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Cotton is typically grown in warm regions in which salinity and nutrient deficiency stresses are ubiquitous and often simultaneously influence plant growth. Under saline conditions, fertilizer recommendation is highly challenging, since nutrient application may increase or decrease plant salt tolerance, which may complicate prediction of crop yield. So far, no investigations have been conducted in salt-affected soils to determine optimum concentrations of potassium (K) and zinc (Zn) fertilizers based on chlorophyll fluorescence (ChlF) and gas exchange (GEx) responses in upland cotton (Gossypium hirsutum L.). Accordingly, in this study, a factorial experiment was conducted in a complete block design with six replicates under controlled conditions. Treatments included various K2SO4 (0, 50, 100, and 150 kg ha−1), and ZnSO4 (0, 50, and 100 kg ha−1) concentrations applied to soil before planting. Cottonseeds were sown in non-saline soils and soils formerly salinized with natural saline water diluted to 15 dS m−1. One month after sowing, results showed that salinity significantly decreased dry weight, chlorophyll content index, photosynthesis rate (A), leaf to air vapor pressure, transpiration rate (E), stomatal conductance, and minimum fluorescence of dark-adapted leaf, but increased root to shoot ratio (R/Sh). Under salinity, combined application of K and Zn boosted physiological properties including yield of photosystem II photochemistry (ФPSII), A, and E without improving biomass. Combined application of K and Zn at highest concentrations decreased R/Sh by 93% compared to the control. Rate of increase was higher in E than that of A leading to reduction in water use efficiency. High Zn concentration in saline soils increased non-photochemical quenching and energy loss in form of heat. Under non-saline condition, Zn application significantly decreased A probably due to inhibitory effect on electron transfer within photosystem II. K significantly increased stomatal conductance and accordingly E. GEx parameters were more sensitive to used treatments than ChlF parameters. Based on GEx and ChlF responses, the most salt-tolerant cotton seedlings were obtained under combined application of 50 kg K2SO4 ha−1 and 50 kg ZnSO4 ha−1, thus these concentrations are recommended for optimal establishment of cotton seedlings under salinity stress.

All existing fertility models are originally derived for non-saline conditions. Under salinity, fertilization is challenging and may lead to amelioration or deterioration of plant salt tolerance. T...

A large area of Iran is located in arid and semi-arid regions; as a result, drought stress is a major problem for the growth of plants. Therefore, it is very important in crop productivity to increase plant tolerance to drought stress. Plant growth promoting rhizobacteria such as Azotobacter may enhance plant growth under drought stress conditions by different mechanisms. In this study, a total of 20 Azotobacter strains were isolated and characterized from 77 rhizosphere soil samples collected from semi-arid regions. The strains were screened for the production of siderophore and IAA, solubilization of phosphate and potassium and growth under drought stress in PEG 6000. The strains were identified by 16S rRNA gene sequencing. The efficient strains were tested on the growth of maize (Zea mays) under drought stress by using three levels of irrigation, including 80, 60 and 40 percent of field capacity in greenhouse conditions. The laboratory results revealed that Az63, Az69 and Az70 were the most effective strains in terms of phosphate and potassium solubilisation, siderophore producion and maximum growth in PEG 6000. At 40 percent of field capacity, the inoculation increased shoot dry weight, plant height, chlorophyll content, nitrogen, phosphorous and iron concentration compared to the control. Az63 and Az70 increased shoot dry weight significantly at 60 percent of field capacity.

Excess accumulation of nitrate in vegetable crops is normally related to the excessive use of nitrogen fertilizers applied in agricultural fields. This study was performed to evaluate the level of nitrate concentration in onion production in Isfahan province of Iran and the potential health risks associated with high level of nitrate in this crop, as an example of a case-study . The risk was estimated by using the United States Environmental Protection Agency (USEPA) method and presented as risk maps. Additionally, the impact of an improved fertilizer management practice in selected vulnerable fields for reducing nitrate concentration in onion production was evaluated. For this assessment, four different onion fields in which onion bulb nitrate concentration was higher than the safety level (70 mg kg −1 FW), provided by Welch (2003) in a survey study, were chosen. The risk maps showed that despite higher risk possibility in adults, in comparison with children, all values were lower than the acceptable level. Further, the split application of nitrogen fertilizers in all fields significantly reduced plant nitrate concentration with no reduction in yield and even observed increase in the overall economic yield production. Therefore, considering crop yields and nitrate accumulation impacts, improved nitrogen management could provide an opportunity to promote onion crop production while reducing negative health effects in high-risk regions in Isfahan province of Iran.

