Scielo RSS <![CDATA[Journal of soil science and plant nutrition]]> vol. 15 num. 1 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[<b>Effect of potassium on nutritional status and productivity of peanuts in succession with sugar cane</b>]]> Potassium contained in sugarcane straw quickly returns to the soil in a form readily available to crops. Thus, the objective of this study was to evaluate the effect of potassium on the nutritional status and grain yield of peanutscultivated in succession with sugarcane harvested without burning. The experiment was installed in Jaboticabal, São Paulo, Brazil, in Dystrophic Red Latosolcultivated with the peanut crop, variety Runner IAC 886. The treatments consisted of the application of 30, 60, 90 and 120 kg ha-1 of K2O and a control (no potassium). The experimental design adopted consisted of randomized blocks with five replications. Parameters evaluated were height, diameter, number of leaves, nutritional status for potassium and grain yield. Potassium resulted in a significant increase in the number of leaves and height, K contents (50-70 g kg-1) and grain yield, obtaining 2790 kg ha-1 at a dose of 120 kg ha-1. The sugarcane straw alone is not sufficient to meet the nutritional needs of peanuts planted in succession with sugarcane, where application of potassium fertilizer is necessary to obtain high yields.Potassium fertilization improved the nutritional status and was reflected in the increased production of grains of peanuts grown in rotation with sugarcane, especially at the dose of 120 kg ha-1 K2O. <![CDATA[<b>Municipal solid wastes and mineral fertilizer as an eggplant transplant medium</b>]]> The fertigation and/or municipal solid waste compost (MSWC)studied in eggplant seedlings. MSWC extracts (between 10-1 and 10-2) accelerated seedling germination. Under nursery conditions, six substrates prepared from commercial peat and MSWC and were further assessed in conjunction with the nutrient application as basic fertilizer (BF) or hydro fertilizer (HF). The addition of MSWC into the substrate inhibited seed emergence and mean germination time, while fertigation accelerated seed emergence in 15% MSWC. Addition of 60% MSWC reduced seedling height, leaf number and fresh weight. BF increased fresh weight in seedlings grown in 15% MSWC. Leaf Chlorophyll b content decreased but total carotenoids increased by adding MSWC into the substrate. The K content decreased, Na content increased while P content did not differ with MSWC addition. Fertigation benefits seedlings nutritive status. Low content (15-30%) of MSWC may act as alternative substitute of peat with more positive effects observed if minerals provided through BF rather than HF. <![CDATA[<b>Evaluating of many chemical extractants for assessment of Zn and Pb uptake by bean in polluted soils</b>]]> Assessment of bioavailability of trace elements, such as zinc (Zn), and lead (Pb), in polluted soils is needful to management and use of these soils. A greenhouse experiment was performed to investigate bioavailability of Zn and Pb for bean by various extractants (DTPA-TEA, AB-DTPA, Mehlich 2, Mehlich 3, 0.01 M CaCl2, and 0.1 M HCl) in 10 polluted soils. The results showed that extraction capacity was as follows: Mehlich 3>AB-DTPA>DTPA-TEA>Mehlich 2>CaCl2>HCl. The average of Zn extracted by Mehlich 3, AB-DTPA, and DTPA-TEA were 25.68, 9.73, and 7.30 mg kg-1, respectively. In addition, the average of Zn extracted by Mehlich 2, CaCl2, and HCl were 6.53, 0.13, and 0.11 mg kg-1, respectively. The average of Pb extracted by Mehlich 3, AB-DTPA, and DTPA-TEA were 12.56, 7.32, and 4.91 mg kg-1, respectively. Also, the average of Pb extracted using Mehlich 2, CaCl2, and HCl were 0.93, 0.62, and 0.44 mg kg-1, respectively. The results of correlation analysis revealed that the Zn extracted by DTPA-TEA, AB-DTPA, Mehlich 3, Mehlich 2, and HCl correlated significantly with Zn uptake. Moreover, significant correlation was found between DTPA-TEA, AB-DTPA, HCl, and CaCl2 with Zn concentration in bean. The concentration of Pb in bean and Pb extracted by DTPA-TEA, AB- DTPA, Mehlich 3, and Mehlich 2 correlated significantly. Therefore, application of extracting methods contains chelating agents would be recommended in the future research on the availability of Zn and Pb in polluted soils. <![CDATA[<b>Effect of fungicides on association of arbuscular mycorrhiza fungus <i>Rhizophagus fasciculatus</i> and growth of Proso millet (<i>Panicum miliaceum</i> L.