جستجوی مقالات مرتبط با کلیدواژه « فسفر » در نشریات گروه « مکانیزاسیون کشاورزی »

Recovery of nutrients from plant residues is a sustainable and economical method in agriculture. Considering the important role of nutrients, it is essential to supply these elements in the soil and achieve the appropriate yield. The amount of nutrients in the plant residues after harvesting is very variable due to the difference between the species used. Each plant residue contains some nutrients that during the decomposition process, these nutrients can be available to the soil and crops in different amounts. In more detail, considering that the excessive use of chemical fertilizers has caused environmental problems and unused plant residues in the environment have created problems for the environment and farmers, therefore, to solve these problems, recovering important elements such as silicon from plant residues can be effective in improving the quality and quantity of many different products and plants. Rice straw, wheat straw and sugarcane bagasse are among the most common plant residues that have been studied in different studies to recover nutrients from them with different methods. In particular, rice straw is known as one of the most important plant residues that can be found in abundance in the north of Iran. Obviously, there is still a need for a better understanding of the amount of nutrients recovery from plant residues with different methods. And there is an effect of these elements on improving the condition of the soil. Considering that the excessive use of chemical fertilizers has caused environmental problems, as well as unused or underused plant residues in the environment have caused problems for the environment and farmers. The purpose of this study is to compare the residues of rice straw, wheat straw and sugarcane bagasse and the methods of recovering nutrients from these residues in order to add macro-nutrients (nitrogen, phosphorus and potassium) and micro-nutrients (iron, zinc, copper and manganese) into the soil. This research was carried out based on a factorial experiment in the form of a completely "randomized" design with three replications during 2022-2023. The treatments of plant residues in three levels (rice straw, wheat straw and sugarcane bagasse) and the methods of recovering elements from these residues in five levels (biochar, straw, digestion, ash and ash with acid) were examined. Soil samples, from a depth of 0-25 cm and with silty loam texture were randomly taken from the forest parts of Mazandaran province, Iran, characterized by a Mediterranean climate, Csa type, with an average annual rainfall of 676 mm, and average air temperature of 14 ℃, and then were air-dried. After preparing the samples, the characteristics of the treatments, macronutrients and micronutrients, including pH, electrical conductivity, total nitrogen, phosphorus, potassium, iron, zinc, manganese, copper, and silicon were measured. Analysis of variance (ANOVA) assessed the statistical significance of the differences in the studied variables among the different treatments. Tukey test was used for the post-hoc comparisons at a p-level < 0.01. Prior to the statistical analysis, QQ-plots were used to check the normality of sample distribution, and the data were square root-transformed whenever necessary. Moreover, the principal component analysis (PCA) was used to cluster the studied variables in groups related to the studied treatments. The results of analysis of variance showed the effect of plant residues and element recovery method on all studied characteristics including soil characteristics (pH, electrical conductivity and organic carbon), macronutrients (nitrogen, phosphorus and potassium) and micronutrients (silicon, manganese, copper, iron and zinc) were significant at the probability level of 1%. The results showed that the biochar treatment of rice straw had the maximum amount of pH (7.66), organic carbon (2.61%), nitrogen (0.24%), phosphorus (46 mg/g), potassium (781 mg/g) and silicon (261.33 mg/g) compared to other treatments. Also, the results of the compare means showed that sugarcane bagasse biochar treatment had the maximum amount of manganese (25.01 mg/kg), zinc (3.20 mg/kg), iron (48.27 mg/kg) and copper (2.20 mg/kg) compared to other treatments. The application of principal component analysis showed that three distinct groups (for rice straw/biochar, sugarcane bagasse/biochar and control treatments) were demonstrated, without clear overlap of the points related to these treatments and their element recovery methods. In general, this study confirmed that the treatment of rice straw residues and the method of recovering its elements through biochar play a significant role in increasing the quality and fertility of the soil and can be recommended to farmers.

Phosphorus (P) is the second essential element and plays a key role in plant growth. The availability of P in the soil depends on the P fractions, which influence the primary productivity of agricultural ecosystems. Having sufficient and accurate information about soil mineral phosphorus is very important for the development of sustainable agriculture in arid regions. Awareness of phosphorus deformation in different soils is also very important for phosphorus fertilizer recommendation. When phosphorus is used in its soluble forms, it is rapidly converted into unusable forms for the plant. Native soil phosphorus is often in unusable form for the plant. Therefore, having enough information about phosphorus deformation in different soils is very important to recommend phosphorus fertilizer. The objective of this study was to find out the effects of long-term use of different sources of phosphorus on available P for pistachio plants in southeast Iran.

