نشریه مدیریت خاک و تولید پایدار
سال چهارم شماره 2 (پیاپی 8، تابستان 1393)

In order to study the effect of potassium, zinc and silicon spray on agronomic characteristics and their absorption on rice grain of var. Tarom Hashemi, a factorial experiment was carried out in randomized complete block design in four replications in 2011 in Amol city. Treatments include potassium (0 and 250 kg of potassium sulfate in hectare) and zinc (30 and 0 kg of zinc sulfate) as soil application and silicon treatment include non silicon and spraying of 5 per thousand of calcium silicate. Results showed that yield of grain increased 2.9 percent by using potassium sulfate and 3.7 percent by zinc sulfate significantly. Zinc concentrations of seed increased by application and non application of zinc sulfate to 65 and 52.81 mg/kg respectively. The spraying of silicon caused the increase in whole numbers of sub-cluster in panicle (6.8 percent), the sub-cluster fullness (0.4 percent), the concentration of silicon in seed (52.11 percent) and the concentration of zinc in seed (27.2 percent) significantly. The highest length of panicle and the greatest numbers of tiller in plant, the whole number of sub-cluster in panicle, the percent of sub-cluster fullness and the maximum weights of thousand seeds were obtained under the interactions of three elements in zinc sulfate treatment without potassium and silicon. Considering the effects of zinc fertilizer on yield and yield components and also their concentration in seed, the above research recommends application of this fertilizer in rice.

Soluble potassium is the most available form of potassium for plants and it is very important for crop production. This study investigates the effect of some salts, different volumes and solutions of leaching on the soluble potassium in soil. The experiments were factorial based on completely randomized design (CRD) using four salt treatments consist of control, calcium chloride, calcium sulphate and sodium chloride; three leaching solutions (distilled water, potassium chloride and potassium sulfate); eight irrigation steps (each irrigation step equals 236 millimeter or 0.25 pore volume) and three replications, which were conducted in laboratory conditions using soil columns. At the end of experiment, the soluble potassium concentration was measured in the soil columns. The results showed that among the salt treatments, the highest amount of the soluble potassium leaching was observed for calcium chloride treatment, but its differences with sodium chloride, calcium sulphate and control were significant. Moreover among the leaching solutions, potassium chloride compared to potassium sulfate and distilled water had higher effect on decreasing soluble potassium in the soil solution. Also with increasing leaching volume, the concentration of soluble potassium significantly decreased. The findings of this research showed that the importance of salinity, leaching volume and potassium fertilizer should be regarded on the soluble potassium in order to prevent the losses of this form of potassium for plants.

In order to investigate the effect of mycorrhizal inoculation on growth criteria and uptake of nutrient in lettuce (lactuca sativa L. cv Syaho), a completely randomized experiment with five replications was conducted in Research Greenhouse of Horticultural Department of Mohaghegh Ardabili University at 2010. Experimental treatments include inoculation of plants by two species of Arbuscular mycorrhiza Glomus intraradices and G. fasciculatum and control. Results from analysis of variance revealed that the effect of mycorrhizal inoculation on plant height, leaf number and surface, chlorophyll content of leaves, fresh and dry weight of plant and stomatal conductance were significant (P≤0.05). Mycorrhizal inoculation enhanced vegetative growth parameters significantly in comparison to control and the highest value for these traits obtained by inoculation of plants with G. intraradices. The effect of inoculation of plants by two species of mycorrhizal fungi on the content of elements such as nitrogen, phosphorous, potassium and calcium were significant (P≤0.01). Inoculation of plants by mycorrhizal fungi enhanced nutrient uptake significantly in comparison to control. In general inoculation by mycorrhizal fungi in addition to enhancing growth parameters can enhance the postharvest quality of lettuce plants via increasing the uptake of potassium and calcium.

