عبدالحسین ضیائیان

Due to the calcareous nature of our country's soils, the plant phosphorus availability is low.  In order to study the effects of soil microorganisms and biochar application on the phosphorous availability, growth and yield of sorghum and some soil chemical characteristics, a pot experiment as factorial in completely randomized design were conducted. In this research, effects of two treatments of inoculation and non-inoculation of phosphate solubilizing bacteria and two biochar consumption treatments (0 and 1.5% by weight) on the four levels of zero, 25, 50 and 75 mg .kg-1 of P2O5 as triple superphosphate source, in three replications were studied. The results showed that phosphate solubilizing bacteria inoculation and biochar application had a significant increase on the volumes, fresh and dry weight of roots, fresh forage yield and phosphorous, nitrogen, potassium and zinc uptake. Using phosphorus increased the forage weight by increasing the height and diameter of the stems. Phosphorus application also increased soil salinity and decreased soil organic carbon, but bacteria inoculation increased the amounts of organic carbon and decreased soil salinity while biochar application increased both of organic carbon and salinity amounts. None of them had a significant effect on soil acidity. Data showed that although single application of the biochar and or bacteria had significant effects on the phosphorus uptake increases, but combined use of biochar and phosphorus and bacteria with phosphorus and also combination of these three treatments caused sorghum yield increases by increasing of phosphorus uptake. In other words, biochar or bacterial had a positive effect on the phosphorus effectiveness so that the highest plant height, fresh and dry forage, and the highest phosphorus, nitrogen, potassium and zinc uptake were obtained from the combined use of phosphorus solubilizing bacteria, biochar and 50 mg P2O5 per kg of soil.

In order to investigate the role of mycorrhiza inoculation and Biochar application on the phosphorus availability, growth, and yield of sorghum and some chemical properties of soil, a pot experiment were conducted as a factorial experiment in completely randomized design, with three replications. In this research, application effects of biochar (0 and 1.5 % by weight), mycorrhiza (inoculation and non-inoculation of mycorrhiza fungi) and phosphorous (four levels of triple superphosphate: 0, 55, 110, and 165 mg .kg-1 soil) on sorghum were studied. The results showed that phosphorus and biochar application significantly (P<0.01) increased foliage and roots weights, roots volume, and also nitrogen, phosphorous and potassium uptake. Furthermore, the application of phosphorus in combination with biochar and inoculation of plant roots with mycorrhiza increased the above-mentioned traits to a higher level. Application of phosphorus or biochar alone increased soil salinity, but their combined application together with the plant root inoculation using mycorrhiza decreased it. Application of phosphorus decreased soil organic carbon, whereas biochar and mycorrhiza significantly increased it. The maximum dry foliage (24.4 g.pot-1) and the maximum phosphorous uptake (79.9 mg.pot-1) were obtained from combined application of mycorrhiza, biochae and 55 mg.kg-1 triple superphosphate. The results showed that biochar and or mycorrhiza application affect the amount of phosphorus consumed[H1] , but it should be noted that prolonged use of biochar could increase soil salinity.

Reference crop evapotranspiration (ETo) is an important parameter for determining crop water requirements in the FAO method, and hence, its accurate estimation is of crucial importance in optimizing crop water use and water resources management. In this research where conducted in Haji Abad region of Hormozgan province for four years, weekly evapotranspiration from grass as a reference crop was measured using a drainable lysimeter. The ETo was also estimated using eleven models including FAO Radiation, Evaporation Pan, Blaney-Criddle, Penman and Penman-Monteith and Papadakis, Ivanov, Jensen-Haise, Hargreavse-Samani, Tork, and Makking models. The estimated ETo values from different models were compared with the data measured from lysimeter using linear regression, root mean square error, mean bias error, index of agreement and variance of the distribution of differences. Results showed that FAO Penman, Ivanov, Papadakis and Jensen-Haise models overestimated ETo, but the FAO evaporation pan, Hargreaves-Samani, Turk and Making models underestimated it. The results also indicated that the FAO Blaney-Criddle and FAO Penman-Monteith models had respectively higher accordance and homogeneity with the real data measured from lysimeter and can predict ETo with higher accuracy than other tested models. Therefore, these models are recommended, respectively, as the most appropriate models to estimate ETo in Haji Abad region and the areas having the same climate.

