نشریه تحقیقات کاربردی خاک
سال هفتم شماره 2 (تابستان 1398)

The effectiveness of different extraction methods for the prediction of available Cu concentration was studied in 21 calcareous surface soils (0-30 cm) in western Iran. The greenhouse experiment was conducted with single cross 704 (SC-704) cultivar of corn plant (Zea mays L.) with three replications. The leaf chlorophyll index, shoot dry weight and shoot Cu concentration were measured at the end of the growing period (after 60 days). Various extractants were applied for extraction of soil available Cu, including DTPA, AB-DTPA, AC-EDTA, Hydroxylamine Hydrochloride, and Ammonium Oxalate. According to results, extracted Cu by various extractants was insignificantly correlated with plant growth indices. However, significantly correlation was found between The Log DTPA-TEA-Cu and Log Root-Cu content. The highest (25.9 mg kg-1) and the lowest (1.57 mg kg-1) concentrations of extractable Cu was extracted with ammonium oxalate and DTPA-TEA respectively. The most significant correlation coefficient (r=0.93**) was obtained between AB-DTPA and AC-EDTA extraction methods.  Results revealed that the DTPA-TEA was the most effective Cu extractant in this study.

Plant-associated rhizospheric bacteria which form biofilms have higher positive effects on plants in fluctuating environments. Thus, to study of these bacteria, 50 rhizospheric samples were taken from grass geramineae roots. After preparing the suspension, 100 microlitere was cultured on TSA medium and then pure culture of bacteria was prepared. Resulted showed that up to 90% of these isolates were able to form biofilm, so that they could be categorized in five groups as: pellicle, very adherent, moderately adherent, weakly adherent and non-adherent. 16S rDNA analysis revealed six different genus of bacteria. Bacillus are the predominant group (80%) of robust biofilm forming in the grass geramineae rhizosphere. The water deficit tolerance of isolates was assessed by rising concentration of sorbitol (1, 10, 20 and 30 %, w/v). All isolates were able to grow in -25 bar matric potential. Isolates showed good potential to producing auxins ranging from 6 - 65 µg mL-1, ACC-deaminase activity (up to 2.14 µmol α-ketobutyrate in 36 h), Ca3(PO4)2 solublization ranging from 1.2 – 251 mg L-1 and K releasing ability 90 to 250 mg L-1. Only three bacteria were able to produce siderophore. It seems that these isolates can be suitable candidates for doing some greeanhaous or pot experiment subjected to protecting plants against water deficit stress. Moreover, they can act as plant growth promoting bacteria as well.

In order to study the different levels of nitrogen and different nitrate: ammonium ratios in saline and non-saline conditions on the content of chlorophyll, the amount of nutrients and essential oil of denaii thyme, a factorial experiment was conducted in a randomized complete block design with 30 treatments and 3 replications. Nitrogen in three levels (5, 10 and 15 mM), nitrate: ammonium ratios in five levels (100: 0, 75:25, 50:50, 25:75, 0: 100) and salinity in two levels (0 and 50 mM Sodium Chloride) were treated. Results showed that the concentration of nutrients, chlorophyll content and essential oil yield were increased by increasing in nitrogen amount. In terms of different nitrate: ammonium ratios, the concentration of potassium, sodium and chlorophyll content in plant were increased by increasing nitrate ratio, whereas the concentration of nitrogen, phosphorus, iron, copper and zinc in plant tissues were increased by increasing ammonium ratio. Salinity reduced the concentration of nutrients, chlorophyll content and essential oil percentage and increased sodium concentration in plant tissues. The highest percentage and yield of essential oil were obtained from the 75:25 ratio in non- saline conditions and from 50:50 ratio in saline conditions.