Materials and Methods:

 For this research were taken depths from 0- 40 cm and 40- 60cm in 63000 ha of Sirjan pistachio orchards of Kerman province. Jiang and Gu method was used to isolate and determine the mineral forms of phosphorus in the soil. Each P fraction was extracted as follows: 1g (oven-dry weight) of sample soil weighed out into a 50 mL polyethylene centrifuge tube. A volume of 40 mL of the first extractant, NaHCO3 (Table 1) was added and placed in an automated mechanical shaker at 25° C with 110 rpm for 1 h to allow time for the solution top equilibrate. The tubes were then centrifuged at 6000 × g for 15 min and the supernatant was carefully filtered through Whatman No. 42 with minimum loss of soil. Reactive P in the supernatant was determined using the ascorbic acid method at 882 nm. This method separates phosphorus in the forms of di calcium phosphate, octa calcium phosphate, aluminum phosphates, iron phosphates, occluded phosphates and apatite.

Results and Discussion :

Results showed that the total P was high in these soil samples and the abundance of P fractions was in order to Ca10-P type≥ Al-P >Ca2-P type> occluded P ≥ Fe-P > Ca8-P type in two depths. These results suggested that continuous P application leads to plant available P convert into unavailable P forms such as Ca10-P. results indicate that NaOH-extractable P has resulted from active Fe oxides. Also, by comparing two depths of soil in the study area, it can be concluded that the occupied phosphorus in the surface layer is more than the deep layer. Finally, it can be concluded that by increasing the stability of various forms of phosphorus, their contribution to other forms of phosphorus increases, so that the concentration of apatite is much higher than phosphate-calcium phosphate. Results showed the amount of available phosphorus (Ca2-P) in the surface layer is more than the deep layer, which can be attributed to surface application of Phosphorus fertilizers. However, there are sections where phosphorus in the surface layer and the bottom is almost equal. Amount of this form of P is less than Al-P and Fe-P. It may be due to increase in Al and Fe contents in in calcareous soils.

High amounts of total P clarifies that by optimally managing the use of phosphorus fertilizers and soil conditions, the required P of the plant can be provided without additional use. From the results, it appears that in the calcareous soils the abundance of different forms of P was in order Ca10-P type≥ Al-P >Ca2-P type> occluded P ≥ Fe-P > Ca8-P. Furthermore, it observed that Fe-P, Al-P and Oc-P are important forms of P and on average constitute 30% of the sum of inorganic P forms. These findings demonstrate that the ability of NaOH to extract Al-P will be reduced with an increase in Al-P content and that NaOH is unable to remove Al-P completely. Therefore, it seems that more research is needed to find some light on whether NH4F can be omitted from the regular P fractionation schemes in the highly calcareous soils of Iran.

Streptomyces is the most important and dominant genus of actinomycetales with more than 664 species which some of its species may stimulate plant growth through nutritional and physiological mechanisms that include: dissolution of phosphates, production of siderophores and phytohormones, biological Nitrogen fixation and production of antifungal metabolites. Silicon has significant positive effects on improving the growth and physiological characteristics of the plant by improving the root system, biosynthesis of phytohormones, resistance to biological and non-biological stresses and nutrient uptake. Improvement of the silicon concentration in the plant depends on its availability in soil. Soil application of resources with appropriate amount of silicon is of great importance in increasing the availability and uptake of silicon. It is also documented that the co-application of plant growth promoting bacteria and silicon is a useful and efficient method to increase plant growth and yield under normal and stress conditions. Due to beneficial effects of plant growth promoting bacteria and silicon in improving crop growth and also the importance of soil application of different silicon sources, the aim of this study was to Investigate the effect of Streptomyces isolate, silicon application using calcium-magnesium silicate source and the combined application of Streptomyces + silicon on growth parameters, chlorophyll content and accumulation of some nutrients in soybean (Glycine max L.).

