Iranian Journal of Soil Research
Year:2017 | Volume:31 | Issue:2 |Papers Count:15

In a 2-year field study, soil moisture and EC of soil extract (ECe) during growing season as well as grain and biological yield and water productivity of barley plant cv. Nosrat were monitored as affected by two salinity levels of irrigation water. Salinity levels of irrigation water were 2 and 12 dS.m-1. The results showed that salinity stress reduced grain, biological yield, and water productivity by, respectively, 36.0%, 52.1%, and 23.0% in the first year, and 48.4%, 69.1% and 31.7% in the second year. Higher losses in the second year were due to lower precipitation. Two-year averages of water productivity in terms of grain yields were 0.87 and 0.64 kg/m3, for 2 and 12 dS.m-1 water, respectively. In all days after imposing salinity treatment, soil moisture in control plots was significantly lower than saline plots. This difference was more distinct in the first depth and continued until the end of the growing season. On average, soil moisture levels in saline plots were higher than the control plots by 16.8% and 22.4% in the first and second years, respectively. In both years, ECe was also affected by salinity treatment, and this effect became more over time. The 2 and 12 dS m-1 salinity treatments decreased and increased ECe, respectively. The highest ECe values were observed at 160 days after planting in all three soil depths. Overall, in this condition, irrigation with saline water increased ECe about twice at the end of season compared to early growth, and increased ECe by 20% over EC of irrigation water. Greater soil moisture in saline conditions is not useful for crops because it is not easily available and has low quality, however, halophytes such as Panicum antidotale, Kochia spp., Salicornia spp. in rotation with barley might use this higher soil moisture and produce acceptable yield with less water.

Due to the importance of sesame as an oil crop, in order to investigate the effects of different levels and application time of nitrogen (N) on quantitative and qualitative yield of this crop, an experiment was conducted in two successive years from July 2009, on JL-13 variety in Jiroft. Experimental design was factorial with Completely Randomized Block Design (CRBD) with three replications. Treatments were 5 levels of nitrogen (0, 25, 50, 75, 100 kg N ha-1) as urea and split application of N (two splits: before planting and before flowering; and 3 splits: before planting+before flowering+before seed pods).Every plot contained four planting rows (five meters length). Spacing between two rows and plants were 50 and 10 cm, respectively. Two central rows were cut for yield and yield components determination. N absorption and nitrogen agronomic efficiency were also measured. Results showed that the effect of N splitting on yield, yield components, and oil content of sesame was not significant. Nitrogen application increased seed yield, yield component, and N agronomic efficiency significantly. Application of 75 kg N ha-1 resulted in the highest seed and oil yield, i.e.1137 and 602 kg ha-1, respectively. Thus, under the condition of this experiment, application of 75 kg N ha-1 in two splits is recommendable.

In this research, the reaction of Satsuma mandarin (on Swingle citromelo rootstock) to calcareous soils was investigated in pots with soils from east of Mazandaran province, using a randomized complete block design. The highest mean of shoot dry weight was obtained in soils with 14% total lime and 5% active lime. The highest chlorosis was observed in soils from west of Neka and east of Sari with 30 and 45% total lime and 14 and 16% active lime, while the least chlorosis was obtained in soils with no lime or with 3% active lime and 2% to 9% total lime. Total and active iron concentration in leaves and root did not have a significant relationship with degree of leaf chlorosis and soils with 2% total lime (south of Babol) and 9% total lime (west of Ghaemshar had the highest total iron concentration in root and the least symptoms of leaf chlorosis.Mean iron concentration in root was about 7.5 times that of leaves that showed iron accumulation and deposition in root. Mean Mn concentration in leaves in most soils was lower than optimum (>25 mgkg-1) while soils available Mn was more than optimum (2.5 mgkg-1) for citrus trees. Mean Mn concentration in roots was about 3.3 times that of leaves. In contrast, although available Zn of some soils was lower than optimum, in most soils, Zn concentration of leaves was in the optimum range. In general, according to results of this research, Satsuma mandarin on Swingle citromelo rootstock is inappropriate in soils with total lime more than 14% and active lime more than 5%. Also, due to low absorption and transmission efficiency from roots to shoots and severe deficiency in leaves, Mn is the most limiting microelement for this rootstock-scion combination.

