Applicable
Precised Equipment
N. Ahangarnezhad1; Rouzbeh Abbaszadeh; Ahmad Norouzian
Abstract
Introduction Plants are able to respond to stresses or environmental factors. Application of electricity, magnetism, monochromatic light and sonic waves for increasing growth rate is called electro-culture. These factors can affect growth of plants. Many studies have shown that magnetic fields can affect ...
Read More
Introduction Plants are able to respond to stresses or environmental factors. Application of electricity, magnetism, monochromatic light and sonic waves for increasing growth rate is called electro-culture. These factors can affect growth of plants. Many studies have shown that magnetic fields can affect the organisms. However, the exact mechanism of this effect is still unclear. A description of possible multiple effects of magnetic field on living organisms is oxidative stress due to increased production of oxygen species that is with the mediation of iron. considering the development of the lawn field in the country and the value of this plant, the aim of this study was to investigate the influence of magnetic field on the growth of grass seeds and determine how to optimize the magnetic field. Materials and Methods In this study, the effect of AC magnetic flux density and exposure time of magnetic field on germination of grass seed (Festuca arandinacea) was investigated using an electro-culture system. Helm Holtz coils were designed to a create uniform field in the electro-culture system. Helmholtz coil radius and its average height were 18 cm, consisting of two coils to create a uniform magnetic field strength. Pulleys were made of polyethylene. After construction of pulleys, 500 turns copper wire with 1 mm diameter was wrapped around the pulleys. In the coil design, dimensions and materials were selected such that they could bear the weight of the wires and the created heat. In order to create distance between the coils, four stands were used. The stands had possibility of changing their length. Sinusoidal alternating magnetic field was created by applying 50 Hz alternating current to the coils, which were connected in series circuit. Magnetic flux densities were 0.1 and 1 mT, exposure times were 15, 60 and 240 minutes and there was a control treatment (without magnetic field). The design was completely randomized with four replications For evaluation of the electro-culture system, germination percentage, germination rate, mean germination time, and shoot length of every treatment were measured. The current of the coils was controlled using Varyak (an electrical transformer with only one coil for voltage control). Multi meter was attached in series between Varyak and Helm Holtz coil. Tesla meter was applied for measurement and detection of the magnetic field. Electromagnetic flux density 0 (for control), 1.0 and 1 mT at duration of 15, 60, and 240 minutes was applied to the grass seeds. Germinator was used with 13 hours of darkness, and 11 hours of light at constant temperature 20 ± 2° C, respectively. Daily counting of the germinated seeds was done for a week and at the specified time. More than two millimeters root seeds were counted as germinated seeds. On the last day, shoot length for at least five explants from each repeats was measured. Then all data was analyzed using SPSS software and factorial test. The analysis of variance and the mean comparison (Duncan) were performed for the data. Results and Discussion For the mean time of germination, due to the lack of significant interaction between factors, the main effect of magnetic flux density was studied. But for other indices, mean comparison was done for the interaction effects too. Generally, increase of exposure time could improve germination. The best treatment was application of 1 mT magnetic field for 60 minutes. The results showed that magnetic field had a significant influence on the measured traits and most of them showed better results comparied to the control treatment. Coparison between control and optimal treatments, showed that germination percentage, germination rate, mean time germination and shoot length improved to 124%, 155%, 8% and 64% respectively. Maximum rate, germination percentage and shoot length of grass seed obtained at 1 mT magnetic field with 60 min exposure time. Grasses have high water requirements during germination and growth and they must be irrigated constantly. If the condition of growth and germination improves, the water could be saved. Magnetic field can affect exchange of ions in the cell membrane. Distinction of this effective mechanism in electric culture requires more studies by researchers of biology and other related areas. The most investigations should be done to study the effect of magnetic fields on germination by magnets or direct current which is usually easy to create, while in this study the alternating field could have different effects. The other advantage of the system is its ability to create a uniform magnetic field and the possibility to create different fields through changing the current. Conclusions An electro-culture system was designed using alternating magnetic field to stimulate early growth of grass seed as a non-chemical, non-invasive and non-destructive driving factor in the growth. It seems electromagnetic field application can improve cultivation of grass seeds. Further is still needed in this area; the effect of fields from 2 to 4 mT at 60 to 240 minutes should be studied. However, for germination tests, a large number of treatments may lead to reducing accuracy and in this regard limitations should be taken into consideration. Further tests are needed to investigate this new approach.
Applicable
Energy and Renewable Energies
M. Soleymani; Alireza Keyhani; Mahmood Omid
Abstract
Introduction Replacing fossil fuels with renewable and environmentally friendly fuels is so essential, due to issues such as climate change, increasing fossil fuels prices, energy security and limitations of fossil fuels resources. Alternatives are wind energy, solar energy, geothermal energy, hydropower, ...
