Ehsan Ghojehpour; Vahidreza Jalali; Azam Jafari; Majid Mahmoodabadi
Abstract
Introduction Spatial and temporal variations of soil characteristics occur in large and small scales. Investigating the variability of soil parameters is considered as one of the requirements for proper management of fertilizer resources in a sustainable agricultural system. Studying of these variation ...
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Introduction Spatial and temporal variations of soil characteristics occur in large and small scales. Investigating the variability of soil parameters is considered as one of the requirements for proper management of fertilizer resources in a sustainable agricultural system. Studying of these variation is very time-consuming and costly especially in large scales. In order to the fast and reliable determination of the soil properties, various interpolation techniques have been developed and applied. The most widely used interpolation technique is the different Kriging types. The copula function is one of the new interpolation techniques that are recently used in sciences such as hydrology. Thus, the aim of this research was to evaluate the spatial variation of some soil chemical properties using the copula function and comparisons with geostatistics techniques. Materials and Methods Sampling by regular networking was done in an area of 484 ha located in 10 km far from the west of Baft city, located in Kerman province, central Iran (latitude of 29° 15′ N and longitude of 56° 29′ E). In the studied area, three agricultural, pasture and industrial sites are located nearby. The common crops of the region are wheat, barley, alfalfa, legumes and orchards of walnuts, pomegranates, almonds and grapes. The average height of the studied area is 2270 meters above sea level, the average annual temperature of the area is 16 degrees Celsius, and the average annual precipitation of the area is 247 mm. The soil used for the experiment was collected from 0 to 20 cm depth of the field. 121 soil samples were air-dried and, some physical and chemical properties were measured. In order to fit the Copula function to the data, first the appropriate marginal distribution function should be fitted to the data. For this purpose, three tests were used: Kolmogorov-Smirnov, Anderson-Darling and Chi-Square. The mentioned tests were carried out in the EasyFit 5.5 statistical software. By fitting the best marginal distribution function, the cumulative value of the marginal distribution function is calculated for each data. After calculating the above values, detailed functions can be fitted to the data. Finally, the accuracy of each interpolation method was evaluated according to the root mean square Error (RMSE), coefficient of determination (R2), mean absolute error (MAE) and mean biass error (MBE) indices. Results and Discussion In all types of geostatistical methods, the first step in interpolation is to fit the semivaiogram to the measured data, so after normalizing the data and validating the models, the appropriate model was selected for fitting the semivaiogram. Among the measured parameters, Pava and Kava semivaiogram followed spherical model and the interpolation of the above variables was done on the basis of this model. Copula analysis showed that the available phosphorous and potassium variables followed from the Wakeby and gamma distribution function, respectively. Also, based on the Pearson correlation coefficient, the correlation between pairs of points was less than 2000 m and the distance more than 2000 m was known as an independent distance. Based on the validation criteria for Pava parameter, Median copula function, Average copula function, IDW, Ordinary Kriging, Disjunctive Kriging, Universal Kriging and Simple Kriging have better estimates, respectively, and in the same way, the best interpolator for Kava parameter Median copula function, Average copula function, Ordinary Kriging, Universal Kriging, Disjunctive Kriging, Simple Kriging and IDW were determined, respectively. The estimation performance based on the coefficient of determination (R2) showed that value of this coefficient for copula function for available phosphorous and potassium were 5% and 4% greater than conventional geostatistics techniques. Also, the error of estimation was less for copula function indicating the better performance of copula to estimate the mentioned soil propertiesConclusion This study was performed to investigate the Feasibility study of Copula function in predicting some soil nutrients and comprising this method with widely used methods of geostatistics. Our results demonstrated that the copula function method is more capable than the classical geostatistical methods in estimating soil properties due to the non-dependence of this method on the normality of the data distribution and outlier data. Therefore, with the help of this method, having a reliable and high-quality data bank of soil characteristics, acceptable maps of other soil characteristics can be presented at various scales.