This research aimed In order to investigated the effects of minimum and conventional tillage systems on the nitrogen and water consumption of wheat., Bby using a split-block design and implementing two single- line- source sprinkler systems, effects of four levels of 0, 90, 135, and 180 kgN.ha-1 as from urea source and four levels of irrigation water (4610, 4240, 3850 and 3395 m3.ha-1), was studied in theseunder conventional and minimum tillage systems, was studied. The results showed that, in both of two tillage systems, by reduceding water consumption, the Nonumber. of spikes. in m-1, grain yield, and wheat nitrogen uptake decreased significantly. In conventional tillage system, grain yield, grain yield components, and nitrogen uptake increased by nitrogen application, until 180 kgN.ha-1 levels; but in minimum tillage system, these parameters increased until 135 kgN.ha-1 and decreased in at 180 kg N.ha-1 level. The results showed that the amounts values of the studied parameters in conventional system were higher than the minimum tillage system, but, but except the No.number of spiklet. in m-1 2 and amounts of grain protein, there were no differencess between the two tillage systems. The results also showed that, in both tillage systems, the heighest water use efficiency (WUE, (1.85 kg.m-3) was obtained from combined application of 135 kgN.ha-1 and 6700 m3.ha-1 irrigation water. but However, the highest grain yield in conventional tillage system (8226 kg.ha-1) was obtained from combined application of 4610 m3.ha-1 of irrigation water and 180 kg.ha-1 nitrogen, with by water use efficiencyWUE of 1.85 kg.m-3. and iIn minimum tillage system, the highest grain yield (8378 kg.ha-1) was obtained from combined application of 3850 m3.ha-1 of irrigation water and 135 kg.ha-1 nitrogen, with by water use efficiencyWUE of 1.79 kg.m-3. In other words, in the minimum tillage system, by using less water and nitrogen, a similar yield similar than to the conventional tillage was obtained.

In this research, using a split-block design and implementing two single-line source sprinkler systems, effects of 0, 90, 180 and 270 kg N/ha as urea source and 9600, 8550, 7500 and 6400 m3/ha of irrigation water on silage corn (Zea Mays L.), S.C. 704 variety in two conventional and minimum-tillage systems were studied. The results showed that there was not a significant difference between water use efficiency, phosphorous uptake and foliages yield of two tillage systems. The main effects of water and nitrogen on the stems height and diameter, fresh foliage yield, nitrogen, phosphorus and zinc uptake and the amounts of soil organic carbon were significant at 1% level and on the dry foliage yield and water use efficiency were significant at 0.05% level. At all levels of nitrogen, agronomic and physiological efficiencies in conventional tillage were higher than those in minimum-tillage system. The optimum amount of foliage yield in conventional tillage system was obtained from combined application of 8550 m3/ha water and 90 kg N/ha and in minimum tillage was obtained from combined application of 7500 m3/ha irrigation water and 270 kg N/ha. In terms of water use efficiency, in conventional tillage, combined application of 180 kg N/ha and 7500 m3/ha of water and in minimum tillage combined application of 180 kg N/ha and 6400 m3/ha of irrigation water were superior treatments. Based on obtained results, minimum-tillage system can be used instead of the conventional system in the similar corn fields but more nitrogen and less water is required.

In order to study the effects of mycorrhizal inoculation, chicken manure pellet, and calcium foliar application on the fruit yield and contents of nutrient elements in leaves of pomegranate (Punica granatum L.), a factorial experiment with a randomized complete block design with three replications was conducted in 2013, in a pomegranate garden in Darab County, Iran. Treatments included two levels of 0 and 500 g. tree-1 mycorrhiza, three levels of 0, 250, and 500 g. tree-1 chicken manure pellet and  foliar spray of calcium at two levels of without and twice foliar spray of 5% calcium chloride. Mycorrhiza and chicken manure pellet were used before flowering while foliarcalcium was applied before and after flowering. The results showed that the main effects of mycorrhizal inoculation, foliar application of calcium, and chicken manure pellet application were significant on most of the studied characteristics. The highest yield of fruits, i. e. 24 kg per tree (42% more than the control), the highest average weight of fruits, kernel weight, and maximum concentration of calcium, phosphorus, iron and copper were obtained from combined application of 500 g mycorrhiza, 500 g of chicken manure pellet, and foliar application of calcium. Based on the results, combined application of calcium foliar spray, 500 g mycorrhiza and 500 g of chicken manure pellet can be recommended in similar conditions. However, since this experiment was carried out in one year, further investigation is needed to achieve results that are more reliable.