Functions that accurately relate penetration resistance to soil properties are important tools for assessing the spatial variation of soil mechanical resistance when the temporal and spatial variability in these parameters cannot be readily measured. The importance of this characteristic has encouraged the soil researchers to model this process for quantitative applications. In this study, the performance of twelve penetration resistance models were evaluated for two depths. i.e. 0-40 and 40-80 cm. For this purpose, the penetration data were obtained using of digital penetrometer from 150 points of different Khuzestan sugarcane agro-industry. The parameters of these models were then determined using the least square optimization method. In order to evaluate the accuracy of the models, the mean error (ME), root mean square error (RMSE), mean absolute of mean error (MAME) and Pearson correlation coefficient (r) statistics were calculated. The results of comparison models performance revealed that the whole proposed regression models based on moisture content and bulk density had lower error and higher r in estimating the penetration resistance. Furthermore, the models proposed by To and Kay based on pore water suction and Dexter et al. based on the slope of the water retention curve at its inflection point and effective stress have highest error and lowest r in estimating the penetration resistance. Generally, all of the evaluated models were systematically over-estimator models.

In order to study the effect of some organic and bio-fertilizers on the analysis of metribuzine residue in soil, a Factorial experiment was conducted in a randomized complete block design with three replications at the Faculty of Agriculture, Shahrood University in 2011. Threatments included three levels of organic fertilizers (vermicompost, cow manure and control) and biological fertilizer in four levels (Pseudomonas putyda, Pseudomonas fluorescens, Azotobacter chrococcum and control). For determination of metribuzine residue, soil samples were taken from 0 to 15 cm soil depth, (2 hours), 3, 8, 32, 55 and 90 days after herbicide application. Then metribuzin residue was measured with HPLC. Results showed that, the bacteria population increased 86 percent by the interaction effects of vermicompost × Pseudomonas fluorescens than control treatment. The rate of herbicide degradation decreased 23 percent and the half-life of herbicide increased 26 percent with application of cow manure × Azotobacter chroococcum than control treatment. However, the application of vermicompost with Pseudomonas fluorescens increased the herbicide decay rate by 37 percent and decreased the half-life of herbicide by 52 percent compared to control treatment. Based on our results, organic and biological fertilizers by their synergistic effects can change the rate of metribuzine degradation and persistence in soil.

In this study, considering the importance of erosion and sedimentation in the forest roads, especially, sediment delivery and transmit to streams and rivers via forest Roads of the Darabkola forest watershed was studied using WARSEM. Therefore, field and direct measurements of the model input factors for 63 different segments of the path length of 12 kilometer of forest roads in the study area was done. In order to evaluate model resultants, erosion and sedimentation rate in the road surface and their different parts was measured using a rain simulator. Also, to evaluate results, paired t-test, Nash-Sutcliffe coefficient, BIAS and RMSE were used. Results showed that the rate of sediment delivery from road surface to streams and rivers the conventional WARSEM and rainfall simulator was 328 and 174 ton per year and sediment production of study roads was 9.9 and 4.1 kilograms per square meter per year respectively. The results of the statistical methods of Nash-Sutcliffe coefficient, BIAS and RMSE for the model were as well as 0.3, 0.2 and 4.5 respectively and in 95% confidence level, there was not any significant differences between observation data and estimation data. Therefore, aforesaid model have the appropriate accuracy and efficiency to estimate the rate of erosion and sediment product of the Darabkola forest roads surface and forested watersheds with a similar Conditions. Also, after assessment and analysis of observed sediment rate in watershed outlet it was specified that according to WARSEM model and direct measurement 16% and 9% of produced and transmitted sediment has been originated from study forest roads surface.

