Journal of Horticultural Science

Abstract Introduction: Environmental stresses are the most important factors that reduce agricultural yield all over the world. The water stress especially in flowering damages yield and yield quality, however, some studies showed that sometimes it does not have any harmful effect on yield. For instance, some studies approved that deficit irrigation improves sugar content and then fruit quality. Therefore, in order to evaluate the effects of potassium sulfate, vermicompost and water stress on yield and quality of four years old nectarine (CV Red gold), an experimental study was carried out on a garden which covers 5000 m² in Eslamdeh (Sari) during 2015 to 2016.
Materials and Methods: A split-split plot experiment based on complete randomized block design (RCBD) with 18 treatments in three replications (totally 54 treatments (trees)) was used in this study. Some complex soil samples were gathered individually from 0-30 and 30-60 cm to determine macro and micro fertilizer demand and were analyzed to determine physicochemical characteristics. Two levels of tree water requirement (50% and 100%) as the main plot, vermicompost in three levels (0, 5 and 10 kg per tree) as subplot, and three levels of potassium sulfate, (0, 200 and 400 g per tree) as sub-sub plothad been applied. The rest fertilizer demand was recommended based on soil analysis. vermicompost, potassium sulfate and other essential fertilizers were applied in late winter and then aeration or digging was carried out. The fruit was picked after ripening and was weighed. Diameter, height and mass weight were measured. Soluble solids, the total sugar content of fruit was measured based on pH-meter, refractometer and Arnon methods. Potassium and chlorophyll were measured by flame photometer and chlorophyll meter.
Results and Discussion: The results showed that the effects of different levels of applied treatments were not significant on fruit pH. In addition, effects of different levels of potassium sulfate on TSS, leaf chlorophyll, potassium sulfate levels of leaf, fruit weight and yield, fruit height, and flesh weight, single fruit weight were all significant at 1 % level. The results also showed that levels of vermicompost on K level of leaf and fruit yield was significant at 1% level, and on fruit weight at 5% level. Effects of other treatments were not significant on other studied traits. Results of mean comparison showed that fruit crop was increased with an increase in vermicompost application. The minimum yield (41.44 kg/fruit) obtained from control and application of 10 and 20 kg/h vermicompost resulted in 58.33 and 60.61 kg/h, respectively. Application of potassium sulfate also showed to be effective on fruit yield. The minimum yield obtained from control, applying 200, 400 g of potassium sulfate, resulted in 54.89 and 61.33 kg/tree. Furthermore, potassium sulfate levels resulted in TSS enhancement. The minimum obtained from control plot (8.083) and maximum obtained from 8.864 and 9.612 with applying 200, 400 g of potassium sulfate, respectively. Potassium application also resulted in fruit level volume. The minimum level observed at control plot (116.2), applying 200, 400 g of potassium sulfate, resulted in 131.5 and 141.3 kg/tree. The interaction effects of different levels of potassium sulfate, vermicompost and irrigation showed that maximum fruit yield obtained from 400 g/K, 10 kg of vermicompost and applying 100% tree water requirement with yield of 70.66 g which was not statistically different with triple interaction of 400 g/K, 10 kg of vermicompost and applying 50% of tree water requirement.
Conclusion: In the current research, the effects of the use of potassium sulfate and vermicompost on maintaining plant balance and fruit quality and also decreasing water use in stress conditions were studied. Results showed that the use of potassium sulfate along with vermicomposts had a significant effect of improving morphological and physiological characteristics of nectarine. Furthermore, they increased nutrition availability for the crop and then increased yield and fruit quality. The following conclusion to be drawn is that fruit was increased with an increase in vermicompost application. Application of potassium sulfate also showed to be effective on fruit yield and TSS enhancement. The interaction effects of different levels of potassium sulfate, vermicompost and irrigation showed that maximum fruit yield obtained from 400 g/K, 10 kg of organic matter and applying 100% tree water requirement with yield of 70.66 g which was not statistically different with triple interaction of 400 g/K, 10 kg of vermicompost and applying 50 % tree water requirement.
