tahereh raiesi; bijan moradi; Behruz Golein
Abstract
Introduction: Citrus is the main fruit group grown in tropical as well as sub-tropical climate of more than 150 countries in the world. In Iran, the total area under citrus crops is 0.284 M ha with a production of 4.345 M ton and a productivity of 17 ton per ha. Citrus is also one of the most important ...
Read More
Introduction: Citrus is the main fruit group grown in tropical as well as sub-tropical climate of more than 150 countries in the world. In Iran, the total area under citrus crops is 0.284 M ha with a production of 4.345 M ton and a productivity of 17 ton per ha. Citrus is also one of the most important horticultural products in Mazandaran, with 112,000ha devoted to its cultivation. Drought stress is frequent in Iran and is common in the dry summer periods in Mazandaran. Therefore, irrigation is essential during mentioned periods in this province. Irrigation scheduling and water requirement of the citrus crops are one of the main concerns of the citrus fruit production. Irrigating based on soil water potential (tensiometer) is one of the irrigation scheduling methodologies. In addition, fertilization is used to promote quantity and quality of fruit production. Potassium has a key role in the osmotic adjustment of plants and alleviate the effects of drought stress. Until now, studies on citrus to evaluate the effects of potassium fertilization to mitigate the negative effects of drought stress have not been conducted. In the present study, we hypothesised that K applications via soil could contribute to osmotic adjustment of citrus and alleviate the effects of drought stress. Thus, the objective of the present study was to evaluate the effects of different soil water potential and rate of potassium (K) application on biochemical indices and growth responses of Thomson navel (Citrus, sinensis (L.) osbeck) orange seedlings on Citrumelo rootstock.
Materials and Methods: This study site was located at the Citrus and Subtropical Fruit Research Center of Horticultural Science Research Institute (36°54′11″N, 50°39′30″E), with a mean annual rainfall of 1200 mm. Thomson navel trees (Citrus, sinensis (L.) were planted at 7 × 6m distances. Soil had a pH (soil-to-water suspension ratio of 1:2) of 6.2 and contained 14.3 g kg−1 organic C and CaCO3<1%. The texture of soil was clay loam. A two-year field study was conducted in a factorial experiment based on randomized complete block design with four selected ranges of soil water potential, two levels of K application, and four replicates. Irrigations were scheduled using soil moisture tensiometers. The irrigation treatments were scheduled when soil water tensions reached 20, 40, and 60 kilopascal (kPa) on the tensiometers per treatment and results were compared with control (none irrigation) treatment. Soil water tensions of 20, 40, and 60 kPa correspond to soil water depletions of 17, 35, and 52%, respectively, of the available soil water for the studied soil. Levels of K fertilizer were 50 (k1) and 100 (K2) g K × age of tree. Potassium fertilizer was broadcast below the tree canopy in March. At the end of each year, yield, available K and some growth indices were measured. In addition, in the last year, proline, ionic leakage and electrical conductivity were also measured. All data were represented as mean of four replicates. Differences in yield, canopy diameter and available K among fertilizer and irrigation treatments and sampling years were analyzed using general linear model two-way analysis of variance (ANOVA) in SAS 9.1. Since the mentioned attributes were measured during two years to take into account annual variation, we used ANOVA procedure for a combined analysis of data. The significance of differences between the mean of treatments were determined by using Duncan test. All the statistical analyzes were performed by SAS 9.2.
Results and Discussion: The results showed that irrigation increased the canopy diameter (P<0.05). Under K1 application, the tree yield was not significantly different (P≥0.05) between irrigation at different water potentials (I1, I2 and I3). However, the K effects on tree yield depended on soil water potential and the positive effects of K2 application were evident only in the I2 and I3 treatments. However, K2 application reduced the yield in irrigation treatments including I0 and I1 significantly (P<0.05) compared with K1 application. In addition, the results of the last year showed that proline and ionic leakage were increased (P<0.05) by reduce of water potential in irrigation time. However, double application of K (K2) increased (P<0.05) proline and decreased ionic leakage as compared with normal application of K (K1). Moreover, available K and electrical conductivity were increased (P<0.05) by excessive application of K and reduce of soil water potential.
