نشریه مدیریت خاک و تولید پایدار
سال دهم شماره 2 (پیاپی 32، تابستان 1399)

Soil contamination is one of the most important pollutants in the environment. Lead (Pb) is one of the heavy metals and important pollutant in arid ecosystem. The use of plants to remove contaminated soil or Phytoremediation is an economical method. Todays due to increasing the pullution of soil sources and resultant problems, identification the resistant plant species against soil pollution is essential. Effeciency of Vetiver and Brassica to Pb uptake has not studied and compared, therefore, this study was carried out in order to compare the Phytoremediation capacity of Pb by two plants i.e. Vetiveria zizanioides and Brassica oleraceae, and to indentify the better specie for this purpose.

A completely randomized design with factorial arrangement in greenhouse conditions was carried out. Treatments included two types of plants (Vetiveria zizanioides and Brassica oleraceae) and three rates of Pb contamination in soil (50, 250 and 500 mg / kg prepared from lead nitrate) in three replicates. After measuring the amount of Pb in soil by DTPA, the concentration of Pb in root and shoot of plants, Translocation factor (translocation from roots to shoots) and Bio-accumulation factor (translocation from soil to roots) were measured, too. Data analysis was performed using JMP software and comparison of means by LSD method.

The results of analysis of variance showed that the effect of plant type, soil contamination rates and their interaction on accumulation content of lead in root and soil were Significant at p < 0.01, while the effect of soil contamination rate on the shoots of plant was Significant at p < 0.05. The highest accumulation contents of lead in roots and shoots were found in Vetiver plant containing 250 mg / kg of soil pollution rate treatment. Also, the highest amount of Pb accumulation in soil was related to Brassica containing 500 mg/kg of soil treatment. Vetiver in root and shoots accumulated Pb 3.5 and 2.1 times more than Brassica, respectively. In addition, the accumulation content of Pb in the roots of Vetiver was 4 times higher than its shoots, while the concentration of Pb in roots of Brassica was 1.5 times greater than its shoots. Translocation factor in both plant was less than 1, while bio-accumulation factor of Vetiver was greater than that of Brassica in all Pollution rates.

Despite the ability of both plants to accumulate lead in their roots and shoots, Vetiver had the better performance in lead uptake from soil and reduced lead amount in soil, so its application is recommended for Phytoremediation purposes.

In most national and regional projects, in order to produce a digital map of soil properties, usually sampling density is low due to costly and time-consuming. Because of this, produced digital maps have a large spatial resolution (more than 90 meters) that can’t be used on a farm scale (spatial resolution less than 30 meters). One way to solve this problem is to downscale of digital maps with coarse spatial resolution using covariates with fine spatial resolution. The purpose of this study was to investigate the efficiency of the Dissever algorithm for producing an organic carbon map with a spatial resolution of 30 m from a carbon-organic digital map with a spatial resolution of 90 meters.

The study area is approximately 14084 hectares and formed a small part of the Karkhe catchment in Kermanshah province. Initially, using 110 random observations and block Kriging method, an organic carbon map was prepared with a pixel size of 90 m. Then a set of 23 environmental covariates associated with scorpan factors including climate, topography, living organisms and maternal materials were used as predictor variables. SRTM digital elevation model and Landsat 5 satellite imagery were used to provide climatic and topographic predictors and vegetation and geology indicators. The dissever algorithm is a repetitive process for approaching a mass balance solution. Multiple regression model, generalized additive model, cubist, random forest, and ensemble model used for production fine spatial resolution map. In order to evaluate the efficiency of different methods, restored maps (obtained by converting downscaled maps with 30 m resolution to maps with 90 m resolution using mean filter) were compared with base map (block kriging map) using validation criteria include Bias, R2, root mean square error, and concordance correlation coefficient. The spatial structure of the restored maps and the base map was also investigated using parameters of their experimental variogram.

The relationship between the covariates and the soil organic carbon using data mining methods in the framework of dissever algorithm resulted in the production of downscaled maps. The results showed that the probability density function of the restored map of cubist model is very close to the base map probability density function. Also, the downscaled map using the cubist model had the highest coefficient of determination (0.75) and concordance correlation coefficient (0.8) and the lowest root mean square error (0.06) and bias (0.001). Thus, cubist model have the highest efficiency of downscaling in compared to the rest of models. . It was also found that the use of ensemble model increases the accuracy and precision of downscaled map compared to single data mining models. The study on the spatial structure of restored maps indicates that the cubist restored maps captured more of the variance of the base map than others.