Soil plays a crucial role in biogeochemical cycles as an important source and sink of nutrients. Soil properties, distribution, and changes are important factors in agriculture. In this study, 600 samples were collected at 100 x 100 m intervals from 0-30 cm depth in 800 hectares of agro-industrial land of Sharif Abad, in Qazvin. Analysis of classical statistics and geostatistical analysis were performed on the collected data. The results showed that changes in soil total nitrogen varied within a range of 0.02% to 0.82% with an average of 0.26%, while Olsen extractable phosphorus varied within a range of 9.58 to 93.07 mg/kg, with an average of 36.21 mg/kg. Changes in ammonium acetate extractable potassium varied within a range of 180 to 1740 mg/kg, with an average of 552.87 mg/kg. Also, cation exchange capacity varied within a range of 11.44 to 50.16 with an average of 28.20 meq/100 g soil. Exponential model was the best semivariogram model for all studied parameters. Effective ranges for N, P, K and cation exchange capacity were, respectively, 510 m, 798 m, 567 m and 1476 m. Kriging estimator was used to prepare zoning map of the studied traits. The results showed that the relative area of zones with less than 0.1% total nitrogen element was zero percent (0% of the total area), between 0.1-0.2% (3.5%); between 0.2-0.3% (74.3%), and for more than 0.3%, it was 22.2%. In addition, for elemental P, the extent of zones for less than 12 mg/kg was zero percent, between 12-24 mg/kg was 7.8%, between 24-36 mg/kg was 48.4%, and for values more than 36 mg/kg, the extent was 43.8%. In the case of elemental K, the extent of zones for less than 250 mg/kg was zero percent, from 250 to 400 mg/kg it was 4.6%, from 400 to 600 mg/kg the extent was 72%, and for values more than 600 mg/kg, it was 23.4%. Moreover, for cation exchange capacity less than 10 meq per 100 g soil, the extent of zones was zero percent, between 10 and 20 meq per 100 g soil, the extent was 13.1%, between 20 and 30 meq per 100 g soil, it was 44.6%, and for more than 30 meq per 100 g soil, the extent of zones was 42.3%.

The effect of organic amendments on phosphorus (P) availability over time is important for developing P fertilizer and organic amendment management practices in soils. This study was conducted to determine the effect of two types of vermicompost, namely, sheep manure (SMV) and municipal waste (MWV), on P availability, its mineral species and fractions in a calcareous sandy loam soil treated with three kinds of phosphorus fertilizer (rock phosphate (RP), diammoniumphosphate (DAP), and triple super phosphate (TSP) during 90 days. Available P data during the incubation period were fitted using the power function equation to describe P transformation rate. The geochemical visual MINTEQ was used to calculate saturation indices and mineral P species in solution at the first and last days (nineteenth day) of incubation. By the end of the incubation period, there was no significant difference (P£ 0.05) between the amounts of available P released in the treated and the control soils, except in soils containing TSP treated with MWV and soils containing DAP treated with SMV and MWV. These results suggest high P fixation capacity in studied soil.Phosphorus transformation rate (the b constant of power function equation) ranged from -0.059 mg kg-1 day -1 (soil treated with SMV) to -0.140 mg kg -1 day-1 (soil treated with TSP). The highest "a" constant of power function was observed in soils treated with TSP and DAP and MWV. As compared to application of phosphorus fertilizer alone, vermicomposts applications with P fertilizer decreased P transformation rate in soils. Available P in soils treated with MWV was higher than with SMV. Phosphorus fractionation at the first and nineteenth day of incubation showed that carbonate and residual fractions were the dominant fractions, respectively. The results showed that P release was controlled by the dissolution rate of hydroxylapatite, and HPO4-2 was the dominant P specie during the incubation.

Phosphorus is an essential element for plant that appears in different chemical and biochemical forms in soil, therefore, it is susceptible to effects by pedogenic processes. In order to investigate effect of pedogenic processes on P forms and their distribution, 8 soil profiles were studied in forest land of Kelardasht. Available P (Pav), total P (TP), organic P (OP), mineral P (MP) and 8 mineral P forms were determined in the genetic horizons and the correlation of these forms with each other and also the physicochemical soil parameters were investigated. The results showed that pedogenic process significantly affected distribution of different P forms. Fe-P and Al-P showed significant positive correlation with Pox, which could indicate simultaneous extraction of poorly crystalline Fe-Al oxide (by dissolution) or adsorbed/absorbed P by Al-Fe oxides (anion and ligand exchange). These poorly crystalline forms, octacalcium phosphate (Ca8-P) and occluded P (Oc-P) correlate positively and significantly with clay content that enhance possibility of these components linkage with clay particles during different chemical reaction and co-migration of P and clay by lessivage and eluviation-illuviation process. Labile mineral P (LPi) and moderately labile mineral P (MLPi) did not show significant correlation with Pav, whereas apatite significantly and positively correlated with Pav. Removal of P from surface horizons can explain this result. Nevertheless, the highest correlation was between Pav, OP, and organic carbon (OC). According to this result, littering and humification may be considered as the most important processes that can influence P availability.