Read More
Introduction Replacing fossil fuels with renewable and environmentally friendly fuels is so essential, due to issues such as climate change, increasing fossil fuels prices, energy security and limitations of fossil fuels resources. Alternatives are wind energy, solar energy, geothermal energy, hydropower, biomass and biofuel. Currently, ethanol produced from sugarcane in Brazil or from corn in USA is the most dominant bioufuel in the world. However there is no comprehensive agreement on the environmental benefits of alternative fuels including ethanol. The aim of this study was to conduct a LCA (Life Cycle Assessment) on ethanol produced from sugarcane molasses in Iran and also to compare its environmental impacts with a conventional fossil fuel. Materials and Methods All required data was obtained from Sugarcane Agro-industry and ancillary Industry Development, Karoon Agro-Industry and also from recorded databases. Economic allocation was chosen to allocate emissions between the main product and the byproducts. Also, Simapro software was applied to model and evaluate the life cycle environmental effects in the life cycle of sugarcane molasses based ethanol (from cultivating sugarcane to burn ethanol into the engine). Two different scenarios of ethanol production (existing system and modified system) were considered and the environmental impacts of these two systems were compared with each other. Finally the environmental impacts of whole life cycle of molasses based ethanol were compared to that’s of diesel as a conventional fossil fuel. Results and Discussion Life cycle inventory results showed that electricity, P2O5 and urea respectively had the most negative environmental impacts through the life cycle of molasses based ethanol. Replacing the fossil fuel originated electricity with electricity from renewable resources can have a significant effect on reducing the amount of these negative impacts. Also, producing electricity in the nearest location to the consumption sites will reduce the power transmission losses and consequently reduce these impacts. Since the major share of electricity is used for pumping water to the field, better management of water consumption is so essential. According to the results, in case of emissions, there was significant difference between diesel fuel and sugarcane molasses ethanol in the base scenario. But by modifying the production system and using bagass to produce biogas or electricity (scenario 2), the environmental impacts of life cycle of sugarcane molasses based ethanol would reduce by 10%. Even now, the amount of greenhouse gas (GHG) emission of ethanol is 60% lower than these emissions of diesel fuel. This reduction will reach 70% if wasted bagass in ordinary production system is used to produce biogas and electricity. Comparing with diesel fuel, Molasses based ethanol had less negative impacts on impact categories such as Respiration Inorganics, Climate Change, Acidification/Eutrofication, and fossil fuels and more negative impacts on categories such as Land Use and Carcinogens, only because of using land and also using herbicides and pesticides to cultivate sugarcane. Greenhouse gas emission in the life cycle of one mega joule molasses based ethanol, estimated by Biograce model, is respectively 69, 70 and 60 percent lower than that of gasoline, diesel and natural gas. Due to undeveloped industries to process sugarcane and its byproducts in Iran, studies on the production of ethanol from molasses or electricity from bagass are in the area of waste management. Therefore, in these cases, even if it there was suitable energy or environmental indicato, continuing the production of these products is justified according to other side issues including environmental benefits and employment. Conclusion In terms of environmental aspects, in the current situation there are no significant differences between ethanol and diesel. But if bagass is used to generate electricity, the environmental impact of ethanol production will reach reduced by 10%. Greenhouse gas emissions of ethanol is 60% lower than that of from diesel and this amount will be 70%, if wasted bagass is used to produce biogas or electricity. It is possible to obtain more environmental benefits by applying appropriate management strategies in ethanol production system (such as producing value added products from bagass or other waste materials). Since sugar is the main product in sugarcane industry in Iran and approximately all other byproducts are wasted, to prevent the loss of this valuable byproduct, producing ethanol from molasses, even if in current situation and with current production system is acceptable.
Applicable
Soil Physics, Erosion and Conservation
Vajiheh Dorostkar; Reyhane Vali
Abstract
Introduction Crop production in arid and semi arid regions especially in saline soils always has many problems. Soil low organic matter content is one of the limiting factors in arid condition. Incorporation of plant residues is a good strategy for increasing the soil organic carbon and consequently ...
Read More
Introduction Crop production in arid and semi arid regions especially in saline soils always has many problems. Soil low organic matter content is one of the limiting factors in arid condition. Incorporation of plant residues is a good strategy for increasing the soil organic carbon and consequently for improving soil physical quality (34). However, some studies have shown that addition of organic matter in to the soil can increase soil water repellency (17, 18). This study was conducted to investigate the effect of grape leaves and pomegranate peels on the soil structural stability and soil water repellency in different salinity levels. Materials and Methods The arable soil was collected from the soil surface layer (0–20 cm) of Bastam Agricultural Research field in Semnan province and passed through a 4 mm sieve. A greenhouse experiment was conducted with three treatments including plant residues type (Grape leaves and pomegranate peels), amount of plant residues (0, 2 and 5 g 100 g-1 soil ) and salinity (1.5, 7 and 15 dS m-1). Plant residues were collected from grape and pomegranate gardens and after drying, milled and passed through a 1 mm sieve. Plant residues were mixed with soil and salinity treatment was applied with calcium chloride salt. Pots were filled with mixture of saline soil and plant residues and incubated in the greenhouse for 50 days. The soil organic carbon, soil hot water and diluted acid carbohydrate, soil microbial basal respiration, water dispersible clay and soil water repellency were measured at the end of the experiment. Results and Discussion Pomegranate peels increased the soil organic carbon content and hot water and diluted acid carbohydrates more than the grape leaves (Table 5) due to greater C:N ratio and lower microbial decomposability (37). Soil microbial basal respiration was 15.5% lower in pomegranate peel treatments than grape leaves and (Table 5). Water dispersible clay decreased by increasing the amount of plant residues (Table 8). Soil organic carbon increased by the amount of plant residues. Soil organic carbon is an important factor in stability of soil aggregate and consequently decreases the soil water dispersible clay (7). Strong negative correlation between soil organic carbon and soil water dispersible clay can confirm these results. In addition, the soil carbohydrates are known as an important factor in stability of aggregate especially for macroaggregates (40). Salinity increment from 1.5 to 15 dS m-1 caused a reduction in water dispersible clay from 45.1 to 31.2 g kg-1 soil (Table 9). Calcium as a divalent cation is an important factor in soil structural stability and probably decreased the soil water dispersible clay (7). Soil repellency index was greater