The modified dissever procedure due to the use of data mining methods and ensemble model is a practical option to downscale soil properties map with coarse resolution. Considering the high efficiency of dissever algorithm, this method can be used to prepare soil properties map at field scale from national and regional maps which can be used in farm management.

The plant growth promoting bacteria (PGPB) inhabiting the phyllosphere of different plants provides a tool for more efficient use of bacteria as a source of biofertilizers. The use of molecular technologies leads to in-depth research of the phyllosphere microorganisms and may provide new avenues for the development and validation of modern agricultural operations and significantly increase productivity. The aim of this research was to investigate the plant growth promoting (PGP) traits of bacteria isolated from maize (Zea mays L.) phyllosphere cultivated in different geographical zones of country (Iran) and their molecular identification by 16Sr RNA sequencing.

In September (2016), 116 samples of healthy mature leaves were collected from the maize fields located in 6 provinces of Iran (Fars, Alborz, Qazvin, Khuzestan, Tehran and Khorasan) and then, phyllosphere bacteria were isolated from them. Growth promoting traits of bacteria including Indole-3 Acetic acid (IAA) production, organic phosphate dissolution, siderophore production, exopolysaccharides (EPS) production and also nitrogenase enzyme activity were measured using standard methods. Superior strains were identified based on 16S rRNA sequencing method.

The 10 from 242 bacterial strains isolated from maize phyllosphere were selected based on their growth promoting traits. All strains selected demonstrated nitrogenase activity, organic phosphate dissolution and IAA and EPS production capability. The highest nitrogenase activity (70.31 nM ml-1 h-1) and organic phosphate dissolution (75.05 g l-1) were observed in THE15 strain, while the lowest amount of these properties belonged to KHO57 (5.55 nM ml-1 h-1) and KHO51 (15.90 g l-1) strains, respectively. The QAZ26 and TEH15 strains had the highest amount of IAA production (31.56 and 30.00 µg ml-1, respectively) and the ALB32 strain produced the lowest amount of IAA (4.50 µg ml-1). The EPS production by strains ranged from 0.120 to 1.805 g l-1. Among the strains investigated, only KUU32, KHU53, ALB32 and QAZ26 were able to produce siderophore. 16S rRNA sequencing revealed that the 10 strains selected belong to Bacillus, Microbacterium, Pseudarthrobacter, Pseudomonas, Stenotrophomonas, Enterobacter and Kocuria genera. The Bacillus with 4 different species (including Bacillus subtilis, Bacillus megaterium, Bacillus paralicheniformis and Bacillus pumilus) was the most dominant genus.

Based on the results of this study, Bacillus was the most dominant genus of plant growth promoting bacteria in the maize phyllosphere. Among the isolated bacteria, Enterobacter hormaechei TEH15 was highly capable of nitrogenase enzyme activity, IAA and organic phosphate solubility. Therefore, this strain deserves further research in greenhouse and field studies of maize cultivation and maize family plants.

Despite the abundance of some nutrients in calcareous soils, the available form of these nutrients is less than the amount required for plant growth, and the deficiency of nutrients is one of limiting factor in the production of plants especially wheat in these soils. The application of plant growth biostimulants may improve the availability of nutrients in calcareous soils and consequently increase yield and grain quality of wheat. Therefore, this study was conducted to evaluate the effect of plant growth biostimulants on quantitative and qualitative characteristics of wheat in a calcareous soil.

This research was conducted in randomized complete design with seven treatments and three replications at Behbahan Agricultural Research Station in one year (2017-2018). Treatments included: control (application of chemical fertilizers according to soil test), free amino acid (L), fulvic acid, seaweed extract, humic acid, grain inoculation with Azotobacter and application of all studied biostimulants (except fulvic acid). Foliar application of amino ccid, fulvic acid and seaweed extract was done at a concentration of 0.5 % at two stages, tillering and heading. Humic acid was used as fertigation at 5 kg.ha-1 in the early stages of growth (prior to tillering). During experiment: plant height, number of spikes per m2, number of grain per spike, 1000- grain weight, grain yield, biomass, grain protein, phosphorus, potassium, copper, zinc, manganes and iron of grain were measured. Varince analysis were done by MSTATC statistical software and meanes were compared using Duncan,s Multiple Range Test at the 5% prpbability level.

