نشریه تحقیقات کاربردی خاک
سال دهم شماره 2 (تابستان 1401)

Phthalic acid esters are synthetic compounds used as emollients in polymer and plastic compounds. The entry of these compounds into the environment and the human food cycle and the development of a variety of cancers has raised global concerns. The purpose of this research was to investigate the concentration of phthalic acid esters (PAEs) in the soil exposed to the leachate (landfill) and finding a microbial consortium capable of the degradation of these pollutants. The concentration of phthalic acid esters in the soil was measured by the ultrasonic method and GC-MS. The results showed that the concentration of diethyl hexyl phthalate (DEHP) in soil (4.52 mg/Kg) was 6 times that of its international standard (0.7 mg/Kg). Microbial enrichment was performed in a mineral salt medium containing phthalic acid esters (30 o C and 120 rpm) and a microbial consortium capable of degrading phthalic acid esters was isolated. To investigate the biodegradation of phthalic acid esters by consortium, the residual phthalate concentration was extracted with ethyl acetate and measured by GC-MS. The results showed that the this consortium was able to degrade more than 96% of low molecular weight phthalates of dimethyl phthalate, diethyl phthalate and dibutyl phthalate (medium molecular weight phthalate) (30 o C and 120 rpm). In the case of DEHP (the world's most widely used plasticizer), the consortium was able to degrade it by 55% at 400 mg/L. Besides, phthalic acid esters separately were degraded almost completely by this consortium (5 days incubation, 30 oC, 120 rpm). Our results demonstrate the biodegradation of phthalic acid esters by this consortium and recommend its use for bioremediation of phthalates in contaminated soils.

The aim of researchers in order to revive sustainable agriculture is to increase the solubility and availability of nutrients in the soil. For this purpose, this study was carried out to assess the effect of leonardite and bacteria on the chemical forms of zinc (Zn) in calcareous soils. A factorial experiment was conducted with three levels of leonardite (0, 2 and 4%) and with two microbial factors (without bacteria and zinc-soluble bacteria) at three incubation time (30, 90, 150 days) in three replications. The chemical fractionation and available forms of Zn in the soil was assayed by using the Tessier and DTPA methods. The results showed that leonardite and bacterial significantly increased Zn available forms (54%) and decreased soil pH (4.1%) during incubation time. Soil biological properties such as microbial population, basal respiration and microbial carbon increased by 36.2%, 77% and 77%, respectively. The distribution of Zn chemical forms and mobility factor also had significant changes affected of leonardite and bacteria as, it increased the exchange forms, binds to organic carbon and the carbonate part, as well as decreased the Zinc binds to Fe and Mn oxides in the soil. The mobility index of Zn ranged from 3.8 to 11.59% and its maximum value was observed in the treatment of leonardite 4% + bacteria. As a result, leonardite as a fertilizer plays an important role in element motility and its application along with solvent bacteria has positive effects on dissolution and increasing the availability of the elements.

Soil properties can be greatly affected by both topography and fire. Topography is one of the factors affecting the fire intensity. The aim of this study was to compare the effect of fire on chemical soil properties at top and toe of hillside slope. In order to sampling, one week after fire, three transects were installed with a length of approximately 100 meters from top to toe and interval of 20 meters from each other on the western slope in each area (burned and unburned) where the fire occurred in the summer of 2018 in Sarvabad area. Totally, 36 soil samples were collected and some properties were measured including: carbon, nitrogen, phosphorus, pH, EC, potassium, calcium and magnesium.The results showed that all chemical soil parameters were lower in the upper position than in the toe position slope in control area. However, the pH and electrical conductivity and calcium of soil increased more at the top than toe position of the slope in the burned area. Also, the amount of carbon and nitrogen of soil has increased at the top less than toe of the slope. The amount of soil phosphorus showed significantly difference in the burned soil at the top of the slope in comparision to the control. In general, the intensity of fire in these two positions can indirectly measure by comparison soil properties at top and toe of slope in burned area. Because of changes on soil chemical properties in the burned area, it seems that the fire intensity was higher at the top of the slope due to heat transfer from the bottom to the top of the slope.