A pot experiment was designed as factorial in a complete randomized design with 3 replications under natural light and temperature conditions. Experimental treatments included soil application of calcium-magnesium silicate source (37.9% silicon dioxide) at four levels 0 (M1), 200 (M2), 400 (M3) and 600 (M4) kg Si ha-1 and two levels of inoculation with Streptomyces isolates (no inoculation (B0) and inoculation with Streptomyces (B1). Surface-sterilized seeds were inoculated with a suspension of (107 CFU mL-1) Streptomyces isolate. The effect of experimental treatments on plant development stage (late vegetative growth period) was investigated. The soybean plants were harvested after 10 weeks of growth period from soil surface. Plant growth parameters including shoot and root biomass, root volume and plant height were determined. Also, chlorophyll content (a, b, Total) and concentration of nitrogen, silicon, phosphorus and potassium in the shoot were measured.

The results of the present study showed a positive and significant effect of the co- application of silicon and Streptomyces inoculation on improvement of the growth characteristics and chlorophyll content compared to their separate application. The highest amounts of shoot biomass (19.3 g per pot), root biomass (7.6 g per pot), root volume (38.07 cm3), plant height (98 cm) and chlorophyll a (18.07 mg / g), chlorophyll b (14.4 mg / g) and total chlorophyll (32.4 mg / g) were measured in the co-application of 600 kgha-1 Si (M4) and Streptomyces inoculation (M4B). .Our results showed the improvement of soybean growth parameters could be due to the positive effect of Streptomyces isolate on plant growth promotion and utilization of calcium-magnesium silicate in soil. Combined application of silicon and Streptomyces inoculation increased the concentration of silicon, nitrogen, phosphorus and potassium in the M4B treatment compared with the lonely application of highest level of silicon source (M4) by 16.25, 7.45, 45.6, 51.7%, respectively.

Based on the results of the present study soil application of calcium-magnesium silicate increased plant growth and physiological factors. Streptomyces inoculation improved the effects of calcium-magnesium silicate levels to enhance growth parameters, chlorophyll content and nutrient concentration (silicon, nitrogen, phosphorus and potassium) in soybeans. This study was carried out in pot experiment at the vegetative growth stage of soybean. Therefore, supplementary studies are necessary in field and harvest stage.Keywords: Streptomyces, inoculation, silicon, soybean, plant growth

In this study, batch series of laboratory-scale anaerobic digesters at 35 and 55 ° C were used to investigate the production of biogas from dairy effluents and reduce its pollution. Dairy effluent sludge with ratios of zero, 10, 20, 30, 40 and 100% was used for inoculation. The interaction effect of sludge percentage and temperature at the level of one percent on the volumetric indices of biogas production was significant for the amount of initial volatile solids, volatile solids removed and chemical oxygen demand removed at the level of one percent. With increasing sludge percentage, the amount of biogas produced per initial volume increased for the removed COD but decreased for the initial volatile solids. The highest biogas production efficiency was obtained based on the removed volatile solids at thermophilic temperature and 40% sludge ratio, with the removal of 47.7% volatile solids and 266.5 ml per gram of removed volatile solids. According to the results, the amount of biogas production at mesophilic temperature, in lower proportions of added sludge, is more than the amount of gas produced at thermophilic temperature, and due to the low volume of sludge production in the dairy industry and higher energy consumption under thermophilic conditions, anaerobic digestion and biogas production are more favorable at 35 ° C. The results also showed that by anaerobic digestion of each m3 of dairy effluent, 20.83 MJ of heat energy can be produced.

Introduction:

 One of the most important needs in crop planning is the evaluation of different systems of plant nutrition. plant nutrition in a correct way can preserve the environment and increase efficiency of agricultural inputs. Humic acid contains many nutrients that increase the soil fertility and soil organic matter content and thus affect plant growth and yield. In the present study, the effect of soil and foliar application as well as fertigation application of humic acid on iron and phosphorous availability of canola (Hyola 308) was evaluated.

Materials and Methods :

The soil was air-dried and ground to pass through a 2-mm sieve and then was analyzed to determine soil physical and chemical properties using standard methods. A greenhouse experiment was carried out with 10 treatments in four replications. Treatments include humic acid soil application at three levels (1, 2 and 4 g.kg-1 soil), foliar application at three levels (0.1, 0.2 and 0.4%) and three fertigation levels (1000, 2000 and 4000 mg L-1) and control). Soil application in the form of humic acid powder and in cropping time based on the soil weight of the pots and for spraying and use along with irrigation water, each of the spraying and together with irrigation water levels is divided into three equal parts and in three stages (plant establishment, stem elongation and flowering). At the end of growth period (for 139 days), vegetative growth indices were determined and then plants were harvested and stem and leaves were separated. Phosphorous content in plant extracts was measured by molybdate vanadate method (yellow method) and iron concentration in the samples was determined by atomic absorption (AAS-Unicam-919). Statistical analysis was conducted via SAS software and mean comparisons carried out by LSD test at 5% probability level.

