Iranian Journal of Soil Research
Year:2016 | Volume:30 | Issue:1 |Papers Count:13

Soils contaminated with cadmium (Cd) may cause a reduction in plants yield and increase the hazard of Cd-contaminated plants consumption by human and animals. In order to study the interaction effects of cadmium and wheat or alfalfa residues on dry matter yield (DMY), concentration, and uptake of micronutrients by corn in a calcareous soil, a greenhouse experiment was conducted in 2014. Results showed that increasing Cd levels significantly decreased manganese (Mn) uptake by corn in soil treated with alfalfa residues but had no significant effect on DMY, concentration, and uptake of other nutrients. Higher levels of wheatresidues significantly increased zinc (Zn) concentration in corn shoots, but decreased DMY, copper (Cu) concentration, and iron (Fe), Mn, and Cu uptake. Increasing levels of alfalfa residues resulted in a reduction of Mn concentration and uptake by corn. In general, addition of alfalfa residues decreased corn DMY and Cu uptake less than those of wheatresidues, but Mn and Zn concentration of corn shoots in wheatresidues treatments were higher compared to those of alfalfa residues. Addition of wheat and alfalfa residues mitigated detrimental effects of cadmium on Fe uptake by corn aerial parts.

A comparison of three methods for the determination of potassium in fertilizers was conducted using 26 fertilizer samples, which were chosen to represent the ones used in the country’ s agriculture. Based on physical and chemical properties, the samples were divided into three categories. The amounts of potassium oxide in fertilizers were determined by gravimetric sodium tetra phenyl boron method, volumetric sodium tetra phenyl boron method and flame photometric method. Potassium recovery rate in the three methods were determined using analytical grade material. The results showed that the recovery rate in the three methods was satisfactory. There was no significant difference at the 5% level between the mean value of potassium oxide determined by gravimetric (22. 24%), volumetric (22. 19%) and flame photometric (22. 47 percent) methods, but the difference between flame photometric method and volumetric method was significant at 5% level. Despite small differences in potassium content measured by flame photometric method and volumetric method, the difference was significant in 15 fertilizers, which can be attributed to our failure to eliminate interfering factors and to use internal standard in flame photometric method. The results showed that there was no significant difference between the two extractions methods (boiling method and shaking method). Based on the results of this study, the flame photometric method has acceptable accuracy and precision and is applicable in all Soil, Water, and Fertilizer Laboratories in the country, thus, it can be introduced as an appropriate method along with gravimetric and volumetric tetra phenyl boron methods that are known and used at international level.

A comparison of three methods for the determination of potassium in fertilizers was conducted using 26 fertilizer samples, which were chosen to represent the ones used in the country’ s agriculture. Based on physical and chemical properties, the samples were divided into three categories. The amounts of potassium oxide in fertilizers were determined by gravimetric sodium tetra phenyl boron method, volumetric sodium tetra phenyl boron method and flame photometric method. Potassium recovery rate in the three methods were determined using analytical grade material. The results showed that the recovery rate in the three methods was satisfactory. There was no significant difference at the 5% level between the mean value of potassium oxide determined by gravimetric (22. 24%), volumetric (22. 19%) and flame photometric (22. 47 percent) methods, but the difference between flame photometric method and volumetric method was significant at 5% level. Despite small differences in potassium content measured by flame photometric method and volumetric method, the difference was significant in 15 fertilizers, which can be attributed to our failure to eliminate interfering factors and to use internal standard in flame photometric method. The results showed that there was no significant difference between the two extractions methods (boiling method and shaking method). Based on the results of this study, the flame photometric method has acceptable accuracy and precision and is applicable in all Soil, Water, and Fertilizer Laboratories in the country, thus, it can be introduced as an appropriate method along with gravimetric and volumetric tetra phenyl boron methods that are known and used at international level.

