ali asadi kangarshahi

Existence of various types of biotic and abiotic stresses has made necessary to investigate different rootstocks in different climatic and soil conditions. In this study, the effect of three important citrus rootstocks of the region on vegetative growth, quantitative and qualitative yield and harvest time of Thomson navel orange was investigated during seven years. The results showed that the affinity between the rootstock and scion decreased in all three rootstock during experiment. With the training of young trees and annual pruning, the maximum volume of canopy was about five m3 and the height of the trees maintained at about 2 m. The characteristics of orange fruit on three rootstocks did not show any significant difference. The canopy of trees on citrumelo rootstock was higher than the two citrange, but the yield efficiency of trees on rootstocks was not significantly different. The fruit harvest index reached more than the acceptable standard level in early November. The weight of the fruit increased until the end of December. The percentage of fruit decay in normal storage was the lowest during early November harvest and the highest during the late November and December harvest. By performing annual pruning, the planting intervals of Thomson orange can be reduced to half the intervals of traditional gardens. Also, to prevent the fruit from growing too large, and reducing fruits marketability, and to reduce the drop before harvesting and the rotting of the fruit in the store, the time of fruit harvesting can be started from early November.

This study was conducted to evaluate potassium fertilization management on citrus orchards as an effort to gain a better understanding of the potassium requirement, amount of fertilization, and proper timing of potassium application as well as potassium uptake and transfer in citrus trees. The findings can be effectively employed in formulating horticultural recommendations toward optimized potassium application. On average, mature citrus trees contain 300 to 750 kg/ha of K, 15 to 20 percent of which is found in the leaves and 45 to 60 percent in the fruits. Long-term citrus fertilization experiments in Iran and elsewhere have revealed that around 50 to 200 kg/ha of potassium as K2O is annually needed to achieve sustainable production, improved fruit yield and quality, and proper tree growth and health. Around 50-70% of this amount is consumed in fruits, about 5% deposited in tree structure and organs, and the balance between the potassium absorbed and that consumed is made up by absorption and desorption reactions at soil exchange surfaces. Studies in the past have shown that the highest K-requirement and K-uptake rate in citrus trees belong to the period from June drop to fruit maturation (i.e., the second stage of fruit growth) but that the lowest uptakes are observed during minimum activity (i.e., in the winter), at the beginning of the growing season, and after harvesting. The potassium stored in older tissues, therefore, plays the greatest role in the growth and development of leaves, branches, flowers, and fruits during the early growing season (i.e., the beginning of twig growth, flowering, and fruit setting) when potassium uptake from the soil is still at its lowest. Like the tree potassium reserves, foliar application of potassium fertilizers will, therefore, play an important role in regulating the supply of potassium to the newly growing and developing organs, especially at the beginning of the growing season. The purpose of potassium fertilizer application is, therefore, to ensure sustainable production, enhanced tree performance, improved fruit storage, and reduced fruit physiological disorders. Obviously, application of potassium fertilizer to soil prior to flowering and fruit setting has been found to have no effects on the development of spring twigs, nor on the current year flowering or fruit setting. It may, therefore, be recommended that producers should stop soil application of fertilizers before flowering and fruit setting, but start K application (percentage of the annual requirement) from the middle to the end of the first stage and gradually increase it to its maximum during the second stage of fruit maturation.

Management of nitrogen fertilizer application for citrus trees was evaluated to obtain an enlightened understanding of plant nitrogen requirements, amount of fertilization needed, appropriate fertilization timing, and nitrogen uptake and storage in these plants. The knowledge thus obtained could be effectively exploited toward formulating recommendations that ensure optimized nitrogen fertilization. Mature citrus trees reportedly contain 500 to 1000 kg N/ha, 40 to 50 percent of which belongs in the leaves and fruits while only 15 to 20 kg N is deposited in their skeletal structure. These findings and the long-term survey of citrus fertilization experiments in Iran and elsewhere indicate that annual application of 200 kg N/ha seems sufficient for stable fruit production, improved fruit yield and quality, and proper tree growth and health. Moreover, it is found that 30-50% of this amount of N application will be incorporated into the fruits while about one tenth will be deposited and stored in the tree, with the balance between nitrogen uptake and consumption by the tree being secured by N leaching from the soil profile and lost as gas into the air. The results of an experiment with labeled fertilizers (15N) showed that the highest N-uptake rate in citrus trees occurred during the period from fruit set to fruit maturity and, further, that N uptake was very low during the post-harvest period, especially during minimum tree activity (winter) and the beginning of the growing season. This indicates that nitrogen storage in older tissues plays the greatest role in the growth and development of leaves, branches, flowers, and fruits at the beginning of the growing season when N uptake from the soil is still very low (i.e., when branches and flowers begin to sprout and fruits are in the form). It has also been reported that the nitrogen present in soil organic matter ranges from 1000 to 2000 kg/ha in orchard soils containing 1 to 2% O.M. and that both the soil nitrogen content and that stored in the tree bodies play important roles in regulating the supply of nitrogen to new organs (i.e., leaves, blooms, and fruitlets), especially in the beginning of the growing season. It follows that the purpose behind N fertilization should be to ensure stable production, proper tree growth, and improved fruit yield and quality such that soil application of fertilizers before the flowering and fruit set stages have no effects on the growth of spring buds or flowering and fruit setting in the current year. Producers are, therefore, recommended to start fertilizer application with a maximum of 10-15% of the annual plant requirement during the period prior to flowering and fruit setting, gradually increase application rate (by some percentage of the annual requirement) as determined by the phenology of fruit growth, and increase it to its maximum rate by the middle of the first stage up to the early second stage of fruit growth. Then, in the middle of the second stage of fruit growth, nitrogen rate should be reduced to its minimum or stopped altogether (depending on plant variety).