Sodium absorption ratio (SAR) and exchangeable sodium ratio (ESR) are two indicators of sodic soils. Accurate prediction on exchangeable sodium ratio (ESR), which is often using costly and time-consuming laboratory tests is important in reclamation of sodium (Na)-affected soils. A significant correlation between ESR and Sodium Adsorption Ratio (SAR) has been documented in many studies in different regions.  The main purpose of this study is to develop a linear regression model between soluble and exchangeable cations in the Sarakhs Plain, Northeast Iran. In this study, 124 soil samples were randomly taken from the surface and subsurface the experimental site. The soil samples collected using a soil auger at 0-30 cm and 30-60 cm depth. Then the linear regression model was used for predicting soil (ESR) in saline soils. The soil ESR values measured in soil samples compared to the soil ESR values predicted using the soil ESR-SAR model. The results revealed that ESR and SAR are highly variable irrespective of depth despite a slight decrease with depth. The statistical results indicate that the linear regression model ESR=0.0182SAR-0.027 (R2= 0.92, P <0.001) and ESR=0.0157SAR-0.020 (R2=0.83, P<0.001) recommended to predict soil ESR from soil SAR in surface soil (0-30 cm) and subsurface soil (30-60 cm), respectively. In conclusion, the soil ESR-SAR model can be used instead of time-consuming and costly experiments in this study area.

The southern region of Kerman province with the production of citrus about 500 thousand tons per year, is ranked third in the country. One of the limiting factors of citrus production in this region in terms of quantity and quality is the concentration of some elements, especially boron in irrigation water. The effect of organic fertilizer, superabsorbent and chemical fertilizer with calcium on reducing the boron toxicity of irrigation water on sure orange rootstock in a factorial experiment was conducted in a randomized complete block design with 4 replications in 1996 and 1997. The factors include cow manure at two levels (0 and 2wt%), superabsorbent with three levels (0, 0.1 and 0.25wt%) and chemical fertilizers at three-level (control, balanced application chemical fertilizers without calcium based on soil test and balanced application of chemical fertilizers with calcium from calcium nitrate source based on soil test). The irrigation was done by drip irrigation with water with EC 845 μs / cm and boron concentration of 1.55 mg / l. The results showed that the simple and combined effects of superabsorbent, chemical and organic fertilizers on the percentage of leaves with boron toxicity symptoms, boron concentration was significant at the level of one percent. The highest concentration of boron per leaf (144.3 mg / kg) was observed in the control treatment with the highest number of leaves with symptoms of boron toxicity (22.97%) and the lowest concentration of potassium, magnesium, iron and zinc. Combined use of 2% organic matter + 0.25% superabsorbent + balanced use of chemical fertilizers based on soil test (without calcium) had the lowest percentage of leaves with symptoms of boron toxicity and the lowest amount of boron, but the highest percentage of magnesium increase (136.4) Showed potassium (197.4), iron (139) and zinc (123) compared to the control treatment. The results showed that separate and combined application of chemical and organic fertilizers with superabsorbent in soils with boron toxicity can reduce the effects of toxicity and improve plant nutritional conditions.

Biochar contributes to sustainable production by improving soil and plant characteristics. In previous studies, less attention has been paid to the effect of particle size and amount of biochar on soil hydraulic properties and plant water use efficiency. The aim of this field study was to investigate the effect of different amounts of biochar with different particle sizes on plant available water (PAW) and stomatal resistance, root dry weight, yield and Wheat water use efficiency (WUE). Factorial experiment with a randomized complete block design was performed with three factors of type, amount and particle size of biochar. Wheat straw and apricot firewood biochar, in the sizes of 0- 0.5 (S1), 0.5-1 (S2) and 1-2 (S3) mm with amount ​​of 0.5 (R1), 1.5 (R2) and 3 (R3) percent were added to the loamy sand soil. Wheat straw biochar with S2 particle size in R3 amount and apricot firewood biochar with S1 particle size in R3 amount further increased PAW. The lowest stomatal resistance in S3 particle size of wheat straw and apricot firewood biochar was observed in R1 and R2 amounts ​​of these biochars, respectively. Wheat root dry weight was less affected by the amount and particle size of those biochars. A significant increase in wheat yield compared to the control was observed in wheat straw biochar with S2 particle size at amount of R3. In some treatments, the yield was significantly lower than the control. The results of this study showed the greater effectiveness of wheat straw biochar in particle size of S2 and amount of R3 on WUE increase.  The effect of a change in the particle size of biochar on studying properties varied depending on the amount of biochar that added to the soil and the characteristics of raw materials for biochar production. The results of this study showed that the effect of biochar on soil properties is not the same.