Health risk from nitrate was predicted for different scenarios of vegetable consumption and nitrate contents in Iran. Finally, certain management scenarios were presented for nitrate risk mitigation under worst-case scenario considering each vegetable contribution in nitrate intake. Two fruit (bell pepper and tomato) and two leafy vegetables (lettuce and mint) were sampled in a combined randomized method from fields, greenhouses, and markets of Isfahan province, Iran during October to December 2015. To assess the potential health impacts of nitrate from the vegetable ingestion, the present status and three different scenarios of increasing vegetable consumption and/or increasing plant nitrate concentrations were considered. Two management scenarios for reducing the total nitrate intake below the allowable values were predicted. By increasing vegetable consumption under scenario 1 and nitrate concentration under scenario 3, the total hazard quotient (THQs) was increased, although the highest increase (12-fold) in the THQs was provided by lettuce. Health risk from nitrate for sensitive groups was effectively reduced by a 70% decrease in lettuce nitrate concentration. In the second management scenario, decreasing upper nitrate concentrations in the other sources (except lettuce) by 30% declined nitrate intake in children (

To investigate the effect of oxalic and citric acids on the uptake and relationship of phosphorus and zinc in corn (Zea mays L.), some greenhouse experiments were performed by individual and combin...

To study the role of citric and oxalic acids on 226Ra transfer factor (TF) from a soil with 10,000 Bq kg−1 of 226Ra activity to corn plant, a greenhouse experiment was conducted. Results revealed that the highest TF in whole plant was 0.063 and in citric acid at 100 mM concentration. It was 1.4 times of control (0.043). Maximum value of TF in shoot and root was 0.015 and 0.049 in citric acid at 10 and 100 mM concentrations, respectively. Organic acids did not extract 226Ra from this soil, while they reduced the pH of soil extracts compared to control.

To study the benefit of including citric and oxalic acid treatments for phytoremediation of 226Ra contaminated soils a greenhouse experiment with corn was conducted. A soil was sampled from a region of high natural 226Ra radioactivity in Ramsar, Iran. After cultivation of corn seed and using organic acid treatments at 1, 10 and 100 mM concentrations, plants (shoots and roots) were harvested, digested and prepared to measure 226Ra activity. Simultaneously, sequential selective extraction were performed to estimate the partitioning of 226Ra among geochemical extraction. Results showed that the maximum uptake of 226Ra in plants was observed in citric acid (6.3%) and then oxalic acid (6%) at 100 mM concentration. These treatments increased radium uptake by a factor of 1.5 than the control. Enhancement of radium uptake by plants was related to soil pH reduction of organic acids in comparison to control. Also, the maximum uptake of this radionuclide in all treatments was obtained in roots compared to shoots. 226Ra fractionations results revealed that 91.8% of radium was in the residual phase of the soil and the available fractions were less than 2%. As the main percent of 226Ra was in the residual phase of the soil in this region, it seems that organic acids had not significant effect on the uptake of 226Ra for phytoremediation by corn in this condition.

The hypothesis was that arbuscular mycorrhizal (AM) fungi are able to alleviate salt stress on plant growth by enhancing and adjusting mineral uptake. The objectives were to determine (1) the effects of soil salinity on mineral uptake by different wheat genotypes and (2) the effectiveness of different mycorrhizal treatments on the mineral uptake of different wheat (Triticum aestivum L.) genotypes under salinity. Wheat seeds of Chamran and Line 9 genotypes were inoculated with different species of AM fungi including Glomus mosseae, G. intraradices, and G. etunicatum and their mixture at planting using 100 g inoculum. Pots were treated with the salinity levels of 4, 8, and 12 dS/m before stemming. Different arbuscular mycorrhizal treatments, especially the mixture treatment, increased wheat mineral uptake for both genotypes. Although Line 9 genotype resulted in greater nutrient uptake under salinity stress, Chamran was more effective on adjusting sodium (Na+) and chloride (Cl−) uptake under salt stress.

Cadmium (Cd) is toxic to animals and humans after it accumulates over decades in the kidney cortex. Food crops grown in Cd-contaminated soils are the primary sources of excessive Cd entry into humans. Although plant available Zn concentration in soil is an important factor which can greatly reduce Cd uptake by plant roots and its translocation into the edible parts, Cd:Zn ratio is suggested to be a more important factor in comparison with Zn concentration alone in determining Cd uptake by plants. In the present study, the physiological mechanisms of Cd absorption by roots and its translocation to leaves of lettuce (Lactuca sativa L.) at various Cd:Zn ratios in the rooting media were investigated. For this purpose, seedlings of hydroponically-grown lettuce were exposed to combinations of four Zn (0, 12.5, 50 and 100μM) and four Cd (0, 0.5, 1 and 10μM) concentrations providing different ratios of Cd:Zn. At each level of Cd, decreasing the Cd:Zn ratio by increasing Zn concentration in the nutrient solution caused significant reduction of root symplastic Cd and also reduced Cd loading into the xylem and Cd transport to and accumulation in leaves. The highest root symplastic Cd (1087mg/kg-1 Dry Weight [DW]) and shoot Cd concentrations (64mg/kg-1 DW) were observed at the highest Cd:Zn ratio of = 0.8 (Zn = 12.5, Cd = 10). At the Cd:Zn ratios of ≤ 0.01, shoot Cd concentration was less than the Detection Limit (< 0.02mg/kg DW). Decreasing Cd:Zn ratio in nutrient solution was accompanied with significant increase in root apoplastic Cd and decrease in the root symplastic Cd. According to the obtained results, at the Cd:Zn ratio equal to 0.01 and less, Cd concentration in lettuce shoots decreased to < 0.02mg/kg.

