Effect of three different crop rotations on seed productivity and soil properties in organic tomato seed production: a comprehensive 13-year field study with three cycles

This study was carried out to investigate the effects of three different crop rotation practices and three cycle periods on tomato seed yield and quality and some soil characteristics in organic farming conditions. The crop rotations included tomato as the primary crop along two intercrops (CR-1: tomato-leek-okra crop rotation, CR-2: tomato-head cabbage-lettuce crop rotation, CR-3: tomato-watermelon-onion crop rotation). At the end of the study, seed yield and quality of other vegetable species (leek, okra, head cabbage, lettuce, watermelon, and onion) included in the trial along with tomato, seed-borne pathogens, and some soil properties of the trial area were determined. The impact of crop rotations and production cycles on seed yield in tomato was found to be statistically significant (p < 0.05). The seed yield in CR-2 and CR-3 rotational treatments (42.50 kg/ha) exceeded that of CR-1 (37.10 kg/ha). In addition, the least amount of seed yield was obtained in the first cycle (2013) at 3.01 kg/ha, whereas the highest seed yield was obtained in the third cycle (2021) at 5.01 kg/ha. Nevertheless, the weight of 1000 seeds, the number of seeds per gram, and germination rate of tomato were not affected by rotation treatments, but the effect of rotation cycles on them was found to be significant. The maximum weight of 1000 seeds was obtained from the second cycle (4.03 g), and the highest number of seeds per gram was obtained from the first and third cycles (312.46 and 314.80 seeds/g, respectively). Furthermore, the first (2013) and second (2017) cycles exhibited germination rates of 94.85% and 95.78%, respectively, which were higher than the 87.80% observed in the third (2021) cycle. Organic matter content, which was measured as 2.15% in the initial soil (2009), varied between 2.30% (2013) and 2.44% (2017) in CR-1, 2.30% (2013) and 2.47% (2017) in CR-2, and 2.29% (2013) and 2.45% (2017) in CR-3. Additionally, seed-borne fungal and bacterial pathogens were screened in organic seeds produced for the vegetable species in rotation, and seed-borne viral pathogens were screened in watermelon, tomato, lettuce, okra, and head cabbage.