Iranian Journal of Soil Research
Year:2015 | Volume:29 | Issue:3|Papers Count:13

Salinity is the most significant abiotic stress limiting agricultural production. In order to study the interactive effects of K and Zn on reduction of salinity harmful effects on vegetation characteristics of wheat plant, a greenhouse factorial experiment was conducted in a completely randomized design with three replications. Treatments included three levels of Zn (0, 5, 10 mg Zn.kg-1 soil), three rates of K (0, 200, 400 mg K2O.kg-1 soil) and two levels of salinity (saline soil, non-saline soil), which were applied to the potting soils. Results showed that applications of K and Zn decreased the dry weight of leaf, shoot and root by, respectively, 14.1%, 18.0% and 20.9%. But, application of 10 mg Zn kg-1 soil increased shoot dry weight (70%). Also, salinity increased shoot K uptake (19.7%) and application of 400 mg K2O kg-1 soil and 10 mg Zn kg-1 soil increased it (36.7%). Salinity decreased K/Na ratio. Thus, nutrient element management, especially K and Zn, could decrease the effects of salinity stress.

To evaluate the effect of phosphorus solubilizing bacteria (PSB) and chemical phosphorus fertilizer on yield and yield components of two rice cultivars an experiment was conducted in Lahijan region during 2011 growing season, using randomized complete block design with three replications. The variables were rice cultivar at 2 levels (Ali Kazemy and Hashemy), phosphorus chemical fertilizer at 3 levels (control, 25, and 50 kg of triple super phosphate/ha), and phosphorus solubilizing bacteria (PSB) at 2 levels (control and Bacillus subtilis). The highest grain yield was obtained in Hashemy cultivar with application of PSB. The largest harvest index was observed in Hashemy cultivar with application of 25 kg/ha phosphorus chemical fertilizer + bacteria. Tiller number in Hashemy cultivar with application 50 kg/ha TSP was more than the others, and the maximum 1000-grain weight was observed in Ali Kazemy cultivar with application of PSB.

In this research, responses of some citrus rootstocks to active and equivalent calcium carbonate in the soils of eastern Mazandaran were evaluated by a factorial experiment in randomized complete block design. The results showed that Swingle citrumello and Sour orange, common rootstock of the region, had maximum and minimum dry weight. Also, average rootstocks chlorosis degree in these soils showed that Swingle citromello had the highest chlorosis degree and C-35, Carizo citrange, Gou tou, Troyer citrange, Smooth flat sevile, and Sour orange ranked after Citromello, respectively. According to the results, with increasing soil equivalent and active calcium carbonate, the average leaf active Fe of different rootstocks decreased. On average, the percentage of total iron in the form of active iron in the leaves was much higher than roots. In contrast, the average of total iron concentration in roots was several times more than that of leaves. Besides, by increasing calcium carbonate, the percent of leaf total iron in active form decreased, but unlike the leaves, the percentage of active iron in roots increased. Also, increase in soil active calcium carbonate did not have any effect on leaf active iron level of Sour orange and Smooth flat sevile. In contrast, leaf active Fe in Swingle citromello, Carrizo citrange, Troyer citrang, C-35, and Guo tou decreased. Therefore, according to leaf chlorosis degree index and trend of reducing leaf active Fe level per unit of active calcium carbonate, Sour orange, and Smooth flat sevile were the most tolerant, while Swingle citromello was the most sensitive rootstock to soil carbonate calcium, followed by Gou tou, Carizo citrange, Troyer citrange and C-35, respectively.