A field experiment was carried out in a semi-arid region of Iran during the 2006–2007 growing season to investigate canola seed yield as affected by nitrogen (N) and natural zeolite (Z) rates. This experiment studied N efficiency and N leaching loss in a sandy soil. Experimental treatments consisted of a factorial combination of three N levels (90, 180, and 270 kg N ha−1) and four zeolite rates (0, 3, 6, and 9 t zeolite ha−1). The result showed that the greatest seed yield (2452.3 kg ha−1) was obtained from the N270Z9 treatment whereas the control treatment (N0Z0) produced the lowest seed yield (1038.3 kg ha−1). Moreover, use of 270 kg N ha−1 without zeolite (N270Z0) led to the greatest amount of N leaching loss (144.23 kg ha−1). Zeolite application clearly reduced N leaching loss in all N rates. This justified low N-use efficiency in high N applications. More N uptake and more canola seed yield is attributed to zeolite application.

Determination of the chemical characteristics of soil for balanced fertilization on large scales is an important factor in achieving a precision agriculture. Laboratory analyses of soil properties are usually expensive and time consuming. Surmounting these problems is possible using geostatistics. Therefore, this research aims at selecting a proper interpolation method using 213 soil samples for alfalfa farmland in Hamadan Province, Iran. Various factors such as pH, EC, , , K, P, Fe, Zn, B and Co were measured. Ordinary kriging and co-kriging were assessed to derive maps of soil physico-chemical properties, using mean absolute error (MAE), mean bias error (MBE), root mean squared error (RMSE) and average kriging standard error (AKSE) as statistical criteria. Variography analysis indicated that the ranges of influence for pH, EC, , , K, P, Zn, Fe, B and Co were 65, 55, 78, 79, 75, 60, 50, 65, 70 and 30 km, respectively, and the measuring error varied between 0.366 and 0.843. The results revealed that, base...

Dynamic ion speciation using DMT (Donnan membrane technique) requires insight into the physicochemical characteristics of diffusion in charged membranes (tortuosity, local diffusion coefficients) as well as ion accumulation. The latter can be precluded by studying the diffusion of neutral species, such as boric acid, B(OH)₃⁰(aq), arsenite, As(OH)₃⁰(aq), or water. In this study, the diffusion rate of B(OH)₃⁰ has been evaluated as a function of the concentration, pH, and ionic strength. The rate is linearly dependent on the concentration of solely the neutral species, without a significant contribution of negatively charged species such as B(OH)₄⁻, present at high pH. A striking finding is the very strong effect (factor of ~10) of the type of cation (K(+), Na(+), Ca(2+), Mg(2+), Al(3+), and H(+)) on the diffusion coefficient of B(OH)₃⁰ and also As(OH)₃⁰. The decrease of the diffusion coefficient can be rationalized as an enhancement of the mean viscosity of the confined solution in the membrane. The diffusion coefficients can be described by a semiempirical relationship, linking the mean viscosity of the confined solute of the membrane to the viscosity of the free solution. In proton-saturated membranes, as used in fuel cells, viscosity is relatively more enhanced; i.e., a stronger water network is formed. Extraordinarily, our B(OH)₃-calibrated model (in HNO₃) correctly predicts the reported diffusion coefficient of water (D(H₂O)), measured with ¹H NMR and quasi-elastic neutron scattering in H(+)-Nafion membranes. Upon drying these membranes, the local hydronium, H(H₂O)(n)(+), concentration and corresponding viscosity increase, resulting in a severe reduction of the diffusion coefficient (D(H₂O) ≈ 5-50 times), in agreement with the model. The present study has a second goal, i.e., development of the methodology for measuring the free concentration of neutral species in solution. Our data suggest that the free concentration can be measured with DMT in natural systems if one accounts for the variation in the cation composition of the membrane and corresponding viscosity/diffusion coefficient.

Boron (B) availability is regulated by its equilibrium concentration that in turn is buffered by adsorption and desorption reactions. Ionic strength, pH, OM content, and the type and amount of minerals are the major factors affecting B sorption reactions. To evaluate the influence of calcium carbonate equivalent (CCE) and ionic strength on B chemical behavior, its adsorption and desorption isotherms were measured in eight calcareous soils differed in CCE (0-85%). Adsorption and desorption data were described by the Langmuir and the Linear adsorption equations, respectively. No statistically significant relation was found between model parameters and soil properties. However, in comparison, soils with higher reactive particles (clay and OM) and higher pH adsorbed more boron. Removing CCE from a soil sample (CCE=18%) lowered B adsorption maximum by 35%. In contrast, increasing electrolyte concentration (0.01 M NaCl) to 0.1 and 0.5M caused to increase B adsorption maximum by 30% and 75%, respectively. At the equi-molar concentration, CaCl(2) increased B adsorption stronger than NaCl. The positive effect of ionic strength was attributed to a better screening of surface charges and compaction of double layer thickness. Desorption data were deviated from adsorption isotherms only at equilibrium concentrations smaller than 2 mM. Analysis of boron solution speciation and adsorption-desorption data revealed that B is mainly adsorbed as spectroscopically proved outer-sphere complex in the studied soil samples. The experimental data and model prediction could be used to manage B bio-availability and to optimize remediation processes in calcareous soils.

