Effect of drought stress and application cow manure on yield, yield component and water use efficiency of Bitter apple (Citrullus colocynthis)

Bitter apple (Citrullus colocynthis) is one of the most important medicinal plant that grow in semi-arid and desert condition which have been used in traditional medicine. In order to evaluate the effect of drought stress and manure application rates on yield, yield components and water use efficiency of Bitter apple, a field experiment was conducted in split plot layout based on complete randomized block design with three replications in two growing seasons (2012-2014) at Sabzevar, Iran. Drought stress were three levels of evaporation from evaporation pan (50, 75 and 100 mm) which was given as main plots and four levels of cow manure (0, 20, 40 and 60 t.ha-1) which was assigned as subplots. The results showed that increasing irrigation intervals reduced the number of fruits per square meter(49%), the dry weight of the single fruit(14%) and consequently reduced yield of fruits(38%) and seeds(40%). Number of seeds per fruit and 100 seed weight was not affected by drought stress. Increased amounts of manure application caused significant increase in yield and yield components (except 100 seed weight) of Bitter apple. The lowest fruit and seed yield and yield components were observed in control treatment and the highest of them were observed as a result of application of 60 t.ha-1 cow manure. Overall, the result of this experiment showed that the highest fruit and seed yield was obtained from application of 60 t.ha-1 cow manure and irrigation after 50 mm evaporation from evaporation pan produced the highest fruit yield.