Phosphorus availability in soils is largely depended on acidic and alkaline phosphatase activities. Soil organic matter content is one of the most important factors influencing the activity of those f enzymes. The present experiment was carried out in a randomized complete block design with three replications on corn planting time in four provinces of Khuzestan, Khorasan, Fars and Mazandaran. Treatments included chemical phosphorus fertilizer (P 100%), caw manure (P0 M2) 20 tons per hectare, organic fertilizer (P0 M4) 20 tons per hectare, the first treatment plus second treatment (P100% M2), the first treatment plus third treatment (P100% M4) and without any chemical phosphorus fertilizer and manure (P0 M0) as control. In all provinces cow manure was used but organic fertilizers were different in each province. In Mazandaran, compost of wood and paper industries; In Khorasan, compost of municipal waste; In Khuzestan, sugar cane bagasse compost and in Fars, municipal homemade was used as organic fertilizer. From each province 36 samples (before and after planting) were collected and a total of 144 samples were analyzed. The results of different treatments showed the positive effect of the simultaneous use of vegetation and organic fertilizers on acidic and alkaline phosphatase in soil samples. In all Provinces, the mean activity of alkaline phosphatase before and after corn planting period, was higher than acidic phosphatase.

There are problems in solubility and bioavailability of nutrient elements in soils of Iran because of parent materials and climate. Sulfur oxidation and sulfuric acid production is one of the strategies for overcoming this problem. Many soil microorganisms including Thiobacillus are capable of oxidizing sulfur and thereby decreasing soil pH. In the present study, the effect of sulfur and Thiobacillus was studied for evaluation of some chemical soil characteristics in a factorial randomized complete block design in research fields of provinces of Khorasan Razavi, Fars, Kermanshah, Khuzestan, Qazvin and Kerman (Kerman and Jiroft). The factors including sulfur at levels of 500, 1000, and 2000 kg.ha-1, Thiobacillus at levels of 10, 20, and 40 kg.ha-1 and triple super phosphate fertilizer based on soil testing and 65% of this recommended rate. The experiment was performed both with and without plant. The results showed that the available phosphorous in soil increased significantly in many regions. The amount of sulfur exceeding 2000 kg caused increase in EC in some regions, therefore, we do not recommended sulfur application over 2000 kg.ha-1. The best treatment for this research was application of 500 to 1000 kg sulfur with combination of 10 to 20 kg Thiobacillus and triple super phosphate.According to the results of this study, application of 2000 kg.ha-1 or more sulfur is not recommended, since compared with 1000 kg.ha-1 , it does not only cause soil pH reduction and increase the availability of the elements, but also increases the electrical conductivity.

In order to investigate the effects of mycorrhiza, potassium, and manure application on the yield and quality of pomegranate fruits, in 2014, an experiment were conducted in a randomized complete block design as factorial with 12 treatments and three replicates. Experimental factors included combinations of two levels of mycorrhiza (0 and 500 g.tree-1), three levels of sheep manure (0, 10, and 20 kg per tree) and two levels of potassium (0 and 500 g K2O.tree-1). The measured traits included yield per tree, contents of carbohydrate, brix, and phenolic acids (sinapic acid, gallic acid, catechin, rutin and ascorbic acid) in the pomegranate fruits. The results showed that the main effects of potassium, mycorrhizae and manure were significant (P