The average yield per hectare of lemon orchards in Iran, compared with the global average, has considerable distance. In general, environmental factors, especially soil and nutritional factors play a crucial role in the performance and growth of plants. That which agents will create more restrictions on Plant, it can be important on plant product management and its quantity improvement. To identify the nutritional status of lemon orchards in Hormozgan and determine the direct and indirect effects of factors affecting yield, the three major regions of the province (in terms of lemon gardens) reviews, the Hashtbandi, central Minab and Rudan and in each region 20 lime orchards (total 60 orchards) were selected. Then yield, some soil properties at two depths, irrigation water characteristics and nutrient concentration in leaves and some fruit quality parameters of lemon trees were determined. Data analysis and interpretation showed, in general, there was no nitrogen, phosphorus and potassium deficiency in most orchards, while an excess of chlorine and boron concentration caused yellowing and leaf margin burn in most orchards. Correlational studies showed that most of the characteristics (like clay, leaf chlorine and boron concentration) were significantly correlated with yield, had a negative impact on that. The result of path analysis showed that leaf chlorine concentration had the highest direct effect on the yield (90 %), while a direct impact of total calcium and magnesium was below one percent on the yield. Generally, the most negative effect on yield was by clay, water boron concentrations, and leaf chlorine concentration that the significant portions of these effects were direct. So it is recommended in order to increase yield that solutions be considered that directly mitigate the harmful factors.

Cation exchange capacity (CEC) is one of the most important soil properties. This property can describe many of soil properties such as soil fertility, specific area and soil water content. Whereas measuring this property is expensive, time-consuming and laboratory tools needed, hence, prediction of CEC using pedotransfer function (PTF) and soil easily properties is very important in soil science studies. So, the objective of the present study was to develop regression pedotransfer functions to predict the CEC using fractal dimension of soil particles. Consequently, 106 soil samples of UNSODA dataset were used. Fractal dimension of soil particle size was calculated and then was used to develop a PTF to predict the soil CEC. Performance of suggested fractal regression was compared the existed functions that use other soil properties as input. Results showed that between all soil easily properties only fractal dimension, % clay and organic matter had a significant coefficient. Suggested fractal regression model (R2= 0.62, RMSE= 5.3 and ME= 0.004) and validation (R2= 0.59, RMSE= 5.4 and ME= 0.054) had a better performance that other functions including suggested function, Bell and Vankulen. With considering of good performance of the suggested fractal function, applying fractal dimension that shows effects of soil texture with a number is approved.

Recognition of the distribution of various phosphorus forms influenced the activity of microorganisms in soil is essential for better understanding of their capacity to maintain and provide phosphorus for plants.  In this study to investigate the role of phosphate solubilizing bacteria (PSB) in the distribution of different forms of soil phosphorus, a surface soil sample (0-30 cm) were selected in West Azarbaijan with a loamy texture, Belongs to the Typic clacixerpts subgroup. An experiment was conducted as a factorial in a completely randomized design with two factors: Microbial treatments (control (no inoculation) and bacterial strains (Pseudomonas fluorescens and Bacillus megaterium) and sampling time (0, 7, 21, 45 days) in six replications. Soil samples were incubated at 28 ° C for a period of 45 days. Then, different forms of inorganic phosphorus, organic phosphorus and Olsen phosphorus were determined by sequential extraction method. Soil pH value 7.7, Clay soil tested 17% and activated calcium carbonate in soil 3.5%. Ca10-P formed was 45% of total phosphorus in the soil and indicates its importance in the calcareous soil. The results showed that the bacterial treatment caused significant changes in the amount of phosphorus, organic phosphorus and mineral phosphorus, the amount of available phosphorus, organic phosphorus and mineral form (di-calcium phosphate (Ca2-P)) in bacterial inoculation compared to control treatment increased 66, 15 and 92%, respectively.  However, the octa-calcium phosphate (Ca8-P) and apatite (Ca10-P) forms in the treatment of bacteria were reduced 13 and 5%, respectively. In addition, the Al -P form was increased 10% compared to control in bacteria treatment. In the treatment of bacterial significant correlation (r=0.84**) between P (Olsen-P) and (Ca2-P, O-P, and Al-P) was present in the soil. The amount of phosphorus in different forms in the treatment of bacteria was as O-P> Ca10-P> Ca8-P> Olsen-P> Ca2-P> Al-P at the end of incubation. The results showed that inoculation of bacterial, increase the solubility of the available phosphorus forms in the soil.

