Abstract

One of the major problems that farmers in the Northwest of Iran contend with after the corn harvest for mechanized cultivation of canola is lack of time and soil moisture over prepared seedbed. Consequently, the effects of five different seedbed preparation methods were analyzed, namely; T1: moldboard plows (conventional tillage), T2: stalk shredder followed by chisel and disk, T3: stalk shredder followed by double-disc, T4: chisel followed by disk and T5: two heavy disk tillage using a randomized complete block design (RCBD) with four replications. Results showed that the soil bulk density in the 0 to 10 cm layer had nosignificant effect, but the 10 to 20 cm depth was significantly higher than the conventional tillage. However,penetration resistance in 10 to 30 cm under T5 was significantly higher than others. Thus, comparison of the soil bulk density, penetration resistance, and plant establishment showed that reduced tillage in canola seedbed preparation was effective. Besides, the surveys indicated that there was significant difference between mean weight diameter (MWD) after primary and secondary tillage and the MWD’s under T2, T3 and T5 were 1.18, 1.01 and 1.22, respectively lower than T1 with 2.06. Maximum plant height and grain yield were obtained under T2, 117.12 cm and 2941.50 kg ha^-1, respectively. Therefore, T2 was recommended as the time limitation on rapeseed bed preparation after corn, due to higher speed of operation and lower cost.

Key words: Corn residues, cone index, reduce tillage and yield of canola.