Changes in soil potassium pools including soluble, exchangeable and non-exchangeable forms at various growth stages of wheat (Triticum aestivum L. ) may be important in management of this macronutrient and knowledge of its dynamic process. To study that issue, an experiment was done in a completely randomized design on a 9-ha field during 2012-2013. Soil samples were taken from depths of 0-15 and 15-30 cm before sowing wheat, and at its various growth stages until ripening. Also, at various growth stages, plant samples were collected and different K forms in soil including soluble, exchangeable and non-exchangeable, and total plant K were determined. Results indicated that soluble K in surface soil decreased severely during early growth stages until stem elongation, and thereafter continued constantly. But, changes in subsurface soil were slower. Significant decreases in exchangeable K in surface soil occurred at stem elongation and ripening stages, but this reduction in subsurface soil occurred at grain milk stage. Non-exchangeable K changes in surface soil were observed at ripening stage, while changes in subsurface soil were not significant. Sum of soluble, exchangeable and non-exchangeable decreased from759 mg kg-1 to 720 and 680 mg kg-1 at stem elongation and ripening stages, respectively. Generally, HNO3-extractable K decreased in surface soil five times more than subsurface soil. Potassium concentration in shoots increased at tillering stage and reached 6. 8 %, followed by a decrease to 1. 1% and 0. 8 % in shoot and seed, respectively, at ripening stage. Generally, results indicated a maximum K uptake by wheat at stem elongation stage that may be considered as a key tool in K fertilizer management. On the other hand, the role of non-exchangeable K and K in subsurface soil may be considered in available K estimation.

In recent years, the use of municipal sewage in certain areas in Zanjan city, Iran, and farms adjacent to Zn and Pb processing plants has led to accumulation of heavy metals in the soil and vegetables. In this research, the concentrations of heavy metals (Cu, Zn, Cd and Pb) in some vegetables (coriander, basil, dill, mint, savory, leek, chard, fenugreek and parsley) cultivated in six regions of Zanjan city were assessed. Results indicated that the highest concentration of heavy metals was in wastewater-irrigated soils, located around the railway. Among the studied heavy metals, Cu concentration of vegetables was higher in wastewater-irrigated farms. Concentrations of Cd, Zn, and Pb exceeded the safe limits for human consumption in all of the vegetables. The highest contaminations of Cd and Zn were found in savory samples (1. 8 and 157. 3 mg/kg fresh weight, respectively) and for Pb and Cu in mint (7. 5 and 18. 3 mg/kg fresh weight, respectively) which were higher than the Institute of Standards and Industrial Research of Iran (ISIRI) permissible values for human consumption. Provisional tolerable daily intake (PTDI) for Cd and Pb was less than ISIRI values. Therefore, long-term use of high intake of vegetables (higher than 0. 058 kg/day) may have dangerous consequences on human health in Zanjan Province. However, the soil Cu concentrations showed positive significant correlation with Cu in mint (p<0. 01) and basil (p<0. 05). Therefore, considering the contamination of vegetables in farms adjacent to Pb and Zn processing plants, it can be concluded that the major source of heavy metals accumulation in leafy vegetables was airborne pollution due to proximity to these industrial plants.

Different resolutions of digital elevation models (DEMs) can generate varied topographic and hydrological features. The objective of this study was determination of suitable cell size of DEMs and its effects on prediction of some soil properties. For this purpose, two study areas were selected with different topographic properties in Selin plain, East-Azerbaijan Province. A total of 31 and 37 points were selected randomly from study area (1) and (2), respectively, and then, elevation, slope, clay and organic matter contents were measured by GPS, manual, hydrometer and Walkly-Black methods. The results showed that the number of cells with sink was more in smaller cell size than bigger cells, causing error in determination of hydrological characteristics. Therefore, they must be removed. Appropriate cell size of DEMs depends on the properties of the area topography, which for the study area (1) and (2) with flat and severely undulating topography, the cell size was 50 and 40 meters, respectively. Geostatistical analysis showed that, in both study areas, spatial correlation linearly decreased with increases in cell size upto 75 m; while in study area (2), it decreased with more intensity, reflecting the loss of large volumes of topographic information. Difference between R2 values for the estimation of soil organic matter and clay from DEMs with different cell sizes was less in area (1) than area (2). Generally, the results of this study showed that lower cell size (<75 m) was recommendable for areas with sever topographic changes and complex morphology, while higher cell size (200 m) was suitable for flat areas.