Results and Discussion:

 Results show that the application methods and the different levels of humic acid had significant impacts (p < 0.01) on the all parameters but they had no significant effects on the numbers of leaves. The maximum leaf fresh weight was 4.34 gr per plant which obtained water irrigated treatments with 2000 mg/lit. However, there was no significant difference between water irrigation with 4000 and 2000 mg/lit humic acid concentrations. Besides, maximum leaf dry weight was 0.37 gr in the plant that was water irrigated with 4000 mg/lit, however there was no significant difference between water irrigation with 4000 and 2000 mg/lit humic acid concentrations. Also, the maximum stem dry and fresh weight was 5.92 and 1.53 gr which observed in water irrigated with 2000 mg/lit. The application methods and the different levels of humic acid had significant impact (p<0.01) on the content and absorption of Fe and P excluding the Fe content in the root. The maximum Fe content in stem and seed were 321.25 and 85 mg/kg was observed in the treatment of humic acid with water irrigation of 2000 mg/lit. Also, in the treatment of spraying with 0.4 % of humic acid, the maximum of Fe concentration (245.46 mg/kg) was obtained. The humic acid molecules can pass from the cell membranes and cause iron reduction in the Apoplast and increase the availability of Fe. Because of the reduction effect of humic acid on the availability and accumulation of Fe in the plant tissue, increasing in the Fe absorption with humic acid treatment is observed. The increase in the accumulation of Fe by humic material might be due to the releasing phenolic material in the root rhizosphere. The maximum P concentration in the leaf, stem and seed were 0.40, 0.72 and 0.897 respectively that was observed in the treatment of water irrigation with 2000 mg/lit with humic acid. Due to the availability of phosphorus and other nutrients for wheat, humic acid increases the plant yield in the reproductive stage of seeding.

Conclusion :

Results of the study show that humic acid can ameliorate the negative effect of a large amount of phosphorus on iron availability. In fact, humic acid, due to providing nutritional balance for the plant, prevents negative effects caused by the high amounts of specific elements such as phosphorus. Also, the results showed that all three humic acid application methods increased vegetative growth parameters, and iron and phosphate availability for canola plant compared to control. But in general, 2000 mg/L acid humic with irrigation water was more effective than two methods of soil and foliar application.

Introduction :

The use of invitro hydroponic culture is one of the useful and practical methods for selection of superior isolates of plant growth promoting rhizobacteria with high colonization potential at root surface. In this regard, the present study was designed to select superior isolates isolated from dry-land farming of Qazvin and Zanjan provinces during the previous stages of this investigation.

Materials and Methods:

 This experiment was carried out based on a completely randomized design (CRD), including: inoculation of wheat seeds with 16 bacterial isolates and culture of seedlings in Hoagland nutrient solution (EC 8 dS/m and osmotic potential (OP) -0.54 MPa) containing tricalcium phosphate (source of low-soluble phosphorus), as well as non-inoculated seedlings was cultured in Hoagland nutrient solutions containing monopotassium phosphate (control with source of soluble phosphorus) and tricalcium phosphate (control with source of low-soluble phosphorus) at three replications in growth chamber for 45 days. The length of the light (with 196 μmol photons m−2 s-1 light intensity) and dark period in these times was 16 and 8 h, respectively, The day and night temperature were 25±2 and 20±2 °C, respectively. At end of experiment (45 days after transportation of seedlings into invitro hydroponic culture) shoots and roots of plants were harvested separately; then, Population of phosphate solubilizing bacteria (PSB) on root surface, pH and concentration of available phosphorus in nutrient solution, fresh weight, dry weight and length of both section of plants, P-concentration and P-uptake of plant, and relative water content (RWC) of leaf were measured. Ultimately, correlation (Pearson) among measured traits were calculated.

