Response of organically grown mini watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai) to different green manure crops and nitrogen fertilization

Green manure and nitrogen (N) fertilization are important agronomic practices under organic farming system. Among summer fruits, mini watermelons [Citrullus lanatus (Thunb.) Matsum. & Nakai] have high consumers favor and their interest can be further strengthened by the introduction of organic crop production, which gives an added value to fruits. A field trial was conducted in Southern Italy (Apulia region) during 2018 to evaluate the response of mini watermelon ('Modellino F1') to different green manure crops and N fertilization. A total of 26 levels of experimental treatments, derived by the factorial combination of two N fertilization levels (0 and 80 kg ha-1) and 13 green manure crops (Trifolium incarnatum, Vicia sativa, Lupinus albus, V. faba, Avena sativa, A. strigosa, Raphanus sativus, Sinapis alba, Triticum aestivum, Hordeum vulgare, Secale cereale, ×Triticosecale, and one control treatment) were applied. The fruit total yield and number of fruits per plant were affected by green manure and N fertilization, whereas no effect was detected for fruit mean weight. Moreover, a significant interaction between green manure and N fertilization was found on yield. The total soluble solids were significantly affected by N fertilization. The best results were obtained by leguminous crops, suggesting that leguminous green manure and organic N fertilization improve the mini watermelon production in organic farming systems.