نشریه مدیریت خاک و تولید پایدار
سال سیزدهم شماره 3 (پیاپی 45، پاییز 1402)

Soil salinity, especially in arid and semi-arid regions, is one of the factors that limit the growth of plants. Excessive accumulation of sodium and chloride ions leads to reduced growth and imbalance of nutrients. The use of exogenous polyamines, including putrescine, spermidine and spermine, is considered as an effective method not only in determining their role in response to salinity, but also as a way to increase plant resistance to salinity. Camelina is an oilseed product of the Brassica family, which contains other bioactive compounds such as flavonoids and phenolic products and as a new source of essential fatty acids, especially omega-3 fatty acids. This study was conducted with the aim of evaluating the effect of different levels of sodium chloride and foliar spraying of spermine, spermidine and putrescine on seed yield and the concentration of leaf and root nutrients in Camelina plant. The experiment was carried out in March 2022 as factorial design based on a completely random design (CRD) in the form of pot culture with 12 treatments and 3 replications. The salinity stress treatment was with Urmia lake water at three levels (0, 15, 30 ds/m). Foliar treatment at 4 levels 1- Foliar spraying with spermine (2 mM), 2- Foliar spraying with spermidine (2 mM), 3- Foliar spraying with putrescine (2 mM) and control (no foliar spraying). The application time of foliar spraying was done every 3 days (totally in 6 stages) after establishing three seedlings in the pot and reaching the four-leaf stage. At the end of the Camelina plant growth season, to calculate the seed yield, the seeds in the capsules of three plants in each pot were separated and weighed. Statistical analysis of data was done using SAS software (version 9.1) and MATATC, and comparison of means was also done by Tukey's test at the five percent level. Excel program was also used to draw graphs. The results of this research showed that the salt stress was 30 and 15 ds/m compared to the treatment without salt decreased leaf potassium (52 and 17%), root potassium (44 and 37%), leaf magnesium (50 and 28%), root magnesium (56 and 24%), leaf zinc (58 and 47%), root zinc (39 and 29%), leaf iron (10 and 2%), root iron (57 and 23%) and seed yield (52 and 10%), but it increased the amount of leaf sodium (89 and 82%), root sodium (39 and 11%), leaf calcium (14 and 6%) and root calcium (76 and 28%), respectively. Also, salinity stress caused a decrease in the ratio of potassium to sodium absorption, but increased the ratio of calcium to the sum of sodium and potassium in the roots and leaves due to the increase in the amount of sodium and the decrease in potassium. At all salinity levels, foliar spraying with polyamines increased leaf and root potassium, leaf and root magnesium, leaf and root zinc, leaf and root iron, by reducing the amount of sodium in leaves and roots. Also, foliar spraying with spermine, spermidine and putrescine compared to no foliar spraying, increased the seed yield by 32, 8 and 21%, respectively. The results of this research showed that foliar spraying with spermine, spermidine and putrescine by improving the absorption of macro and micro elements in roots and leaves, increasing the ratio of potassium to sodium and the ratio of calcium to total sodium and potassium in roots and leaves could moderate the effects of salinity stress and improve the seed yield of camellia under salinity stress conditions and it prevented excessive reduction in seed yield.

More than 60% of the country's soils have less than 1% organic matter. Due to the calcareous nature of most soils, nutrients are insoluble and therefor not absorbed by the plants. One of the effective solutions in this situation is the use of humic acid, because it is the active part of the organic resources and has a higher utilization efficiency than other organic fertilizers. This compound is extracted from various natural sources such as soil, compost, Leonardite (oxidized lignite), sediments, peat and different types of coal. In the present study, humic acid was first extracted from five organic sources (cow manure compost, urban waste compost, vermicompost, sheep manure and poultry manure). Then, added at 5 concentration levels (0, 0.25, 0.5 and 1 g of humic acid per kg of soil) to a calcareous soil under incubation condition (temperature of 25°C and field capacity moisture). After 70 days, forms of nitrogen, available phosphorus and potassium were determined. The highest and lowest amounts of nitrogen, phosphorus and potassium were observed in poultry manure and vermicompost, respectively. The effect of different types and concentrations of extracted humic acid on soil nitrate, ammonium, available phosphorus and potassium was significant at the probability level of 1% (P < 0.01). The highest value of nitrate was found at the level of 1 g kg-1 of humic acid of poultry manure (234.53 mg kg-1) which was about 10 times more than the control (23.97 mg kg-1). The highest value of ammonium at the level of 1 humic acid extracted from poultry manure (144.48 mg kg-1) was approximately 5 times more than the control (30.92 mg kg-1). The maximum value of available phosphorus in humic acid 1 g kg-1 of poultry manure (25.40 mg kg-1) was about 1.8 times more than the control (13.91 mg kg-1) and the highest value of available potassium at the level of 0.5 humic acid of sheep manure (472.47 mg kg-1) was approximately 1.2 times more than the control (394.69 mg kg-1). In general, results showed that with increasing the concentration levels of humic acids, the available forms of nutrients increased in the soil. The greatest effect on the availability of nutrients in the soil was observed in humic acid extracted from poultry manure at the level of 1 g kg-1 soil. In order to better analyzing and understanding the real effect of humic acid, it is better to measure the contents of nitrogen, phosphorus and potassium and other characteristics of humic acids in future studies.