Phosphorus (P) sorption characteristics of soils influence P availability. This study was conducted to investigate P sorption isotherm, standard P requirement (SPR), P buffering capacity (PBC), desorption, and P hysteresis index (PHI) by 10 surface (0-30 cm) and 10 subsurface (30-60 cm) soils in vineyard soils of Malayer area in Hamadan province. Isotherm experiment was carried out by concentrations of P ranging from 0 to 200 mg l-1 of KH2PO4 salt in the presence of 0.01 M CaCl2. Desorption experiments were conducted with 0.01 M CaCl2. Phosphorus sorption characteristics in soil were calculated from isotherm equations. The average values of Olsen's extractable P (Olsen P) in surface and subsurface soils were 24.3 and 19.4 mg kg-1, respectively. In surface and subsurface soils, Olsen P was higher than the optimum concentration of P for most crops (7-10 mg P kg-1). Phosphorus sorption curves were well fitted to the Freundlich, Van-Hay and Temkin equations. The SPR average of surface and subsurface soils, defined as the amount of P sorbed at an equilibrium concentration of 0.3 mgP l-1 was 18.7 mg kg-1 and 19.7 mg kg-1, respectively. The PBC average of surface and subsurface soils, account from Van-Hay equation was 89.2 l kg-1 and 103.5 l kg-1, respectively. The average value of PHI in surface soils (1.7) was greater than subsurface soils (1.6). There was significant negative correlation between SPR with Olsen-P in surface (p£0.01) and subsurface (p£0.05) soils. We found significant positive correlation between PBC with clay (p£0.01) and ECC (p£0.05) of soils. Our finding showed that high level of Olsen P concentration in surface and subsurface soils may decrease the availability of other nutrients. Appropriate P fertilizer management according to isotherm finding is needed.

Soil structure and aggregate stability are physical characteristics that directly and/or indirectly affect the other soil properties and growth of plants. These soil attributes are influenced by factors such as the type and amount of organic matter and soil water conditions. The effects of 0, 0.05%, 0.5%, and 5% organic acid and 1, 4, 8, and 12 wetting-drying (W-D) cycles of 10 days on the soil aggregate stability and size distribution were evaluated in a factorial experiment arranged in a completely randomized design with three replications. Mean weight diameters (MWD) of aggregates increased significantly (by 22%) as compared to the control when 4 cycles of W-D were applied, whereas geometric mean diameter (GMD) of aggregates was decreased by 27% and 23%, respectively, when 8 and 12 cycles of W-D were applied. Application of 4, 8, and 12 W-D cycles resulted in a significant decrease in D10, and application of 8 and 12 W-D cycles decreased D25, D30, D50, D60, and D75, significantly. The uniformity coefficient of the aggregate size distribution curve increased by 13%, 15%, and 11% when, respectively, 4, 8, and 12 W-D cycles were applied. Also, the curvature coefficient of the aggregate size distribution curve decreased by 6% in response to application of 0.05% organic acids. In general, W-D cycles decreased some indices of aggregate size distribution, while organic acids had no significant effect on aggregate stability. Organic acids could mitigate the adverse effects of W-D cycles. Therefore, their application in the regions with W-D cycles is recommended to reduce the adverse effects of wetting-drying process on the soil structure and aggregate stability, and the negative results of the consequent water and wind erosions.

Deforestation has detrimental effects on the environment which could result in increased flooding and soil erosion and degradation. Study on the effect of forest clearing on soil functioning within an ecosystem is evaluated by soil quality indicators, and can provide the basis to control the land degradation and develop sustainable management strategies. This research was conducted to investigate the effect of forest clearing on some of soil quality indicators in Saravan Forest Park, located in Guilan province. This region has been cleared in some parts to allow installation of the high voltage power towers. In overall, 144 soil samples were taken from 0-15 and 15-30 cm soil depths of the cleared part and its adjacent forest from four slope positions and two slope aspects. The data were analyzed to compare the effects of land use type and topography on some soil quality indicators. Some important soil quality indicators including bulk density, weighted mean diameter of aggregates, particle size distribution, pH, cation exchange capacity, organic matter content, equivalent calcium carbonate, total nitrogen, and available phosphorous and potassium were measured. The results showed that organic matter content, aggregate stability, cation exchange capacity, total nitrogen, available phosphorous and potassium of surface soils were decreased by forest clearing, whereas, bulk density, pH and equivalent calcium carbonate were increased. Forest surface soils of the hill slope with northern face had higher organic matter, total nitrogen, available phosphorous and lower bulk density compared to other parts. The results indicated that the lower slope positions had the highest amounts of organic matter, available phosphorous, and aggregate stability, and the lowest bulk density and equivalent calcium carbonate. As a result of forest clearing, average Nemero quality index (NQI) decreased by 67.7%. The results showed that the differences of soil quality indicators among different slope positions in deforested parts were more obvious than in the original forest parts. It can be concluded that deforestation may lead to surface soil degradation, which is mainly due to acceleration of soil erosion and soil transportation from top to down slope positions. Different slope positions in the forest are partly uniform due to relatively conserved soil. Considering the severity of surface soil degradation by forest clearing in power transmission lines and the considerable affected area in the region, it is essential to minimize these negative effects by conservation practices such as crop mulches, planting, terraces and diversion channels at the time of construction of these lines.