Mature fruit of the 'KS 13 ' Asian pear (Pyrus serotina Rehd.) cultivar were harvested from eight-year-old trees grown on European pear seedling rootstocks at Tarbiat Modares University (TMU) research orchard. Water extracts of onion and garlic bulbs were prepared and their effects on polyphenol oxidase activity and browning of Asian pear fruit juice were investigated. The polyphenol oxidase (PPO) of Asian pear was inhibited by onion and garlic extracts, and the inhibitory effect of these extracts on PPO was increased after heating them. The extracts' inhibitory effect increased with increasing heating temperature and time. In addition, results indicated that the inhibitory effect of garlic extract was greater than that of onion extract. The browning of Asian pear juice was retarded by addition of both fresh and heated onion and garlic extracts. The extracts inhibited the PPO activity non-competitively. Therefore, the inhibitory effect of these extracts against juice browning seems to be due to their impact on PPO activity.

Organic acids such as citrate and oxalate have been implicated in enhancing many rhizosphere processes including nutrient acquisition. This study was conducted to determine the importance of organic acid type and concentration on rhizosphere P mobilization and subsequent uptake by wheat (Triticum aestivum L.) roots and its translocation to shoots. A single wheat plant was grown in soil-filled rhizosphere microcosms and allowed to pass through a KH2PO433P-isotopically labeled patch of calcareous soil. Two days after 33P-injection, citrate and oxalate at concentrations of 1 mM and 10 mM were injected into the microcosms at the same patch every day over a period of 4 days. Oxalate resulted in a several-fold enhancement in plant 33P accumulation, while citrate had no such effect. In comparison with oxalate, high rates of citrate mineralization were observed suggesting that this reduced its potential to enhance plant 33P acquisition. This study concludes that organic acids cause an increase in P mobilization and P uptake by wheat but that this response is highly organic acid specific.

Nickel (Ni) is an essential element for activation of urease in higher plants. The effects of Ni as an essential micronutrient on growth and chlorophyll content of wheat plants grew in nutrient solutions supplied either with ammonium nitrate or urea as two different nitrogen (N) sources were investigated. Plants were allowed to grow for six weeks, then leaf chlorophyll content, shoot and root fresh and dry weights, and Ni concentration in shoots and roots were determined. Shoot and root Ni concentration in both urea and ammonium nitrate-fed plants increased significantly with the increase in Ni concentration. Growth and chlorophyll content in leaves of the urea-fed plants increased when Ni concentration in the solution was as high as 0.05 mg L−1 and decreased at 0.1 mg Ni L−1. In ammonium nitrate-fed plants, these parameters increased up to 0.01 mg Ni L−1 and started to decrease with further increase in Ni concentration. Plants that grew in nutrient solutions containing urea had more shoots and r...

The stress of soil compaction, because of using agricultural machinery, may provide conditions such as limiting nutrient uptake, not suitable for plant growth. Here we hypothesized that using arbuscular mycorrhiza (AM, plant symbiotic fungi), as a biological method, may overcome the stress of soil compaction on wheat (Triticum aestivum L.) growth by enhancing nutrient uptake. Soil surface layer of the Experimental Research Field of Soil and Water Research Institute in Karaj, Iran, was sieved, sterilized, and compacted at 10 kg pots in two experiments. At seeding wheat seeds were inoculated with different species of Glomus fungi with different origins. Shoot nutrient uptake of N, P, K, Fe, Mn, Zn, Cu was determined. Soil sterilization significantly increased the nutrient uptake of mycorrhizal wheat even at the highest level of compaction. Even under compacted conditions, increased P uptake, due to AM inoculation had an important role to alleviate the stress. This novel finding may indicate the important role of AM to overcome the stress of soil compaction on wheat nutrient uptake, the independency of AM origin on their functionality, and the great importance of managing soil biological communities in agricultural systems.

Soil compaction is of great importance, due to its adverse effects on plant growth and the environment. Mechanical methods to control soil compaction may not be economically and environmentally friendly. Hence, we designed experiments to test the hypothesis that use of plant symbiotic fungi, arbuscular mycorrhiza (AM) may alleviate the stressful effects of soil compaction on corn ( Zea mays L.) growth through enhancing nutrient uptake. AM continuously interact with other soil microorganisms and its original diversity may also be important in determining the ability of the fungi to cope with the stresses. Hence, the objectives were: (1) to determine the effects of soil compaction on corn nutrient uptake in unsterilized (S1) and sterilized (S2) soils, and (2) to determine if inoculation of corn with different species of AM with different origins can enhance corn nutrient uptake in a compacted soil. Using 2 kg weights, soils (from the field topsoil) of 10 kg pots were compacted at three and four levels (C1, C2, C3 and C4) (C1 = non-compacted control) in the first and second experiment, respectively. Corn (cv. 704) seeds were planted in each pot and were inoculated with different AM treatments including control (M1), Iranian Glomus mosseae (M2), Iranian G. etunicatum (M3), and Canadian G. mosseae , received from GINCO (Glomales In Vitro Collection), Canada (M4). Corn leaf nutrient uptake of N, P, K, Fe, Mn, Zn and Cu were determined. Higher levels of compaction reduced corn nutrient uptake, however different species of AM and soil sterilization significantly increased it. The highest increase in nutrient uptake was related to P (60%) and Fe (58%) due to treatment M4S2C3. Although it seems that M3 and M4 may be the most effective species on corn nutrient uptake in a compacted soil, M2 increased nutrient uptake under conditions (C3 and C4 in unsterilized soil) where the other species did not. Through increasing nutrient uptake AM can alleviate the stressful effects of soil compaction on corn growth.

