Effect of tillage systems and seeding rates on machinery parameters and grain yield in rapeseed (Brassica napus L.)

Suitable seedbed preparation and adequate rate of seeding are necessary to obtain desirable plant population. These management practices are more important for plants with small seeds such as rapeseed. In this research, the effect of different tillage systems and seeding rates on machinery parameters, grain yield and yield components of rapeseed, cv. Orient, was studied in a split-split plot arrangement using randomized complete block design with three replications at the Kabutarabad Agricultural Research Station, Isfahan, Iran in 2003-2004 cropping season. Four primary tillage systems: moldboard plow to a depth of 20-25 cm, chisel to a depth of 15-20 cm and 8-10 cm and disk to a depth of 8-10 cm were assigned to main plots and two secondary tillage

disk and rotary tiller to a depth of 8-10 cm and three seeding rates; 4, 8 and 12 (kg.ha-1) were randomized sub-plots and sub-sub plots, respectively. Tillage methods showed no significant effect on mean weighed diameter of clods. Disk and rotary tiller had maximum and minimum machinery effective field capacity, respectively. By increasing seeding rate from 4 to 8 and then to 12 kg.ha-1, number of days from planting to the end of flowering and flowering duration decreased. Increases in seeding rate increased plant population. Using of 8 kg.ha-1 of seeds produced higher grain yield (2521 kg.ha-1) than 4 kg.ha-1 seeds (2400 kg.ha-1), but was not significantly different from 12 kg.ha-1 (2426 kg.ha-1). Based on these results, it might be concluded that disk harrow method as the secondary tillage with 8 kg.ha-1of seeds as desireable agronomic practices under conditions similar to this study. However, when rotary tiller is used, the seeding rate might decrease to less than 8 kg.ha-1