Supplemental irrigation impact on yield and yield quality parameters of rapeseed

Abstract

Dryland winter rapeseed (Brassica napus L.) produced in the semi-arid regions of Turkey has variable yields. Supplemental irrigation alleviates the adverse effects of soil moisture stress on yield during drought periods. To determine the influence of irrigation timing on yield stability, a 3-yr, on-farm irrigation experiment was conducted to determine the effects of supplemental irrigation on rapeseed yield and yield components in a semi-arid environment. The field experiment considered the influence of six irrigation quantities applied at three growth stages (vegetative, flowering, and early ripening) on rapeseed yield and quality. Supplemental irrigation improved rapeseed yield compared with cultivation under rainfed conditions throughout the three experimental years. Although the greatest seasonal evapotranspiration and rapeseed yields were observed with full irrigation, the highest economic rate and most efficient irrigation rate were for the optimum level to be applied at flowering. Protein content, oil content, and fatty acids increased with irrigation and were highest for the full-irrigation treatment. Irrigation should be applied when 50% of available soil moisture has been consumed in the effective root zone at the early flowering stage. This timing enhances the water use efficiency and yield potential of rapeseed without reducing quality and could be highly beneficial for semi-arid regions.