Results and Discussion:

 Results showed that inoculated wheat seedlings with B18 isolate perished. It seems that B18 isolate was either a highly pathogenic plant or its metabolites were highly inhibitory to the seedling which in short time killed the wheat seedling. Except B (14, 17, and 32) isolates; the rest of isolates had over 6×106 CFU/g root fresh weight. All bacterial isolates compared to the control with source of insoluble phosphorus, increased available phosphorus and decreased pH of nutrient solution. Dissolution of inorganic phosphates by PSB with chelating processes, secretion of inorganic and organic acids has been proven topic. Thus, reducing pH and increasing soluble phosphorus in nutrient solution at PSB treatments are reasonable. B (1, 2, 3, 4, 5, 6, 14, 17, 32) isolates treatments compared to control with tricalcium phosphate, increased RWC of leaf, and also increased length, fresh weight and dry weight of root and shoot of wheat plants. Previous research has shown that inoculation of plants with PGPR under drought and salinity conditions improved RWC of plant leaves and plant growth indices; Of course, result of some experiment show that some of PGPR do not always improve plant growth under all conditions. There was a significant positive correlation among P-uptake, RWC, root length, shoot height, fresh and dry weight of root and shoot of wheat plant. Also, the pH of nutrient solution had a positive correlation with root length, but it had a negative and significant correlation with P-concentration of nutrient solution and P-concentration of plant. PSB population at root surface had a negative correlation with pH of nutrient solution and root length of plant, but with P-concentration of nutrient solution had positive and significant correlation.

Conclusion:

 All of screened and selected PSB isolates in lab (in respect of PGP traits) could not promote plant growth; even some of these isolates (such as B15 and B18) had negative effects on wheat growth indices. Inoculation of wheat with PSB isolates significantly increased the use of insoluble phosphorus. Solubility of tricalcium phosphate by isolates and increased phosphorus availability cannot lonely improve wheat growth indices; it seems that the outcome of the set of PGP effects of these bacteria and the secretion of their metabolites in the presence of plant root are determinative agents for improvement of wheat growth indices. Generally, B (1, 2, 3, 4, 5, 6, and 32) isolates were superior isolates in respect of colonization at root surface, relative water content (RWC) and growth indices of wheat plant; and these isolates are recommended for further experiments in greenhouse and field (in order to production of suitable biofertilizer for dry-land farming of wheat).

Introduction Phosphorus (P) is an essential nutrient for all forms of life on the earth, but in excess concentrations, it can act as a serious water pollutant through eutrophication. Thus, it is very important to remove P from aqueous solutions before their release into natural water resources. Among the various P removal techniques that have been developed, the sorption process is widely accepted to be an effective water treatment technique because of low cost, ease of operation, simplicity of design, and high sorption capacity in dilute solutions. Layered double hydroxides (LDHs) are a type of two-dimensional nanostructure anionic clays with high capacities to sorption of anions. These non-silicate clays consist of positively charged brucite-like octahedral sheets which neutralize by a negatively charged interlayer containing relatively weak bonded anions and water molecules. The positive charges generated by the isomorphous substitution of trivalent cations for divalent cations are balanced by interlayer anions that can be exchanged by other anions making them good anion-exchangers with high selectivity. LDHs have been widely used as environmental sorbents because of their high charge density, large interlayer areas, good thermal stability, and high anion exchange capacities of the interlayer anions. The aim of the present study was to synthesize a Mg-Fe LDH as a sorbent for P removal from aqueous solution. Materials and Methods The Mg-Fe LDH was synthesized using the co-precipitation method. In brief, a mixture solution containing 0.03 mol MgCl2. 6H2O, and 0.01 mol FeCl3. 6H2O was added dropwise into a flask containing 100 ml of 1 M NaOH solution under vigorous stirring at pH=10. The obtained slurry was filtered and washed repeatedly with DW until the filtrate pH reached neutral. Mg-Fe LDH particles were then obtained by drying the filtrate at 70 °C in an oven overnight. The crystallinity of the sample was studied using X-ray diffraction (XRD) analysis. In order to investigate the performance of the synthesized LDH as a P sorbent, batch experiments were carried out in polyethylene centrifuge tubes. The suspensions were shaken for 24 hours at 250 rpm, and the supernatant was then separated by centrifugation at 4000 rpm for 10 minutes and were filtered by Whatman ashless grade 42 filtration papers. Equilibrium P concentration was determined according to the ascorbic acid method using UV-vis spectrophotometer at the wavelength of 880 nm. The effects of pH, initial P concentration, and contact time on P sorption were investigated in the ranges of 2-10, 0-300 mg/L and 0-1440 min, respectively. Results and Discussion The XRD pattern of the LDH sample showed typical structure of hydrotalcite-like compounds with sharp and reflection peaks corresponding to the (003), (006), (012), (015), and (110) crystal planes which are characteristic planes of hydrotalcite-like compounds. The efficiency of LDH to remove P decreased with the increasing of initial P concentration and the maximum removal efficiency of LDH occurred in the range of 5-20 mg/L of initial P concentration. With increasing of initial P concentration from 20 to 300 mg/L, the P removal efficiency of LDH decreased from 98.7 to 24.6 %. The P removal efficiency was increased with time and reached equilibrium at 60 min. The P removal rate of LDH in this time was about 66 % and no significant decrease in residual P concentration was observed after 60 min. The sorption of P on LDH was highly pH dependent, and the maximum P removal was found at pH of 4. The sorption kinetic and isotherm data were well described by pseudo-second-order and Langmuir equations, respectively. According to the Langmuir equation, the maximum P sorption capacity (Qmax) of LDH was obtained as 13.96 mg/g. Conclusion It was found from the results of this study that the mechanisms involved in the P sorption onto LDH included electrostatic attraction, ligand exchange, and surface complex formation. In addition, the results suggested that the synthesized Mg-Fe LDH can be potentially used as an effective sorbent for the removal of P from aqueous solutions. Further research is needed on the regeneration of the LDH after P sorption and the evaluation of desorption behavior of P from LDH under different conditions.

