Reduction in Primary Tillage Depth and Secondary Tillage Intensity for Irrigated Canola Production in a Loam Soil in Central Iran

The introduction of canola (oilseed rape; Brassica napus L.) as a new source of vegetable oil production in Iran prompts evaluation of the performance of this crop under different tillage systems. A field experiment was conducted to determine the impact of depth and in-tensity of tillage on soil physical properties, crop establishment and yield of irrigated winter canola in a loam soil (Typic Haplargids) near Isfahan in central Iran. In a split-plot design, three primary tillage treatments consisted of moldboard plowing to 20 cm (MP20), two passes of a cultivator first to 10 and then to 15 cm (2TC15), and one single pass of cultivator to 10 cm (TC10), were combined with two seedbed preparation treatments (four passes with a disk harrow as opposed to a single pass with a rotary tiller). Results showed that the soil bulk density in the 0-5 and 5-10 cm layers were not significantly affected by primary tillage treatments. Soil penetration resistance (PR) in the 0-10 cm layer was significantly higher in 2TC15 compared to moldboard plowed soil; however, no significant effect of primary tillage was detected on PR in the 10-20 cm depth. A single pass by a rotary tiller was as effective in seedbed preparation as four passes of a disk harrow, as assessed by bulk density, penetra-