than 1.95 in all treatments and ranged from 2.3 and 5.9 in different treatments. These results indicated subcritical soil water repellency in soil. Soil water repellency index increased 38 and 67 percent in treatments with 2 and 5 g residues 100g-1 soil compared to control treatment (no residue) (Figure 3). In addition, soil hydrophobicity was 10% higher in the pomegranate peels treatments than in grape leaves treatments (Figure 4). Soil organic carbon and soil hot water and diluted acid extractable carbohydrates concentration increased by the plant residues addition. The soil organic components have a hydrophobic and a hydrophilic parts and the orientation of hydrophobic parts on the soil particle surface can make a repellent soil surface (6). Soil calcium (Ca+2) concentration increased by salinity. This divalent cation in the soil solution could act as a bridge between the soil particles and functional groups of dissolved organic matters. This bridge could facilitate covering of soil particles by hydrophobic compounds and make a more stable soil structure by flocculating soil particle at high salinity levels (7). The hydrophobic coatings on the soil surfaces increased the solid–liquid interfacial free energy (γsl) and decreased the solid surface free energy (γsg) as indirect effects of salinity on repellency. In addition, water entering into the soil immediately dissolved the soluble salts which had precipitated in the initially dry soil. There is some evidence showing that surface tension of water (γlg) increases with salts. Decrease of γsg and the increase of γsl and γlg might cause the repellency increment (43). Calcium bridge between soil particles could improve the soil structure with salinity increment. Increasing the SE by salinity in this study confirms this hypothesis. The soil SW depends on pore geometry and hydrophobic coating on soil particles, but the soil SE only depends on pore geometry. Thus, increasing the SE might be an indicator for better pores connection and stable structure (15). Conclusion Many grape leaves and pomegranate peels are produced in Iran every year. These plant residues are potentially a good source for increasing the soil organic carbon. Our results showed that incorporation of these plant residues in to the soil could increase the soil organic carbon and carbohydrate concentration and improve the soil aggregates stability. However incorporation of residues into the soil increased the soil water repellency. In addition salinity increment induced soil hydrophobicity. More detailed studies are needed to understand the positive or negative effects of this subcritical hydrophobicity development in saline soils.
Research Paper
Soil Genesis and Classification
Maryam Mohammadzadeh Mohammadabad; F. Khormali; Farshad Kiani; mohammad ajami
Abstract
Introduction Soil degradation is a widespread environmental problem that occurs as a result of land use change and destruction of vegetation cover that may lead to changes in soil structure and porosity. Land use change and land management have significant effects on physical and chemical properties ...
Read More
Introduction Soil degradation is a widespread environmental problem that occurs as a result of land use change and destruction of vegetation cover that may lead to changes in soil structure and porosity. Land use change and land management have significant effects on physical and chemical properties and biological capabilities of soil. The investigating of undisturbed and natural soil structure using microscopic and ultramicroscopic techniques provides invaluable information about the physicochemical, mineralogical, morphological properties and soil genesis and calcification. Image analysis is an advanced method for quantifying soil properties and increasing the precision of morphological and micromorphological studies. Materials and Methods In this study, in order to investigate the impact of different land uses on porous and microstructure of surface soil horizons, 9 profiles in different land uses, including natural forests, artificial forest, abandoned land, orchard and cropland were extracted and described. Then one sample was taken from each horizon for physical and chemical analysis as well as a few undisturbed samples for micromorphological studies. Physical and chemical parameters such as texture, bulk density (BD), calcium carbonate equivalent (CCE), organic carbon (OC) and mean weight diameter (MWD) were measured. After preparation of thin sections of soil, micromorphological studies were conducted by polarizing microscope. Then from each thin section, 20 photos were taken randomly in plane polarized light (PPL) and cross polarized light (XPL) and transferred to image tool software. The percentage of total porosity of soil, feret diameter and area pores parameters were studied quantitatively. Three classes of feret diameter in micrometer and five classes of area in square micrometers were considered for pores in the soil thin sections. After importing photos to the software and performing calibration, grayscale and subtracting two images, the range of pores was identified by the software. Then in the classification section of software, the highest level of classes in each part was determined and the percentage of pores in each class was calculated and data obtained were analyzed by SPSS 16.0 software. Results and Discussion Micromorphological observations showed that in natural and artificial forests, a significant amount of organic matter in the soil has resulted in the formation of granular and subangular blocky dominant microstructure. While in cropland land use the type of microstructure is mainly massive and angular blocky, due to deforestation and agricultural practices, which resulted in the degradation of soil microstructure. Appropriate environmental conditions and dense vegetation in natural and artificial forests land use lead to significant biological features in comparison to other land uses that were subjected to deforestation. In natural and artificial forests land uses, the percentage of channel and large vughs pores is more than other land uses mentioned above. Tillage results in degradation of soil structure in cropland land use, the majority of pores observed in thin section are vugh and plane. Also, the results of image analysis showed that in natural forests and orchard land uses, pores with diameters ranging from 2 to greater than 10 micrometer and areas ranging from 500 to greater than 1000 square micrometers had the highest frequency in terms of percentage of soil pores. Hence, these soils are considered as quite porous class, while in cropland land use, tillage results in the degradation of large pores showed that pores with diameters less than 2 to 10 micrometers and areas smaller than 5 to 50 square micrometers comprised and the highest percentage of soil pores. Conclusion Asignificant amount of organic matter and low bulk density, and the highest percentage of total porosity are found in natural forest and orchard land uses, while deforestation and cultivation in cropland land use has led to compression and destruction of soil structure. This fact reflects itself in the increased bulk density and decreased total porosity. Agricultural practice has a significant effect on destruction of surface soil structure. Microstructure and voids of cropland land use are mainly massive and angular blocky and plane and vughs, respectively. With changes of land use from forest to cropland, and consequently incorrect land management causes decrease in organic matter. Shortage of organic matter causes decreasing biological activity in surface soils. The best way to prevent degradation of the soil in this area is to preserve natural forests and change cropland land use to orchard and artificial forest land uses.
