Soil science
N. Khalili; R. Ghorbani Nasrabadi; M. Barani Motlagh; R. Khodadadi
Abstract
Introduction Actinobacteria are one of the most abundant microbial groups in soil and play a crucial role in preserving ecosystems. They are among the soil microbial groups capable of releasing phosphorus from low-soluble or insoluble phosphorus sources, which enhances plant growth. Their application ...
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Introduction Actinobacteria are one of the most abundant microbial groups in soil and play a crucial role in preserving ecosystems. They are among the soil microbial groups capable of releasing phosphorus from low-soluble or insoluble phosphorus sources, which enhances plant growth. Their application in agricultural systems is recognized as an environmentally friendly strategy to limit the negative effects of chemical inputs and improve the availability of nutrients, especially phosphorus, in the rhizosphere. Additionally, humic acid, as an organic growth stimulant, plays an important role in improving soil fertility and biological communities, and its combined use with actinobacteria increases the efficiency of fertilizer use, particularly phosphorus-based fertilizers. Therefore, the aim of this research was: (i) to screen the phosphorus solubilization potential of actinobacteria isolates at different incubation times, (ii) to investigate the effect of adding humic acid on the phosphorus solubilization capacity actinobacteria isolates under laboratory conditions, and (iii) to monitor the impact of selected actinobacteriun isolate and humic acid, at various phosphorus fertilizer levels, on soil phosphorus content, plant phosphorus uptake, and some biochemical properties of the soil. Materials and MethodsIn this study, five actinobacteria isolates, collected and purified from various agricultural, orchard, and rangeland ecosystems of Golestan Province, were screened based on their morphological characteristics. These strains were utilized for screening purposes. To prepare fresh cultures of the actinobacteria isolates, they were subcultured on solid yeast extract-malt extract agar medium. The effects of incubation time and the application of humic acid on the phosphate solubilization ability of the actinobacteria isolates were then investigated. This experiment was conducted in a factorial arrangement within a completely randomized design, with the following factors. To examine the effect of the selected superior actinobacterium isolate and its interaction with different phosphorus levels and humic acid application, a factorial pot experiment was conducted in a completely randomized design. The experimental factors included a mineral phosphorus source at three levels (control, 20 kg, and 40 kg of phosphorus per hectare from monoammonium phosphate), Streptomyces inoculation at two levels (control and inoculation with the selected isolate), and humic acid application at two levels (control and 2 mg per kg). The experiment was carried out on maize (Single Cross 704) with three replications. For seed preparation, a sufficient number of healthy maize seeds were selected and surface sterilized by immersing them in alcohol for 30 seconds. They were then exposed to 5% sodium hypochlorite for 2 to 3 minutes, followed by rinsing eight times with sterile distilled water. To prepare the microbial inoculum, the selected superior isolate was grown in yeast extract-malt extract medium at an appropriate (107 CFU/mL). The seeds were then placed in pots, and one milliliter of the Streptomyces suspension was applied to the seeds for inoculation. At the end of the experiment, the phosphorus content in the soil and plant, as well as the soil biochemical responses were measured. ResultsBased on the results obtained from this study, the application of humic acid led to an increase in microbial biomass and enhanced phosphorus release by actinobacteria isolates under laboratory conditions. As the incubation period extended from 7 to 14 days, the solubility of phosphate showed an increasing trend. The results showed that the highest phosphorus content in the soil was associated with the combined application of a high phosphorus level (40 mg per kg) along with humic acid and Streptomyces inoculation. Analysis of microbial biomass phosphorus revealed that the highest level was related to the treatment combining the highest level of phosphorus fertilizer and humic acid. According to the findings related to phosphatase enzymes, the combined application of the Streptomyces treatment, humic acid, and phosphorus resulted in an increase in the levels of these enzymes. Additionally, the results of microbial respiration in the soil indicated that the combined treatment of Streptomyces and the highest level of phosphorus fertilizer enhanced microbial respiration in the soil. The phosphorus content in the plants under the combined treatments of Streptomyces, humic acid, and phosphorus showed that the integration of Streptomyces inoculation and humic acid was effective in improving soil phosphorus availability and led to an increase in the phosphorus content of the plants. The results of this study showed that inoculation with the selected Streptomyces isolate, along with the combined application of humic acid, enhanced the efficiency of phosphorus fertilizer utilization, making it more readily available to the plant. Conclusion In general, the results of current study revealed that the simultaneous application of humic acid and Streptomyces inoculation led to an increase in the availability of phosphorus in the soil and the phosphorus content in the plants, as well as an improvement in the biochemical responses of the soil. However, field experiments are necessary to confirm its effectiveness.
