Comparison of various coulter‐type ground‐driven rotary subsoilers in terms of energy consumption and soil disruption

Abstract Hardpans below the normal tillage depth inhibit root penetration and cause drainage problems. Subsoiling is commonly used to disrupt hardpans and provide pathways for water and roots to enter the subsoil. The objective of this study was to develop and compare various types of ground‐driven rotary subsoilers that adequately disrupt compacted soil profiles for conservation tillage systems. To accomplish these objectives, four different coulter‐type ground‐driven rotary subsoilers were designed and manufactured by dividing a 1.2 m diameter coulter into multiple blades. Minimizing the soil resistance was one of the main considerations in forming the shape and number of blades on the coulters. An experiment was conducted in a soil bin to determine the effects of ground‐driven rotary subsoilers on soil disturbance and energy requirements. Treatments were four different types of subsoilers: coulter without blade ( CNB ), coulter with 5 blades (C5B), coulter with 7 blades (C7B) and coulter with 9 blades (C9B), and two tillage depths (25 cm and 38 cm). To determine the differences between subsoilers, soil disturbance, cone index, bulk density and draft were measured. The C5B subsoiler required considerably less draft, draft power and vertical force for both operation depths followed by the C7B, C9B and CNB subsoilers. The CNB subsoiler left the soil surface clean with no spoil while the coulters with blades caused spoils on the soil surface. The soil disruption paths of the coulters with blades have an advantage for row crops due to limited above‐ground disturbance if seeds can be placed in the middle of the disrupted zone.