Plant Growth Promoting Rhizobacteria (PGPR) is referred to a heterogeneous group of beneficial rhizosphere bacteria that could enhance plant yield through one or more mechanisms. In this study, some of Plant Growth Promoting Characteristics such as solubilizing of insoluble inorganic phosphate, ability to production of ACC-deaminase enzyme and auxin were evaluated in 60 Rhizobia (belonged to the species Rhizobium leguminosarum biovar phaseoli, Rhizobium leguminosarum biovar viciae and Sinorhizobium meliloti) selected from Gene Bank, Department of Soil Science, Tehran University. Results showed that all isolates have the ability to produce auxin, ranging from 0.45 to 10.86 mg/l averaged by 2.76. Also, 25 isolates (41.6%) showed the ability to produce ACCtransaminase. The results of evaluation of solubilizing of insoluble inorganic phosphate in sperber solid media revealed 73% of strains was able to phosphate solubilizing and the ratio of halo diameter to colony diameter was ranging from 1.05 to 2.07 in 12 day after incubation. Also, in sperber liquid media the amounts were between 3.2-158.6 mg/l after 120h of incubation. There was a significant negative correlation (r= -0.906**) between solubilized Phosphorus and the final pH of the growth medium. In this study, isolates belonged to the species Sinorhizobium meliloti in all characteristics were powerful than the other isolates. So, it is suggested to select and prepare the inoculum superior isolates belonging to this species and to evaluate their effects for the promotion of quality yield of different agricultural crops, as a biologic alternative and environmental friendly.

In order to reduce Pb phytoavailability for spinach (Spinacia oleracea L.) using P amendment, (DAP, TSP 1:1 ratio acid phosphoric and phosphate rock), a factorial experiment based on completely randomized design was conducted and analyzed 100 days after the P applications using a sequential extraction method. Sequential extraction analysis indicates that P was effective in transforming soil Pb from non-residual fractions (SS, SE, CA, Fe-Mn form and Pb in OM) to a residual fraction. Results revealed that DTPA extractable Pb was reduced in treated soils, however, among these three treatments, DAP at 9 molar ratio of P/Pb was the most effective. Results of greenhouse experiments showed that the amount of lead in aerial parts of spinach had the highest lead in 1:1 ratio of acid phosphoric and phosphat rock and the DAP had the lowest. In DAP treatment, the Pb concentrations in shoots of spinach decreased 72% as compared with the control treatment. The results suggested that P amendments especially DAP can lower the bioavailability and increase the geochemical stability of soil Pb, so it has the potential for in situ remediation in Pb-contaminated soils.

To study the characterization of root colonization index in cowpea and maize by using Mesorrhizobium bacteria and mycorrhiza in intercropping, an experiment was carried out in research field of Shahrood University of Technology province in 2010 in a randomized complete block design with three replications. Experimental treatments include: monocropping maize, Bean monocropping, series based additive intercropping 100% maize and 100% Beans, maize monocropping + Mycorrhizal, Bean monocropping + Mycorrhizal, Bean monocropping + Mesorhizobuim Bacteria, Bean monocropping + Mycorrhizal + Mesorhizobium Bacteria, Intercropping + Mycorrhizal, Intercropping +Mesorhizobium Bacteria Intercropping + Mycorrhizal + Mesorhizobium Bacteria. The results showed that treatment effects on root length of cowpea, root dry weight of cowpea, root nodule number of cowpea, nodule dry weight of roots cowpea, beans and corn roots, colonization index of root cowpea and maize plant height and plants leaves were significant (P<0.01). The highest root length of cowpea, number of root nodules of cowpea and cowpea roots colonization index were observed in intercropping with mycorrhiza fungi and Mesorrhizobium treatment. Also the highest percent of root colonization of maize was 71.33 percent relating to the intercropping treatment. Soil phosphorus was 42.20 ppm relating to the treatment of bean with Mesorhizobium bacteria and the lowest level of phosphorus in soil were intercropping with bacteria Mesorrhizobium treatment.