Availability of applied potassium (K) as a fertilizer to plants is influenced by soil mineralogy, environmental factors, and rates of K application. The objective of this research was to study the effects of clay minerals and K application on K supply characteristics of calcareous soils in Iran. Surface and subsurface horizons of six sites with different ranges of clay content and exchangeable K were selected. The soils were treated with potassium chloride (KCl) solution with different K concentrations. Four wet-dry cycles were sequentially applied. Illites, vermiculites, and chlorites were present in all soils. Smectites were present in larger amounts in one soil. The increase in soluble and exchangeable K was expressed by linear equations in which the slops influenced by the dominant clay minerals. Potassium fixation was much higher in soils with more illites and vermiculites. Results revealed that different forms of K were affected by the dominant clay minerals but were independent from the rate of applied K.

A 90-day study conducted to explore the potential of epigeic earthworms Eisenia foetida and Eisenia andrei to transform the different types of agricultural wastes and spent mushroom compost into value-added product, i.e., vermicompost. Vermicomposting resulted in significant reduction in C:N ratio, pH, electrical conductivity, total organic carbon, TK; and increase in total Kajeldahl nitrogen, TP, and various micro and macronutrients compared to those in the worm feed. Our trials demonstrated that the vermicomposting could be considered as an alternate technology for recycling and environmentally safe disposal/management of the mushroom cultivation complexes’ residues mixed with different types of agricultural waste using epigeic earthworms E. foetida and E. andrei.

Since large areas of agricultural fields in the world become compacted every year, much effort has been made to reduce the adverse effects of soil compaction on plant growth. Mechanical methods to control soil compaction may be laborious and expensive; however, biological methods such as using arbuscular mycorrhiza (AM) may be more useful, economically and environmentally. The objectives of this study were: (1) to evaluate the effects of soil compaction on wheat (Triticum aestivum L.) growth, and (2) to evaluate if using AM of different origin can reduce the stressful effects of soil compaction on wheat growth. Unsterilized and sterilized soils, different levels of compaction and three species of arbuscular mycorrhiza were applied in four replicates. The experiments were conducted in the Soil and Water Research Institute, Karaj, Iran. Soil physical and chemical properties were determined. The AM increased wheat growth in both soils at different levels of soil compaction in both experiments. For root, shoot (P=0.1) and grain (P=0.05) dry weights increases were significant. AM enhanced root growth more than shoot growth under compaction (AM resulted in significant increase in root/shoot ratios, P=0.1). Due to its unique characteristics, AM may reduce the stressful effects of soil compaction on wheat growth, though its effectiveness may decrease with increasing compaction.

The paper compares semi-automated interpolation methods to produce soil-class maps from profile observations and by using multiple auxiliary predictors such as terrain parameters, remote sensing indices and similar. The Soil Profile Database of Iran, consisting of 4250 profiles, was used to test different soil-class interpolators. The target variables were soil texture classes and World Reference Base soil groups. The predictors were 6 terrain parameters, 11 MODIS EVI images and 17 physiographic regions (polygon map) of Iran. Four techniques were considered: (a) supervised classification using maximum likelihoods; (b) multinominal logistic regression; (c) regression-kriging on memberships; and (d) classification of taxonomic distances. The predictive capabilities were assessed using a control subset of 30% profiles and the kappa statistics as criterion. Supervised classification and multinominal logistic regression can lead to poor results if soil-classes overlap in the feature space, or if the correlation between the soil-classes and predictors is low. The two other methods have better predictive capabilities, although both are computationally more demanding. For both mapping of texture classes and soil types, the best prediction was achieved using regression-kriging of indicators/memberships (κ = 45%, κ = 54%). In all cases kappa was smaller than 60%, which can be explained by the preferential sampling plan, the poor definition of soil-classes and the high variability of soils. Steps to improve interpolation of soil-class data, by taking into account the fuzziness of classes directly on the field are further discussed.

Soil compaction is of great importance in agriculture, because its high levels may adversely affect plant growth and the environment. Since mechanical methods are not very efficient and economical, using biological methods to alleviate the stress of soil compaction on plant growth may be beneficial. The objectives of this study were to: (1) evaluate the effects of soil compaction on corn (Zea mays L.) growth, and (2) test the hypothesis that applying arbuscular mycorrhiza (AM) with different origins can partially or completely overcome the stressful effects of soil compaction on corn growth under unsterilized and sterilized conditions. Corn was planted in unsterilized and sterilized compacted soils, while treated with three species of AM including, Iranian Glomus mosseae, Iranian Glomus etunicatum, and Canadian Glomus mosseae, received from GINCO (Glomales in vitro Collection), Canada. Plant growth variables and soil resistance parameters were determined. AM significantly increased root fresh (maximum of 94% increase) and dry (maximum of 100% increase) weights in the compacted soil. AM with different origins may improve corn growth in compacted soils, though its effectiveness is related to the level of compaction and also to the interaction with other soil microorganisms.