Soil science
E. Mirparizi; M. Barani Motlagh; S.A. Movahedi Naeini; R. Ghorbani Nasrabadi; S. Bakhtiary
Abstract
Introduction: Iron deficiency is one of the most common nutritional problems of plants in arid and semi-arid soils especially in calcareous soils. Iron is essential to many cellular activities, required for optimum growth and development, however it is insoluble in aerated soils at neutral or basic pH, ...
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Introduction: Iron deficiency is one of the most common nutritional problems of plants in arid and semi-arid soils especially in calcareous soils. Iron is essential to many cellular activities, required for optimum growth and development, however it is insoluble in aerated soils at neutral or basic pH, therefore, iron deficiency is common in these soils. The problem is usually solved by using iron synthetic chelates which is a very expensive option. There is, therefore, a need for cheaper and more effective alternatives to traditional Fe fertilizers. Several reports have shown that application of Fe factory by-product to soil tends to raise the availability of Fe and reduce Fe deficiency in plants. Application of organic compounds to soil may improve the solubility of the minerals containing micronutrients and correct their deficiencies in alkaline and calcareous soils. A large amount of slag is produced annually at the Sarcheshmeh Copper Complex, Kerman Province, Iran. So far, the copper slag, however, has not been tested as an Fe fertilizer in calcareous soils. Since about 53.8% of slag obtained from copper concentrate melting is composed of iron oxides, we, thus, examined the effect of copper slag along with organic compounds on the level of upper leaf iron, photosynthetic pigments, SPAD index, the activity of plant enzymes and the level of active iron in the upper leaves of sorghum by performing a factorial experiment in a completely randomized design.Materials and Methods: In order to study the effect of copper slag (one of by-products of melting copper concentrate in Sarcheshmeh Copper Complex, Kerman Province) and organic compounds (cow manure and pistachio skin) on total leaf iron content, photosynthetic pigments (chlorophyll a, chlorophyll b, total chlorophyll), antioxidant enzymes activity (Guiacol Peroxidase, Glutathione peroxidase) and concentration of active iron of young leaves developed of sorghum, a pot experiment was conducted in the greenhouse with three replicates per treatment. We applied experimental treatments including 5 levels of organic matter (pistachio skin, cow manure at 2 and 4 wt. % and control sample), and 11 levels of iron (copper slag, copper slag with sulfur, copper slag with sulfur and thiobacillus, acidic slag (each 2 levels each), sequesterine, foliar application of EDTA, and control sample) to a soil sample with low iron content. At the end of the incubation period, sorghum bicolor was cultured in the above treatments. Ten seeds were sown in each pot. Seedlings were thinned to 4 when they were about 10 cm high. During the growth period, pots were irrigated with distilled water as needed. Before harvesting, SPAD, the concentration of photosynthetic pigments, level of active iron and activity of plant enzymes were also measured in fresh plant samples. Furthermore, the concentration of Fe in the leaves was measured. Analysis of variance was performed using software SAS and significant differences were determined based on LSD (Least Significant Difference Test) at p < 0.05 level.Results and Discussion: The interaction between slag treatments and organic compounds showed that treatments of 4 wt. % of cow manure with slag of 4 times of recommended soil test value (C4S4, and 4 wt. % of cow manure with slag of 4 times of recommended soil test value with sulfur and thiobacillus (C4S4S°T), had significant effects on increasing photosynthetic pigments pigments (chlorophyll a, chlorophyll b, total chlorophyll), SPAD index, activity of plant enzymes (Guiacol peroxidase, Glutathione peroxidase) and active iron. The highest active iron level in the young leaves developed (54.06 mg / kg) was observed in (C4S4S°T) treatment which showed a significant increase compared to the control treatment (17.14). Increased concentration of active iron was also observed due to application of treatments (slag, organic compounds and the interaction between treatments) in sorghum young leaves. The photosynthetic pigments (chlorophyll a, chlorophyll b, total chlorophyll), SPAD index and activity of plant enzymes (Guiacol peroxidase, Glutathione peroxidase) were more correlated with active iron in young leaves developed compared to total iron concentration in these leaves. This indicates that active iron can be used as an index to detect iron deficiency.Conclusion: The higher level of active iron in the young leaves developed was more associated with physiological indices of sorghum as compared with total Fe concentration in these leaves. Therefore, this parameter can be used as an index to detect iron deficiency. In this study, increasing the level of slag consumed and consequently increasing Fe concentration in the leaf resulted in a significant increase in chlorophyll a, chlorophyll b, total chlorophyll, carotenoids and activation of the plant enzymes.