Landfills are one of the sources of heavy metal pollution worldwide. The increasing expansion of urban life and the excessive increase of the urban population have caused an increase in the production of all kinds of waste materials. One of the problems of rapid population growth and industrialization in third world countries, especially Iran, is the improper disposal of waste and and pollution caused by it. One of the issues that should be paid special attention to is the burial of these wastes and urban solid wastes, water and gases produced from the decomposition of wastes containing organic compounds. The purpose of this study was to investigate the impact of Gorgan urban waste disposal landfill with a burial history of more than 37 years, in the Hazara Pitch area, on the spatial distribution of heavy metals including nickel, cadmium, lead and copper in the soil of the area. The amount of pollution was investigated using the environmental indicators of spatial distribution of heavy metals, pollution factor, Geo-accumulation and Pollution Load. By conducting preliminary studies and taking into account the existing basic maps, 110 samples were prepared from zero to 30 cm depth with regular intervals and finally, the amounts of heavy metals were measured using an atomic absorption spectrophotometer. The obtained results showed that the concentration of heavy metals in the collected samples was the highest in zinc, lead, copper and cadmium, respectively. The average concentration of heavy metals cadmium, lead, copper and zinc respectively increased by 2.25%, 1.01%, 0.99% and 0.63% compared to the background, which indicates the presence of a source of point pollution in the study area.Spatial distribution according to the extracted maps showed that the high level of concentration of heavy metals in the central and northwestern parts of the studied area was indicated by the location of the landfill. The humid climate and the presence of topography in the area have caused the release of waste leachate by runoff, but with increasing distance from the landfill site, the downward trend of the concentration of pollutants is evident. The pollution factor in the target area indicated moderate contamination for lead, copper and zinc heavy metals and Severe contamination for cadmium metal. The results related to the Geo-accumulation index also showed that the average value of this index in cadmium is in the " slightly contaminated " Contamination class and in copper, zinc and lead it is in the " Uncontaminated to slightly contaminated " Contamination class. Also, according to the average value of the pollution load index, the surface soil has a Moderate contamination load, and the results of the pollution load confirm the contamination of the soil with heavy metals.The highest concentration of heavy metals can be seen in the vicinity of the landfill, and there was a decreasing trend as the distance increased based on the available slope and topography. It seems that the source of heavy metal pollution was the landfill, and the main factor of spreading the resulting leachate was spreading the pollution to the surrounding areas based on the topography of the area and in the direction of the slope.

Soil erosion threatens sustainable agriculture by reducing soil organic carbon, soil degradation, and reducing soil fertility. Organic amendments, with their effect on the physical, chemical, and biological properties of the soil, are a good way to protect the soil, improve soil properties and reduce the use of chemical fertilizers. The aim of this study was to investigate the effect of organic amendments on the physical, chemical, and biological properties of soil on agricultural land.

In this regard, plots with dimensions of 1×2 m2 were established in a completely randomized design with 3 repetitions in 3 agricultural lands. Organic modifiers (control (without a modifier), sheep manure, and municipal waste compost) were added to the plots in the amount of 1.5 kg for each plot. The plots were in wheat-fallow-barley crop rotation. The modifiers were added on the first of June, and soil sampling was done from the plots 3 months after adding the modifiers. During these 3 months, once every 15 days, the plots containing the modifier were moistened (60% of Field Capacity) for the better effect of the added modifier. The experimental was a Randomized Complete Block Design (RCBD). Physical, chemical and biological characteristics of soil including bulk density, electrical conductivity, pH, soil organic carbon, available phosphorus and potassium, microbial biomass carbon, basal respiration and substrate-induced respiration (SIR), microbial metabolic quotient (qCO2) and enzyme activity such as urease, invertase and alkaline phosphatase were measured after experimental treatments.

The results showed that the application of amendments reduced the bulk density and increased soil organic carbon, soil pH, EC, phosphorus, and potassium. The addition of amendments increased carbon microbial biomass and basal respiration and decreased metabolic quotient. The addition of sheep manure and municipal waste compost amendments increased the activity of invertase and alkaline phosphatase enzymes compared to the control.

The use of organic amendments in agricultural soils can increase the productivity of these lands and increase the yield of agricultural products due to the improvement of soil characteristics and the increase of organic matter and microbial biomass. The results of the comparison of the two organic amendments indicate the greater effect of sheep manure than urban waste compost in improving soil characteristics. Other tests should be conducted on the effect of long-term use of this modifier in the soil, as well as the effect of urban waste compost on the concentration of heavy metals or other pollutants so that one of the modifiers can be accurately suggested for wide use in agricultural soils.