</b>]]> The detrimental effects of fungicides on non-target beneficial microorganisms such as arbuscular mycorrhizal (AM) fungi are of interest to agriculture. Rhizophagus fasciculatus was found to be predominant (21%) AM fungus in studied soil compared to other species (2-9%). Hence, we have conducted a study to evaluate the potential effects of fungicides Benomyl (Methyl [1-[(butylamino) carbonyl]-1H-benzimidazol-2-yl] carbamate), Bavistin (methyl benzimidazol-2-ylcarbamate), Captan ((3aR,7aS)-2-[(trichloromethyl) sulfanyl]-3a,4,7,7a-tetra hydro-1H-isoindole-1,3(2H)-dione and Mancozeb (manganese ethylene-bis(dithiocarbamate) (polymeric) complex with zinc salt) on association of R. fasciculatus with Proso millet (Panicum miliaceum L.), an emerging drought-resistant crop that represent a cheap source of nutrients for human in developing country. The results of this study showed significant (P≤0.05) higher AM colonization (69.7%), spore density (193 spores), plant growth (both lengths and weights of shoots and roots) and grain yield (154 grains per panicle) in mycorrhizal Proso millet plants treated with Captan compared to other fungicides and untreated controls. In contrast, Benomyl had adverse effect in all parameters measured (45.3% AM colonization, 123 spores, 105 grains per panicle, etc.). Our results also showed that AM colonization significantly improve growth and grain yield of Proso millet plants compared with non-mycorrhizal plants. Therefore, the present study demonstrated that Proso millet crops could be improved with native AM fungal inoculation, however, the type of fungicide applied in soil and its effect on plant performance must be seriously considered. <![CDATA[<b>Vermicompost leachate as a supplement to increase tomato fruit quality</b>]]> Due to low yields, organic agriculture cannot satisfy the global demand for food, although it can provide products of higher nutraceutical quality. The objective of this research was to incorporate vermicompost leachates (VCLs) into an irrigation system during tomato (Solanum lycopersicum cv. Rafaello) cultivation to evaluate their effects on the lycopene, β-carotene, and phenolic content of tomatoes and on the physical and chemical soil variables. To evaluate the effects of VCLs, three types of substrates were used to create VCLs: mushroom waste (MSHW), leaf-cutting ant waste (LCAW), and cow compost (CC). A total of 0.1 L of leachate per plant was added as a supplement to a nutrient solution (NS) and applied once weekly, twice weekly, or every fifteen days to three different treatments for each leachate. All VCLs had a positive effect on the production of lycopene; the best results were obtained by the application of the MSHW (78 mg kg-1 fresh weight). The VCL decreased the presence of ions phytotoxic to plants by 99% and improved the soil structure by increasing the amount of organic matter and the hydraulic conductivity. However, the VCL had no effect on the physiological variables. The results support the use of leachate from CC via fertigation twice a week at a dose of 0.1 L plant-1 because it increases lycopene content by 67%. <![CDATA[Nitrogen orgdiv2<strong>mineralization in a silandic andosol fertilized with dairy slurry and urea</strong>]]> Knowledge about the size and cycle of inorganic N pool on grasslands is necessary to develop adequate fertilization strategies and to determine the potential pathways of N losses. The objectives of this study were to: 1) quantify the N mineralization rates in permanent grassland on an Andosol of southern Chile; and 2) determine the effect of high N application rates as urea and dairy slurry on this process. Mineralization was measured over a three years period on grassland fertilized with 400 kg N ha-1 yr-1 by acetylene inhibition method, incubating soil cores under field conditions. Subsequently, a laboratory assay was carried out to determine potential residual N mineralization rate by anaerobic incubation method. Higher N mineralization was measured on the urea treated plots (314 - 420 kg NH4+-N ha-1 yr-1) followed by slurry (320 - 344 kg NH4+-N ha-1 yr-1) (p<0.05). Most of the N was mineralized during spring and summer seasons (p<0.05). Laboratory results indicate that slurry treated soil had greater net potential N mineralization rates than urea (p<0.05). Results suggest that in Andosols of southern Chile, N mineralization can be a major N input into the soil N budget, with implications for grassland fertilizer managements and pathways of N loss <![CDATA[Apple fruit quality, yield and leaf macronutrients content as affected by fertilizer treatment]]> During two years we have investigated main fruit quality traits, yield and leaf nutrient content at 120 days after full bloom (DAFB) of ,Idared, and ,Melrose, apples on M.9 rootstock when fertilized with complex NPK (15:15:15) alone, and mixture with natural zeolite (Agrozel) and/or cattle manure. Results showed that fruit quality has been strongly affected by cultivars, whereas fertilizer treatments influenced only yield per tree. Moreover, significant impact of cultivar and fertilizer treatment on leaf P, K and Mg was found. Leaf of ,Melrose, contained higher P and K content, and lower Mg content than those of ,Idared,. In ,Melrose,, NPK alone increased leaf P, whereas in ,Idared, , mixture of NPK+Agrozel and NPK+Manure promoted leaf P, K and Mg content. According to DOP and EDOP indexes, excessive leaf Mg content was found, and deficiency of the rest of nutrients. ,Melrose, exhibited better balanced nutritional values for nutrients as compared to ,Idared,, whereas NPK+M promoted better balanced nutritional values than other treatments. <![CDATA[Evaluation of soil fertility and fertilisation practices for irrigated maize (<i>Zea mays</i> L.) under Mediterranean conditions in Central Chile]]> The main aim of this study was to carry out an evaluation of soil fertility and fertilisation practices for irrigated maize (Zea mays L.) under Mediterranean conditions in central Chile. Soil samples were collected from 31 maize fields for macro- and micronutrient analysis; additionally a crop management survey was carried out in each field. These data were used to identify the range of critical soil-test concentrations of nutrients and the relationships among these soil fertility parameters; to assess the relationship between maize yields and nutrient status of soils; to evaluate the current fertiliser practices of farmers comparing them with nitrogen (N), phosphorus (P) and potassium (K) fertiliser model calculations; and to analyse whether The results showed that there was a dominance of neutral-alkaline soils with low organic matter and N levels, and high P, cations and micronutrient levels. Regression analysis explained at least 59% of the variation in maize yields, when soil pH and available zinc (Zn) content were identified as the most important variables controlling maize yield. Results suggest that in neutral-alkaline soils cultivated with maize and high inputs of N-P-K, there may be a maize yield response to Zn applications. It was found that most farmers over-fertilised with N (from 60 to 360 kg N ha-1) and P (from10 to 120 kg P2O5 ha-1), converting maize fields in an important non-point source of pollution of water bodies in Central Chile. <![CDATA[<b>Dynamic changes of nutrition in litchi foliar and effects of potassium-nitrogen fertilization ratio</b>]]> Field experiments were conducted to determine the annual dynamic changes of element contents in litchi leaves and the effects of the potassium and nitrogen ratio (K2O/N ratios: 0.6, 0.8, 1.0, 1.2, and 1.4) on the yield and planting benefits of litchi. The cultivar ,Feizixiao, litchi planted in a typical acidic upland orchard was used as a subject. The following results were obtained. (1) The elemental contents of litchi leaves significantly varied during the different developmental stages. Throughout the developmental period, the elemental contents in litchi leaves were in the descending order of N > K > Ca > Mg > P > S > B > Zn > Mo. The K content showed a highly significant negative correlation with the Ca and Mg contents and significant negative correlation with the Zn content. The Ca, Mg, and Zn contents exhibited significantly positive correlation with each other. The N content was significantly negatively correlated with the S and B contents in leaves, and the S and B contents showed significant positive correlation with each other. The P content exhibited significant negative correlation