Potential for sunflower to use residual soil water in the dry season after maize in North-West Cambodia

Abstract

A series of experiments was carried out in 2012–2014 in Pailin province, Cambodia, to determine the potential and agronomic requirements for a dry season sunflower crop. The research showed that the six high-oleic sunflower hybrids evaluated were similar for phenological development and yield but two varieties had <50% emergence and poor hybrid seed quality was seen as a constraint to planting under rainfed conditions. Sunflower receiving a basal application of 20:20:15 (N:P₂O₅:K₂O) at 200 kg ha⁻¹ produced achene yield of 2423 kg⁻¹, while side-dressing with urea had no effect on yield. Application of s-metolachlor post-sowing pre-emergence was the most effective weed control treatment and significantly increased sunflower achene yield. Post-emergence weed control was not adequate to prevent yield loss from weed competition. The study showed that sunflower can be grown successfully as a dry season crop in North-West Cambodia when planted no-tillage on residual soil water remaining after maize harvest in October and November. The critical requirements for success are related to preservation and effective use of residual soil water and include minimal soil disturbance, adequate application of fertiliser at sowing, and pre-emergence control of weeds, especially grasses.