Yield and fruit quality of watermelon (Citrullus lanatus (Thumb.) Matsum. & Nakai.) and melon (Cucumis melo L.) under protected organic and conventional farming systems in a Mediterranean region of Turkey

Protected conventional and organic farming systems for watermelon and melon were compared over a two-year period in the Mediterranean Amik plain of southern Turkey. Yield, fruit quality and growth responses of the vegetable crops were measured and compared as a function of conventional management, and three composted sheep-cattle manure treatments of 6 kg m(-2), 12 kg m(-2) and 18 kg m(-2). On average, total and marketable yields of watermelon and melon grown organically under low plastic tunnels showed a two-fold increase under the organic treatments of 12 kg m-2 and 18 kg m(-2) relative to the protected conventional management system (p < 0.05). There was no significant difference in watermelon and melon yields between the manure application levels of 12 and 18 kg m(-2). There were significant changes in mean fruit weight and width between the control and the manure level of 18 kg m(-2) for watermelon and in mean stem diameter between the control and the manure levels of 12 and 18 kg m(-2) for melon (p < 0.05). Multiple linear regression (MLR) models accounted for about 49% and 52% of variations in marketable yields of melon and watermelon as a function of the control and the manure levels of 12 and 18 kg m(-2), respectively. The findings indicate that protected organic watermelon and melon systems in this Mediterranean region can produce more total and marketable yields than protected conventional systems. Protected organic farming systems can assist in compliance with maximum residue limits imposed on exported agricultural commodities and reduce dependency on industrial fertilizers as well as emissions of fertilizer production-related greenhouse gases.