Calcium is an essential element affecting fruit quality. Fruits that have enough calcium have greater capability to transport and warehousing (2, 21 and 22). Mycorrhizal symbiosis due to the increases uptake of water and nutrients, as well as due to increases photosynthesis activities, can increases plant biomass (36 and 37). Plants with mycorrhizal symbiosis, has better growth and higher yield and show greater resistance to stresses (40). Manure can improve soil organic matter and soil health (3 and 6). Amiri and Fallahi (2009) reported that by use of manure in apple, yield and average fruit weight significantly increases (3). In order to study the main and combined effects of mycorrhiza, calcium and manure on the pomegranate production, this research was conducted in Fars province.
In order to achieve the desired goals, in 2014, an experiment were conducted as factorial in a randomized completely block design with 12 treatments in three replicates. Experimental factors were included combinations of two levels of 0 and 500 g.tree-1 mycorrhiza, three levels of 0, 250 and 500 g.tree-1 manure and two treatments of without foliar spray and foliar spray of calcium chloride with 0.5% concentration. Treatments were carried out on two ten-year-old pomegranate trees with almost uniform growing conditions. The measured traits were including yield per tree, contents of pH, berix, carbohydrates and phenolic acids (sinapic acid, gallic acid, catechin, rutin and ascorbic acid) in the pomegranate fruits. All obtained data were analyzed with SAS software.
Results and Discussion The results showed that main effects of different treatments on the decreasing of pomegranate juice acidity were significant. Mycorrhiza application, except sinapic acid, significantly (P The results showed that application of mycorrhiza, manure and calcium spraying in pomegranates are very effective in increasing of its production and improving its quality. The highest yield (24.04 kg.tree-1) were obtained from combined application of 500 g.tree-1 mycorrhiza, 500 g.tree-1 of manure and calcium chloride spray which in compared with the control treatment showed 42.6% increase in yield. In general, due to one year of testing, to achieve more reliable results need to investigate further.

Chemical, bio and organic fertilizers have an important role in increasing of quantity and quality of agricultural products. In order to study the effects of mycorrhizal inoculation, potassium and organic manure applications on the yield and chemical composition of pomegranate leaves, a factorial experiment in a randomized complete block design with three replications was conducted, in Jannatshahr region, located nearby Darab at Fars province in 2013, . Treatments were a combination of two levels of 0 and 500 grams of mycorrhiza, three levels of 0, 10 and 20 kg sheep manure and two levels of 0 and 500 g of potassium oxide per tree. Mycorrhizae and sheep manure were used before flowering and potassium was applied before and after flowering. The measured factors were yield per tree, fruit weight, skin weight, grain weight, grain skin than five fruits and concentration of potassium, phosphorus, iron, manganese, zinc and copper in leaves. The results showed that the main effects of mycorrhiza, potassium and manure application on the most of studied characteristics were significant. The highest average weight of 5 fruits, the highest kernel weight and the lowest skin-to-kernel weight ratio were obtained from combined application of 500 grams mycorrhizal, 20 kg of manure and 500 g of K2O. The maximum concentration of potassium, phosphorus, iron, copper, manganese and zinc were obtained from combined use of 500 grams of mycorrhiza, 500 grams K2O and 20 kg of sheep manure per each tree. The highest yield of pomegranate fruit (44 kg per tree) were obtained from combined application of 500 g mycorrhiza, 10 kg of sheep manure and 500 g of K2O, which compared with the control treatment, showed 127% increase in yield and can be recommended as the superior treatment.