The diversity of cultivars is very important for the sustainable production of citrus. Also, there is little information about the effect of common sour orange substitute rootstocks on new cultivars. The present research was conducted to investigate the vegetative growth of six navel orange cultivars ('Fucumoto'; 'Navelina'; 'Navelate'; 'Thomson navel'; 'Cara cara' and 'Lane late navel') on three poncirus hybrids rootstocks ('Carrizo citrange'; 'Swingle citrumelo' and 'C-35 citrange'), during seven years. Traits related to vegetative growth such as tree volume, rootstock and scion morphological compatibility, leaf nutrient concentration and tree survival were measured. All measured vegetative traits were affected by year, rootstock and cultivar. The rootstocks affected the concentration of all nutrients in the leaves. Tree height and volume and the required area for orange trees on the 'Carrizo citrange' were less than the other two rootstocks. 'Navelate' and 'Lane late navel' cultivars had the highest and 'Fukumoto' had the lowest tree volume. The compatibility of the graft union decreased with the increasing age of the trees. In the last year, there was the lowest compatibitity between 'Fukumoto' cultivar and 'citrumelo' rootstock (0.60) and the highest between 'Navelate' cultivar and 'Carrizo citrange' rootstock (0.77). One tree of 'Fukumoto' and 'Navelina' with 'C-35' rootstock declined in the last year of the experiment, but other rootstocks and cultivars did not show any signs of yellowing. The maximum area required for seven-year-old trees of 18 studied rootstock and cultivar combinations with regular annual pruning was about 9.5 m2, which was recorded in 'Navelate' cultivar on 'C-35 citrange' rootstock.

In order to investigate the fruit puffiness status and the effect of calcium nitrate spray on quality and puffiness of Satsuma mandarin fruit, two separate experiments were conducted. In the first experiment, the puffing rate of Satsuma mandarin (Citrus unshiu 'Sugiyama') fruit in different orchards in the eastern region of Mazandaran was compared. In the second experiment, the effect of calcium nitrate application as foliar spray on reduction of fruit puffines was examined. The experiment was performed in a commercial orchard, with sour orange rootstock, based on a randomized complete block design, with six treatments and four replications. Treatments included: T1. Control (no Calcium nitrate spray); T2. Calcium nitrate spray in late May; T3. Calcium nitrate spray in mid- June; T4. Calcium nitrate spray in early July; T5. Calcium nitrate spray in late May and mid- June; T6. Calcium nitrate spray in late May, mid- June and early July. The results of the first experiment showed that the percentage of puffed fruits in the orchards of different regions varied from 27 to 46%, and the number of puffed fruits increased significantly from the early of November. The results obtained from the second experiment indicated that calcium nitrate spray in T5 (late May and mid- June) and T6 (late May, mid- June and early July) treatments had a significant effect on puffiness, so that the number of puffy fruits reduced by about 20% compared to the control, but this anomaly did not completely prevented. Also, calcium nitrate spray had a significant effect on Ca concentration in fruits. The highest concentration of Ca in whole fruit, fruit peel and inner skin (albedo) occurred in T5 and T6 treatments. Therefore, calcium nitrate spray is recommended at least 2 times (late May and mid- June) up to a maximum of 3 times (late May, mid- June and early July) in Satsuma mandarin Orchards.

The Smooth Flat Seville (Citrus spp. hybrid of uncertain origin) has been reported as one of the rootstocks tolerant to soil lime and Tristeza disease. Therefore, the present study aimed to evaluate the growth trend and tolerance of this rootstock to the calcareous soils of east Mazandaran Province, Iran. An experiment was conducted for two years in a randomized complete block design in seven soils with calcium carbonate equivalent ranging from 2% to 45%. Measurements included vegetative growth trend, dry weight, chlorosis rate, fluorescence index (Fv/Fm), chlorophyll and nutrient concentration in leaves and roots. The results showed that the highest average dry weight of aerial parts was obtained from soils with total lime of 9%. There was no significant difference in the chlorosis rate of the leaves of seedlings on this rootstock in different soils. The average of Fe concentration in the roots was 11.1 times the average concentration in the leaves, indicating accumulation and deposition of iron in the roots. In most soils, the amount of manganese available for citrus trees was excessive, but the mean concentration of leaf was less than adequate. The overall mean Mn concentration in the roots was about 4.6 times more than its mean concentration in the leaf. From macroelements, magnesium and sulfur had the highest and lowest transfer efficiency and, from microelements, active Fe and total Fe had the highest and lowest transfer efficiency, respectively. According to the results of this research, chlorosis rate of the seedlings in different soils did not differ significantly, which shows this rootstock is tolerant to soil lime. Therefore, Smooth Flat Seville can be a good substitute for orange rootstock in calcareous soils (especially with medium and high lime).