Signal molecules are among the major factors required for the legume–bacteria symbiosis. The excretion of signal molecules by plants stimulates the bacterial Nod genes resulting in the production of lipochitooligosacharides (LCOs). LCOs cause root hair deformation (RHD) and induction of nodule cells division, leading to the formation of nodules. The chemical structure of LCOs determines their biochemical activities; for example, removal of the sulfate group can significantly reduce the morphogenic activities of LCOs. Stressful conditions interrupt the excretion of signal molecules by the legumes' roots and consequently the inhibition of LCO production by the bacteria. This research has studied the effect of different concentrations of LCOs on RHD of two soybean [Glycine max (L.) Merr] cultivars, AC Bravour and Maple Glen, under acidity stress. In the first experiment, two different concentrations of LCO (10−7 and 10−6M) and in the second experiment, three different concentrations of LCO (10−7, 10...

Iran's groundwater resources have been over-exploited, often at the expense of deteriorating water and land quality, and there is limited room for expanding its irrigation agriculture. Thus, the possible use of Caspian Sea water, whose salinity is well below that of open seas, for supplementary irrigation has some appeal. The impact of irrigation with diluted Caspian Sea water on the growth and yield of barley and on the characteristics of soil was investigated in field plots and in pot experiments during the 2001–2002 growing season. Three irrigation regimes of well water alone (I0); Caspian Sea water diluted with well water and used at stem elongation (I1); and the same diluted sea water used at ear formation (I2). A rainfed treatment (Ir) was also added to the field experiments. The results of both pot and field experiments show that a 1:1 mixture of Caspian Sea and well water can be used for irrigation without a significant reduction in the growth and yield of barley, provided that it is not applied earlier than the time of ear formation. This would amount to a significantly reduced demand on the limited ground water resources of the region for agricultural use. However, when this mixture was applied at the earlier time of stem elongation, significant yield reduction occurred. All other growth components of barley plants were also adversely affected by this early application of diluted sea water. Soil analysis after harvest showed that the electrical conductivity of the saturation extract had increased significantly in both diluted sea water treatments. This may suggest that the mixing of sea and ground waters at the rates used in these experiments may not be sustainable over a long period of time and soil salinization may occur unless soils are of light texture and sufficient good quality fresh water or winter rain is available to lower the salinity of soil between successive crops. No significant interaction between irrigation salinity and fertiliser treatments was observed.

This research was carried out during the 2000–2001 growing season in a low-density orchard, on a calcareous soil (Fine loamy, mixed, mesic Typic Calcixerept) in northwest Iran, using 25-year old “Golden Delicious” (Malus domestica Borkh.) apple trees on M.9 rootstock. The interactive effects of potassium (K) and calcium (Ca) on K/Ca ratio and its consequences on apple fruit quality were studied. Treatments included: T 1 = control [nitrogen (N), phosphorus (P), and manure]; T 2 = T 1 + micronutrients (deep placement) based on soil test recommendations; T 3 = T 2 + (KCl)1 based on soil test recommendations; T 4 = T 3 + spray of CaCl2 at four times; T 5 = same as T 4 but sprayed at eight times; T 6 = T 2 + (KCl)2 (50% above soil test); T 7 = T 6 + spray of CaCl2 at four times; T 8 = same as T 7 but sprayed at eight times; T 9 = same as T 8 but with an equal amount of K from K2SO4 source. Leaf samples were collected in early July and fruit samples collected in early October and were analyzed for N, K...

Plant growth promoting rhizobacteria (PGPR) may enhance iron (Fe) availability by producing some organic products including siderophores. Accordingly, the potential of fluorescent pseudomonades (selected from among 201 isolated strains) to produce auxin (IAA) and siderophore (Sid) and their effects on 59Fe uptake by two different wheat genotypes (Tabasi and Yavarous) were determined. High siderophore producing super-strains of Pseudomonas putida, P. fluorescens, and P. aeruginosa were isolated from wheat rhizosphere and their potential for siderophore production was evaluated by the chrome azurol-S assay (CAS blue agar). P. putida, the most efficient strain, produced a siderophore complex with 76 % efficiency compared with the standard siderophore, siderophore desferrioxamine B (DFOB). Bacterial siderophores significantly and differently affected the uptake of labeled 59Fe by wheat genotypes (Tabasi the more efficient cultivar) indicating that there may be differences in the chemical structure of the siderophores. Siderophore effectiveness on Fe availability was in the following order: Sid-DFOB> Sid-putida> Sid-fluorescens> Sid-areuginosa.