with Ca and Si, whereas Ca and Si were significantly positively correlated with each other. (2) Under the same N application conditions, the yield and planting benefits of litchi initially increased and then subsequently decreased with increasing K2O/N ratio. litchi had the highest yield and plant benefit when the ratio of K2O to N ranged from 1.0 to 1.2. Thus, this ratio is recommended for the main litchi production areas in China. <![CDATA[<b>Seasonal variation of the productivity and quality of permanent pastures in Adisols of temperate regions</b>]]> With the aim of evaluating the productivity (dry matter yield) and quality (protein and fiber) of pastures in temperate regions of Chile a long-term monitoring experiment was carried out in a representative farm in these regions. The study was carried during the years 2002 - 2012 in a farm located at Region of Los Ríos, Chile. The study area was split into fifteen pasture sites, which were evaluated dry matter production by means of the standardized methodology, which considers the location on each pasture site a grazing exclusion cage. With the information generated during the 11 years of measurements, a trend pattern interpolation was developed by a polynomial regression model using fifth grade and centering the independent variable from the second grade on. Each result was classified according to the ranking provided by the BLUP methodology, comparing the results obtained with the average. The analysis of variance mixed model, determined by the variance components, indicated that 60% of the total variation in dry matter production is attributed to seasonality. Only 2.6% of the variation was attributable to the year while a 0.9% was due to differences between pastures sites, during the eleven years of study, with no significant data (p> 0.05). The seasonal distribution of production, concentrated its performance in spring and highest performing months were November, December, January. The quality measured as protein and fiber content of the pasture, does not present statistical differences between years and only differences were determined by seasonality. <![CDATA[<b>Effect of long-term fertilization on free-living nematode community structure in Mollisols</b>]]> The influence of long-term application of pig manure combined with chemical fertilizer (MCF) or chemical fertilizer (CF) on free-living nematodes was evaluated in this study. The application model of fertilizers lasted 14 years in Mollisols, and treatments included MCF, CF and no fertilizer (NF). A total of 26 free-living nematode genera belonging to seven functional guilds were found in maize fields, and the community structure of free-living nematodes was different in MCF, CF and NF. Pig manure increased the abundance of bacterivores, especially those belonging to c-p1 (Ba1) and c-p2 (Ba2) guilds. Channel index (CI) was higher in NF than in MCF and CF, but enrichment index (EI) was higher in MCF and CF compared to NF. The structure index (SI) was highest in NF among three treatments. Total bacterivores, Ba1 and Ba2 guilds were positively correlated to organic C, total N, available N, total P and available P, but fungivores only had correlation with organic C and soil moisture. The SI index was negatively related to organic C, total N, available N, total P and available P. Collectively, these results indicate that the pig manure or chemical fertilizer normally applied to increase soil nutrition also induce negative influence on soil food web structure as reflected from biological aspect, and that soil nematodes can enhance agroecological assessments of changes induced by long-term fertilizer application in maize field in Mollisols. <![CDATA[<b>Arbuscular mycorrhizal status of pioneer plants from the mouth of lake Budi, Araucanía Region, Chile</b>]]> Abstract Arbuscular mycorrhizal fungi (AMF) have an important role on the ecosystem stability promoting water and nutrient acquisition by plants and allowing their growth under stress conditions including drought and salinity. This study aimed at describing the colonization of native AMF associated to pioneer plant species growing at the mouth of lake Budi, which receive seasonally marine water. For this, root samples and rhizosphere substrate of Polygonum maritimum, Carpobrotus chilensis, Ambrosia chamissonis, Ammophyla