APPLIED SOIL RESEARCH
Year:2018 | Volume:6 | Issue:2 |Papers Count:11

Pharmaceutical antibiotics such as oxytetracycline (OTC) and sulfamethoxazole (SMX) are highly consumed for the treatment of infectious diseases and to growth improvement in livestock and poultry industry every year. More than 90 percent of consumed antibiotics may be excreted from the animal's body as main compounds and bioactive metabolites, and introduced into the soil environment which may impose adverse effects on non-target microorganisms. The effects of antibiotics on soil microbial functions have not been well determined yet. In this study, in order to assess the impact of oxytetracycline and sulfamethoxazole on soil microbial functions, a factorial experiment was conducted based on completely randomized design with factors of concentrations (0, 1, 10, 25, 50 and 100 mg. kg-1 soil), time (1, 4 and 21 days) and kind of antibiotics in the laboratory conditions. Soil microbial community functions were evaluated by measuring the activities of alkaline phosphatase and urease and potential nitrification. The results showed that oxytetracycline severely affected alkaline phosphatase and urease activities in the first day of incubation. But, the activities of these enzymes were recovered with increasing the incubation time. While, sulfamethoxazole significantly inhibited activities of alkaline phosphatase and urease enzymes compared to control treatment during the incubation. The effect of oxytetracycline and sulfamethoxazole on potential nitrification followed the same pattern so that nitrification rate increased with increasing concentrations of antibiotics in the early days of incubation, but these antibiotics had adverse effects on potential nitrification over time. Overall, OTC antibiotic exerted adverse effects on soil microbial functions in the early days of incubation, while SMX antibiotic exerted long term effects on soil microbial parameters.

Soil erodibility (K) index is one of vital parameters in water erosion prediction. Therefore knowledge about spatial variability of this parameter (K) could efficacy help to model water erosion in area of interest. Our purpose is to predict spatial variability of soil erodibility index using digital soil mapping technique in Baneh region (Kanisef area), Kurdistan Province. In this study, based on hypercube sampling methods, 217 soil sampling sites were selected in area of 4000-ha and then samples collected from depth 0-30 cm and some soil analysis (i. e. calcium carbonates, clay, silt, sand, surface special weight and soil organic carbon) in the laboratory measured. Using RETC software soil infiltration values were obtained and then K factor calculated according to Vaezi equation (2008). The relationship between K factor and ancillary data covariates (derived from DEM and Landsat image) was obtained by land-soil models (Solim) and artificial neural network. Result showed that Solim model (R2 and RMSE 0/72 and 0/00013, respectively) have higher performance than artificial neural network (R2 and RMSE 0/67 and 0/00015, respectively) for soil erodibility index prediction. Our result also showed it is possible to map soil erodibility index continuously with reasonable accuracy. Finally digital map of K factor was prepared using Soilm model in the study area. The digital map of K factor obtained by Solim indicated ranging of soil erodibility from 0. 0094 to 0. 0095 ton. ha/Mj. mm. We recommend prediction of spatial variation of K factor by the other digital soil mapping techniques.

Azotobacter is free-living nitrogen-fixing bacteria that it leading to promoting plants growth through various ways. Frequency and distribution of Azotobacter is affected by soil use and its properties. Accordingly, this study aimed to isolate and identify some of plant growth promoting (PGP) Azotobacters. To this end, 50 soil samples were taken randomly from depth 0-25-cm under different land-uses in three provinces viz. Eastern-Azerbaijan, Ardabil and Gilan. Soil paste method was used for isolation of these bacteria and purification was done in LG and NA media. We first isolated 50 bacterial isolates based on the phenotypic and morphological properties. And then we selected nine isolates of them for detailed and deep studies (including 2SP-5, 14SPI, 14SP2-1, 16SP-2, 34SPIII, 35SP, 35SP-2, 43SP-2 and 44SP-2). Results of molecular identification of bacteria (16S rDNA) revealed that among nine isolates, the five isolates (viz. 14SPI, 14SP2-1, 16SP-2, 35SP and 44SP-2) belonged to Azotobacter chroococcum, and isolates 34SPIII and 35SP-2 belonged to Pseudomonas sp. while 2SP-5 and 43SP-2 were identified as Beijerinckia sp. We also found the highest N fixation, and P solubility and auxin production were recorded by A. chroococcum 14SP2-1 and Pseudomonas sp. 34SPIII, respectively. Maximum potassium releasing was observed by A. chroococcum 14SP2-1 and 44SP-2. In this study, all the identified Azotobacteria belonged to A. chroococcum which isolated from the pasture, corn and rice lands of East Azerbaijan and Gilan provinces.