In a two-year pot experiment, the response of Miyagawa satsuma mandarin on Swingle citrumelo rootstock was investigated in soils with different ranges of lime. Furthermore, in a field experiment, the plant growth trend, yield, and quality were studied in two regions (plain and piedmont) for 10 years. In the pot experiment, the highest shoot dry weight was obtained from soils with 14% total lime and in soils with more total lime, shoot dry weight decreased sharply. The most chlorosis rate was obtained in soils with more than 30% lime. The highest total Fe in the roots and the least signs of leaf chlorosis was detected in the soils with less than 9% lime. The average Fe concentration in the roots was about 7.5 times more than that in the leaves, indicating accumulation and deposition of Fe in the roots. The amount of available Mn was excessive in most soils but leaf Mn in most cases was less than adequate. The Mn concentration in the roots was 3.2 times more than that in the leaves. The field experiment showed that tree volume in the plain was always higher than that in piedmont. The trees of the piedmont had alternate bearing cycles. The yield increased from 23 kg per tree at the beginning of the reproductive period to 80 kg in the final year of the experiment. The best harvest time in both regions was early October. Generally, use of this rootstock in soils with less than 9-14% total lime, is recommended.

In order to investigate the state of carbohydrates and the effect of naphthalene acetic acid (NAA) application on yield and alternate bearing of Miyagawa Satsuma mandarin, two separate experiments were performed an Miyagawa Satsuma mandarin oechard. In the first experiment, the trend of changes in the concentration of carbohydrates (soluble sugars and starches) in the leaves and roots of trees were investigated. The second experiment were performed as randomized complete blocks design with 4 replications during 7 years. Treatments included: control; 150, 300 and 450 mg/l NAA spraying before physiological abscission of fruitlets. The results of the first experiment showed that the average changes of starch and soluble sugars in foliar leaves and roots were about 6.3 times and 2.34 times higher, respectively. The results of the second experiment showed that NAA application in the first stage of fruit growth in “on” years, increased yield in “off” years, and gradually yield variation in “on” and “off” years decreased. So that treatment 300 mg NAA l-1 had the highest cumulative yield and the lowest alternate bearing index. However, all NAA treatments reduced alternate bearing index compare to control, significantly. Therefore, based on the results of this project to modulate alternate bearing, spray NAA in “on” at a concentration of 300 milligrams per liter from 25 days after flowering to about 40 days after flowering is recommended.

Due to low efficiency of chemical fertilizers and high nitrogen demand for fruit trees at the first stage of growth, early spring growth, flowering and fruit set in fruit trees is heavily dependent on tree N reserves. Therefore, this experiment was performed to investigate the possibility of urea, zinc sulfate and boron uptake, as well as transmission of these materials from leaves to storage organs and from storage tissues to new developing tissues, in autumn foliar application. On the other hand, nitrogen application in early spring is more often devoted to the vegetative growth of the branches, while nitrogen uptake at the end of the season goes more to the storage organs such as root bark and tree trunks.

The experiment was conducted in a randomized complete block design with seven treatments and four replications for three years on 56 trees with the same age and size trees in the east of Mazandaran. The treatments included: 1. Control, 2. Urea (10 g.l-1), 3. Urea (10 g.l-1) + Zinc sulfate (5 g.i-1), 4. Urea (10 g.l-1) + Zinc sulfate (5 g.l-1) + Boric acid (4 g.l-1), 5. Urea (15 g.l-1) + Zinc sulfate (5 g.l-1) + Boric acid (4 g.l-1), 6. Urea (20 g.l-1) + Zinc sulfate (5 g.l-1) + Boric acid (4 g.l-1), 7. Urea (25 g.l-1) + Zinc sulfate (5 g.l-1) + Boric acid (4 g.l-1).

Urea foliar application increased the nitrogen concentration of leaves in autumn and also increased the concentration of nitrogen in bark and wood in various organs. Foliar application of zinc sulfate and boric acid also increased the concentration of zinc and boron in the leaves. Measuring the concentration of nitrogen, zinc and boron in the leaf tissue of young shoots in the spring showed that in foliar spraying treatments, the nitrogen concentration of young leaves increased compared to the control. Measurement of nitrogen concentration in leaves of young shoots, bark and wood of annual shoots as well as flower and flower buds showed that foliar spraying treatments had a significant effect on nitrogen concentration of bark and wood of these shoots. Thus, the nitrogen concentration increased from 0.53% in the control treatment to 0.92% in the treatment 25 gl-1 urea + 5 gl-1 zinc sulfate + 4 gl-1 boric acid.

According to the results of this experiment, in order to increase the storage of nitrogen, increase the fruit set, and reduce the flower and fruitlets drops, it is strongly recommended to do foliar application of urea at 20 to 25 gl-1 + zinc sulfate at 5 gl-1 + boric acid at 4 gl-1 in autumn, when 10 to 15 percent of the leaves are yellow.