R. Khodadadi; Reza Ghorbani nasrabadi; M. Olamaee; S.A. Movahedi Naini
Abstract
Introduction: Worldwide studies have shown that inappropriate land uses over the past 45 years have resulted in salinization of 6% of the world's land. Salinity has negative effects on soil physicochemical properties and microbial activities. The imbalance in nutrient uptake, ion toxicity and ...
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Introduction: Worldwide studies have shown that inappropriate land uses over the past 45 years have resulted in salinization of 6% of the world's land. Salinity has negative effects on soil physicochemical properties and microbial activities. The imbalance in nutrient uptake, ion toxicity and decreasing water consumption due to high osmotic pressure are resulted from high accumulation of solutes in soil solution. One of the strategies to mitigate soil salinity is the inoculation of crops with different types of beneficial soil bacteria and fungi. Plant growth promoting bacteria (PGPB) are a diverse group of bacteria capable of promoting growth and yield of many crops. The most important growth promoting mechanisms of bacteria are the ability to produce plant hormones, non-symbiotic nitrogen fixation, solubilization of insoluble phosphate and potassium, biocontrol of plants pathogens through producing hydrogen cyanide and siderophore production. Plant inoculation with growth promoting bacteria causes an increase in several indices such as shoot fresh and dry weight, root dry weight and volume as well as chlorophyll content. The synergetic effect of Azotobacter and Azospirillum on the plant has been documented by increasing the absorption of nutrients, production of hormones that stimulate plant growth such as auxin, and influencing the root morphology. Due to the wide area of saline soils, appropriate methods to reduce the negative effects of salinity are of great significance. Given the importance of using bacteria adapted with climatic conditions and soil ecosystems in each region, as well as the efficiency of the combined application of growth promoting bacteria, this study was conducted to investigate the effect of growth promoting bacteria as a single and combined application at two levels of salinity calculated based on the threshold of barley yield reduction (Karoon cultivar) and 50 % reduction in barley yield.
Materials and Methods: In order to record the Azotobacter isolates, 15 soil samples were collected from salt affected lands of Golestan province. Thirty two Azotobacter isolates were isolated by physiological and biochemical tests and cyst production in old culture. Then, their ability to grow in different concentrations of salinity, drought stress tolerance, polysaccharide production, auxin production, phosphorus and potassium solubilization, hydrogen cyanide synthesis and biological fixation of molecular nitrogen were investigated. Based on physiological and growth stimulation tests, Az13 isolate was selected as the superior isolate of Azotobacter for greenhouse test. Azospirillum superior isolate was then prepared from the microbial bank of Soil Science Department, Gorgan University of Agricultural Sciences and Natural Resources. A soil with 16 dS/m salinity was selected to determine the effects of experimental treatments at two threshold salinity levels of yield reduction and 50 % reduction of barley yield. Then, soil salinity was reduced to 8 dS/m (yield reduction threshold) by leaching. After reaching to the desired salinity, the soil was removed from the pots and air dried. The sample was sifted through a 2 - mm sieve and again transferred to the pots. The barley seeds, Karoon cultivar, were used. To prepare the inoculum, firstly the bacterial isolates were grown in the pre-culture nutrient broth medium, and then incubated at 120 rpm in a shaking incubator at 28°C for 48 hours. Afterwards, each seed was inoculated with one milliliter of the bacterial inoculant with a population of 109 CFU/ml. This experiment was conducted as factorial in a completely randomized design with three replications in the greenhouse at Gorgan University of Agricultural Sciences and Natural Resources. The treatments included four levels of bacteria (without inoculation, Azotobacter inoculation, Azospirillum inoculation, combined inoculation of Azotobacter and Azospirillum) and two levels of salinity (8 and 16 dS/m). After 70 days (late vegetative growth period), some growth and physiological indices and concentration of nutrients uptake were measured.
