Fruit Yield in Seedless Watermelon (Citrullus lanatus L.) as Affected by Irrigation Rates

There is an increasing concern about sustainable use of water in vegetable production.  Research efforts are intended to increase water and fertilizer use efficiency.  Watermelon is often irrigated excessively resulting in water waste and nutrient leaching.  The objective was to evaluate the effects of irrigation rates on plant growth and fruit yield and quality in watermelon.  The experimental design consisted of a randomized complete block with five treatments [irrigation rates (33%, 67%, 100%, 133%, and 167% the rate of crop evapotranspiration)] and four replications.  We used a seedless watermelon cultivar (‘Tri-x 313’ as female, and ‘Ace’ as the pollenizer) that is commonly grown in the southeast U.S.  The incidence and severity of Phytophthora capsici were negligible, thus, the effects of irrigation rate on the disease could not be determined.  Fruit yields and average fruit weight were not drastically affected by irrigation rate, although fruit yields were lowest at the lowest irrigation rate (33% ET).  Fruit quality was affected by irrigation as shown by the reduction in the concentration of fruit soluble solids with increasing rates of irrigation.  In conclusion, watermelon plants irrigated at 67% the rate of crop evapotranspiration had fruit yields and quality similar to plants irrigated at 100%-167% the rate of crop evapotranspiration.  Thus, there seems to be potential for significant reductions in the current rates of water application to watermelon in the southeast U.S. with the consequent increases in water (and possibly fertilizer) use efficiency.