using the Mississippi State Budget Generator (MSBG). The machinery complement was commensurate with that found on farms in the region. Net returns above total specified costs (NRAT) rather than above direct costs were calculated to reflect the decision framework of a producer. A profitable yield response was obtained from subsoiling in dry soil on deep alluvial clayey and silt loam soils but not on the thin loessial silt loams. Net returns to subsoiling wet were not significantly higher than those to conventional shallow tillage. Tillage with a chisel plow as deep as it could be operated (approximately 15 cm) was not a substitute for subsoiling because yield responses from deeper tillage were not comparable. The 45° subsoiling in dry soil tended to be superior to all other tillage treatments.