In Mazandaran Province, use of Carrizo citrange (Citrus sinensis Osb. × Poncirus trifoliata L. Raf.) as an alternative rootstock for citrus is expanding. Also, due to great changes in lime content  of the soils (0- 45%) and soil texture, it is necessary to study the response of this rootstock to the soils conditions. Therefore, the present study aimed to evaluate the growth trend and tolerance of this rootstock to calcareous soils of East Mazandaran. To this end, an experiment was conducted for two years in a randomized complete block design in seven soils with different textures (sandy to clay loam) and calcium carbonate content (2- 45%). Measurements included vegetative growth trend, dry weight, chlorosis rate, fluorescence index (Fv/Fm), and nutrient concentration in leaves and roots. The results showed that the highest dry weight of aerial parts was obtained from soils with loam texture and total lime of 2% and soils with loamy sand texture and total lime of 40%. The highest chlorosis rate was obtained from soils with loam texture and 45% lime with 16% active lime and the lowest chlorosis rate was obtained from active- lime-free soils and 2% total lime. The average of Fe concentration in the roots was about 8.94 times the average concentration in the leaves, indicating accumulation and deposition of iron in the roots. In most soils, the amount of manganese available for citrus trees was excessive, but the mean concentration of leaf was less than adequate. The overall mean Mn concentration in the roots was about 6.67 times more than its mean concentration in leaf. The most limiting element for Carrizo citrange rootstock and scion was Mn and its low transfer efficiency from root to leaf. The results of mean chlorophyll content and chlorophyll fluorescence index (Fv / Fm) of leaves showed that soils with loam texture and low total lime and soils with light texture and high total lime had the highest amount of chlorophyll and fluorescence index. According to the results, soil texture influenced tolerance of Carrizo citrange rootstock in calcareous soils and, in relatively medium and heavy texture soils, the use of this rootstock in soils with total lime less than 14% is recommended, but in light-textured soils, its use in soils with total lime about 40% is also recommended. Therefore, in choosing this rootstock, it is recommended to consider soil texture and lime content.

Today, the existence of various biotic and abiotic stresses has necessitated research with different rootstocks in different climatic and soil conditions. So, the growth trend and some characteristics of Miyagawa Satsuma mandarin on Swingle citrumelo rootstock in alluvial and piedmont plain in East Mazandaran during 10 years were evaluated. The results showed that the trees on this rootstock were vigorous and had high yield (62 kg per tree). The affinity of scion and rootstock in both locations was 0.8. The tree canopy volume at the end of the experiment was 19.09 in alluvial and 11.62 m3 in piedmont plain. So it is recommended to increase the number of alluvial and piedmont plain trees to more than 600 and 800 plants/hectare, respectively. Despite several frost stresses during 10 years, the survival of rootstock and scion compound was 100 % in both locations, however, the piedmont trees entered the alternate bearing cycle as at the end of the experiment, the trees alternate bearing index was 0.23 % in alluvial and 0.67 % in piedmont plain. The best harvest time for both locations was early October. Fruits of the alluvial plain had more weight and extract (7.6 g and 5.8 %), smoother peel, and higher harvest index (1.64 units); In contrast, fruits of the piedmont was more oblate and had thicker peel (0.35 mm) and higher peel weight, sugar, total acid and vitamin C (8.7, 25, 62 and 28.6 %, respectively). In general, the trees in alluvial location had higher visual quality fruits and a more regular and stable annual yield.

Today, the existence of various living and non-living stresses has necessitated research with different rootstocks in different climatic and soil conditions. Thus, the growth trend and some vegetative and reproductive characteristics of Miyagawa Satsuma mandarin on C-35 citrange rootstock in plain and foothills of east Mazandaran were evaluated during 10 years. The trees on this rootstock had medium growth and yield. The canopy volume at the end of the experiment was 13.75 and 5.90 m3 in plain and foothills, respectively. Despite several frost stresses, the survival of trees was 100% in both locations, however, the trees in foothills entered an alternate bearing cycle, and the alternate bearing index reached 0.27 and 0.65 percent in plain and foothills, respectively. Tree yield in plain and foothills was 48 and 35 kg and considering planting distances, the yield was 24 and 18 tons per hectare, respectively. Fruits in foothills had more total soluble solids, titratable acid, and ascorbic acid (24, 72, and 16 percent, respectively) and less harvest index (3.1 units). The best harvest time in plain was late September and in foothills was early October. In general, the plain had higher external quality fruits and a more regular and stable annual yield.

One of the strategies for improving citrus yield and fruit tolerance to frost in citrus gardens is practicing balanced fertilization. So that if the concentration of each element is lower than the optimum concentration, the yield of the plant will be reduced. Therefore, the aim of this study was to investigate the role of optimum fertilizer application on increasing quantitative and qualitative yield of oranges and also resistance to cold stress.

In order to investigate the role of balanced fertilization on some of the characteristics of citrus fruits, including increased resistance to frost, a two-year trial was conducted on Thomson and Bloody Thomson with two treatments and five repetition in the years of 2016-17 and 2017-18 in a citrus garden in Neka city in Mazandaran province. treatments included, T1= control (Traditional fertilization method, i.e. every year in late autumn, 2 kg of urea, 1 kg of triple superphosphate per tree, along with animal manure under droppers) and T2= balanced fertilization according to the soil and leaf analysis results, i.e. every year in late autumn, 2 kg ammonium sulfate, 1.5 kg potassium sulfate 1 kg magnesium sulfate and 0.5 kg zinc sulfate mixed with animal manure and surface soil with deep placement under droppers. It should be noted that in both years, the same fertilizer sources were used. Also, in the summer of second year, for each tree, 0.5 kg of soluble potassium sulfate with zinc (SSOP+Zn-EDTA) was used in two split times (July and August).