Analytical and Applicable Papers
Behrooz pourmohamadali; M.H. Salehi; S.J. Hosseinifard; H. Shirani; I. Esfandiarpour Borujeni
Abstract
Introduction In recent decades, due to a significant increase of pistachio cultivation and uncontrolled exploitation of groundwater resources as well as reducing rainfall precipitation, groundwater level has dropped and the quantity and the quality of water has also been reduced. Therefore, agricultural ...
Read More
Introduction In recent decades, due to a significant increase of pistachio cultivation and uncontrolled exploitation of groundwater resources as well as reducing rainfall precipitation, groundwater level has dropped and the quantity and the quality of water has also been reduced. Therefore, agricultural producers, researchers and policy makers need to pay more attention to appropriate land management as an important strategy to achieve greater yield per unit area and optimal use of soil and water resources. Crop yield prediction regarding its temporal and spatial variations has an important role in developing proper management programs. However, few studies have been carried out in relation to pistachio yield prediction using an acceptable range of features on regional scale. In the present study, pistachio yield modeling was performed by multivariate linear regression and artificial neural networkbased on soil, water and management features. Materials and Methods 129 orchard plots in different areas of Rafsanjan and Anar were identified and selected. The study area is located between 54° 56′ and 56° 41′ E, 29° 54′ and 31° 13′ N. Soil sampling, was performed from the areas under pistachio canopy and three soil depths of 0 to 40, 40 to 80 and 80 to 120 cm in each plot, fully expanded sub-terminal leaflets were randomly collected from non-fruiting branches, during the late July through August. Irrigation water of all orchards was also sampled. Moreover, for each orchard, a questionnaire was prepared to collect management and yield data. Soil quality indicators including particle size distribution, pH in saturated soil paste, electrical conductivity of saturated extract, soluble sodium, soluble calcium, soluble magnesium, available phosphorus and available potassium were determined for soil samples. The concentrations of phosphorus, potassium, iron, zinc, copper, manganese, calcium and magnesium in leaf samples and electrical conductivity in water samples, were also calculated. Finally, a dependent variable (pistachio yield) and 50 independent variables including soil, water and plant characteristics were used for modeling. For this purpose, stepwise multiple linear regression and artificial neural network technique were applied. Then, the study area was divided into 4 parts with the highest pistachio orchards densities and regression models were run for each part, separately. The ability of models to yield prediction was evaluated using the root mean square error (RMSE), relative root mean square error (% RMSE), adjusted coefficient of determination (adj - R2) and Durbin - Watson statistic (D – W). Results and Discussion The average of yield in the study area is about 1,700 kilograms per hectare. Results indicated that multiple linear regression could explain only 26 percent of the pistachio yield variation, but its accuracy increased when data became more homogeneous via dividing the study area into four parts. The model adjusted-R2 for Noogh, Anar, eastern suburbs and western suburbs orchards rose to about 92.4, 81.5, 95 and 53.6 percent, respectively. In all regression models except the model of western suburbs, at least one of the characteristics associated with irrigation water was significant. Artificial neural network with 9 neurons in a hidden layer, Tangent - sigmoid activation function and Levenberg - Marquardt training function, has a 98.3 percent accuracy in predicting pistachio yield in the study area (% RMSE = 13.8). Conclusion Multivariate linear regression model did not accurately predict the pistachio yield for the whole of study area whereas increasing data homogeneity and decreasing sources of variations, reduced complexity of relationships between features which resulted in increasing of the efficiency of linear regression to modeling these relationships. These models were highly sensitive to irrigation water features. Therefore, special attention should be paid to modern irrigation techniques and proper management approaches in order to enhance water efficiency. Overall, artificial neural network had greater accuracy compared to multivariate linear regression for pistachio yield modeling. This indicates the existence of non-linear and complex relationships between pistachio yield and the factors affecting yield and also the necessity of using modern and robust data mining tools for crop yield estimating. It seems that artificial intelligence techniques can be used as an efficient tool for developing proper management programs.