Land suitability evaluation is technically explained as the assessment of land performance when used for a specified target, particularly to use them based on their capability and production potential. This study aimed to determine the suitability of lands for Pomegranate and Pistachio using PROMETHEE II techniques in an area located in the Miandoab region, Iran. Eleven soil series were found in study area. To explain the land suitability, some criterions including soil texture, soil acidity, salinity, organic carbon, soil exchangeable sodium (%), soil carbonate calcium (%), the number of households, both male and female population, illiteracy and literacy education, main occupation and age were determined. Then the entropy-weight method, which is based on Shannon Entropy theory, was utilized. Results showed that exchangeable sodium was found with maximum weight while age and occupation had the minimal weight for the both crops. Next, weighted values of criteria were analyzed using the PROMETHEE II technique. The results showed that for both pomegranate and pistachio Su. Wt and Su series with proper phi respectively, 0. 417 and 0. 328 for pomegranate and 0. 438 and 0. 358 for pistachio were characterized to have the highest potential, while Ch and Fa. Wt series with proper phi respectively,-0. 258 and-0. 522 for pomegranate and-0. 326 and-0. 478 for pistachio were found to have a significantly lower suitability. 20. 11% of the region is very good, 23. 6% is good, 36. 26% is moderate and 20. 03% is poor for pomegranate and 27. 23% of the region is very good, 23. 9% is good, 38. 87% is moderate and 10% is poor for pistachio.

Soil structural properties which are function of pore size distribution are important physical indicators of soil that affect the growth and development of plant and root. Irrigation water quality alters the soil structure by affecting salt concentration and sodicity of soil solution. This study was carried out in order to investigate the effects of different water qualities on pore size distribution, aeration porosity, soil water characteristic and mechanical resistance curves of a clay loam soil, irrigated with different water qualities. A combination of three levels of EC (1, 6 and 10 dS m-1) and SAR (1, 5 and 12 (meq L-1)0. 5) values were used to simulate the different types of irrigation water. The undisturbed soil samples (45 mm length and 51 mm inner diameter) were treated with solutions for 5 cycles of saturation and drying. Results showed that at each SAR, as water EC increased, the soil macroporosity and aeration porosity were enhanced as a result of flocculation which is effective in development of stable structure. Due to increasing the micoporosity and water holding capacity, the amount of retained water in filed capacity was increased. Saturated water content was increased due to the effects of salinity on pore alteration, as a result of contraction of diffuse double layer and particle’ s flocculation. It is also seen that penetration resistance decreased probably due to development of macro pore. At each EC level, as the sodicity of irrigation water (SAR) increased, the moisture content at field capacity and retained water were increased due to structural disruption, clay swelling and dispersion which lead to increased adsorptive and interlayer surfaces. It was also observed an increase in miroporosity and penetration resistance and decrease in macroporosity and aeration porosity with increasing in SAR.

This study was conducted to evaluate the effect of earthworms (Eisenia fetida) and arbuscular mycorrhiza fungi (F. mosseae) as well as their interactions on the root colonization, soil pH and soil dissolved organic carbon and nutrient concentration of iron, zinc, copper and manganese in maize. Experimental treatments included control, earthworm, mycorrhiza and earthworm + mycorrhiza was conducted in a completely randomized design in research greenhouse of Ferdowsi University of Mashhad with three replications. The results showed that the presence of earthworms in mycorrhiza + earthworm treatment had no significant effect on mycorrhizal root colonization compared with mycorrhiza treatment. The experimental treatments significantly reduced soil pH compared to the control treatment. Although experimental treatments significantly increased shoot dry weight, dissolved organic carbon and availability of iron, copper, zinc and manganese in the soil compared to control, however, it had a different effect on nutrient uptake by the plant. The highest concentration of Zn and Mn in shoot was obtained in mycorrhiza treatment that was statistically significant compared to other treatments (p<0. 05). The presence of earthworms in the mycorrhiza + earthworm treatment, reduced the uptake of zinc and manganese, 32 and 15. 5% relative to mycorrhizal treatments, respectively, that probably due to the negative impact of earthworm on the destruction of fungal hyphae. While the earthworms activity had no significant effect on the uptake and concentrations of iron and copper in earthworms + mycorrhizal treatment.