Knowledge of the spatial variability of soil properties is vital for improving productivity and sustainable management of agricultural practices, as it is directly contributing to variability in crop yields. This study was conducted to investigate the spatial variability of some soil properties and their relationships with spatial variability of tea yield in the Fouman region of Guilan province. Soil samples were collected from 0 to 40 cm depth in 70 observation points. The green tea leaves were harvested at a 4 m2 plot at each site. Physicochemical soil properties and tea yield were determined according to standard methods. In order to address the cumulative impact of soil properties on tea yield, some soil physicochemical layers were subjected to delineate the study area into management zones. Soil parameters varied throughout the study area and their coefficients of variation ranged from 5.1% to 37.2% for pH and available potassium, respectively. Experimental semivariograms indicated moderate to strong spatial dependencies for all selected parameters. Spatial distribution maps, derived by kriging interpolation, showed that the spatial trend of the yield was approximately similar to pH, organic carbon and available potassium, which expresses the spatial correlation of these soil properties with the tea yield in the region. Correlation analysis revealed that tea yield was significantly positively correlated with organic carbon and available potassium (0.53 and 0.37, respectively) while negatively correlated with pH (-0.45). The results suggested the significant effect of soil properties, especially pH, organic carbon and available potassium on the tea productivity. The results indicated that the study area was successfully delineated into four distinct management zones based on spatial variability of soil properties. The spatial variations of soil properties can be used to identify the major sources of variability in crop yields and also to delineate the management zones. Therefore, the spatial variability of soil properties provides a basis of information for sustainable production in the tea gardens in the study area.

In this study, two types of superabsorbents (Aquasorb and Stockosorb) and four types of salt including sodium sulfate, potassium chloride, calcium chloride and sodium chloride with the concentrations of 0.005, 0.05 and 0.1 M were used. The results showed that in the early stages of the experiment, the absorption capacity of Aquasorb was higher than the Stockosorb and after 30 to 45 min, the absorption capacity of Stockosorb in most cases was increased in comparison to the Aquasorb. The NaCl and CaCl2 salts in all concentrations had the minimum and maximum effects on the decreased of absorption, compared to the reference solution for both superabsorbents, respectively. The rate of absorption in all solutions decreased over time. Also, increasing the concentration of solutions reduced the absorption rate. In all solutions, in the early stages of the experiment, the reduction in absorption rate by Aquasorb was lower than of the Stockosorb. After the water absorption by Aquasorb in all concentrations, the salinity order of solutions was as follows: Na2SO4 > CaCl2 > KCl > NaCl. However, in the case of Stockosorb, there was no consistent trend among the different concentrations of solutions. According to the obtained results and based upon the more absorption capacity of Aquasorb compared to the Stockosorb at initial times, application of Aquasorb absorbent is recommended in the areas in which cloudburst takes place at times less than 30 min and in the dry farming areas. Also, according to the absorption results obtained within 24 h and the high absorption capacity of Stockosorb in comparison with the Aquasorb, the application of Stockosorb is recommended in the irrigated agriculture conditions.

Salinity as one of the major abiotic stresses severely affects crop productivity. Plant growth promoting bacteria is being considered to ameliorate salinity stress. Fifteen samples of salt affected soils from Golestan province were collected to isolate Azotobacter. Thirty- two bacterial isolates were isolated and purified. Physiological and biochemical tests confirmed twenty-three isolates belongs to Genus Azotobacter. The isolates were assessed for their growth in liquid medium supplemented with 2, 5 and 10 % of salt. Exopolysaccharide production, drought stress tolerant and some selected growth promoting properties such as nitrogen fixation, solubilization insoluble potassium, tri-calcium phosphate solubilization, indole acetic acid and hydrogen cyanid production capability was evaluated. Results showed that increasing salt concentration had negative effect on bacterial growth. Exopolysaccharide production (0.4-5.6 g L-1) was positive by 78.2% of the isolates. Higher levels of polyethylene glycol reduced growth of the isolates. Plant growth promoting tests showed tri-calcium phosphate solubilization (52.5-218.1 gL-1), IAA production (2.4 - 60.2 mg L-1), potassium solubilization (12.9-28.3 mg L-1) and biological nitrogen fixation (2.9 - 5.1 nmol ethylene hr-1). Among the 23 isolates to Azotobacter, based on physiological tests of bacteria in different levels of salt and drought and PGPR tests, isolate AZ13 was selected as the superior isolate.