The most abundant of agricultural soils in Iran, are calcareous. In calcareous soils, phosphorus fertilizers use efficiency is low. The usage of soil microorganisms is one of the effective ways to increment the uptake of phosphorus in calcareous soils. This microorganisms using various mechanisms, including the production of plant hormones or the production of organic and inorganic acids to dissolve the insoluble phosphorous compounds. Mycorrhizal symbiosis is also one of the most recognized and important symbiosis relationship found in the world. In a mycorrhizal symbiosis,plants can be able to absorb more nutrients and water from soil and fungus plays a protective role as a growth enhancer and make the plants more tolerable to biotic (pathogens) and abiotic (drought, cold and salinity) stresses .This research conducted to study phosphate solubilizing bacteria and mycorrhiza roles on sorghum growth and phosphorus availability to this plant.
To achieve the desired goals, a pot experiment was conducted as a factorial in completely randomized design with sixteen treatments in three replications. The treatments were combination of four P levels of zero, 25, 50, and 75 mg kg-1 P2O5 from triple super phosphate source, the two treatments of inoculation and without inoculation of phosphate solubilizing bacteria and the two treatments of inoculation and no inoculation of mycorrizal fungus. Required fertilizers based on initial soil test results were supplied. Accordingly, the same amount of nitrogen, 80 mg kg-1 (30 mg kg-1 before planting and 50 mg kg-1 after planting twice) as urea source, 10 mg Zn kg-1 and 5 mg kg-1 Cu per kg soil as the forms of Zinc sulphate (ZnSO4.7H2O) and copper sulphate (CuSO4.H2O) were added to each soil sample. Required Phosphorus also was calculated based on treatments and added to potting soil. Each pot size was 5 kg. every sample was thoroughly mixed and then were placed in pots. At the same time the seeds were inoculated. In harvesting time, some parameters such as plant height and diameter, wet and dry foliage yield, and phosphorous uptake were measured and analyzed statistically. After harvesting time also soils phosphorous content were measured and analyzed.
Results The results indicated that by utilizing the phosphate solubilizing bacteria, stem diameter, dry matter yield, phosphorous uptake, and soils phosphorous content after harvesting significantly increased. These findings indicated that the use of phosphate solubilizing bacteria affected plant growth. Such results have been previously reported. Ramezanian (31) reported that application of PGPR will be increase wheat stem height and diameter. Li et al (18) and Larsen et al (16) reported that soil microorganisms, including growth promoting bacteria through a variety of mechanisms such as ACC deaminase production or an increase in available phosphorus can stimulate plant growth and increase height and diameter of the stem. Glick et al (13) showed that plant growth promoting bacteria through the production of plants hormones increases plant height and stem diameter, and ultimately improve plants yield. Increases yield of plants through the use of phosphate solubilizing bacteria previously has been reported by other studies. Mycorrizal inoculation also had a significant effect (P

The aim of this research was to study the effects of water stress on nitrogen and growth parameters of corn in a line source sprinkler irrigation system. For this purpose, effects of four levels of 0, 90, 180, and 270 kg N/ha from urea source and four level of irrigation water (6400, 7500, 8800 and 9500 m3.ha-1, I1, I2, I3, I4, respectively) in minimum tillage system were investigated by using a split-block design. In this tillage system, a combined cultivator was used and all tillage and cultivation operations were performed in one step. The results showed that the main effects of irrigation treatments on plant height, stem diameter, fresh yield, concentration and total uptake of nitrogen were significant at (P

Azotobacter is a plant growth promoting rhizobacterium that can stimulate the growth of plants by different mechanisms, including nitrogen fixation, production of phytohormones and ability of solubilizing phosphorous. In this research 10 isolates of Azotobacter chroococcum (selected form previous investigations) native to Iranian soils, were used for field experiments. The field experiments were conducted with ten bacterial inoculation treatments and control in randomized completed block design with three replications in some provences in Iran. The inoculums were prepared in powdery forms with perlite as carier. The inoculums were used as seed inoculation. Diverse results were observed s in different provinces. In Azerbaijan Sharghi, 9 isolates increased the total yield of wheat and one isolate (T7) increased significantly the straw and stubble compared to control. T3 and T4 increased significantly the thousands-seed weight over control. The results in Khorasan Razavi province revealed that T11 increased the height and yield of straw and stubble and T10 isolate increased significantly the nitrogen content in the flag leaf. In Fars province, T8 isolate had the highest mean on seed yield and shoot dry weight. There was not significant effect of inoculation on growth indices of wheat in Kordestan and Azerbaijan gharghi provinces.

