Z. Dianat Maharluei; M. Fekri; M. Mahmoodabadi; A. Saljooqi; M. Hejazi
Abstract
Introduction: Today, soil pollution is an important environmental issue that should be taken into account. Industrial activities cause pollution and accumulation of heavy metals in the soil. Soil pollution significantly reduces the quality of the environment and threatens human health. Heavy metals are ...
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Introduction: Today, soil pollution is an important environmental issue that should be taken into account. Industrial activities cause pollution and accumulation of heavy metals in the soil. Soil pollution significantly reduces the quality of the environment and threatens human health. Heavy metals are one of the most important pollutants in the environment, which has received a lot of attention in recent decades. Heavy metal pollution is a serious problem in developing countries and urban areas. Among heavy metals, lead is found in large amounts in the Earth's crust, which has several effects on human health and the environment. Lead is an essential element for the plant and one of the most important pollutants, which is toxic even at very low concentrations. Its presence in the culture medium has a negative effect on germination rate, water status in the plant, dry root weight and aerial part of the plant, photosynthesis, absorption of nutrients and enzymatic activity. Much research has been done to use alternative and modern methods to clean the environment of heavy elements. One way to stabilize heavy metals in the soil is to use biochar. Due to its cation exchange capacity and high specific surface area, biochar is able to reduce the pollution caused by organic pollutants and heavy metals, stabilize heavy metals and improve the condition of plants and soil in terms of pollution. The aim of this study was to investigate the effect of modified biochars rice husk and almond soft husk on lead desorption kinetics in contaminated calcareous soil. Materials and Methods: To conduct this research, a sufficient amount of soil from a depth of zero to 30 cm was collected from the farm of Shahid Bahonar Agricultural College in Kerman. Physical and chemical properties of the studied soil were measured after air drying and passing through a 2 mm sieve. To prepare the biochars (rice husk and almond soft husk), the residues, after collection, were air-dried and ground and then packaged in aluminum foil to limit the oxygenation process. They were then placed in an oven at 500 0C for four hours to produce a charcoal called biochar. Also, to prepare the modified biochar (NaOH and HNO3), one gram of biochar was added to 100 ml of distilled water and then 10 ml of concentrated acid (or 10 g of alkali) was added to it. Stirring at 60 0C for 24 hours. Finally, it was filtered using a centrifuge and washed several times with distilled water to neutralize the pH. The produced powder was dried at 70 0C for 24 hours. The lead desorption kinetics experiment was studied at several times (5, 15, 30, 60, 120, 240, 480, 960, 1440 and 2880 minutes) in two levels of biochar (0 and 4 wt %) and three levels of lead (0, 300 and 600 mg kg-1), which were incubated for 5 months under field moisture in a greenhouse. Results and Discussion: The kinetics results showed that the desorption of lead has the same pattern in all the time studied. Early rapid desorption occurred in the early desorption times (initial 30 minutes) followed by low-velocity desorption (8 hours) and finally, equilibrium was observed in the treated and control samples. The significant difference between the amount of lead released from the treated soils and control indicated a positive effect of both used engineered biochars on reducing lead desorption. The highest amount of lead desorption was observed in soil without biochar, while the lowest desorption rate occurred in treatments of rice husk and almond soft husk modified by sodium hydroxide. The application of modified biochar rice husk highly reduced lead desorption, compared to modified biochar almond soft husk. Conclusion: According to the results, the modified biochar with sodium hydroxide caused a significant reduction in lead desorption compared to other treatments, and this reduction was more in biochar rice husk than the almond soft husk one. It can be stated that rice husk biochar has been more successful than almond soft husk biochar due to its more porous structure and cation exchange capacity. Among the equations used for lead desorption estimation, the two-constant rate equation was selected as the best model for data fit due to high explanatory coefficient (R2) and low standard error (SE). According to the above, the use of biochar can be recommended as a modifier in lead contaminated soils.
H. Hosseini; M. Fekri; Mohammad Hady Farpoor; M. Mahmoodabadi
Abstract
Introduction: The availability of the applied phosphorus (P) is controlled by sorption-desorption reactions in soil. Since the sorption-desorption reactions are affected by physical and chemical properties of the soil, the presence of organic matter (OM) and carbonates can also effect on the ...
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Introduction: The availability of the applied phosphorus (P) is controlled by sorption-desorption reactions in soil. Since the sorption-desorption reactions are affected by physical and chemical properties of the soil, the presence of organic matter (OM) and carbonates can also effect on the P sorption capacity in soil. The purpose of this study was to investigate the effects of OM and carbonates on phosphorus sorption isotherms in some calcareous soils of Kerman province.