The results revealed that a) In the first year, while the average yield in T1 for Thompson Blood Orange and Thompson Novell Orange were 40 and 75 kg, in T2, it increased up to 72 and 175 kg per tree and in the second year, also these figures were increased significantly from 80 and 140 kg and 155 and 305 kg per tree, respectively. In both years, the differences were significant at 1% level. The main reason for this performance in the second year was due to split application of SSOP+Zn during the summer. b) While the average dry matter percentage for Thompson Blood Orange and Thompson Novell Orange for the first year in T1 were 15.6 and 22%, in T2 they were increased to 17.1 and 24.4%, respectively. For the second year, they were increased from 18.1 and 22.3% in T1 to 20 and 25.2% in T2, respectively .c) While frost tolerance in Thompson Blood Orange and Thompson Novell Orange during the first year in were 0 and -1 degrees Celsius in T1, frost tolerance were increased in T2 up to -2 and -5 degrees Celsius. In the second year, these figures were changed from -1 and -3 to -4 and -9, respectively. One of the main reasons for this improvement in frost tolerance of citrus fruits was due to increase in their dry matter percentage and positive effects split application of K and Zn fertilizers.

While the superiority of balanced fertilization has been proven, it is highly recommended that for producing valuable citrus fruits, this practice should be generalized in all citrus gardens.

Witches’ broom disease of lime (WBDL), caused by ‘Candidatus Phytoplasma aurantifolia’, is major limiting factor for Mexican lime (Citrus aurantifolia Swingle) production in southern Iran. In this investigation, leaf nutrient profiling of the healthy and infected rooted Mexican lime during WBDL progression (90-330 days) as well as to distinguish the infected from the healthy Mexican limes under greenhouse condition. For this aim, the healthy and infected plants were sampled 90, 150, 210, 270 and 330 days after inoculation with phytoplasma and leaf nutrient concentrations including nitrogen, phosphorus, potassium, calcium, magnesium, boron, iron, manganese, zinc and copper were measured during WBDL progression. The results showed phytoplasmal infection mostly caused to a marked decrease in the concentration of nitrogen, calcium, boron, manganese, and significant increase in phosphorus, magnesium, potassium, iron, and zinc in the infected leaves. In Mexican lime leaves, copper concentration did not significantly change after inoculation with phytoplasma with respect to the healthy plants. In addition, the principal components analysis (PCA) based on the concentration of nutrients could not distinction infected and healthy plants in the early stages of sampling (before the appearance of symptoms), but PCA revealed a clear distinction between the leaf nutritional profiles of healthy and infected plants after the appearance of symptoms during the progression of WBDL. In conclusion, this study provides new insights into the lime response to phytoplasma infection during the progression of WBDL and it can be useful in adopting strategies to improve and increase the economic efficiency of trees infected with WBDL.

In recent years, floods and waterlogging conditions in the northern and southern provinces of Iran have become important challenges, which directly and indirectly affect the solubility and availability of most of the soil nutrients. To investigate the effects of waterlogging, seven soils were selected from the orchards of different regions of East Mazandaran (Ghaemshahr, Sari, and Neka). In a pot experiment, the soils were placed under continuous waterlogging conditions for 70 consecutive days, and the trend of changes in oxidation-reduction potential (Eh), electrical conductivity (EC), pH, concentrations of Ca2+, K+, Na+ and iron (Fe2+ and Fe3+) of these soils were studied. The results showed that the mean Eh values of soils dropped within 2 days of waterlogging, then increased slightly in the third day, and then began to drop again, and this drop trend continued until the end of the period, from 552 mV at the beginning of waterlogging and reached -99 mV at the end of the period. The average soil pH decreased from 7.8 to 6.88 after 10 days of waterlogging, and then increased and reached a relatively stable equilibrium (about 7.05). The average EC values of soils, increased after the first day of waterlogging, then, declined to 2.13 dS/m, and again increased to the maximum value (about 3.09 dS/m) after 10 days. The concentration of Ca2+, K+, and Na+ in the soil solution increased after waterlogging and reached the maximum within 2 days, then gradually decreased and reached a relatively constant amount. The concentration of Fe within the first days after waterlogging was 1.95 mg/L, increased to 6.67 mg/L after 10 days, then decreased to 4.27 mg/L after 20 days, and eventually increased to 9.98 mg/L at the end of the period (70 days). Based on the results of this study and considering the trend of EC changes and concentrations of nutrients in soil solution, application of chemical fertilizers to soils should be avoided after waterlogging occurrence. Also, due to the changes in soil Eh, the continuation of waterlogging for more than 5 days can lead to relatively anaerobic conditions in the soil and damage to fruit trees, therefore, drainage of excess water is recommended.

Citrus trees are sensitive to zinc deficiency and zinc deficiency in citrus trees is a common nutritional disorder that causes changes in the anatomy, morphology and cytology of citrus trees, leading to reduced flowering, fruit set, performance and production stability. Due to the limitation of zinc in the soils and the economic importance of citrus for Mazandaran province, the study of zinc status in citrus orchards and the management of Zn application (accordance to growth phenology) and its effect on Zn deficiency and quality of Thomson Navell fruits were conducted.