Seed bed preparation is the first important step in planting each crop. This study was conducted in order to investigate the effects of three different tillage methods (T1: moldboard plow, T2: subsoiler, T3: subsoiler with decompactor) at two depths on some physical propertiesof a soil classified asfine mixedthermic typic Haploxereptswith silty clay texture. A factorial experiment in a completely randomized block design and three replications was performed at Sari Dashtenaz Research Farm in 2011. Results showed that the lowest bulk density was observed when subsoiler was used and the maximum was related to the moldboard plow. Interaction of soil depth and tillage method had significant effect on porosity. As to soil water retention capacity, there were significant differences among treatments such that the subsoiler and decompactor had the maximum amount of soil water retention capacity. With regard to field capacity and permanent wilting point, there were significant differences between treatments and the highest effect was related to the subsoiler and decompactor, which were almost equal to moldboard plow. In addition, the plot where subsoiler and decompactor were used had the highest amount of available water for plants. With respect to the aggregate stability, it was observed that there were significant differences between treatments: the use of moldboard plow had the highest stable aggregate and the lowest was related to sub-soiling with decompactor.Sub-soiling and sub-soiling with decompactors treatments compared to moldboard plow reduced cone index. In addition, results showed that sub-soiling increased the infiltration rate of water into the soil.

Understanding the processes that control the activity of boron (B) in the soil solution is important for maintaining water quality and soil fertility management. Since these processes are influenced by the physical and chemical properties of soil, in this research, the effects of soil properties on B adsorption-desorption reactions and the degree of reversibility were studied. For this purpose, B adsorption and desorption isotherms were measured in 14 calcareous soils. Adsorption isotherms were described by using the empirical models and the effects of soil properties were analyzed by using the multi-variables regression. Results showed that B adsorption followed Langmuir equation with maximum adsorption in the range of 3-14 mmol.kg-1. Calculations indicated that soil cation exchange capacity (CEC) and reactive calcium carbonate equivalent (CCEr) were primarily responsible for B retention in the calcareous soils. Organic carbon, CCEr, and aluminum oxide described about 94% variability in the average coefficient of boron distribution (kd-) (CCEr and CEC were directly related to the degree of reversibility (hysteresis) of adsorption reactions. The two-surface Langmuir isotherms indicated that adsorption maximum could be useful in predicting B availability in soil. On the contrary, the binding energy coefficients in both high and low B concentrations failed to show any practical benefit. Regression model (as a function of CEC and adsorption equation coefficients) confirmed the practical use of Freundlich and Langmuir coefficients to predict B availability in calcareous soils.

Evaluating sampling accuracy is of great importance prior to sampling practice. Since it is expected to be a relationship between soil properties and ancillary environmental variables, proper sampling points are those that better simulate the probability distributions of these variables. The possibility of sampling from low probability tails is very low for random and regular network methods, while the Latin Hypercube Sampling (LHS) method divides the input probability distribution into equal intervals and one sample is taken from each interval. The satellite images band and digital elevation model (DEM) were used as inputs to determine the sampling points in LHS. Three methods including random, regular network and LHS sampling strategies were employed in three sampling densities of 100, 50 and 25 points in the study area of 52,000 ha to simulate the probability distribution of Landsat ETM+ bands and DEM. The simulated probability distributions were then compared with the population distribution and soil salinity data. Results indicated that there is no significant difference between the sampling strategies in 100 and 50 sampling densities to simulate the mean of population, as the sampling density decreased, the Residual Mean Square Error (RMSE) increased. In 25 point sampling density, the RMSE for LHS, regular network, and random sampling methods were 4, 7.83, and 17.5 percents, respectively. Results further indicated that LHS can efficiently simulate the input probability distribution even in low sampling densities. The RMSE values for estimating soil salinity in the original population were 4.22 and 8.66 dS/m in 100 and 25 sampling densities, respectively. Although the calculated RMSE was larger than that of input parameters of image bands and DEM, it could simulate the population probability distribution of soil salinity with enough accuracy. In conclusion, the best sampling method in this research was Latin hypercube method with a density of 25 sampling points.

