Effect of organic and conventional farming system and sowing date on yield, seed oil and protein content in rapeseed cultivars.

Rapeseed is one of the major oil crops, grown in various agroecological conditions. Interest in organic rapeseed is rising, with increasing importance to breeders to determine the need for specific organic breeding programs. The objective of this study was to determine the adaptive value of rapeseed cultivars in organic farming environments. Five winter rapeseed cultivars were grown in conventional and organic plots, each with three sowing dates in four replications. The trials were organized using a randomized block design. The effect of cultivar and farming on emergence, percentage of harvested plants, yield, oil and protein content were investigated. Locally recommended agricultural practices were used to keep the fields free from weeds, insects and diseases. In organic field, weeds were removed mechanically while insects were treated using organic insecticide. The seed samples for analysis of oil and protein content were taken during harvest. Considering agricultural practices, it was found that rapeseed can be successfully grown in organic agriculture, but further improvements are needed to increase stability of production. Early sowing date provides enough time for rapeseed growth before the winter and good overwintering. The cultivars had higher oil content in the conventional farming, while there was no significant effect of farming system on protein content. For cultivar Slavica, higher yield was recorded in organic system, while cultivars Banaćanka and Nena had high yield in both farming systems. The results suggest that the existing conventional breeding material can be used as a good starting point for further trait improvements in organic farming. [ABSTRACT FROM AUTHOR]