To study zinc(Zn) status and its effect on yield and quality of Thomson navell orange, two separate experiments were conducted in East of Mazandaran Province, Iran. The first experiment was conducted in citrus orchards of the region, and the second, as a randomized complete block design with seven treatments and four replications was conducted in an orchard of Thomson navel on sour orange rootstock. Treatments included: 1- First control (without zinc); 2- Second control (without zinc and with urea spray); 3- 200 g zinc sulfate per tree as soil application, before leaf development; 4- 200 g zinc sulfate per tree as fertigation, in the first stage of fruit growth; 5- 200 g zinc sulfate per tree as fertigation, in the first and second stages of fruit growth; 6- zinc sulfate spraying in the first stage of fruit growth; 7- zinc sulfate spraying in the first and second stages of growth.

The first experiment showed that the orchards of Behshahr and Galogah had the lowest deficiency symptoms and Ghaemshar and Juybar had the most deficiency symptoms. The results of the second experiment showed that soil application before leaf development had no effect on chlorosis, yield, fruit and zinc concentration in leaf and fruit, but its application as fertigation and spraying increased fruit yield, diameter, and fruit weight, in leaf and fruit zinc concentration. The highest leaf Zn concentration was obtained from spray treatment in the first and second stages of fruit growth. Fertigation treatment significantly increased the root Zn concentration compared to the control.

Generally, according to the results of this experiment, for orchards with a history of mild symptoms of zinc deficiency or probable zinc deficiency, the application of zinc sulfate as fertigation or spray after petal fall in the first stage of fruit growth is recommended, However, for orchards that have severe symptoms of zinc chlorosis, two fertigation or foliar application with zinc sulfate at the first and second stages of fruit growth is recommended.

To increase yield and reduce alternate bearing of satsuma mandarin trees, an experiment was performed in randomized complete block design during seven years. Treatments include: control; winter urea spraying (before flower bud differentiation); urea spraying at full bloom (at the opening of at least 50% of flowers) and summer urea spraying (after summer physiological abscission of fruitlets). Results showed that yield difference between “on” and “off” years in the first and second years was very high as from 94.19 kg for each tree in the first (on) year reached to 13.69 kg in the second (off) year which had about 80 kg difference. But yield difference in following “on” and “off” years (third and fourth years of experiment) reach to about 40 kg that was about half of previous alternate bearing cycle. Therefore, urea spraying adjusts alternate bearing during years of experiment, gradually. Treatments of urea spraying had significant difference on cumulative yield at 5% as the highest obtained from control and at flowering spray treatments. Also, effect of different urea treatments on alternate bearing index was significant. Control trees, had the most alternate bearing index and winter and spring spray treatments had the least alternate bearing index. All urea spray treatments increased fruit average weight compare to control. Therefore, based on the results of this project to modulate alternate bearing, winter and spring spraying of urea recommended.

In this study, the response of Miyagawa Satsuma mandarin (Citrus unshiu) on Swingle citrumelo rootstock to calcareous soils of the east of Mazandaran in Iran was investigated. Research

The experiment was done by seven soils with different calcium carbonate (2-45%) for two years.

Soils with 14% total lime and 5% active lime had the highest shoot dry weight. Soils with 30 and 45% total lime, and 14 and 16% active lime had the highest chlorosis and soils with no lime or 3% active lime and 2 to 9% total lime had the least chlorosis. Soils with 2 and 9% total lime had the highest Fe concentration in root and the least chlorosis. Fe concentration in the roots was about 7.5 times that of the leaves, which show Fe accumulation and inactivation in the root. Mn concentration in leaves in most soils was lower than optimum, while available Mn in most soils was more than optimum (2.5 mg kg-1). Mn concentration at the roots was about 3.2 times of that in the leaves. In contrast, although available Zn of some soils was lower than optimum, in most soils the Zn concentration of leaves was in the optimum range. Research limitations: No limitations were founded.

Mn, due to low uptake and transmission efficiency from roots to shoots and severe deficiency in leaves is the most limiting microelement in this rootstock-scion combination. According to this research, Swingle citrumelo rootstock is appropriate in soils with total and active lime less than 14% and 5%, respectively.

Due to the spread of Tristiza disease in east of Mazandaran province and the sensitivity of the region's common rootstock, C-35 rootstock is being promoted as an alternative rootstock tolerant to this disease. Considering the changes in the lime content of the soils in the region, in this study, the response of Satsuma mandarin on C-35 rootstock to calcareous soils east of Mazandaran province was investigated in a randomized complete block design. The results showed that the highest mean dry weight of aerial parts was obtained from south Babol soils with total lime content of 2%. The highest leaf chlorosis was obtained from West Sari soil with 10% active lime and 25% total lime, and the lowest chlorosis was obtained in the soil without active lime and 2% total lime. In southern Sari soil with 14% lime, the highest concentration of total iron and the lowest concentration of active iron were in the roots. The average concentration of total iron in the roots was about 11 times the average concentration in the leaves, indicating accumulation and deposition of iron in the roots. The amount of available manganese for citrus trees was excessive in most soils, but the mean concentration of leaf manganese in most cases was less than adequate. The overall mean manganese concentration in the root was about 4.7 times more than its mean concentration in leaf. For C-35 rootstock and scion, the most restrictive element was Mn deficiency and its low transfer efficiency from root to leaf. The results of mean chlorophyll content and chlorophyll fluorescence index (Fv/Fm) of leaves showed that the soils with low total lime (south of Babol and west of Ghaemshahr) had the highest amount of chlorophyll and fluorescence index. In general, according to the results of this study, soil texture has influence on tolerance of C-35 rootstock in calcareous soils, and in relatively heavy and heavy textured soils with a total lime less than 9-14%, use of this rootstock is recommended