Introduction Zinc is one of the imperative micronutrients required relatively in small concentrations in tissues for healthy growth and reproduction of plants. Zinc deficiency in plants leads to reduced membrane integrity and synthesis of carbohydrates, auxins, nucleotides, cytochromes, and chlorophyll and develops susceptibility to heat stress. The solubility of Zn is highly dependent upon soil pH and moisture and hence arid and semiarid areas are often zinc-deficient. The use of microorganisms with the aim of improving nutrients availability for plants is an important practice and necessary for agriculture. Zinc-solubilizing microorganisms can solubilize zinc from inorganic and organic pools of total soil zinc and can be utilized to increase zinc availability to plants. Therefore, the present study was carried out to isolate and characterize native zinc-solubilizing bacteria from Zea mays rhizosphere and evaluate their zinc-solubilizing potential and the effect of zinc solubilizing isolate on Zea mays growth. In vitro zinc solubilization assay of isolates was done using 0.1% zinc from zinc oxide in both plate and broth assays. Actively growing cultures of each isolates were spot-inoculated (7 µL) onto the agar and plates were incubated at 28°C for 48 h. The clearing zone around colony was recorded. Quantitative study of zinc solubilization was studied in 150 mL conical flasks containing 50 mL of liquid mineral salt medium. The broth was inoculated with 10 µL of overnight grown bacterial inoculum and incubated for 72 h at 160 rpm in an incubator shaker at 28°C. After incubation, the culture broth was centrifuged and the concentration of Zn in the supernatant was estimated in atomic absorption spectrophotometer. Among these isolates, 18 isolates with a solubility index of 1 and higher were selected based on morphological, biochemical and physiological characteristics for further studies. An isolate with more ability to dissolve zinc, phosphorus, potassium and auxin production were selected for investigation the effect of isolate on Zea mays growth. Maize seeds of cultivable variety were surface sterilized with 1% sodium hypochlorite for 5 min and washed several times with sterile distilled water. Seeds were treated with inoculum containing 108 cfu•g−1 of isolate. A factorial experiment in a completely randomized design with five replications was conducted. The treatments included two levels of bacteria B1 (control), B2 (Stenotrophomonas) and zinc sulfate fertilizer at three levels of Zn0 (control), Zn20 (20 kg/ha) and Zn40 (40 kg/ha). After 60 days of sowing, plants were removed from the tubes carefully and biometric parameters like root length, shoot length and dry mass of plants were recorded as the indicative of plant growth. A total of 50 bacterial isolates were isolated from corn rhizosphere. Of all, sixteen isolates showed solubilization halo on plate agar medium. Among the cultures, Z1, Z3, Z16 and Z12 showed the highest solubilisation zone in ZnO amended medium with maximum solubility index (1.3). Quantitative assay for zinc solubilisation revealed that Z14 were able to dissolve 44.8 ppm from ZnO in liquid medium. While solubility index of this isolate was lower that above mentioned isolates (1). Of all, the isolate Z14 with highest zinc solubilisation by broth assay was characterized and identified as Stenotrophomonas
species based on Gram-negtive reaction and other biochemical and physiological properties. This isolate was able to produce auxin and dissolve insoluble phosphorus and potassium from the source tricalcium phosphate and vermiculte, respectively. One of these strains (Z14), Stenotrophomonas was used as inoculum in corn culture.
Seed bacterization of maize with zinc solubilising Stenotrophomonas enhanced the plant growth significantly after 15 days. Results indicated a significant interaction effect of bacterium and fertilizer on shoot dry weight and chlorophyll content (P<0.01). The maximum spad index and wet weight of aerial part obtained at present of bacterium and without using of zinc sulfate. The main effect of bacterium on wet and dry weight of root and wet weight of aerial part, root length and shoot height was significant (P<0.01). Application of bacterium in all treatments caused to increased all measured parameters in th eperesence of zinc fertilizer or absence of zinc fertilizer. PGPR is known as a group of useful rhizospheric bacteria that increase plant growth. Today, the increasing use of PGPRs in agriculture as an alternative to chemical fertilizers to prevent environmental contamination.