arenaria were collected and analyzed. Mycorrhizal root colonization, spore and hyphal density, and some soil chemical properties (pH, conductivity, organic matter -OM-, and microbial activity) were determined. Results showed that A. Arenaria presented the highest root colonization (53%), mycelium (10 m g-1) and AMF spores (300 spores in 100g of substrate) densities, which were highly correlated with an elevated OM content (1.64%; r=0.53, r=0.48 y r=0.87, respectively) and soil microbial activity (3.57 µg fluoresce in g-1 h-1; r=0.89 r=0.76 and r=0.53, respectively). On the other hand, a low AMF species richness was found in the rhizospheric soils of all four evaluated plants, finding a total of five AMF species. Nevertheless, one of these corresponds to a new specie (Corymbiglomus pacificum), which was associated to A. arenaria. Our results suggest an important role of AMF associated to pioneer plants in saline ecosystems, especially enhancing the establishment of A. arenaria and Amb. chamissonis, which could promote a further nurse effect that allow the establishment of other plant species. AM fungi could be considered as a biotechnological tool since they could be used for stabilization of coastal ecosystems, and in soils under saline or hydric limitations. <![CDATA[<b>Short-term study shows that phytate-mineralizing rhizobacteria inoculation affects the biomass, phosphorus (P) uptake and rhizosphere properties of cereal plants</b>]]> Cereal production in southern Chile is based on volcanic soils (Andisol) that are phosphorus (P) deficient for plant nutrition. Phytate-mineralizing rhizobacteria (PMR) have been suggested as soil inoculants to improve P uptake and growth of plants cultivated in P-deficient soils. In this study, a greenhouse experiment was conducted to investigate the effects of inoculation with PMR (Bacillus sp. N1-19NA, Enterobacter sp. N0-29PA, Pseudomonas sp.N1-55PA and Serratia sp. N0-10LB) on biomass and P uptake of cereal plants (wheat, oat and barley) grown in a Chilean Andisol with out P fertilization. Results showed that inoculation with Enterobacter sp. N0-29PA significantly (P≤0.05) increased the biomass and Puptake of oat plants.Changes in rhizosphere properties as soil enzyme activities (acid phosphatase and urease), and auxin production potential were also produced by Enterobacter sp. N0-29PA inoculation. Despite the possible value, Enterobacter sp. N0-29PA as a soil inoculant for P-deficient soils, other PMR assayed did not consistently enhanced biomass and P uptake of plants. In addtion, polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) combined with non-metric multidimensional scaling (nMDS) analysis revealed that PMR inoculation induced changes in rhizobacterial community composition, suggesting that PMR application substantially modify the microbiological characteristics of rhizosphere. However, long-term studies at field level are still needed to practical use of PMR as inoculants in Chilean Andisols. <![CDATA[<b>Soil moisture derivation using triangle method in the lighvan watershed, north western Iran</b>]]> Soil moisture determination plays a major role in water and crop management. In this research, the accuracy of the Triangle Method (TM) was evaluated to predict surface soil moisture content using Moderate Resolution Imaging Spectro-radiometer (MODIS) satellite images with 1km resolution. The investigation was carried out within an area of 76 km² in Lighavn watershed in East Azerbaijan, North West of Iran. The analysis was based on ground measurements of soil moisture at 225 points (45 pixels) across the catchment on 2 different days. Ground measurements from the first day were used to train the models, while those from the second day were used for validation. A range of polynomial regressions from 1st to 4th orders were established between the ground measured soil moisture and MODIS Normalized Difference Vegetation Index (NDVI) and Land Surface Temperature (LST). The best results were obtained for the 4th order polynomial of the TM with the efficiency error (ER) and adjusted determination coefficient (R²adj) criterions, respectively, equal to 11.0% and 0.63 for calibration and 15.9% and 0.60 for validation stage. Therefore, the TM was found to provide reliable estimates of soil moisture, without the need for prior