With the increasing of demand for medicinal plants, the world consumption of garlic in many continues is growing. Therefore, the quality can influence the acceptability of the products by consumers. The study was conducted to investigate the effect of Zinc (Zn) and Manganese (Mn) micronutrients on yield and growth parameters of garlic (Allium sativum L.).  The experiment was laid out in Hamedan province during 2010-2012 as factorial experiment based on randomized complete block design with three replications. The experimental was conducted with four levels of Zn (0, 20, 40 and 60 kg ha-1) and three levels of Mn (0, 20 and 40 kg ha-1). As the results, the yield and growth parameters correlated significantly with increasing of zinc concentration. The highest yield (7997 kg ha-1) was obtained by application of 20 kg ha-1 zinc sulfate respective to the control (6099 kg ha-1). Significant correlation was obtained between Mn concentration and plant yield, and soluble solids concentration only. The interaction of Zn and Mn application were significant on number of gloves and brix. In general, to increase the yield and improvement the quality of garlic, application of 20 kg ha-1 zinc sulfate and 40 kg ha-1 manganese sulfate could be recommended for regions and conditions like of current project conditions.

Rill erosion is a major factor of soil loss in the marl formations. The marl formations are very susceptible to water erosion processes and cover a wide area in some watersheds in arid and semi-arid regions. Knowledge of temporal variation of rill erosion and its effect during a rainfall event can provide information on the mechanism of rill erosion in the hill slopes. Therefore, this study was conducted to investigate the temporal variation of flow characteristics and rill erosion in a marl soil under different simulated rainfalls. A laboratory experiment was carried out using 10 simulated rainfall intensities ranging from 10 mm h-1 to 100 mm h-1 with three replications. Soil samples were collected from the marl formations in west of Zanjan and separately purred to a flume with 4m in length and 0.94 m in width putted on 10% slope. Rill erosion and flow characteristics (discharge and concentration) were measured at 5-min from starting flow/ runoff in each rainfall intensity. Results indicated that there are substantial differences in the flow starting time, flow concentration and rill erosion among the rainfall intensities (P< 0.0001). Rill flow and erosion rapidly occurred with increasing rainfall intensity. Rill erosion increased speedily during rainfall and reached to approximately constant value in the last times (about 45 min). The flow concentration appeared also a similar trend with the rill erosion, while flow discharge showed an increasing trend in the last times. The study revealed that the threshold and pick time of rill erosion were strongly varied during rainfall. The variation trend of rill erosion during rainfall increases with increasing the rainfall intensity.

In order to study the effects of topography on morphological, physicochemical and mineralogical properties of soils, a toposequence composed of three land types (hills, plateau and piedmont plain) in Heydarabad region in the south west of Urmia Lake between Urmia and Mohammadyar cities was investigated. Considering the variations in slope and elevation, type two soil profiles were dug, described and classified in each land and soil samples were taken from genetic horizons and their physicochemical and mineralogical properties were determined using standard methods. According to the results, the depth of soil, solum thickness, the depth and thickness of calcic horizons, the values of clay content, organic carbon, cation exchange capacity, electrical conductivity and calcium carbonate equivalent of soils were increased with decreasing in the slope and elevation of region to the downward of toposequence. Additionally, in the lower part of toposequence (piedmont plain land type), vertical translocation of clay has been lead to the formation of argillic horizons. According to clay mineralogical investigations, illite, smectite, chlorite, kaolinite, vermiculite and palygorskite were the major clay minerals in these soils. Clay mineralogical investigations revealed that in the higher parts of toposequence (soil profiles 1 and 2, hills land type) illite and chlorite were the common clay minerals. Gradually, with decrease in slope, the content of smectite in soils were increased and reached to the highest value and become the dominant clay mineral in the lower part of toposequence (soil profiles 5 and 6, piedmont plain land type). In soil profile 4 (plateau land type), in addition with smectite and illite, palygorskite is present as one of common clay minerals. Variations of topography from hills to plateau and piedmont plain have been effected the value of runoff, the amount of penetrating water and vertical translocation of salts and so affected the development and evolution of soils. Finally, differences in physicochemical and mineralogical properties of soils have been lead to the differentiation of soils along toposequence and their classification in three orders Entisoils, Inceptisols and Alfisols.