Changes in climatic variables that affecting access to water can play a key role in the sustainable development of agriculture and the environment. Since ET0 is the most important variable affecting access to water resources after rainfall. Therefore, the present study examines temporal and spatial variations of ET0, temporal analysis of trend, sensitivity and relative contribution rate of climatic variables including Sun Duration (SD), Relative Humidity (RH), Wind Speed (WS), air pressure (P), maximum Temperature (Tmax) and minimum Temperature (Tmin) for a period of 30 years (1988-2017) at 7 synoptic stations on the southern shore of the Caspian Sea at different time scales. The spatial distribution of ET0 in the Caspian Sea basin showed that ET0 increases from west to east. The results showed that on the annual and monthly time scale including March, May, June, July, August and September, all stations had upward trend at 5% probability level of Significance. While the results of sensitivity analysis showed that ET0 has the highest sensitivity to variables of RH, Tmax and WS respectively, but results of relative contribution rate showed that variables of RH, WS and Tmin are the main actors on ET0, in the southern shore of the Caspian Sea during the last 30 years, respectively.

L-tryptophan is a precursor of auxin synthesis by PGPRs. In soil, this precursor derived from hydrolysis of soil organic matter protein. Lack of sufficient soil organic matter especially in rained condition could be limiting factor in this topic. For this purpose, an experiment was designed to evaluate the effect of tryptophan in the presence and absence of growth promoting bacteria on wheat growth. The results showed that in LB and root exudate mediums auxin was produced respectively 41.1 and 20.9 mg.L-1 by B. simplex 16 just when tryptophan added at 5 mM concentration. Bacterial inoculation of wheat seeds, addition of 100 mg.L-1 tryptophan and co-application of tryptophan and bacterial inoculation treatments respectively increased 9%, decreased 16% and decreased 20% the dry matter yield of wheat shoots compared to the control. Due to the use of tryptophan in both bacterial and non-bacterial inoculation conditions, root tissue density decreased 60% but root volume increased 70%. Microscopic studies and whole root images showed that both bacteria and tryptophan treatments caused morphological changes, especially in the hair roots section. According to the results of this study, the use of tryptophan at a concentration of 100 mg.L-1 is not recommended to increase wheat growth due to the potential for auxin stress and developmental disorders.

Soil hydraulic conductivity is one of the important parameters to estimate soil erodibility, soil water flow, estimate runoff, and design drainage systems. This study was carried out to determine the hydraulic saturation (Ks) of surface and subsurface loess soils of Aghemam watershed (2) that located in the northeast of Golestan province. For this purpose, three types of soils in this area including hill, loess plateau and alluvial terrace in two surface and subsurface layers were sampled. In this study, in addition to determining Ks using the falling head method, some physicochemical properties of soil samples such as salinity, neutral lime, organic matter and soil texture were measured in the laboratory and their relationship with Ks was investigated. Then, the spatial variations of surface and subsurface saturation hydraulic conductivity in the study area were plotted using GIS software and IDW method. The spatial variations of Ks in both layers indicated its direct relationship between the two layers. However, the value of this parameter in the surface layer is more than for the subsurface layer. Also, the amount of Ks is relatively high in the two types of loess plateau and hill (3.9 cm/h), except in the alluvial terrace type, which is generally low (0.9 cm/h). The statistical results of linear multiple regression and stepwise methods showed that among the variables studied, the organic matter and neutral lime parameters, respectively, have the most impact on determining the amount of surface Ks (R2 = 0.9556) and subsurface (R2=0.8607) in the study area.

To study the effect of sawdust and different Moisture levels on morphological characteristics of greenhouse cucumber, an experiment was conducted in a complete randomized design with three replications in Moghan callege of agriculture. The main and secondary factors were different moisture levels (without stress, 45 and 65% of field capacity) and mixture ratios of sawdust (without sawdust, 5, 10, 20 and 40% sawdust content), respectively. Among different sawdust treatments, 20% sawdust resulted in higher weight of fresh root weigh, with a significant difference with other treatments at the level of 1% based on Duncan's multiple range test. 10, 40, 50 and zero percent of sawdust were ranked in the next order, respectively. The highest root length was observed in control, followed by the treatment of 10% sawdust mixture in 65% moisture level conditions. Also, non-stress treatment with 5% had the lowest root length, but in terms of root length, all treatments at the level of one percent, were placed in similar group. With increasing moisture depletion from 0 to 65%, the yield of 0% sawdust was reduced by approximately 62% of control treatment. And in the 5%, the yield reduction increased to 55%. Also, the yield reduction in 10, 20 and 40% sawdust was estimated at 18, 10 and 25%, of control treatment respectively. The highest yield was 134 tons per hectare obtained for control treatment in 20% and 40% with 128 tons per hectare was in second order and in all applied moisture depletion, the yield of sawdust treatments is higher than the control treatments. Therefore, in the studied sandy-clay-loam soil, using 20% of sawdust mixing ratio, in control treatment and applied moisture depletion, will have better performance.