Plant residue pyrolysis and its conversion to biochar for soil application may improve some soil properties, as well as carbon sequestration and air pollution reduction. The purpose of this investigation was the evaluation of the effect of five kinds of biochar on some properties of a calcareous soil. The used biochars were produced from pyrolysis of residues of wheat, maize, cotton, sesame, and maize cobs at 500oC for three hours under limited oxygen condition. Then, the effect of 2% biochar application to a calcareous soil was studied in a randomized complete block design with three replicates. Soil samples were incubated at 22±2oC and 50% of saturated moisture content for 90 days. Then, soil properties including pH, electrical conductivity, cation exchange capacity, and organic carbon as well as potassium pools distribution, total N, and available P, Fe, Mn, Zn, and Cu were determined. Results indicated that cotton and sesame biochars significantly increased soil pH. All biochars increased soil OC and EC, significantly. Soluble, exchangeable and non-exchangeable potassium were affected by biochars application and its kind. Biochars increased soluble K by 4.4 to 7 times. Increase in exchangeable K was from 144 to 209 mg kg-1 for cotton and sesame biochars application, respectively. Non-exchangeable K was also increased from 290 to 532 mg kg-1. Availability of N, P, Zn, and Cu was not affected by biochar application, but cotton and sesame biochars increased available Fe. Available Mn was also increased by all biochars. With respect to considerable increase in different K forms by biochar application and considering K deficiency problem in some calcareous soils of southern parts of Fars province, use of biochar as a K-rich component in K fertility management may be recommendable.

The presence of oil contaminations in soil may be poisonous for human and other living organisms and can also pollute underground water. Petroleum hydrocarbons are one of the most common organic pollutant groups in environment which cause concern because of their ability in environmental degradation. Thus, it is very important to reclaim such polluted areas. This study was performed in Bakhtiardasht area (Isfahan Province) to determine distribution and intensity of oil contamination caused by the disposal of oil refinery waste in soil and their influence on soil water repellency using geostatistical methods. One hundred samples were taken from 100 nodes of a network pattern with 100 meters spacing. Total petroleum hydrocarbons (TPH), soil water repellency, and some other factors of soil were measured as test variables. Based on the results, the variables followed the spherical semivariogram model and had the medium spatial structure. The TPH concentrations were higher than the international permissible limit (0.1 percent) in most parts of the soil. The variability and spatial distribution of soil water repellency were mostly related to TPH. The surfaces of soil particles were covered by TPH and this caused an increase in water repellency. Most of the soils were in the groups of relatively water repellent (5 to 60 s) to extremely water repellent (< 3600 s) because of different concentrations of oil pollutants in soil. This may lower infiltration rate and can cause a decrease in soil moisture content and, consequently, increase in runoff and limitation of soil water for plant growth.

Conversion of rock phosphate to phosphorus fertilizers is expensive and their consumption can increase the risk of soil pollution via accumulation of heavy metals like cadmium. Increasing p availability of rock phosphate is important in plant P nutrition. In this research, potential use of phosphate solubilizing and Thiobacillus bacteria were studied for increasing rock phosphate efficiency and pistachio seedling growth. The greenhouse experiment was factorial with five bacterial and three salinity levels as completely randomized design with four replications. Inoculation treatments included a control without fertilizer and inoculation (T1), rock phosphate (T2), rock phosphate with two phosphate solubilizing strains contain pantoea dispersa and p. thivervalensis (T3), rock phosphate with sulfur and three Tiobacilluce isolates (T4), and rock phosphate with sulfur, two phosphate solubilizing strains and three Tiobacilluce isolates (T5). Also, three salinity levels including S0, S1, and S2, respectively, 3, 8, and 16 dS/m were applied.Increasing salinity significantly reduced wet and dry weights of shoot and root, average height and number of leaves per seedling, total uptake of P and Fe, had no significant effect on P concentration and Zn uptake. Bacterial treatment had significant effect on wet and dry weight of shoot and root, average height and number of leaves per seedling, P and Fe concentrations, and total uptake of P, Fe, and Zn. Use of phosphate solubilizing bacteria with rock phosphate had the highest effect on wet and dry weights of shoot and root, average height and number of leaves per seedling, and increased them by, respectively, 36.1%, 37.8%, 11.5%, and 27.1 per cent compared with the control. Combination of sulfur oxidizing bacteria with sulfur and rock phosphate (T4), and also combination of phosphate solubilizing and sulfur oxidizing bacteria with sulfur and rock phosphate (T5), had the highest effect on phosphorus concentration and uptake. The T4 treatment in case of P concentration and uptake and the T5 in case of P uptake had significant difference with the control in all salinity levels. However, application of rock phosphate increased P concentration and uptake, but the effect was significantly less than bacterial treatment.