In order to increase the storage of nitrogen, zinc and boron of peach trees and its effect on flowering and fruit set, an experiment was conducted in a randomized complete block design with seven treatments and four replications for three years (2015-2018) on 56 trees with the same age and size trees in the east of Mazandaran. Treatments included: 1) control, 2) Urea (10 gL-1), 3) Urea (10 gL-1) + Zinc sulfate (5 g.i-1), 4) Urea (10 g.l-1) + Zinc sulfate (5 g.l-1) + Boric acid (5 g.l-1), 5) Urea (15 gL-1) + Zinc sulfate (5 gL-1) + Boric acid (5 gL-1), 6) Urea (20 g.L-1) + Zinc sulfate (5 gL-1) + Boric acid (5 gL-1), and 7) Urea (25 g.L-1) + Zinc sulfate (5 gLl-1) + Boric acid (5 g.L-1).   The results showed that urea was quickly absorbed by leaves, so that nitrogen concentration in leaf tissue increased shortly after spraying. The measuring trend of nitrogen concentration at different times in foliar spray treatments showed that nitrogen concentration in leaf tissue increased initially and then began to decrease again. Therefore, in treatments 7, nitrogen concentration at 4, 24, and 48 hours after spraying increased from 2% before spraying to, respectively, 3.15%, 3.07%, and 2.06%. That indicates the absorption and then removal of nitrogen from the leaf tissue. Zinc concentrations in the leaves increased in all treatments by foliar spray of zinc sulfate, and this trend of absorption and increase of zinc concentration in the leaf tissue lasted for 48 hours after spraying. Boric acid foliar spray also increased the concentration of boron in the leaf tissue, such that the concentration of boron in the leaf tissue reached the maximum after 4 hours, and then decreased gradually. Results showed that fallspray treatments were effective in increasing fruit set and reducing abscising fruitlets, and this increase in fruit set was statistically significant. However, treatment seven that accelerated leaf loss had the highest effect on fruit formation, and was about 50% higher than the control. Therefore, to increase the fruit set and reduce the flower and fruitlets drops, applying treatment 7 in autumn, when 10-15% of the leaves are yellow, is recommended.

An important issue in some citrus varieties including Satsuma mandarin is alternate bearing. Therefore, to reduce alternate bearing in Satsuma mandarin trees, an experiment was conducted as randomized complete block design with 4 treatments and 4 replications. The experiment was done during 7 years with 32 Satsuma mandarin trees which were almost the same age and size. The experimental treatments of nitrogen use management included T1= Control (three splits, the first split late in March, the second late in April after fruit formation, and the third one month after the second split); T2= Summer application (15% before flowering, 30% after fruit formation, 20% at the time of physiological drop, and 35% after the beginning of fruit development); T3= Autumn application (15% before flowering, 30% after fruit formation, 30% at the time of physiological drop and 25% after fruit harvest); T4= Summer and autumn application (15% before flowering, 30% after fruit formation, 20% at the time of physiological drop, 20% after starting development, and 15% after fruit harvest). Results showed that fruit yield had the greatest difference in the first and second years of experiment and then the yield difference gradually decreased. The lowest cumulative yield (379  kg/tree) was obtained from the control and the highest cumulative yield (446 kg/tree) was obtained from summer and autumn N treatment. Results showed that the control had the highest alternate bearing index (0.40) and autumn N application treatment had the lowest treatment index (0.18). Also, year had a significant effect on fruit average weight as the highest fruit average weight was obtained in the fifth year. In all N application treatments, fruit average weight was significantly more (at 5% level) than the control. Based on the results of this study, to minimize alternate bearing, the time and amount of nitrogen fertilizers are recommended in the following four stages: 15% at the beginning of flowering, 30% between fruit set and the beginning of June drop; 30% at the beginning of June drop to early phase of the second growth of fruits; and 25% after fruit harvest.

To study manganese (Mn) status and its effect on fruit yield and quality of Thomson navel oranges, two separate experiments were carried out in East of Mazandaran Province, Iran. The first experiment was conducted in citrus orchards of the region, and the second was conducted in an orchard of Thomson navel on sour orange rootstock, using a randomized complete block design with seven treatments and four replications. Treatments included: 1) First control (without manganese); 2) Second control (without manganese and with urea spray), 3) 300 g manganese sulfate per tree as soil application, before leaf development, 4) 300 g manganese sulfate per tree as fertigation, in the first stage of fruit growth, 5) 300 g manganese sulfate per tree as fertigation, in the first and second stages of fruit growth, 6) Manganese sulfate spraying in the first stage of fruit growth, and 7) Manganese sulfate spraying in the first and second stages of growth. The results showed that the orchards of Sari and Neka had the most deficiency symptoms. The results of the second experiment showed that soil application before leaf development had no effect on yield, fruit quality, Mn concentration in leaf, fruit and root, but its application as fertigation and spraying increased fruit yield, diameter, and weight, leaf and fruit manganese concentration. The highest leaf Mn concentration was obtained from the first and second stage of fruit growth treatment. Fertigation treatment significantly increased the root Mn concentration compared to the control. In general, according to the results of this experiment, for orchards with a history of mild manganese deficiency or probable manganese deficiency, application of manganese sulfate as fertigation or spray after the fall of petals in the first stage of fruit growth is recommended. However, for orchards that have severe symptoms of manganese chlorosis, two foliar applications or fertigations with manganese sulfate, after petal fall and second stage of the fruit growth, before the growth of the fall flash, is recommended.