The diagnosis and recommendation integrated system (DRIS) is a potential method for interpreting plant foliar nutrient composition. The objective of our study was to compare DRIS with the nutrient sufficiency range (NSR) for corn (Zea mays L.). We used published standard DRIS norms and Colorado DRIS norms calculated from ear leaf composition at tasseling to silking of corn yielding 11 Mg grain ha -1 or higher. Our NSR values are based on the minimum and maximum nutrient concentration values found in the literature. We changed the minimum value of 21 g kg -1 for N to 26 g kg -1 . For identifying nutrient needs of corn, the NSR was superior to DRIS regardless of the DRIS norms used. Identified flaws of DRIS are: (i) very high levels of one nutrient can cause false relative deficiency (imbalance) diagnosis of other nutrients, and (ii) an optimal ratio between two nutrients produces maximum yields only when both nutrients are in their respective sufficiency ranges. We recommend use of the NSR technique in combination with a soil test to avoid the misdiagnosis of Zn and Cu deficiencies in corn when N is extremely deficient

Herbicides are an important source of contamination in paddy fields. Monitoring their fate and chemical interactions is therefore imperative for sustaining the environment and human health. To meet this purpose, field experiments were conducted to investigate kinetics of thiobencarb and oxadiargyl dissipation in soil and water of two paddy fields. Their adsorption and desorption isotherms were also determined in the soil samples. Variation in concentration was monitored for 60 d in soil solution phase and for 315 d in soil solid phase. In soil solution, concentrations of both herbicides were rapidly reduced within 5 d and reached steady state within 20–30 d. Analysis of experimental data resolved a half-life ≈2–4 d for both herbicides. In soil solid phase, adsorption reaction played a dominant role in the first 10 d. Afterwards, degradation reactions regulated the process. Variation in concentration was minimized after about 150 d for thiobencarb and 80 d for oxadiargyl. The half-lives were calculated ≈50 d for thiobencarb and ≈20 d for oxadiargyl, indicating that association with soil particles protect them effectively against degradation reactions. Adsorption isotherms confirmed that both herbicides were strongly adsorbed on soil particles. Furthermore, desorption data indicated that after four successive desorption steps, less than 9% thiobencarb and 1% oxadiargyl were released. This denotes that electrolyte ions in solution cannot adequately compete with and replace adsorbed thiobencarb and oxadiargyl molecules. This would lead to a considerable hysteresis between adsorption and desorption isotherms as was observed experimentally. Overall, it was concluded that both herbicides are among non-persistent and immobile herbicides in the paddy soils.

Boron (B) is an essential element for plants and animals growth that interacts with mineral surfaces regulating its bioavailability and mobility in soils, sediments, and natural ecosystems. The interaction with mineral surfaces is quite important because of a narrow range between boron deficiency and toxicity limits. In this study, the interaction of boric acid with goethite (a-FeOOH) was measured in NaNO3 background solution as a function of pH, ionic strength, goethite and boron concentration representing as adsorption edges and isotherms. Boron adsorption edges showed a bell-shaped pattern with maximum adsorption around pH 8.50, whereas adsorption isotherms were rather linear. The adsorption data were successfully described with the CD-MUSIC model in combination with the Extended Stern (ES) model. The charge distribution (CD) of inner-sphere boron surface complexes was calculated from the geometry optimized with molecular orbital calculations applying density functional theory (MO/DFT). The CD modeling suggested dominant binding of boric acid as a trigonal inner-sphere complex with minor contributions of a tetrahedral inner-sphere complex (at high pH) and a trigonal outer-sphere complex (at low pH). The interpretation with the CD model is consistent with the spectroscopic observations. © 2010 Elsevier Ltd.

The effects of continuous rice cultivation on chemical properties and fertility status of selected paddy soils in four physiographic units, i.e. low land, river alluvial plain, flood plain, and piedmont plain in northern Iran, were studied. These soils have been under continuous rice cultivation at least for the past 30 years. In each physiographic unit, a soil profile and two adjacent auger holes both from paddy and non paddy fields were sampled for analyses. The paddy and non‐paddy fields were located within similar mapping units and a few meters apart. This study indicated that in spite of the high annual rainfall, particularly in Gilan province pH of dried samples taken after rice harvest were higher than 7.0 in most of the soils, and no significant differences were usually observed between paddy and non‐paddy soils. However, pH values of the saturated soil surtace measured during the middle stage of rice growth shifted toward neutrality. Eh of the surface horizons of the paddy soils measured...

The Diagnosis and Recommendation Integrated System (DRIS) has been successfully applied to many different annual and perennial crops. This system represents an approach to the nutrient contents of crops and is in fact an integrated set of norms. The successful applicability of DRIS to crops as a foliar diagnostic tool has demonstrated a need for the development of DRIS norm for corn in calcareous soils of Iran. Preliminary DRIS norm for corn (Zea mays L.) was developed from more than 50 sets of data on both plant and soil composition of high‐yielding population farms for the years of 1988 and 1989. Soil and leaf samples of com plants were taken at the silking stage. Soil and plant samples were analyzed by conventional methods. Letzch and Sumner's (1983) norms was taken as independent indices for DRIS data. Based on the almost average amount of nutrients in the leaf samples of high‐yielding populations, preliminary DRIS norms have been suggested as follows: N = 2.50; P = 0.25; K = 2.20; Ca = 0.50,...