information of the soil surface roughness or the vegetation type and water content. <![CDATA[<b>Chlorophyll <i>a</i> fluorescence in sweet potatoes under different copper concentrations</b>]]> Photosynthesis is one of the main plant metabolic processes affected by copper deficiency and toxicity. The objective of this study was to evaluate the effects of different copper concentrations on transient chlorophyll a fluorescence and modulated fluorescence in sweet potatoes. Sweet potatoes were placed in a hydroponic system and grown for six days with a complete nutrient solution. The plants were then transferred to solutions with different copper concentrations (0.041, 0.082, 0.123 and 0.164 mM) for nine days. The solutions were renewed every three days, and the plants were evaluated at the end of the experiment. Increased copper availability (0.123 and 0.164 mM) positively influenced the structure and functionality of photosystem I (PSI). The increase in Cu availability also reduced the apparent electron transport rate in the PSII [ETR(II)], and the plants treated with 0.082 and 0.123 mM Cu were able to dissipate the excess light energy in the PSII and protect its units (NPQ and qN). A joint analysis of the data shows that high copper concentrations in the nutrient solution lead to reduced photochemical activity of the PSII, increased dissipation of light energy from this same photosystem and increased PSI efficiency in sweet potatoes. <![CDATA[<b>The stimulatory effects of L-tryptophan and plant growth promoting rhizobacteria (PGPR) on soil health and physiology of wheat</b>]]> During the present study, Pseudomonas moraviensis and Bacillus cereus, were isolated from rhizosphere soil of halophytic weed (cenchrus ciliaris L.) of Khewra salt range, and used as bioinoculants. The plant growth promoting rhizobacteria (PGPR) were applied to wheat (Triticum aestivum) by seeds soaking, and aqueous solution of tryptophan was added to the rhizosphere soil at 1ug/L, after seed germination. Experiment was conducted at Quaid-e-Azam University Islamabad both in pots (filled with sterilized soil) under axenic condition and in field under natural condition, for two consecutive years. The inoculation of Pseudomonas moraviensis and Bacillus cereus, significantly increased the organic matter, P, K, Ca, and NO3-N availability of soil. The inoculation of these PGPR positively enhanced growth and physiology of treated plants, and this affect was further augmented in the presence of tryptophan. Addition of tryptophan with Pseudomonas moraviensis and Bacillus cereus increased the fresh weight, proline contents and activities of antioxidant enzymes significantly over control. Added tryptophan with both PGPR, improved the number of plants at yield and seeds establishment by improving number of seeds/spike and spike length. Effects of PGPR inoculation alone and with tryptophan were more pronounced in pots grown plants. It is inferred from the results, that tryptophan addition is a competent source for increasing potential of PGPR, thereby improving wheat growth, and physiology. <![CDATA[<b>PGPR mediated Zinc biofertilization of soil and its impact on growth and productivity of wheat</b>]]> Objectives: This study describes Zinc biofortification of wheat using a rhizospheric isolate, Pseudomonas fluorescens strain Psd. Methods: The strain was used as a bio-ionculant in soil deficient in zinc and the plant-growth promoting potential and biofortification was assessed using a number of physical and biochemical parameters. The enzymatic studies indicated towards the zinc supply mediated by the strain Result: This plant-growth-promoting strain, apart from the Zn accumulation potential, has the ability to solubilise Zn and was also able to leach out Zn from ore-tailings. The application of a Zn-laden biomass of the strain in soil resulted in increased growth and productivity of wheat crop as demonstrated by pot experiments. The beneficial effect was also reflected in increased activities of some enzymes. In addition, grain Zn2+ content was enhanced by ~85% in comparison to wheat grown in Zn2+-deficient soil. <![CDATA[Impact of calcium associated to calcareous amendments on ectomycorrhizae in forests: a review]]> There is currently little information available on calcium-soil-ectomycorrhizal (ECM) interactions. However, for