Introduction The most important constraint in maize crop yield in developing contries worldwide, and especially among resource-poor farmers, is soil infertility. Therefore, maintaining soil quality can reduce the problems of land degradation that decreases soil fertility and rapidly declining production levels that occur in large parts of the world which needing the basic principles of good farming practice. For optimum plant growth, nutrients must be available in sufficient and balanced quantities. After nitrogen, phosphorus is the most limiting nutrient for crop yields, and is essential for maize growth and development. Large quantities of chemical fertilizers are used to replenish soil N and P, resulting in high costs and severe environmental contamination. Maize quantity and quality are increased by utilization of fertilizers, which has become the most important objective of these products worldwide. Phosphorus, is the second most important macronutrient required by the plants, next to nitrogen, and is reported to be a critical factor of many crop production systems due to its limited availability in soluble forms in the soils. The low availability of P to plants is because the vast majority of soil P is found in insoluble forms, and plants can only absorb P in two soluble forms, the monobasic (H2PO4-) and the dibasic (HPO42-) ions. Crop plants can therefore utilize only a fraction of applied phosphorus, which ultimately results in poor crop performance. To rectify this and to maintain soil fertility status, frequent application of chemical fertilizers is needed, though it is found to be a costly affair and also environmentally undesirable. Moreover, phosphorus (P) is an essential nutrientionl element for plant growth. Calcareous soils are frequently characterized by the low availability of P for plant uptake due to the low solubility of P compounds present in soils at high pH and the formation of relatively insoluble complexes, e.g., Ca-P. Many soils in Iran have received large amounts of P fertilizer and consequently contained a high level of available P. On the other hand, the root exudation of organic acids has been suggested to increase P availability in calcareous soils. The most common low-molecularweight organic acids (LMWOAs) identified in soils include oxalic, succinic, tartaric, fumaric, malic, and citric acids and are derived from the decomposition of soil organic matter in the upper soil horizons, microbial metabolites, canopy drip, and root exudation. The concentrations of organic acids in the rhizosphere or in soil solutions vary greatly and range from 10-2μM to over 80 mM. The ability of organic acids to release inorganic anions, such as P, has been reported and has been attributed to desorption of inorganic anions and solubilization of phosphate compounds. LMWOAs and their corresponding anions play a very important role to increase P bioavailability. Many studies have been conducted about the role of organic acids in increasing P availability, but these studies focused on acid soils in which Fe- or Al-bound P is the main P fraction. For calcareous soils where Ca-bound P is the main P fraction, questions that whether organic acids can mobilize P or not still exist. Although, a number of results show that addition of organic acids, especially citric and oxalic acids to soils can solubilize significant quantities of fixed P and reduce the sorption of newly applied fertilizer P. However, there are few studies on the transformations of P fractions induced by organic acids or organic anions, which are important for understanding the mobilization mechanisms of P and for exploring better ways of using different forms of P in soils. The objective of this study is to examine the effects of some organic acids and anions on the solubilization and plant uptake of soil P in some calcareous soils of Golestan province, Iran.
Material and Methods For this purpose, a factorial pot experiment in a completely randomized design with three replications was conducted on maize. The first factor was comprised of 6 soil types from various areas of the province and the second factor was consisted of a combination of phosphorus fertilizer and organic acids (1) control, (2) 50 mg P kg-1, (3 and 4) 50 mmol kg-1 of organic acids (oxalic and malic acids), (5) P oxalic acid and, (6) tomato fruit residue (25% w). After 10 weeks, plants were harvested and the parameters such as plant height, fresh and dry weights, phosphorus concentration and its uptake were determined.
Results and Discussion Results indicated that soil type effect was statistically significant on the plant fresh and dry weights (P≤ 0.05), height, concentration and uptake of P (P≤ 0.01), respectively.
Results also showed that the tomato fruit residue treatment in comparison with P fertilizer and malic acid treatments results in a significant increase in P taken up, and fresh and dry weights (P≤ 0.05). There was a significant difference between P fertilizer oxalic acid and oxalic acid alone treatments in only plant height (P≤ 0.05). Also, no significant differences in terms of measured plant parameters were observed between malic acid and blank treatments (P≤ 0.05).
Conclusion Application of tomato fruit residue rather than P fertilizer can help to take up residual soil P, to grow plants and to decrease of environmental pollution, and to be also affordable economically.