Diagnosis and Recommended Integrated System (DRIS) norms and indices for N, P, K, Ca and Mg were developed for apple trees in Canterbury, New Zealand, based on surveys of nutrient levels of apple leaves in field experiments before and after N and K fertiliser applications and in four orchard surveys over a period of three years. Comparisons were made between calculated norms based on mean sufficiency nutrient levels and published norms. Results obtained showed that calculated norms and indices from sufficiency range provide a good indication of the order of apple nutrient requirements. High N and low Ca were identified as major nutrient problems. The best period for sampling leaves for nutrient analysis is at 3 to 5 months after blossom (i.e., December to January in New Zealand).

In order to study the effects of micronutrients on wheat production in calcareous soils, 25 field experiments with wheat were conducted in the Dorodzan region, about 50 km west of Shiraz in south of Iran in 1998–99. Five fertiliser treatments including control (nitrogen, phosphorous and potassium based on soil tests), control + Fe, control + Mn, control + Zn and control + Cu were tested in a completely randomized block design with three replications. The soils of the selected fields contained high amounts of calcium carbonate equivalent (31–40%). The results showed that Fe, Mn, Zn and Cu fertilisation caused significant increase in grain yield, straw yield, 1000 grain weight, and the number of seeds per spiklet. With the application of these nutrients, their concentration and total uptake in grain and flag leaves and the grain protein content increased significantly. Based on the DTPA method, the critical soil levels were found to be 4.3 mg kg−1 for Fe and Mn and 0.9 mg kg−1 for Zn and Cu.

Nanoparticles (NPs) have emerged as one of the most innovative and promising application in agriculture. Since plants are recognized as essential component of all ecosystems, the effects of NPs on plants may pave a new insight to the ecosystems. Here, uptake and translocation of superparamagnetic iron oxide NPs (SPIONs), with various surface charges, on soybean has been probed; in addition, the effects of SPIONs on variations of chlorophyll, in hydroponic condition, together with their ability for reduction of iron deficiency chlorosis were explored. We find that SPIONs, which were entered and translocated in the soybean, increased chlorophyll levels, with no trace of toxicity. Furthermore, it was found that physicochemical characteristics of the SPIONs had a crucial role on the enhancement of chlorophyll content in subapical leaves of soybean. The equivalent ratio of chlorophyll a to b, in all treatments with conventional growth medium iron chelate and SPIONs (as iron source), indicated no significant difference on the photosynthesis efficiency. Finally, it was observed that the effect of SPIONs on the soybean chlorophyll content may have influence on both biochemical and enzymatic efficiency in different stages of the photosynthesis reactions. © 2013 American Chemical Society.

This study was conducted to evaluate the effects of organic acids on the concentrations of metals and anions in soil solution. Three soils with contrasting CaCO3 contents were extracted with organic acid solutions (citrate and oxalate) of different concentrations for different time periods and analysed for Fe, Mn, Zn, Cu, P, and Ca. The soils showed a significant change after the addition of the organic acids to the soil. The mobilisation of metals from the solid phase was dependent on concentration and ionic form of organic acid. High concentrations of citric acid were more effective than oxalate in mobilising Ca, Fe, Mn, and Zn. Overall; oxalate was slightly more effective than citrate in mobilising P. Generally, the higher the organic acid concentration of the extractant solution, the greater was the amount of elements extracted from the soil. Citrate tended to be more effective than oxalate at mobilising elements from the soil. All pH changes were dependent on organic acid concentration.

Different concentrations of urea and ammonium sulfate were sprayed to 15-year-old `Golden Delicious' and `Redspur Delicious' “on” selected apples trees, after 8, 9, and 10 weeks of full bloom. Leaf samples were taken 1 week before and after sprays for protein analysis with Near Infrared Reflectance (NIR). Percentage of flowering and fruit lenght-to-diamater ratio (L/D) were measured in both cultivars. Number of fruit only in `Redspur Delicious' during “on” and “off” years were recorded. Spray of nitrogen and sulfur chemicals increased the leaf protein contents up to a certain extent. Leaf protein content was not significantly affected by spray concentration, time of application, or cultivars. Foliar application of these chemicals at different periods reduced flower density, but did not have a significant effect on fruit L/D ratio. Foliar sprays increased the number of fruits in `Redspur Delicious' in the “on” year, but did not affect different treatments during the “off” year. The sprays after 8, 9, and 10 weeks of full bloom intensified alternate bearing in the following “off” year.

Two experiments were conducted to investigate effects of application rate and timing of calcium chloride (CaCl2) on fruit quality and control of physiological disorders in ‘Red Delicious’ apple (Malus spp.) grown at five locations in Iran. In first year, the experiment was conducted with three application rates (0, 1%, and 2% CaCl2, w/v) at two application times for each rate. In second year, four rates of CaCl2 (0, 0.5%, 1%, and 1.5%, w/v) were applied, and each rate was applied four times. Fruits were kept in regular atmosphere storage at 2°C for 4.5 months. All CaCl2 treatments, except 0.5% treatment in second year, enhanced fruit firmness at harvest and after storage and resulted in fewer physiological fruit disorders because of higher fruit Ca. Other fruit quality traits and mineral nutrients were not affected by CaCl2 applications. Calcium chloride at 1 % application was optimum for improving fruit quality.