حسین میر سیدحسینی

Cadmium (Cd) contamination has been a widespread concern in paddy soils because of its subsequent transfer to the food chain. Biochar amendment is proposed to stabilize Cd in the contaminated soils. However, the pristine biochar shows limited functionality towards Cd sorption in practice. Recently, Mg-modified biochars have attracted much attention for their low toxicity. These biochars are coated by MgO or Mg(OH)2 precipitates during the pyrolysis process. Magnesium chloride (MgCl2)-modified biochars have been used widely in the removal of heavy metals from the aqueous solutions. However, there is little literature about their performance in soils. The present study therefore was conducted to investigate the effects of application of unmodified and MgCl2-modified rice husk biochars on the kinetics and isotherms of Cd sorption in a calyey paddy soil.

The unmodified and MgCl2-modified biochars were produced from rice husk at 600°C. Some relevant characteristics of the produced biochars (including elemental composition, pzc, pH1:10, ash content and BET surface area) were determined. Moreover, the studied soil was taken from a paddy field (0-20 cm) in the Qaemshahr region of Mazandaran province. The biochars (< 0.5 mm) were added to the soil samples at three levels (0, 3, and 5% w/w) and the amended soils were incubated at 25°C for 45 days. Then, the kinetic experiments of Cd sorption at a concentration of 375 mg Cd/L at times of 0.25, 0.5, 1, 2, 4, 8, 16, 24 and 48 hours and the isothermal experiments of Cd sorption at concentrations of 50, 100, 150, 200, 300, 350, 400, 600 and 800 mg Cd/L were performed. In both kinetic and isotherm experiments, a 0.01 M KCl solution was used as the background electrolyte. Finally, the relevant kinetic and isotherm models were fitted to the sorption data and their parameters were calculated.

Biochar characterization indicated that modification with MgCl2 resulted in an increase of the O/C ratio (from 0.27 to 0.48) and pH (from 7.67 to 8.60). This modification also increased the H/C ratio (from 0.032 to 0.071) and the specific surface area (from 195.6 to 231.2 m2/g). As a result, the MgCl2-modified biochar was more hydrophilic and less carbonized than the unmodified one. Moreover, the characteristic peaks of the MgCl2-modified biochar (3700, 1428 and 500 cm-1) were present in its FTIR spectrum. The results revealed that about 74 to 89% of the Cd sorption by the soils occurred in times less than 2 hours. With MgCl2-modification, the sorption equilibration time was reduced from 48 hours to 24 hours. In contrast, the unmodified biochar had no considerable effect on the Cd sorption kinetics. Among the kinetic models, the Elovich model with lower SEE was the best to fit the Cd sorption kinetic data. The intra-particle diffusion model was not satisfactory for Cd sorption on the biochars. Freundlich model with lower SEE well described the Cd sorption isotherms. Application of 3% and 5% MgCl2-modified biochar increased the Freundlich KF parameter by 2.4 and 2.8 times as compared to the control. Moreover, the aforementioned treatments increased the heterogeneity parameter of the Freundlich model (n) from 3.48 to 6.08. The Temkin model could not reasonable fit the sorption data. In contrast, the unmodified biochar did not show any considerable effect on the Cd sorption capacity of the clayey soil used in this research. This finding means that the unmodified biochar could not improve the sorption performance of negatively charged soil clay particles.

According to the results obtained, it could be concluded that the Cd sorption behavior of the soil treated with unmodified rice husk biochar was similar to that of the untreated soil. Whereas, the MgCl2-modification improved both sorption rate and sorption capacity of the soil for Cd. Application of MgCl2-modified biochar improved the Cd sorption properties of a clayey soil with high intrinsic sorption ability. Thus, this may be a promising approach in remediation of Cd-contaminated paddy soils with the aim of reducing Cd mobility and availability. However, there is need to do more research to create awareness about the importance of biomass nature as well as pyrolysis temperature, the ratio of MgCl2 to biomass, the mechanism of Cd stabilization and the desorption of Cd from soils treated with MgCl2-modified biochars.

