Long Term Effects of Tillage System and Crop Rotation On Soil Physical and Chemical Properties in a Brookston Clay Loam At Ridgetown, Ontario.

Long term studies allow for quantification of the effects of crop production practices such as tillage and crop rotation on soil quality and soil C and N stores. At Ridgetown, ON, two long term studies were established: 1) in 1991, a RCBD tillage trial with six replicates in a soybean-corn (S-C) rotation compared treatments of no-till (NT), fall moldboard plow with spring cultivation (conventional tillage, CT) and fall chisel plow with spring cultivation (chisel-T), and 2) in 1995, split-plot tillage-rotation trial with four replicates compared NT to CT within continuous corn (cC), continuous soybean (cS), S-C, soybean-winter wheat (S-W), and soybean-wheat-corn (S-W-C) rotations.  Soil samples were collected in 5, 10, and 20 cm increments to 120 cm depth from both trials in 2006 for soil organic C (SOC) and total C and N quantification. In 2009, 0-15 cm depth was sampled for the Cornell Soil Health Assessment (CSHA) in tillage-rotation trial only.  The CSHA overall soil quality score was higher with S-W rotation than cC, cS, S-C, but S-W-C rotation was not different from all rotations.  Other than soil hardness score, all parameters and the CSHA overall soil quality score were higher in NT than CT.  On an equivalent weight basis, SOC and total N were higher with NT compared to CT in both trials and chisel-T tended to be intermediary.  Compared to CT, the NT system had higher SOC within cC, cS, and S-W-C rotations. There was no difference between tillage systems within the S-W rotation; however, in the S-C rotation, SOC was higher in CT than NT. Thus, to improve soil quality and C sequestration, growers on clay loam soil are recommended to adopt NT production and include winter wheat in the rotation.