The low solubility of nutrients in the soils of most arid regions, such as Khuzestan, limits or reduces plants growth. Application of organic sulfur to the soil reduces soil alkalinity, increases nutrient absorption and plant growth. This experiment was conducted in a randomized complete block design with split plot design. Experimental treatments consisted of three date palm offshoots weights including 5-8, 8-11, and 11-15 kg in the main plots and four organic sulfur compounds levels as 0, 400, 800, and 1200 gram per plants in sub plots with 4 replication. The study was conducted at Date Palm and Tropical Fruit Research Institute. Results of leaves analysis after performing the experiment showed that organic sulfur compounds improved soil condition around the roots and caused significant increase in leaf nutrient uptake. The highest levels of nitrogen, and potassium content were 2. 025 and 2. 262 percent and belonged to treatment of 1200 g. organic sulfur per plant. In addition, date palms offshoots weight treatments showed significant differences in growth. The highest rates of growth in trunk diameter and length, seedling length, leaf length, and width were, respectively, 6. 7, 16. 4, 80. 8, 8. 4, and 6. 8 cm, and were observed in the heaviest offshoots. Organic sulfur treatments had significant effects on stems and leaf growth. The highest rates of growth in trunk diameter and length, seedling length, leaf length and width, were 7. 7, 20. 1, 85. 3, 10. 8 and 8. 1 cm and 8. 6 leaves, belonging to the highest level of organic sulfur treatments. Comparison of the interactions also showed that organic sulfur compounds application at any shoot weight increased growth rate significantly. Finally, the off shoots weight range of 11-15 kg and application of 1200 grams of organic sulfur compounds can be recommended for date palm cv. Mejool offshoots growth.

Differences in physicochemical and mineralogical properties of soils close to Urmia Lake in two groups of soils (affected and unaffected by Urmia Lake), were studied in Dizaj-Dol region. Variance analysis of physicochemical properties of these soils showed that the values of OC and CEC in these two groups of soils were significantly different (P ≤ 0. 1), and the values of EC, SAR, ESP and exchangeable Na of these soils were highly significantly different (P ≤ 0. 01). However, soil depth and clay content in these two groups of soils were not significantly different. Clay mineralogical studies showed the presence of smectites, illites, kaolinites, chlorites and vermiculites in both groups of soils. Illites, chlorites and kaolinites are inherited from parent material, while smectites and vermiculites have pedogenic origin and have been formed via transformation of illite. In the soils which have been affected by Urmia Lake, neoformation from soil solution is the main origin of smectites. Comparision of clay minerals in the two groups of soils showed that the rising level of Urmia Lake during 1994-1995 caused the presence of high amounts of smectite and some hydroxy interlayer vermiculite in the soils affected by Urmia Lake.

Although a better understanding and quantitative knowledge of digital elevation model scale will help to improve soil predictions, the influence of pixel size has not been investigated in detail. The aim of this study was to investigate the role of spatial scale on soil clay content prediction by empirically testing the interaction between pixel resolution and window size with regression tree model. In two different areas in terms of their geomorphology and soil (area 1, Maybod located in Yazd province covered 400 km2; area 2, Iasokand located in Kurdistan province covered 400km2), 120 surface soil samples (0-30 cm) were taken and their clay contents were measured. From 121 digital elevation models representing different scales, 22 attribute were extracted and used for soil clay content prediction. Results showed that Maybod area had the minimum RMSE (9. 0%) and maximum R2 (0. 47) and dependence of tree model on pixel size was significant for clay prediction[H1]; however, in Iasokand area, the minimum RMSE (5. 65%) and maximum R2 (0. 77) were obtained and window size was significant for clay prediction.

In order to evaluate the effect of tillage depth and speed on soil physical and hydraulic properties, this research was performed in a clay loam soil. Moldboard plow treatments in three replications were employed in a completely randomized block design with a split tape according to both speed and depth of tillage. Infiltration of soil was determined in undistributed samples by using disc infiltrometer apparatus under-15,-6,-3 and 0 cm H2O suctions (K15, K6, K3, Ks). The results revealed that the tillage speed had significant effect on K3 and Ks at 5% and 1% probability level, respectively, whereas deep tillage as well as interaction of the factors did not affect them. Both of the studied factors (depth and speed) and their interaction had no significant effect on K6 and Gardener α coefficient, while they had significant effect on the bulk density of top soil at 5% probability level. Furthermore, K15 showed significant differences under the effect of tillage depth at 5% probability level. The results also indicated that speed of tillage had no effect on the bulk density of sub-surface layers.