Conclusion: In summary, regarding this experiment, irrigation at 60 kPa (depletion coefficient =52%) and potassium application rate of 50 g K × age of tree was the best treatment.
fateme Hasanzadeh Naranjboni; reza ebrahimi; B. Moradi; T. Raiesi
Abstract
Introduction: Type and source of fertilizer in fruit trees nutrition play an important role in increasing yield and fruit quality, shelf-life prolonging and reducing waste in harvested fruit. Evaluation of the possibility of integrated use of organic and inorganic fertilizers or gradual replacement of ...
Read More
Introduction: Type and source of fertilizer in fruit trees nutrition play an important role in increasing yield and fruit quality, shelf-life prolonging and reducing waste in harvested fruit. Evaluation of the possibility of integrated use of organic and inorganic fertilizers or gradual replacement of chemical fertilizers with organic manures is necessary in nutrition of kiwi vines, due to environmental issues resulted due to application of chemical fertilizers as well as increasing market value of organic fruits. Studies in this regard, especially comparison between organic manure and chemical fertilizer effects in kiwi fruit production is very limited. Therefore,this research was performed to investigate the short-term effects of four types of organic fertilizers as compared to chemical fertilizers over the amount of nutrients in leaves and fruits in Kiwi- Hayward variety.
Materials and Methods:This short-term field research was conducted in a randomized complete block design with six treatments including (azola, azocompost,vermicompost, cow manure, chemical fertilizer and control treatments) and four replications inHorticultural Science Research Institute, Citrus and Subtropical Fruits Research Center in Ramsar.Fertilizers were mixed with topsoil in canopy,weed control and drop irrigation was performed. The amount of nutrients, including nitrogen, phosphorus, potassium, calcium and magnesium in kiwi leaves and fruits were measured. In addition, relationship between nutrients in leaves and fruit yield was examined. The correlation analysis between mineral elements and the characteristics of qualitative and quantitative fruit firmness, dry matter, total soluble solids, titratable acidity and ratio of soluble solids to titratable acidity was performed. Stepwise regression equation between treatments with nitrogen, phosphorus, potassium and calcium was written on kiwifruit leaves and fruit. In addition, stepwise regression, the overall equation between yield and nutrient content of kiwifruit were reported.
Result and Discussion: The results showed that concentration of nitrogen, phosphorus, potassium, calcium and magnesium in leaves and fruits in Kiwi trees are higher than control treatment and the amounts of these elements in leaves and fruit werein optimum condition. Fertilization increased the amount of nitrogen, phosphorus, potassium, calcium and magnesium in leaves and fruit of kiwifruit trees in fertilizer treatments, compared to the control. Azocompost treatment had the highest amount of nitrogen and calcium in leaves and fruit compared to other treatments. Azocompost and vermicompost treatments had the highest potassium content in the leaf. As well as cow manure, vermicompost and Azocompost treatments resulted in the highest amount of potassium in fruit. Increasing theamount of nutrients in the leaves of kiwifruit had a direct impact. The correlation between the amount of elements in the leaves and fruit showed a direct and significant relationship between nitrogen, phosphorus and potassium leaves and nitrogen, phosphorus and potassium in fruits. Increasing of nutrients in kiwifruit leaves had a direct and positive impact on fruits. In stepwise regression equation there was a significant relationship between the yield andamounts of nitrogen, phosphorus and potassium and kiwi fruit trees, and by increasing of these elements and yield wasincreased. Correlation analysis between minerals and firmness in kiwifruit showed that there are negative correlations between the nitrogen content in mature fruit and firmness at harvest time at probability level 5 percent. In addition, positive and significant correlation between the calcium content in mature fruit and firmness, as well as between the percentage of dry matter and phosphorus and potassium contents of mature fruit at harvest time was obtained. Results showed that a significant negative correlation was between soluble solids with calcium and between titratable acidity with phosphorus, and of soluble solids ratio to titratable acidity with nitrogen and phosphorus the mature fruit at harvest mature fruit.
Conclusion: In general, according to these research results we can say that use of organic fertilizers like chemical fertilizers in kiwifriut orchards increasethenutrient amounts in leaves and fruit of kiwifruit. In addition,there was a significant positive correlation between quantitative and qualitative characteristics of kiwifruit and its leaf and fruit nutrients. Nitrogen, phosphorus and potassium have significant positive effect in increasing fruit yield.Chemical fertilizers leaching and environmental problems caused by the consumption of these fertilizers, motivated to useof organic fertilizers, such as vermicompost and azocompost in kiwifruit orchards, in order to produce fruit in north of the country.