The effect of sugarcane rhizospheric secretions and phosphate solubilizing bacteria on soil phosphorus desorption kinetic was examined at greenhouse conditions. The experiment was carried out with two treatments, including phosphorus levels (0% (blank, P0), 50% (P50) and 100% (P100) and phosphate solubilizing bacteria strains (Enterobacter cloacae R13 (R13) and Enterobacter cloacae R33 (R33). Soil sampling was conducted in 60, 95 and 140 days after planting. Statistical evaluation was performed as completely randomized factorial design with three replicates. The kinetics of phosphorus desorption was investigated by successive extraction method during 30 to 5760 min. According to results, high percentage of phosphorus fertilizer and phosphate solubilizing bacteria lead to increase of phosphorus desorption. Desorption kinetics was described by second order and power function equations well. Comparison of power function equation parameters among various treatments showed that the maximum coefficients were obtained at the lowest phosphorus fertilizer and phosphorus solubilizing bacteria. The reverse relationship was found between soil available phosphorus concentration and kinetic power function parameters, based on correlation analysis. Using of phosphorus solubilizing bacteria enhance the phosphorus bioavailability for plant.

Water infiltration is one of the most important properties of soil. The importance of infiltration process has led to development of several theoretical and empirical infiltration models. However, the applicability of these models is strongly subjected to the method of infiltration measurement. In this study, double ring infiltration data were collected from different regions of Iran with different soil textures. On the other hand, HYDRUS-1D model was used to simulate vertical infiltration through forward solution of the Richards’ equation. Van Genuchten-Mualem model was used to quantify the soil hydraulic properties. For this purpose, the hydraulic parameters of van Genuchten-Mualem model were optimized using inverse modeling in the HYDRUS, for each region's soil and were used for simulation. In order to evaluate the accuracy of the Horton, Kostiakov, Kostiakov-Louis and Philip models, based on measured and simulated infiltration data, mean error (ME), root mean square error (RMSE), mean absolute mean error (MAME), Pearson correlation coefficient (r) and modeling efficiency (EF) statistics were used. The results indicated that the Kostiakov-Lewis model has had the best performance in different soil textures based on measured double ring infiltration data. Horton model has had the best performance based on HYDRUS simulated infiltration data in different soil textures. The Philip model had the least efficiency in estimating cumulative infiltration based on both measured and simulated infiltration data.

Different factors may affect potassium (K) content in calcareous soils. Potassium forms distribution as a function of various soil physicochemical properties was examined on seventy surface (0-20 cm) and subsurface (20-40 cm) soil samples of Kohgilouye and Boyerahmad province, southwest of Iran. Soil physical, chemical and mineralogical properties were determined according to standard methods. The soil was classified in Xeric and Ustic moisture regimes and Mexic, Termic, and Hyperthermic thermal regimes. As the result, the common clay minerals associations were found to be illite, smectite, chlorite and palygorskite with less content of vermiculite, kaolinite and quartz. Smectite, illite, and palygorskite were the main clay minerals occurring in humid and arid regions respectively. Soil soluble, exchangeable, non-exchangeable and structural K concentrations ranged from 1.2-12.1, 111-521, 153-1705 and 4584-10379 mg kg-1 at the surface and 0.2-5.0, 25-403, 72-1016 and 3227-9541 mg kg-1 at the subsurface soil samples respectively. Exchangeable, non-exchangeable, structural and total K concentrations positively correlated with soil clay content and cation exchange capacity (CEC), however negatively significant correlation was obtained with calcium carbonate content. Different forms of K (except soluble K) had positive and significant relationships with each other (r of 0.48-0.99) and this indicated the equilibration among K forms. Mineralogical studies indicated the positively influence of clay minerals, especially illite and smectite, on exchangeable and nonexchangeable soil K. While the structural and total K contents most affected by smectite and illitic clay minerals. Future studies are required about the mineralogy of soil sand and silt fractions and their influence on soil K status.