Soil Physics, Erosion and Conservation
Hossein Kheirabadi; Vahidreza Jalali; Hormozd Naghavi
Abstract
Introduction: The trap efficiency of sediment catcher plays an important role in the study of wind erosion and its measurements. The sediment trap efficiency generally varies with particle size distribution and wind velocity. Worldwide, wind tunnel facility has been used by many researchers to determine ...
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Introduction: The trap efficiency of sediment catcher plays an important role in the study of wind erosion and its measurements. The sediment trap efficiency generally varies with particle size distribution and wind velocity. Worldwide, wind tunnel facility has been used by many researchers to determine the efficiency of sediment samplers designed for the measurement of the deposition of Aeolian dust. Therefore, this study was conducted to investigate the efficiency of BSNE sampler, the transportability of sediment particles per wind velocity, using wind tunnel facility under laboratory conditions. In addition, a new parameter by which sediment transportability can be quantified was introduced. Materials and Methods: The wind tunnel experiments were carried out in an open circulation wind tunnel at the Soil Erosion and Conservation Laboratory, Shahid Bahonar University of Kerman, Iran. The wind tunnel consists of three sections including 1) wind generator section for producing different wind velocities, 2) test area section in which soil sample is placed and 3) sediment collector section. The wind tunnel has a uniform cross section with width and height of 80 cm by 80 cm and a total length of 12 m, with a working section of 7 m in length. The wind velocity can be varied continuously from 1 to 30 m s-1 at 40 cm height equal to 175 km/h at 10 m height. The soil used for the experiments is taken from the surface layer (0-20 cm depth) of a cultivated land from Kerman province (30 14 N and 57 06 E). The soil sample at first was air-dried, thoroughly mixed and then crushed to pass separately through 2, 4.75 and 8 mm sieve sizes in order to prepare three subsamples with different max size of 2 (D2mm), 4.75 (D4.75mm), 8 (D8mm) mm. Experiments were done as factorial based on completely random design with three replications. The factors were the height of sampler, wind velocity and soil aggregate size. Three wind velocities of 6, 10, 14 m s-1 at 40 cm height were introduced over the leveled soil surface with 7 m length and the sediment was collected using BSNE sampler at different heights of 10, 30, 50 and 70 cm at the outlet of the wind tunnel. Also, the total mass of soil loss was measured by differential weighing method for each erosion event. Results and Discussion: Results showed that the sediment flux decreased with increasing height at different wind velocities and was quantified using an exponential function, satisfactorily. The sediment transport rate near soil surface for soils D2mm, D4.75mm and D8mm ranged from 0.28 to 2.11, 0.19 to 1.06 and 0.23 to 0.65 g cm-2 min-1, respectively. This implies the soil having coarser aggregates exhibits less erodibility. Moreover, sediment flux at all heights was increased with increasing wind velocity, whereas it was reduced as soil surface roughness increased. In general, the efficiencies of the BSNE samplers varied from 53.2% to 82.1%, depending on soil aggregate size and wind velocity. The efficiency of BSNE obtained for D2mm, D4.75mm and D8mm, at wind velocity of 6 m s-1 was 61.4, 53.2 and 77.5%, at wind velocity of 10 m s-1 was 56.5, 78.7, 69.5% and at wind velocity of 14 m s-1 was 62.4, 79.1, 82.1%, respectively. Also, the results indicated that the transportability of sediment particles per wind velocity decreased with height, which was described through an exponential function. Overall, the particles in the size range of 125 to 500 micron exhibited the maximum selectivity and frequency in the sediments collected at 10 and 30 cm heights. The finding of this study revealed the high importance of vertical distribution of sediment size particles and their selectivity in wind erosion studies. Conclusion: The finding of this study indicated that most sediment particles were transported near the soil surface, this means that by appropriate conservation practices such as making sufficient roughness through this height, wind erosion can be reduced, significantly. Also, it was found the soils containing coarser aggregates due to higher random roughness show less erodibility and wind erosion rates. Finally, the efficiency of sediment sampler was found to be affected by some other factors, therefore, more attention is needed in the application of these types of samplers while the calibration is of importance, as well.