Materials and Methods: Six surface soil composite samples (0-30) were collected from Kerman Province located in southeast of Iran. The soils with a wide range of OM and calcium carbonate were selected for sampling. Samples were air dried and passed through a sieve of 2 mm. Physicochemical properties of the soil samples were determined according to the Soil Survey Laboratory Manual. Thereafter, the soil samples were divided into three parts. One portion was used for treatment with sodium hypochlorite to remove organic matter. The second part was treated with sodium acetate buffer (pH = 5) to remove carbonates. The third was used as a control without any treatment. Batch experiments were carried out to determinthe P-sorption isotherms in soil. The sorption behavior of P was studied by Langmuir and Freundlich isotherm models. All experiments were conducted in three replications.
Results and Discussion: The results showed that organic matter and equivalent calcium carbonate, removed from the studied soils with an average efficiency of 86.7% and 84.9%, respectively. Although the isotherms data showed that both Langmuir and Freundlich equations fits to data,Langmuir equation with higher mean of correlation coefficient (R2=0.982) and lower standard error (0.022) showed the best fit to P-sorption data for all soil samples (with and without treatment). Removal of organic matter by sodium hypochlorite increased the phosphorus adsorption capacity in the studied soils. After removal of soil organic matter, an increase in phosphorus adsorption capacity in the studied soils. With respect to control, removing the organic matter increased the adsorption capacity parameters (qmax and kf) about 37 to 104 mg.kg-1 and 11 to 23 L.kg-1, respectively. These results indicate that Fe- and Al-oxides and other available adsorption sites on the mineral surfaces are coated by organic matter and are activated after removal of OM. Removal of carbonates from the soil significantly reduced the P-sorption capacity. qmax and kf were decreased by 17% and 32%, respectively, compared to untreated soils. It is, therefore suggested that available P adsorbing surfaces decreases by removing carbonates from the soil.Constants related with bonding energy increased by 17.03% and decreased by 28.78% by removal of OM and calcium carbonate, respectively. The P maximum buffering capacity is an important indicator for assessing phosphorus stabilization capacity in soil. The greater P buffering capacity, the fewer ability of phosphorus replacement to soil solution. After removal of carbonates, this parameter decreased by an average of 42.5%. The results suggested that carbonates is an important factor in availability of phosphorus in soil. The required phosphorus standard increased by 14.43% by removing OM in the studied soils. However, the removal of carbonates reduced the need of soil for phosphorus by 40.5%.
Conclusion: In this study was investigated the effect of removing organic matter and carbonates on phosphorus sorption isotherms in some calcareous soils of Kerman province. The results of this study showed that P sorption capacity is affected by the amount of carbonates and organic matter. Removal of organic matter from the soil increased the sorption capacity of phosphorus due to Fe- and Al-oxides. Other available adsorption sites on the mineral surface which are coated by the organic matter are active. Carbonates is known as an active site for maintaining phosphorus in the soil and its removal from soils reduces the phosphorus adsorption capacity. Applying/Preserving organic matters to/in soil can increases the efficiency of phosphate fertilizer application and improves plant nutrition. The removal of carbonates from the studied soils reduced their need for phosphorus. Therefore, as well as the addition of organic matter to soil, the removal or reduction of carbonates from agricultural soils is important for improving phosphorus utilization efficiency and plant nutrition management.
babak motesharezadeh; somayeh rezaezadeh; majid fekri
Abstract
Introduction: Boron is one of the seven essential microelements for the natural growth of plants. The toxicity of this element occurs in arid and semi-arid regions, which is because of its high level in soils and the irrigation water of mentioned regions. The aim of this study was to evaluate the effect ...
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Introduction: Boron is one of the seven essential microelements for the natural growth of plants. The toxicity of this element occurs in arid and semi-arid regions, which is because of its high level in soils and the irrigation water of mentioned regions. The aim of this study was to evaluate the effect of nitrogen application on boron toxicity tolerance in pistachio, Badami-Zarand variety. The effects of three nitrogen levels (0, 250, and 350 mg/kg of soil) on the reduction of toxicity due to the three levels of boron (0, 15, and 30 mg/kg of soil) were examined in Badami-Zarandi variety of pistachio under greenhouse conditions. After 7 months from sowing the seeds, pistachio seedlings were harvested and desired traits were measured. The results showed that by increasing boron application level, boron concentration in the shoot and root of seedlings increased whereas their dry weight decreased. Using of nitrogen reduced the negative effects of boron on the dry weight and led to increase dry weight and decrease boron concentration in the shoot and root of pistachio, Badami variety. Nitrogen application at the levels of 250 and 350 mg N per kg of soil reduced boron uptake in shoots by reinforcing plant vegetative system and increasing chlorophyll content by 13.5% and 30.2%, respectively and finally led to diluted boron concentration in the plant (dilution effect) and reduced the effects of boron toxicity. Hence, optimized nitrogen application is suggested as one of the management methods in controlling Boron toxicity under these conditions.