The usage of soil microorganisms which they have ability of dissolving fixed phosphorus, is one of the effective ways to increment the uptake of phosphorus in calcareous soils. In order to study the roles of phosphate solubilizing bacteria on the availability of P in the sorghum, a pot experiment was conducted as a factorial in completely randomized design with eight treatments and three replications. The experimental factors were different phosphorus levels and phosphate solubilizing bacteria (Bacillus megaterium). The treatments were combination of four P levels (zero, 25, 50 and 75 mg/kg P2O5 from triple super phosphate source) and the two treatments of phosphate solubilizing bacteria (with bacteria inoculation and without bacteria inoculation). The results indicated that utilizing the phosphate solubilizing bacteria increased significantly (P<0.01) the dry matter yield, nitrogen, phosphorus and potassium uptakes but had not significant effects on iron, manganese and zinc uptake. Phosphorus application also had a significant effect (P<0.01) on some indicators such as plant height and diameter, dry matter yield, shoot P concentration and shoot P uptake. Combined using of both phosphorus and phosphate solubilizing bacteria had a significant effect (P<0.01) on the stem diameter, dry matter yield, shoots phosphorus concentration, nitrogen, phosphorus, iron and manganese uptakes by sorghum.

Sulfur has an important role in plant nutrition, aciditification of rizosphere zone and finaly in increasing zinc availability of calcareous soils. In order to study the effects of sulfur and zinc on corn production, a three years experiments were conducted in Kermanshah, Qazvin and Behbahan reseaech fields. In these studies, by using a factorial test in randomized completely block design, main and combined effects of four levels of zinc (0, 10, 20 and 30 kg.ha-1 Zn as zinc sulphate) and three levels of sulfur (0, 200 and 400 kg.ha-1) were compared. The results indicated that main effects of sulfur and zinc on the most of studied parameters such as grain yield, 1000 grains weight, zinc content and zinc uptake by shoots were significant. Although the combination of sulfur and zinc improved parameters were studied, but only had a significant effect on the shoot Zn concentration and grains protein content.

In order to evaluate the effects of phosphorus solubilizing microorganisms, to study the biological phosphate fertilizers effectiveness, and to compare them with chemical phosphorus fertilizers in corn cultivation in Iran, a 3-year field experiment was conducted in corn fields of Fars province, Khozestan (Dezful area), Varamin, and Karaj. In each site, an experiment was performed in the form of randomized complete block design with 4 treatments and three replications. The treatments were: a) control (without phosphorus application), b) application of phosphorous as microbial phosphate source, c) application of phosphorus as Golden Bio-phosphate source, and d) application of phosphorus as triple super phosphate. Fertilizers rates were based on soil test. Since there was some organic matter, sulfur, and zinc in the organic fertilizers, equivalent amounts of these compounds were also applied to the other treatments. Results showed that, there was a positive and significant effect of P application on grain yield. In all study sites, triple super phosphate was more effective than the other sources. Microbial phosphate effects were the same as triple super phosphate and were in the second place. Although Golden bio-phosphate fertilizer had a positive and significant effect on grain yield in Varamin and Dezful, but in overall, there was no significant difference between the control and Golden bio-phosphate source. In general, application of microbial phosphate can be recommended instead of triple super phosphate, but additional research is needed before recommendations can be made regarding use of Golden bio-phosphate for corn.

In order to evaluate the possibility of biological phosphate fertilizers application and compare them with phosphorous chemical fertilizers in corn production, a 3-years field experiment, in the form of Randomized Complete Block Design with 4 treatments and three replications, was conducted in corn fields of Fars Province. The treatments were 1) without phosphorous fertilizer application (control), 2) application of phosphorous based on soil test as microbial phosphate source (Bio fertilizer), 3) application of phosphorous based on soil test as Golden Bio-phosphate source (Bio fertilizer) and 4) application of phosphorous based on soil test as triple super phosphate (chemical fertilizer). Based on soil test, it needs 75 kg.ha-1 P2O5 in every 3 years. Since there was some organic matter, sulfur, and zinc in the organic fertilizers, the calculated amount of these elements was also applied to other treatments. Results of statistical analysis showed that the highest total yield and grain yield, 15000 and 9559 kg per hectare, respectively, obtained from triple superphosphate application but were in a same statical group with microbial phosphate fertilizer. In addition there was a significant difference (P<0.01%) between triple super phosphate and control or Golden Bio-phosphate. In general, the results show that in same conditions firstly corn needs phosphorous fertilizers, secondly application of microbial phosphate source in corn fields is recommended and third using of Golden bio-phosphate source in corn fields is not recommended.