Plant Nutrition, Soil Fertility and Fertilizers
Majid Hejazi
Abstract
Zinc (Zn), an essential micronutrient for both plants and humans, is involved in a number of physiological and biochemical processes. Calcareous soils cover more than 30% of the earth’s land and are characterized by the high pH and low availability of plant nutrients. Zinc (Zn) that is freely available ...
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Zinc (Zn), an essential micronutrient for both plants and humans, is involved in a number of physiological and biochemical processes. Calcareous soils cover more than 30% of the earth’s land and are characterized by the high pH and low availability of plant nutrients. Zinc (Zn) that is freely available in acid soils is only sparingly available in calcareous soils, due to their poor solubility at high pH. Zinc deficiency in most of the world’s soils has resulted in significant loss of agricultural yields. Information about Zn availability in soils is very important in the view point of Zn nutritional status of plant and human. Several soil physicochemical properties including organic matter, CaCO3, pH, moisture and total Zn concentration affect soil Zn availability to plants. Under Zn deficiency, plants tend to release organic acid in the rhizosphere which in turn increases soil Zn availability. Oxalic acid is the simplest dicarboxylic acid with two pKa values, 1.23 and 4.19 and it occurs in sediments, forest soils, and agricultural soils, especially in the rhizosphere. Oxalic acid is able to chelate with the poorly soluble nutrients in the soil and consequently influence their bioavailability. It is known that Zn availability is controlled by adsorption, release, precipitation and dissolution reactions. Study of kinetic models is a useful method to describe the changes in the nutrient availability with time. A knowledge of desorption kinetics may provide important information concerning the nature of reaction and the rate of Zn supply to plants via soil solution. Materials and methods Composite samples of the two soils were collected from 0-30 cm depth of agricultural areas in Kerman province, Eastern Iran. The samples were air dried, crushed and passed through a 2mm sieve. Some soil chemical and physical properties of soil sample including Particle size distribution, Electrical conductivity and pH, Organic carbon, carbonate calcium equivalent, cation exchange capacity, available Zn and Total content of Zn were done according to standard procedures. For the kinetic study, soil samples were weighed (1.5g), placed in a 20 mL centrifuge tube and then 15 mL of oxalic acid with two concentrations of 1.1 and 2.2 mµ L-1 was added. The tubes were shaken from 1 to 72h at 25±2°C. Two drops of toluene were added to each tube to inhibit microbial activity. After shaking, the solutions were centrifuged and filtered through Whatman filter paper No. 42. Zinc concentration was determined in the filtrate using a Vario atomic absorption spectrometer. Several kinetic equations including zero-, first-, second- and third order, parabolic diffusion, Power function and simple elovich were also fitted to experimental data. Results and discussion Zn release by oxalic acid increased with time and the amount of Zn release differed between soils. The difference in the amount of Zn release may be attributed to differences in (i) the total amount of labile Zn which sorbed in the soil; (ii) types, quantities and relative proportions of the soil components by which the Zn is retained and (iii) other soil properties such pH and CEC. The release pattern of Zn included an initial fast reaction followed by a slow reaction that continued up to 72 h. The two phases of Zn release can be due to the heterogeneity of adsorption site with different adsorption affinities. The release kinetic of Zn in soils was poorly described by first- and second-order equations while Time dependent Zn release was best modeled by the simple Elovich, power function and parabolic diffusion equations. Based on the relatively higher values of r2 and the lower values of S.E., the simple Elovich showed the best fitness on the cumulative release of Zn. At each specified time, the lower dose of oxalic acid released Zn from soil more than the higher dose. Organic acids may increase the sorption of metal ions on soil particles through electrostatic interactions, ternary metal–ligand–surface complex formation or surface precipitation. It seems that Zn may interact with oxalic acid where adsorbed to solid phases and resulted in decreased Zn release. The rate parameters derived from the best-fitted model were used to compare Zn release by different concentrations of oxalic acid. The results showed that the rate parameters “ab”, Kp and β decreased with the oxalic acid concentration. Conclusion From the present study, oxalic acid, especially at the lower rate, can increase Zn release and its bioavailability in calcareous soils.
H. Shamsaldin; V. Jalali; A. jafari