Applicable
Plant Nutrition, Soil Fertility and Fertilizers
Faranak Ghasemi; ُSaeid Hojati; Ahmad Landi; Roya Zalaghi
Abstract
Introduction Clay minerals are considered as the main source of ion exchange and storage of nutrients in the soil. Knowledge of change and transformation of minerals, in relation to plant nutrition, fixation and release of elements is important. Sepiolite and palygorskite are fibrous clay minerals widely ...
Read More
Introduction Clay minerals are considered as the main source of ion exchange and storage of nutrients in the soil. Knowledge of change and transformation of minerals, in relation to plant nutrition, fixation and release of elements is important. Sepiolite and palygorskite are fibrous clay minerals widely distributed in arid and semi-arid soils. Both minerals are rich in Mg and therefore, their weathering can significantly affect the chemistry of Mg in soil. Biological weathering which is carried out by living organisms (i.e. plant roots, soil fungi and bacteria) plays an important role in providing nutrients to plants. Hence, the use of microorganisms such as mycorrhizal fungi in the rhizosphere of agricultural crops has become more widespread. In recent years several studies have been conducted in relation to the weathering of minerals in the rhizosphere soil. However, few studies in terms of mycorhizal symbiosis with plant roots were carried out on release of Mg from sepiolite and palygorskite. Therefore, a pot experiment with a factorial arrangement through a completely randomized design was conducted to identify how symbiosis of sorghum roots with Glomus mosae mycorhizae affects release of Mg from sepiolite and palygorskite. Materials and Methods Pots containing sterile quartz sand and sepiolite or palygorskite (25-53 µm) were prepared and fungal treatments including presence or absence of fungus Glomus mosae were applied to the pots and then sorghum seeds were sown. Johnson nutrient solutions containing magnesium and without magnesium were used to feed plants during 70 days of experiment. After harvesting, the chlorophyll content, plants height and stem diameter were measured by SPAD, tape measure and caliper, respectively. Afterwards, the roots and shoots were separated and plants biomass and the percentage of roots colonization determined. Then, plants were oven-dried, ground, and the magnesium contents of them after extraction with 1M hydrochloric acid were determined using Agilent 7000 ICP analyzer. The chemical composition of palygorskite, sepiolite, and quartz sand was determined using X-ray fluorescence (XRF) and their mineralogical composition was determined using X-ray diffraction (XRD) approach. Results and Discussion Analysis of variance for the main effect of treatments on plant height, stem diameter, shoot dry weight and root dry weight showed that the effect of different sources of magnesium on plant height, stem diameter and shoot dry weight was significant (P < 0.01). The highest and lowest height, stem diameter, root and shoot dry matter were found in treatments fed with complete Johnson solutions and the palygorskite, respectively. The results also illustrated that application of Glomus mosae symbiotic mycorhizae significantly increased plant height, stem diameter, and root and shoot dry matter compared with non-mycorhizal treatments. This could be attributed to the fact that Mycorrhizal fungi (Glomus mosae) absorb more water and nutrients through increased photosynthesis and plant growth, consequently leading to improved plant characteristics when compared with non-mycorhizal crops. The results also showed the highest percentage of root colonization in palygorskite treatments and the lowest one in control. In general, a symbiotic relationship is created to improve low nutrition of elements that the amount of them in the soilwith a little mobility. Therefore, anything that exacerbates this deficiency, leads to an increase in symbiosis between plants and fungi. On the other hand, When plant is faced with more nutrient deficiencies, the demand for a symbiothic fungusGlomus mosae increases. Besides, the greatest magnesium concentration and chlorophyll contents were found in control, sepiolite and palygorskite treatments, respectively. In all treatments, magnesium intake was sufficient to grow sorghum, but as the results show, the amount of magnesium in the control and that of sepiolite was much more than palygorskite. These results clearly show that sepiolite mineral is able to release more Mg than palygorskite. The results also showed that the presence of the fungus Glomus mosae has significantly affected the release of Mg from both minerals. Conclusion In both sepiolite and palygorskite treatments, magnesium and chlorophyll content increased in symbiosis with fungi. This shows the positive effect of Glomus mosae fungus on release of Mg from these two minerals, especially sepiolite. Although, both sepiolite and palygorskite were able to provide enough amounts of Mg for sorghum plants, however, it seems that in long-term Mg released from sepiolite can more easily meet the need of plants when compared with palygorskite.
Applicable
Soil Physics, Erosion and Conservation
E. Karami; S. Ghorbani Dashtaki; Bijan Khalilimoghadam
Abstract
Introduction Soil erodibility can be viewed as the integral result of the processes determining the infiltration of rain into the soil and of the processes determining the soil’s resistance to the detachment of its particles and their subsequent transport (Lal, 1988). It is generally considered ...