The effect of biostimulants on grain yield was significant at the 1% prpbability level. A significant increase in grain yield observed in plants treated with biostimulants compared with control. The highest plant height (99 cm), number of spikes per m2 (633), number of grain per spike (43.33), 1000-grain weight (46.12 g) and grain yield (8617.71 kg.ha-1) were recorded in the combined treatment. The differences of grain yield among this treatment and other treatments were significant. Application of biostimulants significantly increased the grain protein percentage, the concentration of potassium, copper, zinc, manganes and iron of grain at the 1% prpbability level. These formulations had no significant effect on grain phosphorus. Application of combined biostimulants significantly increased the grain protein percentage, potassium, copper, zinc, manganes and iron of grain compared with control. Among growth biostimulants, the highest increase in the grain protein percentage and grain iron was achieved by amino acid while the highest increase in potassium, copper, zinc and manganese of grain was obtained by humic acid compared with control.

The combined use of plant growth biostimulants produced the best grain yield and quality in comparision to alone of these substances.Therefore, inoculation of wheat seeds with Azotobacter, use of humic acid as fertigation at in the early stages of growth and foliar application of amino ccid and seaweed extract at two stages of tillering and heading, are recommended. According to the results, among growth biostimulants, application of amino acid or humic acid is preferred.

Soil salinity is one of the most serious limiting factors for crop growth and production in the arid and semi-arid regions. Zinc is an essential micronutrient for humans, animals and plants, which act either as the metal component of enzymes or as a regulatory co-factor of a large number of enzymes. Zinc is required for chlorophyll synthesis and plays an important role in biomass production. Zinc is required for pollen function, fertilization and germination plays an important role. Zinc deficiency is recognized as a critical problem in plants, especially grown on saline conditions with high pH values. But, recent researches have shown that a small amount of nutrients, particularly Zn applied by foliar spraying can affect ability of plants to salinity stress. So, the aim of this study was to investigate the effects of foliar and soil application of zinc on photosynthetic pigments, chlorophyll fluorescence and grain yield of wheat under soil salinity

A factorial experiment was conducted based on randomized complete block design with three replications in research greenhouse of faculty of agricultural and natural resources, University of Mohaghegh Ardabili in 2018. Factors experiment were included soil salinity in four levels (non-salinity, salinity 30, 60 and 90 mM by NaCl), foliar and soil application of zinc in four levels (without zinc as control, soil application of ZnSo4, foliar application of nano zn oxide, both application of ZnSo4 and nano zn oxide).

The results showed that both application ZnSo4 and nano zn oxide under non-salinity condition, increased chlorophyll a, b, total chlorophyll, cartenoeid and grain yield (65.2, 52.72, 62, 50.43 and 34.56 % respectively) in comparison with no application of zinc under salinity of 90 mM. Also, both application of ZnSo4 and nano Zn oxide under without salinity, increased maximum fluorescence (Fm) and variable fluorescence (Fv). Grain yield decreased 34.56% under salinity of 90 mM and without application of zinc in comparison with both application ZnSo4 and nano zn oxide under non-salinity condition due to increasing minimum fluorescence (F0) and decreasing chlorophyll content.

It seems that both application of ZnSo4 and nano zn oxide can increase grain yield of wheat under salinity stress due to improving Potosynthetic pigments and chlorophyll fluorescence components.

The results showed that both application ZnSo4 and nano zn oxide under non-salinity condition, increased chlorophyll a, b, total chlorophyll, cartenoeid and grain yield (65.2, 52.72, 62, 50.43 and 34.56 % respectively) in comparison with no application of zinc under salinity of 90 mM. Also, both application of ZnSo4 and nano Zn oxide under without salinity, increased maximum fluorescence (Fm) and variable fluorescence (Fv). Grain yield decreased 34.56% under salinity of 90 mM and without application of zinc in comparison with both application ZnSo4 and nano zn oxide under non-salinity condition due to increasing minimum fluorescence (F0) and decreasing chlorophyll content.

It seems that both application of ZnSo4 and nano zn oxide can increase grain yield of wheat under salinity stress due to improving Potosynthetic pigments and chlorophyll fluorescence components.

Soil and water salinity is the major limiting factors for plant growth and crop production. Water and soil salinity almost limit plant growth through increasing osmotic pressure, specific toxicity of some ions such as sodium and color, and nutritional imbalance. In addition to, salinity stress reduces root and plant growth via increasing hormone level. One of the strategies to deal with salinity is inoculation of seeds with plant growth-promoting rhizobacteria (PGPR).