Results and Discussion: The results showed that salinity stress had a significant (p < 0.01) negative effect on growth and physiological traits and nutrient uptake of the plant. The combined application of Azotobacter and Azospirillum bacteria showed a positive significant influence (p < 0.01) on growth, dry weight, and root dry weight in the plant under salinity stress. The combined application of bacteria increased the chlorophyll a, b and a + b content at a salinity level of 16 dS/m by 136.49, 117.86 and 127.97 %, respectively. The combined application of bacteria resulted in a 65.39 and 55.94 % increase in proline amino acid content at salinity levels of 8 and 16 dS/m, respectively. The results revealed that nitrogen, phosphorus and potassium levels increased by 81.97, 80 and 66.67%, respectively, at 16 dS/m salinity level in combined application of both bacteria. Sodium ion accumulation in all bacterial treatments decreased in both salinity levels compared to control treatment and the highest reduction was observed in combined bacterial inoculation. These findings underline the positive effect of bacterial inoculation, particularly their combined application, on the growth and nutrients uptake of barley under salt stress.
Conclusion: Our results indicate that increasing salinity level significantly decreased shoot dry weight, root dry weight, plant height, chlorophyll content and nutrient concentrations of barley. Inoculation of salt-resistant bacteria, including Azotobacter and Azospirillum, reduced the adverse effects of salinity on growth and physiological traits, which was more pronounced in Azotobacter than Azospirillum. The combined application of Azotobacter and Azospirillum had a significant effect on root dry weight, plant height, chlorophyll content, increasing nutrient concentration efficiency (nitrogen, phosphorus, and potassium) and decreased sodium concentration at both salinity levels (8 and 16 dS/m) compared with the individually inoculated bacteria. Hence, the application of Azotobacter and Azospirillum isolates is an appropriate method for pot experiments with saline soils. To apply these results, field experiments in saline soils must be carried out to evaluate the effect of these bacterial isolates on the crop growth, yield and physiological characteristics.
A. Jahandideh; M. Barani; E. Dordipour; R. Ghorbani Nasrabadi
Abstract
Introduction: One of the most important needs in the farm planning is the evaluation of different systems of plant nutrition. By supplying the correct way of plant nutrition, one can preserve the environment and increase the efficiency of agricultural inputs. Humic acid contains many nutrients that increase ...
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Introduction: One of the most important needs in the farm planning is the evaluation of different systems of plant nutrition. By supplying the correct way of plant nutrition, one can preserve the environment and increase the efficiency of agricultural inputs. Humic acid contains many nutrients that increase soil fertility, soil organic matter content, and access to macro- and micro-nutrients by preventing the formation of insoluble salts and chelating properties. Phosphorus and humic acid stimulate vegetative growth, improve reproductive growth, and increase the quantitative and qualitative yield of plants. In this regard, the positive effects depend on the amount and how they are applied. The present study was conducted with the aim of investigating the effects of different levels of humic acid and phosphorus fertilizer on phosphorus availability and photosynthetic pigments (a, b and carotenoids) in canola (cv. Hyola 50).
Methods and Materials: The soil used in this study was collected from 0-30 cm layer of a soil profile passed through a 2-mm sieve after air-drying. The soil chemical and physical properties were then determined. The pot experiment was conducted as factorial based on completely randomized design with three replications. Treatments include phosphorous fertilizer as super phosphate in three levels (0, 50 and 100 mg/kg) and humic acid in three levels (0. 0.5 and 1 gr/kg soil), phosphorous and humic acid application ways. Humic acid and phosphorous treatments were mixed in various forms including simultaneous mixing of humic acid and phosphorous fertilizer in the soil matrix, application of humic acid and phosphorous via irrigation water and coting of phosphorous fertilizer via solid humic acid before soil application. Then 10 canola seeds were planted in each pot at 2-cm depth which were declined to 4 plants in each pot after emerging and greening phases. At the end of the growth period (158 days), the plants were harvested. Determination of phosphorus concentrations of plant extracts by molybdenum vanadate or yellow method and chlorophyll content (a, b and ab) and carotenoids were measured precisely before harvesting using Barnes method. After harvesting the plants, the soil was immediately air-dried and passed through a 2mm sieve. Then, the amount of phosphorus was determined by sodium-DTPA and sodium bicarbonate. The statistical results of the data were analyzed using SAS software and LSD test (at 5% level) was used for comparing the mean values.
