Effects of tillage method and drainage management on some soil physical properties

Tillage is one of the most important practices affecting soil physical and hydraulic properties. Its effects may vary intensely according to the tillage method. This study aims to evaluate the effects of different tillage methods (moldboard plow+disk harrow, moldboard plow+rotary tiller and chisel plow+disk harrow) and drainage (subsurface drainage and non-drainage) on soil physical properties in a clay loam soil. The experiment was conducted in split-plot in time statistical design. Soil bulk density, aeration porosity, organic matter, aggregate mean weight diameter (MWD) and water infiltration rate were measured after planting and after harvesting of winter-wheat crop. Results revealed that the tillage method had significant effect on organic matter content, such that the lowest (1.18%) and highest (1.35%) values were observed in moldboard plow/disk harrow and chisel treatment, respectively. Tillage effect was significant on saturated moisture content, MWD, aeration porosity and infiltration rate. The effect of time was significant on all investigated factors. The effect of drainage was significant on MWD and infiltration rate. Evaluating the interaction effect of tillage and drainage indicated that the contribution of drainage on changing MWD is higher than the tillage methods. Further, it was concluded that the selection of tillage method had an important role on aeration porosity and MWD in no drainage condition, so that moldboard plow makes much more aeration porosity (25.48% against 17.17%) and less MWD (2.40 against 2.80 mm) compared to chisel. According to the result, the treatment combination including drainage/after planting/moldboard plow and disk harrow had the lowest MWD and also, combined treatment of no drainage/after harvesting/chisel plow) had the highest MWD. The application of chisel is not recommended in no-drained areas having high level of groundwater, because of the highest saturated moisture content and MWD along with the lowest aeration porosity compared to moldboard plow.