Use of sewage sludge as a cheap and nutrients-rich fertilizer has been common in some regions of Iran. But, using sewage sludge in large quantities can lead to accumulation of heavy metals in plant. The goal of this study was to evaluate the effects of sewage sludge on heavy metals concentrations in plants and some morphological characteristics of lettuce. This research was conducted in greenhouse of Faculty of Agriculture at Lorestan University. Treatments included five levels of sewage sludge: control (no sludge), 25, 50, 75 and 100 tons per hectare (t/ha), with four replications based on a completely randomized blocks design. Plant tissue analysis showed that sludge application significantly increased concentrations of Fe, Cu, Cd and Pb in lettuce shoot, root, and stalk. In 100 t/ha treatment, the highest concentrations of Fe (6.16 mg.kg-1) was in shoots and the highest concentrations of Cu and Pb, (1.49 and 1.20 mg.kg-1, respectively) was observed in the root and highest concentrations of Cd (0.43 mg.kg-1) was found in lettuce stalk. The results showed that application of sewage sludge significantly increased dry weight of biomass and root, plants height, root length, and leaf area index of lettuce, but had no significant effect on chlorophyll content. The highest amounts of these growth parameters were obtained in the treatment of 100 t/ha. Thus, because of concentration of heavy metals in sewage sludge, its long term application poses risk of heavy metal contamination in the soil and, consequently, health risk to the human and animal food chain. Therefore, according to the research results, it is recommended that sewage sludge should not be used for growing edible food crops. Indeed, before using sewage sludge in different farms, it is necessary to be examined for microbial load and suitable recommendations should be made based on local conditions, vegetation type, and soil characteristics.

Emission of heavy metals pollutants caused by human activities is one of the most important issues in today’s society. The management and application of organic wastes in agricultural lands decreases environmental risks and increases utilization of these materials. A greenhouse factorial experiment was conducted to investigate the effect of Arak municipal sewage sludge on corn Cd uptake in a loamy soil, using a randomized complete block design. Treatments consisted of applying sewage sludge (0, 15 and 30 t ha-1) polluted with cadmium at the rates of 0, 5, 10 and 15 mg kg-1 and DTPA at the rates of 0 and 1.5 mmol kg-1 soil. Sixty days after corn sowing, soil physico-chemical properties and soil and corn Cd concentrations were measured. Increasing the loading rates of sewage sludge from 0 to 30 t ha-1 caused a significant increase in cation exchange capacity (3.5 units) and a significant decreasing in soil pH (0.3 units), respectively. Applying 1.5 mmol DTPA chelate in a soil treated with 15 and 30 t ha-1 polluted sewage sludge (15 mg Cd) increased the plant Cd availability by 8.2% and 15 percent, respectively, and decreased phosphorous availability by 4% and 14 percent, respectively. Almost 79 % of Cd uptake changes were estimated by shoot Cd concentration. The result of this study showed that applying DTPA chelate can increase corn Cd uptake and its phytoremediation efficiency.

Different forms of potassium (K) in soils are closely related to clay minerals and soil physicochemical properties. The present research was conducted to investigate the relation between soil physicochemical and mineralogical properties with different forms of K in soils of Ghrehbagh plain, Fars Province. Eleven soil pedons with the maximum soil variation were selected. Clay mineralogy was determined for surface and subsurface horizons of each pedon, where physicochemical characteristics and different forms of K were analyzed for all horizons. Soluble, exchangeable, non-exchangeable, and structural K were among different forms of potassium studied. Entisols, Inceptisols, Mollisols, Alfisols, Histosols, and Aridisols were identified. Illite, kaolinite, vermiculite, chlorite, smectite and palygorskite were the dominant clay minerals investigated. Different forms of K (with the exception of soluble form) showed negative correlation with sand and calcium carbonate contents, but a positive correlation with clay and cation exchange capacity (CEC). In the studied area, the highest amount of soluble K (42.4 mg.kg-1) was observed in Histosols with a high percentage of organic carbon (18.7%). Results of the study showed that the lowest amounts of all different forms of K were found in Entisols with sandy loam texture and high CaCO3 content (87.5%). On the other hand, the highest amount of exchangeable (286.6 mg.kg-1), structural (6607.1 mg.kg-1), and total (7309.4) K were observed in Alfisols. In the studied area, maximum non-exchangeable K (505.7 mg.kg-1) was measured in Inceptisols with Vertic properties, high clay (40.6 %) and moderately low CaCO3 (37%) contents. Total K contents in Histosols were low, that is why the ratios of soluble, exchangeable, and non-exchangeable K contents to total K were the highest among other studied soils.