Soil and water salinity is the major limiting factors for plant growth and crop production. Water and soil salinity almost limit plant growth through increasing osmotic pressure, specific toxicity of some ions such as sodium and color, and nutritional imbalance. In addition to, salinity stress reduces root and plant growth via increasing hormone level. One of the strategies to deal with salinity is inoculation of seeds with plant growth-promoting rhizobacteria (PGPR).

The effect of four strains of Fluorescent pseudomonads on uptake of micronutrients in rice was studied under saline irrigation. Greenhouse tests were performed as factorial experiment in a completely randomized design with four replications. First factor was salinity water in five levels (0.7, 1.4, 2.8, 4.2 and 5.6 ds/m originated from sea water) and the second factor was pseudomonads strains (Pseudomonas putida 4, 11 and 108, and Pseudomonas fluorescens 169 and a non-inoculated control). Root of rice (cv. Tarom) transplants was inoculated with mentined strains before planting in pots. During growth period, the pots were irrigated with the abovementioned saline water upto saturation point. In the flowering stage, flag leaf samples were collected to determine Manganese, Iron, Zinc and copper concentration. The content of micronutrients in seed samples was also measured.

The results showed that increasing the salinity level significantly reduced all microelements contents in the leaf and seed. Rice inoculation with different strains of P. fluorescens and P. putida affected on nutrients concentrations under saline irrigation and it increased content of the elements compared to control. Also, the interaction of Pseudomonas strain × salinity level had a significant effect on copper and iron concentration in leaf, and copper and Manganese concentration in seed (P < 0.01). At all salinity levels, maximum iron concentration observed by inoculation of roots with P.fluorescent 169.

Inoculation of rice with various strains of bacteria Fluorescent pseudomonads and putida affected the concentration of micronutrients under saline water irrigation in rice and caused to increase these elements more than control. Therefore, in saline conditions, using strains of Fluorescent Pseudomonas can be growth up of rice plant.

Soil contamination with heavy metals is one of the main important environmental issues. Soils around mines have a high concentration of heavy metals that can affect the health of humans and animals. A cheap method to remediate soils contaminated with heavy metals is the, immobilization of heavy metals in soils. The use of environmentally friendly compounds that have the ability to immobilize of heavy metals in the soil environment has taken attention of many researchers. For this purpose, silicon compounds were used in the study to immobilize lead (Pb) in the contaminated soil.

In this study, four types of compound such as calcium silicate, potassium silicate, sodium silicate and pure silicon were used at five concentrations (0, 50, 100, 200 and 400 mg / kg soil) in terms of Si content. The Silicon compounds were added to the pots containing 700 grams of Pb contaminated soil, and maintained for one month at ambient temperature and soil water content equivalent to field capacity. The available Pb was then extracted with DTPA and the Pb concentration was measured by atomic absorption. The distribution of chemical forms of Pb was determined before and after of incubation time with sequential extraction method. This experiment was carried out in a factorial arrangement in a completely randomized design with three replications.

The results showed that among the 4 silicon compounds, calcium silicate at a concentration of 400 mg / kg soil had the highest rate (54%) of Pb stabilization. In general, all of four silicon compounds, at the concentration of 400 mg / kg soil, had the most Pb stabilization capability among the all of applied rates. The results of sequential extraction showed that by using silicon compounds in Pb contaminated soil and increasing the concentrations rates from 50 to 400 mg / kg the soluble and exchangeable form, the form attached to carbonates and the iron and manganese oxides reduced but the forms of Pb co-exist with organic matter and the residual form of Pb increased. The highest reduction in the form of exchangeable, carbonate and bounded to iron and manganese oxide, Conversely, the highest increase occurs in the form of residual and was belong to calcium silicate treatment.

In fact, by the increase of silicon compound rates application, more amount of these compounds are available for Pb immobilization. The Silicon can form a complex with heavy metals and thereby reduce the available concentration of them. The Calcium silicate has a higher specific surface area than potassium and sodium silicates, hence, it can initiate more complex with Pb ions. However, Potassium and sodium silicates had a greater ability to stabilize Pb ions than pure silicon. Therefore, pure silicon had less ability to decrease the available Pb concentration among the all treatments. In general, it can be concluded that silicon compounds are able to reduce the mobility of Pb ions in soil environment and these compound environmentally friendly compounds.