Urea is the most common form of nitrogen fertilizer used in sugar beet cultivation. Urea has a high solubility and its losses are high and consequently its efficiency is low. It is supposed that urea solubility can be limited and its efficiency can be increased by using slow-release nitrogen fertilizers. By conducting an experiment in three important sugar beet cultivation areas of Khorasan Province, the effects of Urea (soluble form of N-fertilizer) and Urea formaldehyde (slow-release N-fertilizer) application in sugar beet cultivation were investigated. In each area, by using a randomized complete block design replicated three times, effects of six fertilizer treatments including three levels of 75, 100 and 125 percent of nitrogen requirement calculated based on soil test from two sources of Urea and Urea formaldehyde were evaluated. Soil samples were taken before cultivation and three times during the growing season and their NO3-N and NH4-N content were determined. During the growing season, leaf samples were taken three times and their NO3-N content was determined. In addition, the quantity and quality of roots were determined after harvesting. The results showed that application of 250 kg N.ha-1 from Urea formaldehyde (equal to 650 kg. ha-1 Urea formaldehyde), with mean root and white sugar yields of 48.836 and 6.544 t.ha -1 respectively, improved the root and white sugar yields for 1500 and 300 kg.ha -1 respectively as compared with the control treatment. Application of Urea formaldehyde as compared with urea increased the NO3-N and NH4-N content of the soils. In two out of the three sites, the increase in white sugar yield due to this treatment was more than one ton per hectare. This finding necessitates more research concerning the application of Urea formaldehyde in sugar beet production.

To examine the effect of slow-release nitrogen fertilizers and its comparison with urea, several experiments were conducted in Khorasan Province during two years. In the first year, the eight fertilizer treatments included two-stage application of 140 and 200 kg N. ha-1 (equal to 70% and 100% of the recommended level) from urea source, one-stage application of 140 and 200 kg N. ha-1 from urea form (before cultivation), one-stage application of 140 and 200 kg N. ha-1 from methylene urea before cultivation, application of 100 kg N. ha-1 from urea form before cultivation followed by 40 kg N. ha-1 as top dressed from urea, and application of 100 kg N. ha-1 from methylene urea (before cultivation) followed by 40 kg N. ha-1 as top dressed from urea source. The experiment had a Randomize Complete Block Design and was replicated 3 times. In the second year, the effects of seven fertilizer treatments consisting of 150, 200, and 250 kg N.ha-1 from urea (at three stages) and urea-form (at one stage) with a control plot (without nitrogen application). The treatments were conducted in two soils with different textures (loam and sandy loam) as a Randomized Complete Block Design, replicated three times. The results of the first year showed that application of nitrogen fertilizers had a significant effect (α=1%) on tuber yield, and nitrogen concentration in leaves. The maximum tuber yield (54.66 ton.ha-1) was produced by applying 200 kg N.ha-1 from methelen urea, which had a slight difference with the same amount of nitrogen from urea formaldehyde source. The economical evaluation of different treatments in the first year showed that, in spite of the maximum economic net profits obtained through application of 200 kg N.ha-1 as urea formaldehyde and/or methelene urea, the maximum economic efficiency was obtained by the application of 140 kg N.ha-1 from methelene urea source (equal to 70% of the control plot). The results of the second year experiment showed that, in both soils under study, the maximum tuber yield was obtained through the application of 250 kg N.ha-1 (25% more than the nitrogen recommended level) from urea form source. The leaf and soil analysis of different treatments showed that there was no difference among the treatments concerning leaf N concentration and soil N at different stages of the crop growth. This indicates the ability of ureaform in slow releasing of nitrogen, since in all stages of sampling; the concentration of nitrogen in leaf and soil of the urea form treatments was even more than the corresponding values in the urea treatments. On the whole, it can be concluded that, in similar conditions, using slow release nitrogen fertilizers (urea form and methylene urea) in potato farming is economically feasible and increases nitrogen use efficiency.