Soil cone index as one of the criteria that states mechanical strength of the soil is affected by many factors including soil moisture content and soil compaction. Despite widespread progress in the development of precision agriculture, crop production management in relation to soil physical properties goes back to the last few years. One of the most important soil characteristics that affects crop yield is soil mechanical resistance. This characteristic is expressed generally by soil cone index maps. In this study, for measuring and determining the factors affecting soil cone index, field experiments were carried out on three soil types. Within each soil type, the factorial experiment based on randomized complete block design (RCDB) with five replications was used. The effects of soil moisture content at three levels (dry, semi-humid and humid), sampling depth at three levels (0-10, 10-20 and 20-30 cm) and number of tractor traffic at three levels (0, 10 and 20 Time passes) was investigated on soil cone index. After data analysis, it was revealed that the effects of soil type, sampling depth, different levels of soil moisture and tractor traffic were significant on soil cone index values (P<0.01). In order to develop a mathematical model for soil cone index, multivariate linear regression was used. Independent factors were soil moisture content, soil bulk density, electrical conductivity and sampling depth whereas soil cone index was the dependent factor. The results showed that the effect of all independent variables on soil cone index as the dependent variable were significant at probability level of 1%. Back propagation neural networks with three different training algorithms (gradient descending algorithm with momentum, descending scaled gradient and Levenberg-Marquardt) were adopted for predicting soil cone index parameter. Back propagation neural networks with Levenberg- Marquardt training algorithm presented better accuracy in simulation and prediction as compared to others. Using Levenberg-Marquardt training algorithm with two hidden layers with 34 neurons in each layer presented the best performance than other algorithms and even Levenberg Marquardt training algorithm with one layer. Comparison of results of artificial neural network models and regression models to predict the soil cone index indicated that the neural network model could model soil cone index values with higher accuracy than the regression models. The results of this study could be utilized in soil compaction management of Ardabil plain soils and also in determination of the optimum tillage depth in these areas.

This study was carried out to determine different forms of potassium in relation to chemical and mineralogical properties of soils of Eskan Ashaier region, Nour-Abad Mammasani of Fars Province. For this study after field studies and preparing soil maps, four soil profiles have been selected. Some physical, chemical, different forms of potassium (soluble, exchangeable, non-exchangeable and total) and types and relative amounts of clay minerals of selected soils were determined. The results showed that the soils of hills and alluvial-colluvial fans are Entisols, while in piedmont plains they are Inceptisols and Mollisols. The results of mineralogy of clay showed that the dominant mineralogy of soils of hill physiographic unit are illite, chlorite, smectite and quartz. The dominant minerals of alluvial-colluvial fans are illite, chlorite, smectite and kaolinite and finally the dominant minerals of piedmont plains physiographic unit are smectite, illite, chlorite, kaolinite and vermiculite minerals. The Mollisols order located on piedmont plains by having a high clay content, high cation enchange capacity and dominant smectite mineral, have also higher amounts of structural and total potassium than in any other orders. The Entisols order located on piedmont plains have a greater relative amounts of illite and chlorite, exchangeable and nonexchangeable potassium than in the other other orders. The Entisols located on hill have higher soluble potassium content than the other order and Inceptisols located on the piedmont plains, by having more than 55 percent carbonates and less than 25 percent clay content, have the lowest amounts of different potassium forms.

Bioreduction of ferric iron in anoxic conditions with respect to biological and environmental aspects is an important process. This process is considered in paddy soils and mostly controlled by microbial activities. Ferric iron is one of the most terminal electron acceptor in these soils. Present study with the aim of isolation and identification of some bacteria with high ability in ferric iron reduction in paddy soils of northern Iran was conducted. Testing of ability of isolated ferric iron reducing bacteria was conducted in nutrient broth according to biogenic Fe (II) produced and the results was compared with Shewanella sp that showed the highest concentration of ferrous iron. Then three superior bacteria were chosen and genomic DNA of these bacteria tested by using of PCR and fd1 and rd1 primers for 16S rRNA amplification sequence analysis. By using the BLAST program of these isolates and isolates in data bases, all selective isolates were belonged to Bacillus sp. Sequence of PS11 isolate showed 99.4% of homology with Geobacillus stearothermophilus and PS23 showed 98.4% homology with PS23 and B. subtilis. Sequence of PS23 also showed 98% homology with B. subtilis and B. thuringiensis that these isolates have ability to reduce ferric to ferrous iron in vitro conditions.