 

Abstract Introduction: Pomegranate (Punica granatum L.), belonging to Punicaceae family, is a tropical and subtropical attractive deciduous or evergreen shrub and is one of the native fruits of Iran. With total production of 941804 tons in 2013, Iran is one of the most important pomegranate producers in the world. Pomegranate is an important source of bioactive compounds. Despite the high nutritional values of pomegranate fruits, the overuse of synthetic fertilizers and pesticides in conventional systems reduces nutritional and functional quality of pomegranate fruits. On the other hand, world demand for organic products is growing rapidly in developed countries, especially in Europe, USA, Japan and Australia. Previous studies showed that organic fruits contain higher minerals, vitamins and oxidant activity than conventional crops. Therefore, the aim of the present paper was to compare organic, integrated and conventional management systems in pomegranate orchard on mineral contents and qualitative attributes of pomegranate fruit. Materials and methods: Pomegranate (cv. Rabbab-e-Shiraz) grown under organic, conventional and integrated management systems in a commercial orchard, in Nourabad Mamsani, Fars province, was used for this study. Pomegranate fruits were harvested at commercial harvest stage and transported in an air-conditioned vehicle to the laboratory of Horticultural Science Department, University of Guilan, Rasht. Some factors like fruit, aril and peel weight, aril length, weight ratio of peel to aril, peel to fruit and aril to fruit, and seed firmness (Penetrometer, with the diameter of 11 mm) were assessed. In addition, qualitative properties (Total Soluble Solids (TSS), TA (Titratable Acidity), TSS/TA and pH), antioxidant compounds (total phenol, flavonoids and anthocyanin content) in pomegranate juice and mineral nutrients (N, P, K, Ca and Mg) in peel and arils were measured. The experiment was conducted in a randomized complete block design with 4 replications. Results and discussion: The results showed that fruit, arils and peel weight and fresh weight of peel were significantly higher in conventional system than organic management system. Fruit weight depends on plant nutrition, which, in turn, significantly influences postharvest quality. It is possibly due to smaller cells and less intercellular spaces in organic fruits. In this study, fruit size in organic management system was significantly lower than conventional system; our results in this regard are in accordance with the previous studies reported on kiwifruit, apple and grape . Fruit taste is determined mainly by juice TSS and the ratios between TSS and TA. In this study, juice TSS in conventional and integrated management systems was higher than organic fruits at harvest time. Our findings are in agreement with Beng et al. (6), who reported higher amount of TSS in kiwifruit obtained from conventional system than organic system due to more mature fruit and greater use of nitrogen fertilizers. No difference was found for pH, TA, TSS/TA, seed firmness, total anthocyanin and flavonoid content among the three management systems. The antioxidant activity properties of pomegranate juice were attributed to polyphenols, sugar-containing polyphenolic tannins and anthocyanins. In this study, total phenolic content and antioxidant activity in fruits obtained from organic management system were greater than conventional management system. These results are in agreement with the findings reported in blueberry, peach and grape, apple, kiwifruit and strawberry fruits. Mineral nutrient analysis showed that the concentrations of P, Ca and Mg in peel, and N, P, K, Ca and Mg in aril of organic fruits were lower than fruits of conventional system, but the ratio of Ca to other elements in the arils of organic fruits was significantly higher than conventional system fruits. In apple, N concentration of conventionally grown fruits was higher, while K, Ca, Na and Mg concentrations of organic fruits were higher than conventional fruits. There were positive correlations between total phenolic content and antioxidant activity in pomegranate juice, which was in agreement with the results reported in kiwifruit and grape fruits. Conclusion: The results of the current study indicated that fruit quality of pomegranate cv. Rabbab-e-Shiraz was affected by the type of orchard management system. Although fruits obtained from organic system had smaller size in comparison with the fruits of other systems, the amount of total phenolic content and antioxidant activity was higher in organic system compared with conventional system, representing a higher nutritional value of organically grown fruits than conventionally grown fruits. Furthermore, organic fruits had higher Ca to N, Mg and K ratio, which can affect the shelf life and postharvest quality of pomegranate fruits.