Soil management changes can have either negative or positive impacts on crop production, depending on many factors including region, rotation, soil properties, tillage intensity, and at the same time, alter soil fauna diversity. Little attention has been paid to the response of soil fauna to changes in soil tillage methods. Results showed that soil fauna groups and natural enemies affected by conservation tillage resulting in changed soil fertility and small habitats accessibility. Thus, the aim of this study was to investigate the effect of conservation and conventional tillage on soil macro-fauna communities and species diversity in wheat (Triticum aestivum L.)-corn (Zea mays L.) rotation.

In order to evaluate the effects of soil tillage methods (conventional tillage (CT), reduced tillage (RT), and No-Till (NT)) and crop residue (residue returned and exported) on soil macro-fauna in a wheat-corn rotation, a 1-year field experiment (two growing seasons) was conducted in 2016-2017 based on split-plot design in three replications, in Zarghan, Fars province. Sampling was done by pitfall traps and species diversity indices were measured using Past software. Data were collected and performed with the function of split plot design using SAS 9.3 software. Means were separated using Duncan’s Multiple Range test at 5% probability level.

Results showed that soil macro-fauna abundance increased up to 6% in corn cultivation compared to wheat, when plant residue returned. Soil macro-fauna abundance was positively affected by conservation tillage and residue retention, so that applying RT and NT systems increased soil macro-fauna compared to CT system approximately one time. Shannon index in NT, RT and CT systems were 1.88, 1.91 and 1.92, while Simpson and Berger-parker indices were 0.83, 0.84, 0.85 and 0.31, 0.28, 0.25, respectively, when residue returned. The highest Hill index (0.68 and 0.71) was obtained by CT system and plant residue removing in wheat and corn, respectively.

Although there is a wide range of responses among different species, most macro-fauna groups have greater abundance in RT system and residue retention compared to CT and NT systems due to increasing and creating diverse habitats on the soil as a result of plant residue retention and reducing soil tillage operations. Overall, greater knowledge of different soil tillage methods and residue management effects on soil macro-fauna groups will allow for a better understanding of interactions between soil macro-fauna and natural enemies with crops and would aid the development of pest management strategies as components of sustainable agricultural programs.

Soil salinization and sodicity are two most important factors in land degradation, especially in arid and semi-arid regions of the world. Considering that saline-sodic soils have poor physical, chemical and biological properties that reduce the absorption of nutrients by plants and eventually decline their growth and yield. Application of the soil amendments, such as organic matter, can be a suitable method for improving the fertility of saline-sodic soils.

In this study, a saline-sodic soil was chosen from Alborz, and then it was mixed with three levels of 1%, 3% and 5% (weight) of Cow manure, Vermicompost and Azolla, and incubated for 5 months at the moisture of field capacity and temperature of 20 ° C. Then, safflower seeds were planted and treatments were placed in a greenhouse for two months. During this period, soil moisture was maintained at the field capacity, through weekly weighing and irrigation with distilled water. After this period, plant indices including: height of shoots, fresh and dry weight of shoots and roots, chlorophyll content of leaves and safflower leaves area were accurately measured.

After the incubation period and then the cultivation period, the addition of modifiers was observed to change the growth of safflower plant compared to the control. The lowest stem height was related to 5% cow manure treatment and the highest safflower height was related to 5% vermicompost fertilizer, which had the significant differences with control treatment. The 3 and 5% vermicompost and 1% Azolla fertilizer had the highest fresh weight of root and shoot compared to others, indicating the highest amount of water in these treatments for use of safflower plant. Different treatments did not have a significant effect on dry weight increasing of safflower plants. The chlorophyll content of safflower leaves was not significantly different in treatments than control, except for 5% cow manure application, which significantly decreased and 3% Azolla fertilizer treatment showed a significant increase compared to control. The leaf area was significantly increased in 5% vermicompost and 1% Azolla treatments and 5% cow manure had the lowest leaf area.

Safflower plant growth changes were mainly negative in cow manure treatment, while Azolla fertilizer treatment was almost unchanged and Vermicompost fertilizer treatment showed significant positive changes in most plant analyzes. More precisely, vermicompost fertilizer at 5% level and then Azolla fertilizer at 3% level could provide the most suitable substrate for safflower growth in saline-sodic soil. Therefore, according to the results obtained in this experiment, under similar conditions, the use of cow manure in saline-sodic soils is not recommended.