Results and Discussion: The interactions of humic acid and phosphorus and its application methods were significant for all measured traits at the 5% level. The results of the triple effects of humic acid levels and its application at the presence of phosphorus treatments showed that the highest chlorophyll (a, b and ab) and carotenoid content was obtained at 100 mg/kg phosphorus and 1 g/kg humic acid along with irrigation water. The highest concentration of plant shoot phosphorus with an average of 0.30% was observed in 1 g/kg humic acid with irrigation water at the level of 100 mg/kg phosphorus, although had no significant difference with 0.5 g/kg of humic acid with irrigation water. Maximum amount of P was extracted by Olsen method with the mean of 16.14 mg/kg and Soltanpour and Schwab method with the mean of 5.24 mg/kg obtained in 100 mg/kg phosphorus and 1 g/kg soil humic acid application. There was a significant correlation between the phosphorus extracted by Olsen method and Soltanpour and Schwab method (r = 0.95), which was significantly correlated with concentration of phosphorus (r = 0.84) and (r = 0.85) (P<0.05). There was also a significant correlation between fresh and dry above-ground biomass, types of chlorophyll (a, b and ab) and carotenoids with phosphorus extracted by Olsen and Soltanpour and Schwab methods at 5% significance level.
Conclusion: P adsorption capacity is a function of many factors. Application of phosphorous fertilizers in calcareous soils, due to the presence of calcium with high activity, results in the formation of calcium phosphates, which becomes insoluble, over time. Humic material in interaction with phosphorus in the soil can reduce phosphorus stabilization and increase plant available phosphorus. The results of this study showed that the use of phosphorus with humic acid, rather than the use of phosphorus alone, could increase the available phosphorus in the soil and also the phosphorus concentration within the plant.
Taleb Nazari; mojtaba barani; Esmaeil dordipour; Reza Ghorbani nasrabadi; Somayeh Sefidgar shahkolaie
Abstract
Introduction: Fe is the first identified micronutrient for crops and required in higher amount than other micronutrients. Fe plays important roles in enzyme metabolism, protein metabolism, chlorophyll construction, chloroplast evolution, photosynthesis, respiration and reduction-oxidation reaction as ...
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Introduction: Fe is the first identified micronutrient for crops and required in higher amount than other micronutrients. Fe plays important roles in enzyme metabolism, protein metabolism, chlorophyll construction, chloroplast evolution, photosynthesis, respiration and reduction-oxidation reaction as well as organic acids metabolism. Iron, as an essential micronutrient, has great contribution in important antioxidant enzymes activity and through which affects plant tolerance against environmental stresses. Plant enzymes including superoxide dismutase, catalase and glutathione peroxidase are among the most important enzymes scavenging the hydrogen peroxide have iron in their structure, so they affected by iron deficiency. In this study, the effect of soil, foliar and fertigation application of humic acid on iron availability, chlorophyll types and superoxide dismutase, catalase and glutathione peroxidase enzymes in canola (Hyola 308) were evaluated.
Results and Discussion: Results showed that highest total iron content in plant leaves was obtained in 0.4 percent foliar application and the lowest was belonged to control treatment. Highest iron content in plant stem and active iron was obtained in humic acid application through irrigation at 2000 mg L-1 by 85 and 44.86 mg kg-1, respectively, and lowest amounts were obtained in control by 54.62 and 20.40 mg kg-1. Also, greatest concentration of chlorophyll a, chlorophyll b and total chlorophyll were recorded under0.4 percent humic acid foliar application by 3.58, 1.79 and 5.37 and the lowest chlorophyll contents were associated to control. Highest activities for plant enzymes superoxide dismutase and glutathione peroxidase were obtained under0.1 percent foliar application of humic acid by 4.20 and 1.95 (Iu/gr. FW) and the highest activity for catalase enzyme by 4.46 Iu/gr FW in 1000 mg L-1 humic acid through was irrigation and the lowest enzyme activity obtained in control treatment. Findings showed that application of various levels of humic acid increased plant enzyme activity compared to control in all of three application method (soil, foliar and application through irrigation water). Increasing humic acid concentration decreased enzyme activities. Also, there was negative correlation between activity of plant enzymes and concentation of chlorophyll types and active iron.
Conclusions: Active iron and antioxidant enzymes represent iron status within cell cytoplasm. Based on the results of this study, active iron concentration and activity of antioxidant enzymes are appropriate indices for evaluating plant tolerance to iron deficiency compared to assessing total iron content in leaves.