Airborne particles, commonly known as aerosols, can carry polluting and harmful particles and elements. Street dust refers to particles smaller than 70 micrometers that enter urban environments due to the resuspension of particles from human activities or dust storms. These particles host various pollutants, including heavy metals, which are produced from various anthropogenic and natural sources. The sources and amounts of these metals can be seasonally and spatially highly variable. The objectives of this research were to investigate seasonal changes in the concentration and pollution level of selected heavy metals in street dust and soil samples around a few cities in Isfahan province, and also to compare them with selected cities in the world.

Street dust samples were taken in the first half of the second month of each of the four seasons in 2018 including 80 samples from Isfahan, and 40 samples for each of the cities of Flavarjan, Najafabad, Shahreza, Khomeinishahr and Natanz Each dust sample (about 300 g) was collected from the surface of pedestrian walkways and stored in plastic containers. All the samples were then extracted by digestion with 6N nitric acid, and the concentration of selected heavy elements including copper, zinc, lead, and cobalt was measured in the extracts by an atomic absorption spectrometer. Finally, the contamination indices including geoaccumulation index and Nemerrow pollution index were calculated in the samples and the seasonal and spatial changes in the concentration and rate of heavy metal pollution were investigated.

Spatial and seasonal changes in the concentration and contamination level of copper and lead showed that the highest pollution rate of these elements happened in Isfahan in spring. They also indicated that the highest degree of street dust pollution with zinc was found for the city of Flavarjan in the spring season. As far as cobalt, the highest pollution level was found in Shahreza city in the winter season. For all the elements, the lowest concentration and level of pollution were obtained for Natanz city in the summer season, and lead showed the lowest concentration in fall. Besides, except for cobalt, soil samples taken from non-urban areas showed the least concentration and pollution level. The comparison of the obtained results with the data reported for other cities of the world showed a higher level of pollution of the street dust in the urban area of Isfahan compared to other big cities of the world. The concentration of copper in the street dust of Isfahan is almost similar to that in Ahvaz and Huainan (China), and that of zinc is lower than Avilés (Spain) and Zhuzhou (China). Furthermore, the concentration of lead is lower than that in Zhuzhou and Huludao (China). Also, cobalt concentration in the street dust of selected cities was higher than that in all the studied cities except for Rabat-Saleh highway (northwestern Morocco) and Huainan (China).

The results of this investigation and their comparison with those of other studies indicated that the mean concentration of copper, zinc, and lead elements in street dust was highest in all the cities, except for Natanz. This is mainly due of higher traffic, more population and the density of machinery, the presence of more and larger constructions in big cities, the transit of vehicles, and the presence of more intense atmospheric dust storms in the central areas of Isfahan province, drought and lack of sufficient rain. Lower concentration of selected heavy elements in the street dust of Natanz city is probably due to the lower population density, different types of parent materials as compared to other cities, and its low industrial activities.

Salinity is a serious problem and one of the main factors in reducing agricultural productivity worldwide. The use of microorganisms to improve plant growth in low quality soil is a potential solution to address this problem. The salinity resistant microbiome improves the health of the salinity affected soils, maintains ecological functions and enhances plant growth. Salt tolerant plant growth promoting rhizobacteria (ST-PGPR) are able to adjust the salinity stress adverse conditions for their symbiotic plants through several mechanisms. This study aimed to isolation, identification and investigation the characteristics of salt tolerant-plant growth promoting rhizobacteria from the rhizosphere of halophyte plants.

Salinity tolerant plant growth promoting bacteria were isolated from the rhizosphere of native halophyte plants collected from the north of Iran. Bacterial isolates were selected according to their ability to growth in 2 M sodium chloride and traits of the motility, inorganic phosphate solubilization ability in PKV-Agar medium using phosphate solubilization index calculation, and siderophore production capacity in CAS-agar medium by calculating of its production index. Then, the top 10 isolates were selected and the ability of nitrogen fixation in Burk's medium, potassium dissolution in Aleksandrov's medium by using potassium solubilization index, as well as, the production of intrinsic IAA and the tryptophan-dependent IAA were investigated. Finally, molecular identification of selected bacterial isolates was performed based on 16S rDNA gene sequencing.

Four genera of Bacillus, Klebsiella, Proteus and Halomonas were identified after 16S rDNA gene sequencing. All isolates were motile. The most of isolates belonged to the genus Bacillus. Species belonging to Klebsiella and Halomonas genera had the highest salt tolerance. Klebsiella genus showed phosphorus and potassium solubilizing ability more than other isolates. The highest amount of siderophore production was observed in the isolate belonging to Proteus genus. All isolates were able to fix nitrogen. Among the studied isolates, Bacillus isolates had the highest rate of intrinsic IAA, and the tryptophan-dependent IAA production in B. licheniformis was higher than other isolates.

Isolation of wide range of salt-tolerant bacteria with favorable characteristics from the rhizosphere of halophyte plants indicates the microbial richness potential of this area, which provides the possibility of finding useful microorganisms that promote plant growth and reduce the adverse effects of stress in plants. Keywords: Plant growth promoting bacteria, Salinity stress, Halophyte plants, Indole acetic acid