The usage of soil microorganisms which they have ability of dissolving fixed phosphorus, is one of the effective ways to increment the uptake of phosphorus in calcareous soils. In order to study the roles of phosphate solubilizing bacteria on the availability of P in the sorghum, a pot experiment was conducted as a factorial in completely randomized design with eight treatments and three replications. The experimental factors were different phosphorus levels and phosphate solubilizing bacteria (Bacillus megaterium). The treatments were combination of four P levels (zero, 25, 50 and 75 mg/kg P2O5 from triple super phosphate source) and the two treatments of phosphate solubilizing bacteria (with bacteria inoculation and without bacteria inoculation). The results indicated that utilizing the phosphate solubilizing bacteria increased significantly (P<0.01) the dry matter yield, nitrogen, phosphorus and potassium uptakes but had not significant effects on iron, manganese and zinc uptake. Phosphorus application also had a significant effect (P<0.01) on some indicators such as plant height and diameter, dry matter yield, shoot P concentration and shoot P uptake. Combined using of both phosphorus and phosphate solubilizing bacteria had a significant effect (P<0.01) on the stem diameter, dry matter yield, shoots phosphorus concentration, nitrogen, phosphorus, iron and manganese uptakes by sorghum.

The present study was carried out to study the germination and growth capability of three plants including alfalfa (Medicago sativa L.), flax (Linum usitatissimum L.) and wheatgrass (Agropyron elongatum (Host). Beauv) in contaminated soils with petroleum sludge produced by Isfahan Oil Refinery in a greenhouse experiment. The air-dried petroleum sludge sample was added to an uncontaminated soil at ratios of 0 (control), 10 and 20% (w/w) and mixed thoroughly. Plastic pots were filled with called mixture (2 kg). The experimental layout consisted of split-plots were arranged in a completely randomized design with three replicates. The results showed that with increasing sludge from 0 to 10 and 20%, the wheatgrass germination decreased significantly (P≤0.05). In alfalfa and flax, no significant differences were observed in seed germination percentage among petroleum sludge treatments. The mean values of plant heights and root and shoot dry weights for wheatgrass in 20% petroleum sludge showed a significant reduction when compared with control. By increasing the amounts of petroleum sludge from 0 to 20%, Root and shoot dry weights decreased by 46.6 and 93.3% in alfalfa and 41.1 and 82.2% in flax respectively. Although both alfalfa and flax have higher germination capability in comparison with wheatgrass but they showed less biomass production. Therefore, cultivation of alfalfa and flax is not recommended for petroleum phytoremediation, explicitly due to lower biomass production. In brief, wheatgrass could be a suitable species for phytoremediation of sludge petroleum, as this plant produces more roots than shoots and more fibrous root systems.

Continuous operation and improper tillage in agricultural lands resulted in soil organic matter loss and soil structure destruction which in turn yield reduction would be caused. The aim of this study, is to assess and compare the amount of soil carbon sequestration in Aq Qala plain in Golestan province under different tillage systems (including: no-tillage, minimum and conventional tillage). In this study, soil samples were taken from 0-25 and 25-40 cm depth in each field. Treatments were replicated three times in a randomized complete block design. Some soil properties such as soil organic carbon, bulk density, carbon sequestration were measured. The results showed that the amount of carbon sequestration increased 36% and 33% and organic carbon increased 1.8% and 1.7% respectively by no-tillage and minimum tillage. Similarly, bulk density was 1.63, 1.62 and 1.62 grams per cubic centimeter, respectively for no-tillage and minimum and conventional tillage. Based on the results of this study, no-till system would be a useful method to site preparation because of its positive role on soil fertility and conservation in agricultural land.