Effects of crop rotation on yield and quality parameters of grafted watermelon (Citrullus lanatus L. (Thumb.) Matsum. & Nakai.) under organic management conditions

Grafted watermelon seedlings have been recently demanded by Turkish farmers due to early harvesting, high yield and resistance against soil-borne diseases. Similar challenges also effect watermelon production under organic agriculture conditions. Therefore, the aim of this study is to determine the effects of crop rotation and certified organic fertilizers on yield and several quality properties of the grafted watermelon onto Cucurbita moschata under organic agriculture conditions. The study was carried out with 4 rotated crops and 2 fertilizer applications. Rotation plants are broccoli (Brassica oleraceae var. italica), faba bean (Vicia faba), common vetch (Vicia sativa) and natural vegetation (fallow). The plants were cultivated in compliance with organic agriculture regulations valid in Turkey, and biomass was incorporated into soil as a green manure before transplanting of the grafted watermelon seedlings. Harvesting was done twice depending on maturation level of the fruits and yield values were recorded per hectare and per plant. Some fruit quality parameters (total soluble solids (TSS), fruit flesh color, fruit sizes, etc.) were also measured at the first harvest. Statistical analyses showed that the effects of crop rotation and fertilizer application on yield (t ha(-1)) were statistically important (p <= 0,05), and the highest yield was found in plots treated with fertilizer (74.31 t ha(-1)). Additionally, the highest yield within fertilizer applications is obtained from plots where vetch was the pre-crop (87.65 t ha(-1)). Although pre-crops have no statistically significant effect on fruit weight, fertilizer application (7.94 g) significantly increased fruit weight (p <= 0.05). There are clear differences found in fertilizer applications regarding the TSS content of the fruit (10.73%). Broccoli pre-crops with and without fertilizers had the highest fruit firmness value (1.28 kg). Vetch and fertilizer combination seemed to be more effective treatments in enhancing yield and quality in grafted watermelon production.