Today, in order to increase the efficiency of fertilizer use and reduce environmental pollution, the production and consumption of slow-release fertilizers is considered. The objective of the current study was to apply three methods of rotary drum (A), insitu hydrogel synthesis (B) and two-stage (C) to reduce the solubility rate of urea fertilizer using starch as a cheap and environmentally friendly source and evaluation the comparative efficiency of these samples on the growth and nutritional responses of tomatoes. At first, fertilizers were synthesized in three methods. Then, the effects of synthesized samples (A,B and C) were compared with un-coated urea granules on morphological characteristics of tomatoes. A factorial based on completely randomized blocks design were utilized with three replications in 2020 in greenhouse conditions, at 180 and 420 kg/ha of each fertilizer treatment. The results showed that urea release rate after 6 hours from synthesized (A, B and C) fertilizers was reduced 87.33, 32.08 and 29.22%, respectively compared to un-coated urea. Comparison of coating methods showed that the highest amount of dry weight (roots and shoots), stem length, chlorophyll content and number of leaves and lateral branches were observed in C fertilizer treatment. Nitrogen use efficiency and apparent nitrogen recovery in C fertilizer treatment increased 36.54 and 27.04% compared to urea, respectively. The use of starch as a natural biopolymer in the structure of these fertilizers reduces nitrogen loss and environmental pollution.

Considering that most of the calcareous soils of Iran are deficient in one or more micronutrients, optimal nutrition of nutrients such as silicon under the influence of biological treatments can be highly effective in these conditions. Therefore, this study was conducted to investigate the effects of silicon and phosphate-soluble bacteria on the availability of micronutrients for wheat. We used a completely randomized design in three replications and treatments included 0, 150, 300, 600 mg/kg silicon from a source of silicic acid and three levels of bacteria (non-inoculation of bacteria, Bacillus and Pseudomonas). The study was conducted in the greenhouse of Soil and Water Research Institute. The results showed that the combined use of silicon and phosphate-solubilizing bacteria increased the uptake of manganese and iron compared to the control treatment. However, the antagonistic effect between nutrients reduced zinc uptake at higher levels of functional silicon. The effect of inoculation with Bacillus and Pseudomonas on the amount of zinc, manganese and iron uptake by wheat was superior to the control bacterium. On the other hand, application of silicon (600 mg silicon/kg soil with Pseudomonas bacteria) significantly increased the concentration of phosphorus in wheat to the optimum level. Since excessive use of phosphate fertilizer in calcareous soil reduces absorption of micro nutrients, the combined use of silicic acid and phosphate-soluble bacteria can be recommended as an effective method for increasing availability of micro nutrients in greenhouse conditions.

A significant part of the nitrogen fertilizers due to the high solubility in water, penetrates into the lower parts of the soil and become unavailable to the plant. To prevent nitrogen losses, various methods have been used, of which coatings is the most widely used methods to reduce the rate of dissolution in water. The objective of the current study was to produce novel slow release fertilizers (SRFs) using starch-based polymer nanocomposites (in terms of environmental compatibility and degradability) and to investigate the comparative efficiency of these samples on the growth and nutritional responses of tomatoes. Firstly, two formulations of urea fertilizer coated with starch-based polymer nanocomposite reinforced with biochar nanoparticles (A) and pristine polymer without nanoparticles (B) were synthesized. Then, the effects of two levels (180 and 420 kg/ha or 60 and 140 mg/kg) synthesized SRF samples (A and B) and un-coated urea granule fertilizer (as a control) on morphological characteristics of tomatoes were investigated. A factorial design based on the completely randomized blocks with three replications was performed at Agricultural Biotechnology Research Institute, Karaj. The results showed that the presence of nanoparticles increases the release time of urea from the coating layer, and it was prolonged with increasing the amount of NCNPs because of favorable interfacial polymer-filler interactions. So that, the nitrogen release rate from sample A, at pH= 2, 6 and 10, was respectively decreased 49.46, 18.52 and 45.13% as compared to sample B. Moreover, application of SRF samples increased nitrogen use efficiency, nitrogen agronomic efficiency and apparent nitrogen recovery. So that, the nitrogen use efficiency in fertilizer treatments A and B with usage of 420 kg/ha was respectively increased 7/85 and 14/68% compared to urea fertilizer.