Soil moisture characteristic curve (SMC) is a fundamental soil property for predicting and modeling water flow and solute transport in the unsaturated soil, but its direct measurement is tedious and time consuming. Therefore, various indirect methods (e. g., pedotransfer functions, PTFs) have been developed to predict SMC from easily available soil properties (EASP). We develop a procedure to predict SMC from ESAP and soil liquid limit (LL), and plastic limit (PL). Forty three soils were sampled from north-west of Iran. All of soil samples were divided in two groups; 28 and 15 soils samples were used to train and evaluate of the models, respectively. The SMC, (water content at the suctions 0. 1, 0. 2, 0. 3, 0. 4, 1, 2, 3, 5, 10 and 15 bar) and LL, PL and ESAP were measured through standard methods. Multiple linear regression analysis was used to make correlation between LL, PL and ESAP data as independent variables along with SMC data as the dependent variable, using the SPSS software and the stepwise algorithm. Results showed that among all measured soil properties, the clay content, bulk density, LL and PL had high correlation with the soil moisture content at different suction heads. Values of the coefficient of determination (89%) and root mean square error (0. 028), obtained by the statistical analysis, and indicated the validity of the models in the all of the suction heads.

Application of silicate minerals and potassium solubilizing microorganisms is a common method for supplying of potassium to plants. This study with the aim of isolation of potassium solubilizing fungi from rhizosphere soil and evaluation of quantitative ability of released potassium from different sources of silicate by strains was carried out as factorial experiment based on completely randomized design with three replications. Laboratory factors were including potassium sources in four levels (biotite, phlogopite, illite and muscovite), incubation time in six levels (0, 1, 3, 5, 7 and 10 days) and microorganisms in four strains (Aspergillus niger, Aspergillus terreus, Trichoderma harzianum and Penicellium sp. ) and greenhouse factors were including potassium sources in five levels (control, soluble potassium, phlogopite, illite and muscovite) and microbial inoculation in two levels (non-inoculated control and inoculation with fungi). Results showed that the highest potassium content (3. 21 μ g ml-1) was released ten days after incubation from biotite by strains of KSB2 that was not significantly different from other fungal strains. The microbial inoculation increased 25. 47 and 30. 37 percent plant high and root dry weight compared to control treatments, respectively. The application of silicate minerals and microbial inoculation had a significant effect on some growth indices (stem diameter and shoot dry weight) and the content of potassium. The microbial inoculation increased potassium content of shoot and root in illite 3. 37 and 1. 43 times higher than control treatment, respectively. In general, the application of fungal inoculum had significant effect on potassium release of silicate minerals and plant growth.

In order to design and accurate management of drip irrigation systems, it is necessary to have sufficient information regarding the dimensions of wetting front (diameter and depth of the soil wetted by drippers) for various soil textures. Such important parameters as soil hydraulic functions, drip discharge and irrigation time influence the dimensions of created wetting front. In this study, new semi-empirical models for determination of depth and maximum diameter of soil wetting front under point source in several soil textures were developed. For this purpose, HYDRUS-2D software was run for an application discharge (3 Lhr-1) in several soil textures. Using Backingham π theorem and obtained values from software, including depth and maximum diameter of soil wetting front, the equations which estimate the wetting front dimensions were presented for several soil textures. Soil saturated hydraulic conductivity, irrigation time and dripper discharge were the parameters of developed equations. Statistic indices results for all equations (min Correlation Coefficient about 0. 968, max Root Mean Square Error about 2. 120 and max Mean Absolute Error about 1. 376) firm the ability of presented equations in calculation of wetting pattern dimension in different soil structures. On the basis of obtained results, presented equations can be used properly for designing and optimal management of drip irrigation system which is located in any soil textures.