Read More
Introduction Soil erodibility can be viewed as the integral result of the processes determining the infiltration of rain into the soil and of the processes determining the soil’s resistance to the detachment of its particles and their subsequent transport (Lal, 1988). It is generally considered as an inherent soil property with a constant value for a given soil type and widely adopted as an important factor in soil erosion prediction models, such as the Universal Soil Loss Equation (USLE), and the Revised USLE (RUSLE). The erodibility factor, commonly known as the K factor, in the USLE was defined as the average rate of soil loss per unit of rainfall erosivity index from a cultivated continuous fallow plot, on a 9% slope 22.1 m long. Soil erodibility factor K is not only an internal factor indicating the amount of soil loss, but also the basis for the quantitative study of soil erosion. Soil erodibility is closely related to the basic physicochemical characteristics of soils. The total aggregate content, 1–10 mm aggregate content, aggregation degree, aggregate dispersion coefficient and erosion rate are indexes for the analysis of soil anti-erosion capability. Not only may soil erosion be different for various types of soils, but also it is different for the same type of soil under different climate conditions or land use management. Different land use systems might alter several soil properties and processes. Kosmas et al. (2000) reported that land use change could impact soil physical, chemical, and biological properties. Studies by Duiker et al. (2001) showed that land use changes from natural and semi-natural vegetation to cultivated and grazed lands affect soil bulk density, porosity and water storage, water infiltration and water flow characteristics and surface runoff. Abbaszadeh Afshar et al. (2010) found that organic matter content and bulk density were greater in pasture soils than in dry farm soils. Kay (2000) showed that large aggregate sizes and high organic matter content protect soils against splash detachment. Although there are many studies on land use impacts on soil erodibility, to the best of the authors’ knowledge, no study has of yet been reported on the effects of land use change on soil erodibility in Zayandeh-Rood watershed. Therefore, the objective of this study was to investigate the impacts of different land uses on soil erodibility in a part of Zayandeh-Rood watershed. Materials and Methods For this purpose, soil properties including particle size distribution, gravel percent, bulk density, permeability of soil profile, Structure code and permeability code, organic matter, calcium carbonate equivalent, mean weight diameter of aggregates and surface shear strength were measured. Soil erodibility was measured with a rainfall simulation device with rainfall intensity of 30 mm h-1 and 30 min duration in a plot with 0.25 m2 area and 9% slop in two land uses, namely pasture and degraded pasture. A completely randomized design was used in which soil texture and the land use changes were analyzed. The multiple-linear regression analysis was used to relate soil erodibility factor to different soil parameters. Results and Discussion The influence of land use change on soil erodibility was investigated based on simulated rainfall in field conditions. The findings of this study demonstrated that a considerable amount of soil erodibility occurred in the study region characterized by low organic matter and mismanagement. On average, soil erodibility was significantly affected in the Zayandeh-Rood watershed, Iran, by the land use system (i.e., soil structure and management practices) rather than by the soil textural class. Average soil erodibility was obtained in pasture land use 0.05 (ton h MJ-1 mm-1) and in degraded pasture 0.09 (ton h MJ-1 mm-1). Low soil organic matter content in the degraded pasture land is probably caused by livestock overgrazing and ultimately grazing. Based on the results obtained of the transfer functions in each land uses, it was observed that clay and coarse sand particles (R2=0.86) in pasture land uses and surface shear strength and permeability code (R2=0.90) in degraded-rangeland at the 5% level compared to other soil properties were more suitable parameters for estimating of soil erodibility. Thus, vegetation cover protection was recommended to soil conservation in this region.
Applicable
Soil Biology, Biochemistry and Biotechnology
S. A. Hosseini; mhsen olamaee; S. A. Movahedi Naeini; F. Khormali; R. Ghorbani Nasrabadi
Abstract
Introduction Potassium is one of the essential and macro elements in the growth of plant cells. This element plays an important role in improving the quality of agricultural products. The amounts of available potassium levels in most soils decrease more quickly and potassium balance is disturbed in many ...
Read More
Introduction Potassium is one of the essential and macro elements in the growth of plant cells. This element plays an important role in improving the quality of agricultural products. The amounts of available potassium levels in most soils decrease more quickly and potassium balance is disturbed in many fields. Cultivation and lack of the application of potassium fertilizers in agricultural soils of Iran have caused the depletion of potassium and the amount of available potassium in most soils has reached below the critical level. The compensation of depleted potassium in the soil through indigenous resources and use of potassium bio-fertilizers is therefore very important. Weathering of silicate minerals by bacteria is considered as one of the essential K source for plant growth and development. The objective of this study was to isolate and identify potassium solubilizing bacteria from the shale containing glauconite mineral in Golestan Province and determine some traits related to plant growth promotion and selecting a superior strain in order to incubate in wheat lands. Materials and Methods Accordingly, a total of 5 samples 1 kg of rhizosphere of wheat from a depth of 0 to 30 cm and 5 samples 1 kg from shale stone (containing glauconite) were collected from Aitamir formation in Golestan Province in May 2015 and were transferred to the laboratory of Gorgan University of Agricultural Science and Natural Resources. Isolates were transferred to Aleksandrov media containing glauconite and muscovite and incubated for 10 days and the isolated strains were stored in the refrigerator at 4 oC. The amount of potassium release in solutions after 10 days was measured. Some biochemical and morphological properties of isolates were determined based on standard methods. PGPR tests were done in the isolates which were morphologically different and had high potential in releasing K. Finally, a strain whith high ability in releasing potassium and growth promoting properties was identified using nucleotide sequence of 16S rRNA gene. Results and Discussion Results showed that 40 strains from the first stage, 20 strains from rhizospherial soil and 20 strains from the soil resulting from glauconite mineral powders were isolated. Biochemical and potassium release tests showed that the highest released potassium was related to isolate No. 39 with an amount of 34.2 mg l-1 in muscovite, and 31.8 mg. l-1 in glauconite. The amount of siderophore produced in the superior strains showed that the lowest and the highest ratios of the diameter of the colony, were 1.12 and 3.1 related to isolate No. 19 and No. 39, respectively. The highest and the lowest auxins produced were also related to the isolate No. 39 and No. 27 with the amount of 