Abstract:
Productivity of sunflower (Helianthus annuus L.) is strongly regulated by the availability of water and greatest yield losses occur when water shortage occurs at flowering. Field experiment was carried out to study the water requirement of sunflower in a tropical humid-coastal savanna environment in Ghana to evaluate the response of sunflower to discretionary supplementary irrigation. Randomized Complete Block Design (RCBD) was used with 5 treatments and 3 replicates. Can-irrigation system was used to irrigate the crop at different levels and time intervals. The results show that all the plant parameters measured (plant height, leaf area index, head diameter and seed yield) increased consistently with an increase in water input until T4 beyond which any increase occurred at a decreasing rate. The field estimate of water requirement of sunflower was determined as the optimum level ofwater required to reach maximum head diameter. Water requirement of sunflower (by the field method) was estimated at 672.4 mm/season or 7.1 mm/day. The consumptive use of sunflower estimated using the Blaney-Criddle method was 4.3 mm/day. The Blaney-Criddle method estimated the water requirement of sunflower at 361.2 mm/season. The field value was considered the water requirement of sunflower since this includes both soil losses and losses in the soil-plant-atmosphere continuum. It was concluded that even though sunflower is considered to be tolerant to water deficit to some extent, in areas of low rainfall, supplementary irrigation can boost the productivity of the crop
