Corn residue retention by a combination chisel plow

Using combination chisel plows in corn (Zea mays L.) residue can reduce surface residue cover to below levels that will protect the soil against erosion. Equipment operation and setup changes can alter the residue amount incorporated into soil. We evaluated the operational effects of using a combination chisel plow, equipped with coulter gangs, on corn residue cover on two silt loam soils. Variables included timing of chiseling, point selection, speed and depth of chiseling, and coulter-gang engagement. Chisel plowing left 21 to 46% residue cover in the fall, and 13 to 33% residue cover in the spring. Differences were negated when overwintering losses after fall chiseling were considered. Only three of the eight spring chiseling treatments left >30% residue cover: (i) the DMI Tiger-C point with coulter-gang engagement, (ii) the DMI Tiger-C point without coulter-gang engagement, and (iii) the 406-mm sweep with gang engaged. Ranking of residue-retention coefficients for the chisel points was as follows: 406-mm low-crown sweep (0.42-0.53) approximate to DMI Tiger-C specialty point > 51-mm chisel point (0.33-0.40) > 102-mm twisted shovel (0.17-0.25). Depth of chiseling did not affect residue retention. Slowing the speed of operation from 6.4 to 3.2 km h(-1) (resulting in 27-42% increased residue retention) had more effect than slowing from 9.6 to 6.4 km h(-1) (19-24%). Primary tillage of corn residue using a combination chisel plow can provide adequate (>30%) soil surface protection from erosion processes. Residue-cover levels following secondary tillage and planting operations will likely fall below 30%.