Materials and Methods: A factorial experiment based on randomized complete block design with four replications was carried out. Soil sampling was done in 0-30 cm depth in a zeekzack way from a pistachio garden that located in mahmoodiye area in Rafsanjan. The soil sample was air-dried and passed through a 2mm sieve. The soil chemical and physical properties were measured. In this study, badami-zarand cultivar seed was used because it is one of the most important pistachio cultivars. The seeds were soaked in water for 24 hours and disinfected by benomyl fungicide. When the seeds germinated, they were planted in the pots containing 4.5 kg soil and without drainage, so nutrients balance was kept during growing period. After 7 months, the seedlings were harvested and B was measured.
Results and Discussion: The results showed that increasing the boron levels from 0 to 30 mg kg-1 led to decrease shoot dry weight from 3.72 to 2.45 gram and root DM from 2.28 to 1.50 gram. Increasing 30 mg kg-1 boron led to 2.8 times increase of shoot boron concentration. The averages of shoot boron concentration in the levels of 15 and 30 mg kg-1 boron were 87.6 and 122 mg kg-1DM, respectively. The boron toxicity level in Badami-Zarand cultivar is 8.9 mg kg-1 DM (Sepaskhahet al, 1994), so these levels were the cause of boron toxicity and boron toxicity symptoms were seen as leaf burn, often at the margins and the tips of older leaves.
The results showed that increasing nitrogen levels led to decrease shoot boron concentration and increase their weight. The results also showed a significant negative correlation between the nitrogen levels and boron uptake. Boron uptake in the shoots of seedlings about 13.5 and 30.2 percent decreased when nitrogen levels increased. Shoot dry weight decreased when boron application increased, but it increased when nitrogen was used (Koohkan and Maftoun, 2009).
Conclusion: The reduction of dry weight and increasing boron concentration occurred when increased boron application. The Maximum of boron uptake was seen by leaves, and boron toxicity symptoms were appeared as leaf burn especially at the tips and margins of older leaves. Since, boron is immobile in pistachio; it is absorbed by mass flow, so the accumulation of boron at older leaves is persuaded. Nitrogen reduced the bad effects of boron on dry weight and the bad effects of increasing boron concentration by the synthesis of chlorophyll, so it was more useful in shoot than root. Boron uptake was also reduced by nitrogen application. This effect of nitrogen is probably concerned to the increase of dry weight more than boron concentration (Dilution effect). On the other hand, nitrogen caused to increase leaf index and increase the number of seedling leaves. The injured leaves due to boron toxicity were restored, because of high leaf chlorophyll. It is suggested that this study will be done under field conditions for fertilizer application recommendations and to be used for creation of tolerant cultivars of pistachio.
M. Mahmoodabadi; O.L. Rashidi; M. Fekri
Abstract
This study focused on the effect of organic manures as well as potassium fertilizer on some soil properties and onion yield at the field condition. The experiments were carried out as factorial in a randomized complete block design with three replications. The treatments were poultry manure (10 t ha-1), ...
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This study focused on the effect of organic manures as well as potassium fertilizer on some soil properties and onion yield at the field condition. The experiments were carried out as factorial in a randomized complete block design with three replications. The treatments were poultry manure (10 t ha-1), alfalfa residue (10 t ha-1) and control each together with two levels of potassium fertilizer as K2O (0 and 250 kg ha-1). The results showed that application of poultry manure and alfalfa residue resulted in yield increasing about 57.7 and 40.9 % in comparison to the control, respectively. On average, the onion yield for the potassium treatment was 7.8 % higher than for the untreated one. The application of poultry manure and alfalfa residue increased final infiltration rate 73.2 and 56.1 %, respectively. Inversely, potassium fertilizer caused a significant reduction in the final infiltration rate. Moreover, application of organic manures particularly poultry manure, significant increases in saturated moisture, porosity, EC, organic carbon and available phosphorous and decrease in bulk density and pH was observed, while potassium only increased soil EC, significantly. Application of poultry manure and alfalfa residue increased soil organic carbon 129.8 and 80.2 % and available phosphorous 104.8 and 51.9 %, respectively. Among different soil properties, organic carbon showed the highest influence on yield increase.