Water infiltration and storage affected by subsoiling and subsequent tillage

Benefits of subsoiling are difficult to predict. Objectives were to (i) determine effect of subsoiling on water infiltration and storage and (ii) evaluate longevity of tillage-induced soil structure. Experiments were conducted during two years and on two soils that were not subsoiled (NoSS), subsoiled (SS), and subsoiled plus secondary tillage (SSplus). Soils were Dooley fine sandy loam and Williams loam (fine-loamy, mixed, superactive, frigid Typic Argiustolls) near Culbertson, MT. Subsoiling, to a depth of 0.3 m, in Exp. 1 was with a paratill and with parabolic shanks in Exp. 2. Secondary tillage was with a disk in Exp. 1 and with sweeps in Exp. 2. Infiltration was measured using a sprinkler infiltrometer. Final infiltration rate, after two simulated storms, was 14 mm h(-1) on NoSS, 29 mm h(-1) on SS, and 7 mm h(-1) on SSplus. Penetration resistance (PR) measurements suggest that soil subsidence following simulated rainstorms was less on treatments with no secondary tillage. Average water drainage from the 1.83-m profile was 1.4 mm h(-1) during the first 3 d after water application. Average drainage was 0.23 ram h(-1) during Days 3 to 7 and 0.09 m h(-1) during Days 7 to 15. Regardless of improved water infiltration under SS, all soil profiles (1.83 m deep) drained to approximate to444 mm of water in 15 d. Results reveal a difficult soil management problem. Subsoiling initially improves infiltration, but no additional water storage was discernable after 15 d. Further, excess water percolation has potential to leach nitrate-N from the profile.