Water productivity of sunflower under different irrigation regimes on Gezira clay soil, Sudan

PhD candidate: Eman Rahamtalla Ahmed Elsheikh

Department of Water Science and Engineering

Chair Group Land and Water Development

UNESCO-IHE institute for water education

Westvest 7, Delft

Sunflower has become an important crop for both farmers and consumers in Sudan. It is a crop that fits well in the local cropping system and is considered one of the most important oil crops of the country. Regular irrigation intervals could be reduced in order to increase total yield and maximize water productivity. In contrast prolonged irrigation intervals during sensitive growth stages may result in reduction in total yield. The application of water below the evapotranspiration requirements is termed deficit irrigation (DI). The experiments were conducted at Gezira Research Station Farm, WadMedani, Sudan, in a randomized complete block design with three replications. In this study irrigation intervals every week during the whole growing period, 10, 15 and 20 days intervals after flowering stage and 10, 15 and 20 days intervals after the seed filling stage were applied to study the effect of full and deficit irrigation on yield and yield components of sunflower during the two growing periods 2011/2012 and 2012/2013. Results showed that water stress decreased the number of filled seeds per head, weight of full seed and seed yield. The highest seed yield of (3130 and 3140 kg/ha) was obtained from the full irrigation treatment and the lowest seed yield of 2082 and 2130 kg/ha was obtained from irrigation every 20 days after the flowering stage in the first and second season respectively. Results indicated that there were no-significant differences on head diameter, plant height and stem diameter when the water deficit occurred after the flowering stage. Lower water productivity of 0.21-0.26 and 0.21-0.27 kg/m3 were obtained when sunflower was irrigated every 20 days after the flowering and seed filling stages in the first and second season respectively. Results revealed that water productivity was low under Gezira conditions.

In addition, the  AquaCrop model was used to simulate seed yield and water productivity under different irrigation strategies. AquaCrop simulated seed yield accuratley with a root mean square error (RMSE) that ranged between 0.01 and 0.12 t/ha and 0.04 to 0.16 t/ha for the sunflower varieties Hysun 33 and Bohooth-1 respectively. The corresponding values of d-index of agreement ranged between 0.89 - 0.99 and 0.92-0.99 respectivley in 2012 and 2013. Results revealed that the AquaCrop model can be adequately applied to simulate seed yield response to water deficit and to explore the best irrigation stratgies that can maximize yield under current climatic conditions.