52.25 and 5.15 mg per liter, respectively, measured at 72 and 96 hours. The results showed that the soluble phosphorus between different isolates was significantly different (P <0.05), its greatest concentration at 72 hours was related to isolates No. 39 with an amount of 295 mg per liter and the lowest at 24 hours was related to isolate No. 31 with an amount of 80 mg per liter. Also, the production of hydrogen cyanide test showed that none of the isolates was capable of producing siderophore. The obtained results from nucleotide sequence of 16S rRNA gene showed that the selected strain belonged to Arthrobacter phenanthrenivoran species. Conclusion It can be concluded that silicate bacteria contribute to the dynamics and mineralizing of elements in the soil and eventually K release from glauconite containing shale minerals mainly by reducing rhizosphere pH, the secretion of organic anions and complex formation with the surface cations of mineral and secreted extracellular Polysaccharides and soluble compounds and decomposition of soil organic matter. Among 40 isolated strains and the various tests and the results of released potassium in both minerals, the results showed that the potential of potassium releasing was different between the tested strains. Moreover, this study showed that in addition to the effect of these strains on potassium releasing, siderophore production, auxin and inorganic phosphate solubility, they can be effective in plant growth and in land inoculation. This study revealed the potential of indigenous bacteria species in the release of K from shale containing glauconite. It is anticipated that shale containing glauconite can provide a part of the need of the crops for potassium.
Applicable
Plant Nutrition, Soil Fertility and Fertilizers
Esmaeil Dordipour; Zeinab Bastamikojour; Mojtaba Baranimotlagh; Abdolreza Gharanjiki; Mohsen Olamaee
Abstract
Introduction The most important constraint in maize crop yield in developing contries worldwide, and especially among resource-poor farmers, is soil infertility. Therefore, maintaining soil quality can reduce the problems of land degradation that decreases soil fertility and rapidly declining production ...
Read More
Introduction The most important constraint in maize crop yield in developing contries worldwide, and especially among resource-poor farmers, is soil infertility. Therefore, maintaining soil quality can reduce the problems of land degradation that decreases soil fertility and rapidly declining production levels that occur in large parts of the world which needing the basic principles of good farming practice. For optimum plant growth, nutrients must be available in sufficient and balanced quantities. After nitrogen, phosphorus is the most limiting nutrient for crop yields, and is essential for maize growth and development. Large quantities of chemical fertilizers are used to replenish soil N and P, resulting in high costs and severe environmental contamination. Maize quantity and quality are increased by utilization of fertilizers, which has become the most important objective of these products worldwide. Phosphorus, is the second most important macronutrient required by the plants, next to nitrogen, and is reported to be a critical factor of many crop production systems due to its limited availability in soluble forms in the soils. The low availability of P to plants is because the vast majority of soil P is found in insoluble forms, and plants can only absorb P in two soluble forms, the monobasic (H2PO4-) and the dibasic (HPO42-) ions. Crop plants can therefore utilize only a fraction of applied phosphorus, which ultimately results in poor crop performance. To rectify this and to maintain soil fertility status, frequent application of chemical fertilizers is needed, though it is found to be a costly affair and also environmentally undesirable. Moreover, phosphorus (P) is an essential nutrientionl element for plant growth. Calcareous soils are frequently characterized by the low availability of P for plant uptake due to the low solubility of P compounds present in soils at high pH and the formation of relatively insoluble complexes, e.g., Ca-P. Many soils in Iran have received large amounts of P fertilizer and consequently contained a high level of available P. On the other hand, the root exudation of organic acids has been suggested to increase P availability in calcareous soils. The most common low-molecularweight organic acids (LMWOAs) identified in soils include oxalic, succinic, tartaric, fumaric, malic, and citric acids and are derived from the decomposition of soil organic matter in the upper soil horizons, microbial metabolites, canopy drip, and root exudation. The concentrations of organic acids in the rhizosphere or in soil solutions vary greatly and range from 10-2μM to over 80 mM. The ability of organic acids to release inorganic anions, such as P, has been reported and has been attributed to desorption of inorganic anions and solubilization of phosphate compounds. LMWOAs and their corresponding anions play a very important role to increase P bioavailability. Many studies have been conducted about the role of organic acids in increasing P availability, but these studies focused on acid soils in which Fe- or Al-bound P is the main P fraction. For calcareous soils where Ca-bound P is the main P fraction, questions that whether organic acids can mobilize P or not still exist. Although, a number of results show that addition of organic acids, especially citric and oxalic acids to soils can solubilize significant quantities of fixed P and reduce the sorption of newly applied fertilizer P. However, there are few studies on the transformations of P fractions induced by organic acids or organic anions, which are important for understanding the mobilization mechanisms of P and for exploring better ways of using different forms of P in soils. The objective of this study is to examine the effects of some organic acids and anions on the solubilization and plant uptake of soil P in some calcareous soils of Golestan province, Iran. Material and Methods For this purpose, a factorial pot experiment in a completely randomized design with three replications was conducted on maize. The first factor was comprised of 6 soil types from various areas of the province and the second factor was consisted of a combination of phosphorus fertilizer and organic acids (1) control, (2) 50 mg P kg-1, (3 and 4) 50 mmol kg-1 of organic acids (oxalic and malic acids), (5) P + oxalic acid and, (6) tomato fruit residue (25% w). After 10 weeks, plants were harvested and the parameters such as plant height, fresh and dry weights, phosphorus concentration and its uptake were determined. Results and Discussion Results indicated that soil type effect was statistically significant on the plant fresh and dry weights (P≤ 0.05), height, concentration and uptake of P (P≤ 0.01), respectively. Results also showed that the tomato fruit residue treatment in comparison with P fertilizer and malic acid treatments results in a significant increase in P taken up, and fresh and dry weights (P≤ 0.05). There was a significant difference between P fertilizer + oxalic acid and oxalic acid alone treatments in only plant height (P≤ 0.05). Also, no significant differences in terms of measured plant parameters were observed between malic acid and blank treatments (P≤ 0.05). Conclusion Application of tomato fruit residue rather than P fertilizer can help to take up residual soil P, to grow plants and to decrease of environmental pollution, and to be also affordable economically.