Soil salinity is a major environmental threat for survival of plants Some plant growth regulators including salicylic acid improve the plants resistance to environmental stresses such as heat, cold, drought and salinity. A pot experiment was conducted, using a factorial based on randomized complete design, to study the effect of salicylic acid (SA) application on some morphological characteristics and elements uptake of grapevine (Vitis vinifera L. ) cv. Bidaneh Sefid under salinity stress condition. Well-rooted grapevine cuttings were treated with five levels of salinity 0 (control), 25, 50, 75 and 100 mM NaCl and four levels of SA (foliar application), 0 (control), 100, 200 and 300 mg l-1. The results indicated that the fresh and dry weight of shoot and root decreased by increasing the salinity levels. In this regard, these variables decreased by 65. 76 and 75. 9%, respectively at the salicylic acid application (300 mg l-1) under salinity (100mM). At the 100 mM NaCl treatment, NO3-, K+, Ca2+, Mg2+, Fe2+ and Zn2+ content in leaf decreased by 56. 9, 73, 62. 4, 43, 54. 35 and 75%, respectively, in compared to control plants. . Under 100 mM salinity level and without any application of salicylic acid, the concentration of Na+ and Cl-in the leaves increased by 100 and 20. 77-fold, respectively, in compared to control. However, SA reduced the accumulation of Na+ and Cl-ions in leaves. By and large, the application of salicylic acid (200 to 300 mg l-1) ameliorated the adverse effects of salt stress, particularly at the lower than 50 mM of salt concentrations.

Low availability of some nutrients is one of the major factors for the widespread occurrence of plant nutrient deficiency in calcareous soils. Therefore, any strategy for solution of this problem is important. This study aimed to evaluate the elemental sulfur (So) effect along with Thiobacillus bacteria on some chemical properties of soil (pH, EC, P, S-SO4, Fe and Zn) and nutrients uptake by maize (Single Cross 704). For this purpose, an experiment was carried out in four sites (Chogha Narges, Mahidasht, Najaf Abad and Ghomsheh) with different levels of available sulfur (7, 13, 18, 27 mg kg-1soil) in Kermanshah Province. Sulfur was applied at 0, 250, 500, and 1000 kg ha-1 as So and Thiobacillus neapolitanous inoculation using randomized complete block design with three replications in a during cropping season 2015-2016. Soil samples at 6-7 leaf, silking and post harvesting stage from each treatment plot was collected for determining pH, EC, P, S-SO4, Fe and Zn. The result showed that So significantly decreased the soil pH and adversely, increased EC, P, S-SO4, soil DTPA-extractable Fe, and Zn in the Chogha Narges, Mahidasht (p<0. 01) and in Najaf Abad and Ghomsheh (p<0. 05) at 6-7 leaves, silking and post harvesting stage compared with the control. The lowest pH and highest EC, P, S-SO4, Fe and Zn value was observed with 1000 kg ha-1 So at silking stage. Soil pH of Chogha Narges, Mahidasht, Najaf Abad and Ghomsheh, respectively 0. 62, 0. 6, 0. 33, 0. 24 decreased compared with the control. In contrast, soil EC 1. 01, 0. 91, 0. 69 and 0. 7 dS m-1, respectively was enhanced. P also in levels of 2. 4, 3. 7, 1. 5 and 1, available sulfur 18, 16, 15. 7 and 24, Fe 1. 4, 1. 48, 1. 3 and 0. 9, Zn 0. 51, 0. 57, 0. 34 and 0. 18 mg kg-1soil increased compared with control. After harvesting due to the reduced amount of sulfur oxidation and buffering capacity of soil, pH and nutrients gradually returned to its initial state. However, N, P, S-SO4, Fe and Zn uptake by maize was significantly increased with the application of So compared with the control. The highest nutrients uptake was observed with 1000 kg ha-1 So along with Thiobacillus bacteria.