decades calcareous amendments have been made in forest soils subject to acid rain in Europe without any clear knowledge of their impact on ECMs and the roots of their host plants. We have therefore performed a review to assess the impact of Ca associated tocalcareous amendments in the soil-ECM-host plant system, which has highlighted: (1) the influence of Ca and its salts (carbonates and oxalates) of biological origin in ECM fungal communities; (2) the impact of Ca on the growth patterns of the host tree roots; (3) the importance for the plants of the rock-eating processes associated to ECMs; and (4) the impact on ECMs of the soil Ca cycle (associated to the litterfall). A greater knowledge of the cause-effect relations between Ca and the soil-ECM-plant system in Mediterranean and temperate forests could have positive repercussions on reforestation projects, actions associated to soil management, the commercial production of ECMs, and the economy of different rural zones in these forest areas. <![CDATA[<b>ACC-deaminase</b> <b>and/or nitrogen fixing rhizobacteria</b> <b>and growth of wheat (<i>Triticum Aestivum</i></b> <b>L.)</b>]]> Plant growth promoting rhizobacteria (PGPR) are beneficial bacteria, which can enhance the growth of the plants, when applied to crops. A pot experiment was conducted to examine the effect of six PGPR isolates on the growth of wheat. Inoculation with rhizobacterial isolates increased the all measured physical, chemical and enzymatic growth parameters compared to control (CK). However, the WAN1 isolate had the highest effect, and significantly (P < 0.05) increased the root length (3.51-fold), shoot length (3.22-fold), seedling fresh (3.41-fold) and dry (3.91-fold) weight, chlorophyll a (3.90-fold), chlorophyll b (3.51-fold), carotenoid contents (7.23-fold), plant macronutrient uptake i.e. N (7.20-fold, 6.71-fold), P (7.41-fold, 5.01-fold), K (5.51-fold, 3.91-fold), Ca (6.40-fold, 5.21-fold) and Mg (5.82-fold, 7.11-fold) in shoot and root, plant micronutrient uptake i.e. Zn (6.40-fold, 9.11-fold), Cu (7.31-fold, 7.02-fold), Fe (6.41-fold, 7.52-fold) and Mn (4.57-fold, 5.21-fold) in shoot and root and plant antioxidant enzymes i.e. glutathione S-transferase (7.51-fold), peroxidase (5.21-fold) and catalase (5.01-fold) respectively. Our results revealed that inoculation of agricultural crops with PGPR is a very useful approach to increase the plant growth. The ACC (1-aminocyclopropane-1-carboxylate) enrichment technique is an efficient approach to select promising PGPR. The PGPR containing dual abilities i.e. both ACC-deaminase and nitrogen fixing ability are more effective than PGPR possessing either ACC-deaminase or nitrogen fixing activity alone for growth promotion of crops. <![CDATA[<b>The effects of some humic substances and vermicompost on phosphorus transformation rate and forms</b> <b>in a calcareous soil</b>]]> The role of some humic substances (HS) on phosphorus (P) bioavailability and fractions was investigated in a greenhouse study using a calcareous soil from Eastern, Iran. Soils were treated with two levels (2 and 4%) of Humic Acid (HA), Fulvic acid (FA), Vermicompost (Verm) and their mixtures including FA+HA and FA+HA+Verm, and incubated for 24, 360, 720 and 1080 h. The Olsen-P was determined in amended and non-amended soils after incubation time. The P release was modeled by Parabolic, Power and Elovich equations to determine the transformation rates. Since the maximum P release was found in vermicompost treated soil, P was sequentially extracted with H2O, NaHCO3, NaOH and HCl at 24 and 1080h after incubation. The highest released P was measured in vermicompost treatment and decreased as follows: HA+FA+Verm>HA+FA>HA>FA>CO. The decrease of P release data was best described by Parabolic equation (r²=0.83-0.93, SE=0.51-2.91). Higher transformation indices of vermicomopost amended soil than other treatments showed more efficiency of vermicompost to release of phosphorus in soil. H2O-P, NaHCO3-P and NaOH-P increased after vermicompost application and converted to HCl-P fraction so that at the end of the experiment, calcium phosphates comprised 69 and 43% of inorganic P (Pi) at 2 and 4% vermicomopost treatments, respectively. Results of the study showed that humic substances could increase P extractability and availability in soil.