The area under citrus cultivation in Mazandaran Province amounts to 120,000 ha. The soils in the area contain calcium carbonate (lime) that increases as we move from the central to the eastern stretches of the province. Moreover, the citrus rootstock in the region (sour orange) is sensitive to the CTV disease. These considerations require a substitute rootstock that is not only tolerant or resistant to the disease but is also adaptable to calcareous soils. The present study was conducted to evaluate the vegetative and nutritional responses as well as tolerance of Troyer citrange to different levels of calcium carbonate (lime) in the soils in this region. More specifically, the study was conducted in a randomized complete block design to determine the response of Satsuma mandarin on Teroyer Citrange rootstock to the calcareous soils in eastern Mazandaran. The highest average dry shoot and root weights were obtained for soils with total and active lime contents of 14% and 5%, respectively. The highest leaf chlorosis levels were recorded for soils with active lime contents of 14% and 16% and total lime contents of 30 and 45%, respectively. Also, the highest and lowest increments in diameter were obtained with soils containing 9% and 25% lime, respectively. Soils with total lime contents of 14% and 30% yielded the highest total iron concentrations in the root. Mean total iron, manganese, and zinc concentrations, respectively, in the root were about 12.5, 8, and 4.6 times their concentrations in the leaves, indicating their accumulation and precipitation, especially iron and manganese, in the roots. Average leaf Mn concentrations were less than adequate in all the plants grown in all the soils, while available manganese in most soils was higher than optimal for citrus trees. Based on the results obtained, calcium and magnesium from among the high consumption elements recorded the highest while sulfur and phosphorus exhibited the least root to leaf transfer efficiencies. From among the low consumption elements, iron and manganese exhibited the least root to leaf transfer efficiency. In general, Teroyer Citrange is a semi-tolerant rootstock for calcareous soils and may not be recommended for cultivation in soils with total and active lime contents beyond 20% and 10%, respectively.

Root systems in citrus trees develop from rootstocks. They have, thus, direct effects on water and nutrient uptake and translocation. The present study was conducted to evaluate the effects of three rootstocks common in northern Iran (i.e., sour orange, Swingle citrumelo, and Troyer citrange) on the nutrient uptake, translocation, and accumulation (NAI) as well as their translocation indices (NTI). For this purpose, one-year old seedlings of sour orange, Swingle citrumelo, and Troyer citrange were cultivated in a loamy soil under glasshouse conditions. After six months, the seedlings were harvested to measure their dry weights as well as their leaf, stem, and root concentrations of phosphorus, potassium, calcium, iron, manganese, zinc, and copper. Also, the rootstocks investigated were discriminated based on their nutrient accumulation and translocation indices as determined by factor analysis. Results showed the superiority of Troyer citrange in terms of phosphorus and iron uptake; citrumelo in terms of potassium and copper uptake; and common sour orange in terms of calcium and manganese uptake. The order recorded for the rootstocks in terms of their nutrient accumulation indices was sour orange>Troyer citrange~Swingle citrumelo. It was also found that the nutrient translocation indices of the three citrus rootstocks decreased in the following order: Swingle citrumelo > Troyer citrange > sour orange. Clearly, the citrus rootstocks investigated exhibited differential nutritional behaviors and different capacities with respect to utilizing plant nutrient elements.

Summer fruit drop (June drop) is one of the main reasons for low yield in some citrus varieties in northern Iran. Recognition of physiological changes in fruit abscission zone (calyx) and application of suitable treatments would reduce or control abscission. Hence, the changes of auxin, cellulose, and polygalacturonase in calyx of Thomson navel fruitlets were measured and their relations with abscission and mineral nutrition of fruitlets as well as the effect of different treatments on them at June drop were evaluated. A randomized complete block design (RCBD) experiment was performed with 8 treatments and 4 replicates. Treatments were as follows: 1. control; 2. urea (1%); 3. urea 2,4-D (15 mg l-1); 4.urea GA3 (15 mg l-1); 5.urea sucrose (1%); 6.urea ZnSO4 (0.5%); 7. urea ZnSO4 2,4-D; and 8. urea ZnSO4 GA3. Results showed that abscission had a significant negative correlation with auxin and a significant positive correlation with cellulase and polygalacturonase of the calyx. The control group had the lowest auxin and the highest cellulase in calyx. Maximum effect (Approximately 24% reduction in abscission) was obtained after foliar application of urea sucrose (treatments 5). The use of urea alone or in combination with 2, 4-D and GA3 had no effect on abscission; however, using it in combination with sucrose was the most efficient treatment in this experiment. Furthermore, the combination of urea and Zn provided an effective treatment. A majority of micronutrients (Mg, Fe, Mn, Zn, Cu and B) had a positive correlation with auxin and a negative correlation with enzymes. Therefore, nutritional management and providing an appropriate condition to maximize photosynthesis can balance physiological metabolism and reduce fruitlets abscission.