Low nitrogen use efficiency (NUE) is a global problem in crop production, and agriculture of Iran is not exempt in this regard. Nitrogen (N) fertilizers as a source of nitrogen can be very effective in water, soil and air environmental pollution. Nitrification is a key process in agricultural ecosystems since it results in changes of ammonium to nitrate and eventually loss of considerable amounts of soil nitrogen through leaching and denitrification. The application of nitrification inhibitors (NI) together with nitrogen fertilizers is a strategy to reduce N losses. Thus, the objective of this study were to evaluate the effect of inhibitor 3,4-Dimethylpyrazole phosphate (DMPP) on nitrification rates and nitrification inhibition percentage in some soils of Iran containing representing differences in organic matter content and texture.

An incubation experiment was conducted to evaluate the effect of DMPP on nitrate and ammonium concentration changes in different times and abundance of ammonium (AOB) and nitrite (NOB) oxidizer bacteria in five soils with different texture and organic carbon (O.C). The treatments of experiment included NI at three levels (without N and NI, 200 mg/kg N as ammonium sulfate without NI, and 200 mg/kg N as ammonium sulfate containing 0.8 % NI), five soil types (sandy loam 1 with 0.58% O.C, sandy loam 2 with 0.3% O.C, loam with 0.73% O.C, clay loam with 0.87% O.C, clay with 1.47% O.C), and five sampling times (0, 14, 28, 42, and 56 day).

The results showed that application of N containing DMPP compared to N without DMPP in all soils had significant effect (P<0.001) on reducing nitrification, which was reduced 44.7% on average. DMPP efficiency on nitrification inhibition in experimented soils had significant difference, indicating that nitrification occurs rapidly in soils containing more clay and O.C compared to soils with more sand and low O.C. Nitrification inhibition percentage after 56 day incubation in SL1, SL2, and L were 57%, 46%, and 12%, but in two other soils were about zero. Also there were a positive significant correlation between abundance of AOB and NOB with nitrate concentration (r = 0.6), O.C content (r = 0.9), and total soil N (r = 0.9).

soil nitrification rate are different under influence of factors like soil textural properties and soil O.C content, and DMPP efficiency had inverse relationship with some soil properties including clay%, O.C content, and nitrifier bacterial population. Further these properties can be used in predicting the short term effects of inhibitors.

Soilless cultivation systems are used to attain higher performance, improve crop quality, conserve water and land, and protect the environment better. This study has attempted to use some agricultural wastes and organic matter, and management practices to optimize water holding capacity of cultural media, which are suitable for the growth of tomato seedlings (Solanum lycopersicum.). Fifteen different substrate (growth media) mixtures with a mineral fraction (sand and perlite) and organic fractions (bagasse, oak tree bark, poplar wood chips) were prepared and compared. Sand (2-4mm) and perlite (4-6 mm) were mixed at 0, 10, 20, 30 and 40 percent volume ratios with organic fractions at 0, 30 and 60 percent. The experiment was arranged in a completely randomized design with 15 treatments and 3 replications with 6 observations per treatment. During the seedling growth period (45 days), every 7 days, 90 seedlings were harvested (data for three periods were used) to determine the effect of the growth media on different growth parameters(plant dry matter and leaf area) and indices (RGR, NAR, and SER). The growth rate of tomato seedlings generally increased over time the rate of which varied with treatments. Seedling height, stem diameter, plant fresh weight and dry matter indicated that the highest length (25.91 cm) and diameter (4.83 cm) of the tomato seedlings was in treatment eight (S30P10T30B0C30). It was also shown that the sand fraction as a mineral component had a better performance compared to perliter in growth parameters. For the organic component of the growth media, tree bark treatments were better than wood chips or bagasse. The bagasse treatment had the lowest fresh weight and dry weight of shoot and root. The treatments with water holding capacity of 90-100% showed the best response in the growth of tomato seedlings.