Applicable
Precision Agriculture
Mojtaba Naderi-Boldaji; Abbas Hemmat; T. Keller
Abstract
Introduction Soil compaction is a serious concern in modern agriculture. Field traffic using machines with high axle loads is likely to compact the soil below the plough layer. Compaction of the subsoil should be avoided since soil productivity is at risk of being reduced, and because the effects are ...
Read More
Introduction Soil compaction is a serious concern in modern agriculture. Field traffic using machines with high axle loads is likely to compact the soil below the plough layer. Compaction of the subsoil should be avoided since soil productivity is at risk of being reduced, and because the effects are very persistent, perhaps even permanent. Precompression stress is widely applied as a border between elastic and plastic soil deformations under stress application. As long as the stress does not exceed the precompression stress, soil deformation is expected to be recoverable after the removal of stress (i.e. passage of the tire). The precompression stress is conventionally determined using the standard procedure of Casagrande from the log stress – void ratio curve resulting from confined uniaxial compression of intact soil samples taken at the field. With advances in the technology of precision agriculture, site specific management of machinery traffic is under focus by researchers. Field mapping of soil precompression stress would allow for site specific modifying the machine parameters (e.g. the tire inflation pressure) to control the applied stress below the precompression stress. For example, where the soil moisture is high, a decrease in tire inflation pressure increases the soil-tire contact area and thus decreases the severity of stress propagation in soil. However, the conventional method of estimating the precompression stress is time-consuming, labor intensive thus not suitable for mapping applications. Horizontal penetrometer is a popular device for on-the-go measuring of soil strength. Horizontal penetrometer resistance is an attractive measurement because it is relatively simple, fast and cheap, can be carried out on-the-go, thus yielding spatial information with a high resolution. A multi-tip horizontal penetrometer would also allow for discrete-depth measuring the soil strength. As penetrometer resistance and precompression stress are both measures of soil strength, it was hypothesized that they are highly correlated. Therefore, the relationship between precompression stress (σpc) and horizontal penetrometer resistance (PR) was investigated in a wide range of soil textures. This would suggest an alternative for on-the-go measurement of σpc for field mapping and site-specific management of soil trafficability. Materials and Methods Field measurements were conducted in different soil textures in Switzerland. The clay content of the soils varied from 189 to 584 g kg-1. Horizontal penetrometer resistance was measured at 0.25 m depth at a traveling speed of 0.25 m s-1. Cylindrical core samples were taken at the local minima and maxima of PR along the transects. Cone index measurements were also performed to a depth of 0.5 m at the points of core samples. The samples were subjected to stepwise compression stresses by an Oedometer and the resulting deformation was recorded. The void ratio was calculated with particle density and bulk density at the end of each stress step. The precompression stress was estimated at the point of maximum curvature of log stress- void ratio with fitting Gompertz function. Correlation and regression analyses were performed in SAS software. Results and Discussion The results showed that the Gompertz function explains well the void ratio versus log of stress for different soil textures. The Gompertz parameters were characterized with respect to soil physical characteristics. Precompression stress decreased with increasing soil moisture, soil clay and organic matter content. A relatively strong correlation was found between σpc and PR (R2= 0.47, RMSE= 15.4 kPa) which was significantly improved (R2= 0.59, RMSE= 13.7 kPa) with the effect of soil water content. The high scatter of the relationship between precompression stress and horizontal penetrometer resistance was discussed to be likely due to the difference between the soil failure mechanisms around a penetrating tip and under uniaxial compression. A comparison of different compaction tests (e.g. semi-confined and plate sinkage) with PR may suggest stronger correlations. A strong correlation (R2= 0.6) was also found between PR and cone index (CI). CI was found to be larger than PR for all the soils. Conclusion It was concluded that the soil compaction characteristic (log stress versus void ratio) is strongly governed by the soil initial void ratio with an increase of precompression stress with decreasing the initial void ratio. In the range of variations tested, the relationship between PR and σpc was not affected by soil texture (clay content). The study suggests that measurement of PR can be a fast alternative for mapping of soil precompression stress by compensating for the effect of soil moisture (by e.g. a dielectric sensor). therefore, a combined horizontal penetrometer needs to be employed.