Salinity limited plant growth and will decrease the yield with decrease in solution osmotic pressure, nutrient imbalance and toxicity of some specific elements. Application of amendment materials such as gypsum and cattle manure can adjust the undesirable effects and increase the nutrient elements in leaf and grain. In this regard a pot experiment was conducted during 2009 growing season based on split factorial with four replications in complete randomize design. In this experiment the main factor was inclusive different level of salinity in irrigation water {0, 3, 6, 9 and 12 dS/m as NaCl and CaCl2 (1:1 w/w)} and subsidiary factors were inclusive gypsum (0, 15 and 30 ton/ha) and the cattle manure (0 and 30 ton/ha). The results showed that increasing the salinity content of irrigation water causes reduce the amount of phosphorus and increase nitrogen and potassium in wheat leaves. Also, with increasing in salinity of irrigation water the amounts of phosphorus and potassium in grain decreased and the amount of nitrogen in grain increased. Application of gypsum increased the amounts of the nitrogen, phosphorus and potassium 6.31, 10.89 and 14.82 percent in leaves and the amounts of the nitrogen, phosphorus and potassium 10.32, 10.84 and 3.45 percent in grain, respectively. Using manure at different salinity treatments was significant affecting on the amounts of nitrogen and phosphorus in leaves and phosphorus and potassium in grain. The highest amounts of nitrogen and phosphorus in leaves and grain were obtained using 15 and 30 tons of gypsum per ha while the highest amount of potassium in leaves and grain were obtained using 30 tons of gypsum per ha.

Reduction of chemical fertilizer consumption in the production of agricultural products, using bio-fertilizers as a suitable substitution or complementary for chemical fertilizers has privileges from ecology and economical aspects. The advantages of applying of bio-fertilizer are providing plant with different nutrients in accordance to the natural ability of plant, enhancing and improving soil biodiversity, resistance to plant diseases, developing biological activities, conservation and supporting the non- renewable natural resources such as ground water and soil. In this study, the effect of different fertilizing methods on protein percentage and phosphorus and grain yield of lentil (Lens culinaris Cv. Gachsaran) were evaluated in the research field of College of Agriculture, Lorestan University, Iran in 2009. The experiment was conducted on basis of a randomized completely block design with three replications. Treatments included three levels of chemical fertilizer of super phosphate triple [50 (C1), 100 (C2), 150 (C3) kg/ha-1], three levels of phosphatic biofertilizer Barvar-2 [25 (B1), 50 (B2), 75(B3) g/ha-1], six levels of integrated fertilizer [I1= (C1+ B1), I2= (C1+B2), I3= (C1+B3), I4= (C2+B1), I5= (C2+B2), I6= (C2+B3)] and control treatment (C0B0) Results showed that the effect of various treatments on grain yield was significant (P<0.01), and the maximum (I3) and minimum (control) corresponding values were equal to 442.6 and 279.1 kg/ha-1, respectively. The effects of different treatments on the percentage of seed phosphorus were significant (P<0.05), and the maximum (I5) and minimum (control) corresponding values were equal to 0.39% and 0.26%, respectively. The percentage of seed crude protein in the lentil was not significantly affected. The results showed that use of integrated fertilizing method increased grain yield and the percentage of grain phosphorus, on the other hand this method decreased application rate of chemical fertilizer of super phosphate triple, so integrated fertilizing method could be means to achieve the goals of sustainable agriculture.