Sowing Date and Rate Effect on Winter Oilseed Rape (Brassica napus L.) Yield Components’ Formation

Crop yield per area is the product of plant density and productivity of an individual plant. Plant density and the time of winter oilseed rape sowing influences yield components (parameters of individual plant productivity), such as pod number per plant, seed number per pod, plant productivity, seed weight, and plant branching. The aim of this three-year (2008–2010) study was to investigate winter oilseed rape yield components depending on sowing date (five sowing dates) and sowing rate (four sowing rates for each variety) as initial cause of plant density at harvest for two type winter oilseed rape varieties (open pollinated ‘Californium’ and hybrid ‘Excalibur’). Field trials were carried out at the Research and Study Farm “Vecauce” of the Latvia University of Agriculture. Winter oilseed rape yield components (pod number per plant and seed number per pod, plant productivity (seed number per plant and plant productivity in g) as well as the number of primary branches per plant) were affected (p < 0.05) by sowing date and rate for both varieties. In general, no significant effect of sowing rate on 1000-seed weight was observed (p > 0.05), but sowing date influenced this component significantly (p < 0.05). A yield compensation mechanism was demonstrated by significant (p < 0.05) negative correlations between plant density at harvest and parameters of individual plant productivity.