نشریه پژوهشهای خاک (علوم خاک و آب)
سال سی و پنجم شماره 2 (تابستان 1400)

Biochar is one of the organic matter sources and it can be effective in improving P adsorption in the soil. This experiment was conducted to investigate the effect of poultry manure (PM) and its derived biochar at temperatures of 200, 300 and 400 °C on P adsorption capacity in a calcareous soil. Poultry manure and its derived biochars were mixed with 400 g of the soil and incubated at appropriate temperature and humidity for 90 days. Phosphorus adsorption isotherms were measured by the modular method at the concentration range of 0 to 90 mg.L-1 of P, and adsorbed P was calculated. The results showed that the P adsorption rate decreased with increasing P concentration in the equilibrium solution in all treatments. Adsorption data were fitted with Long Muir model. In biochar-treated samples, average P adsorption gradient at the low and high P concentrations in equilibrium solution was, respectively, 56% lower and 116% higher than the control. Biochar produced at 300 and 400 °C had, respectively, the minimum and maximum impact on the amount of slope and maximum P adsorption. The maximum adsorbed P in B300 and B400 treatments were 144 and 246 mgkg-1, respectively. At low P concentration in equilibrium solution, P adsorption gradient in B300 and B400 was, respectively, 5.42 and 10.1 mgkg-1 for each unit change of P concentration, and it was 1.50 and 4.59 mgkg-1 at the high P concentration. The behavior of B300 in P adsorption indicates the higher possibility of using it in agricultural lands to improve P availability, compared to the other studied biochars, while B400 behavior indicates the possibility of using it to remediate P-contaminated soil.

Traffic emissions are one of the largest sources of heavy metal pollution, leading to ecological imbalances in roadside soils. This study was conducted to determine the content and assess the pollution and potential ecological hazard of Zn, Pb, and Ni in some suburban roadside soils of Hamadan, in 2019. In so doing, 63 surface soil samples were collected along 700 m from a 9.0 km section of Goltepeh, Razan, and Kermanshah roads. After samples preparation, content of the elements was determined by induced coupled plasma optical spectroscopy (ICP-OES). Also, pollution factor (CF), geo-accumulation index (Igeo), and cumulative potential ecological risk (RI) were calculated. Statistical analysis was performed using SPSS software. The maximum mean content of Zn, Pb and Ni in the soil samples was 122 ± 3.24, 26.4 ± 0.730, and 22.2 ± 0.360 mg/kg for, respectively, Razan, Kermanshah, and Razan and indicated the effect of traffic intensity. The positive and significant correlation between Zn and Pb (p <0.05) and Zn and Ni (p < 0.01) in the soil samples point to the common sources of these elements. The results of calculating CF, Igeo and RI indices showed acceptable soil quality in the studied stations and fell in the category of no ecological hazard. Moreover, the average values ​​of the calculated monomial potential ecological risk factor (Er) for the studied elements had a decreasing trend in the following order Pb > Ni > Zn. From the results of the current study, it may be concluded that regular monitoring of concentrations and assessment of ecological hazards of metal pollutions is necessary in order to manage and protect the soil quality.

In order to investigate the effect of nitrogen, zinc, boron, and magnesium and the time and stages of foliar application on the grapevine (Vitis vinifera L.), a factorial experiment in the form of a randomized complete block design was conducted for three years. Treatments consisted of 12 fertilizer treatments including C1 (Control), C2 (N), C3 (Zn), C4 (B), C5 (Mg), C6 (N + Zn), C7 (N + B), C8 (N + Mg), C9 (Zn + B), C10 (N + Zn + B), C11 (Zn + B + Mg), and C12 (N + Zn + B + Mg) and two spraying times (T1= One-stage foliar application in the bud swelling stage and T2= Two-stage foliar application in bud swelling stage and after fruit formation). The results showed that nutrient foliar application treatments at two foliar application times and in three consecutive years did not have a significant effect on vegetative growth characteristics, including leaf area size and branch diameter, but it had a significant effect on yield components and fruit quality like cluster weight, berry weight, berry size, the yield of each shrub, anthocyanin, soluble solids (TSS) and total acidity (TA) of fruit. The tripartite interaction of year, foliar application time, and nutrient treatment had a significant effect on yield, panicle weight, and anthocyanin. The highest average of fruit yield per tree in three years was observed in C2 (N), C3 (Zn), and C4 (B) treatments, respectively, and almost all treatments showed a significant difference compared to the control. The grapevines that received no dietary treatment, along with C10 (N + Zn + B) and C11 (Zn + B + Mg), had the lowest fruit yields, respectively. Therefore, it can be concluded that despite the usefulness of spraying nitrogen, zinc, and boron nutrients, the use of nutrients together has negative effects on rainfed grapes.

Water and nitrogen are two important factors that affect yield and plant growth. Excessive use of chemical fertilizers in recent decades, especially nitrogen fertilizer, has caused to nitrate pollution in soil, water and environment. This study was carried out to investigate the effects of different amounts of water and nitrogen fertilizers on the accumulation of nitrate in soil, tomato and potato plants. Research was performed on farms of Mashhad plain. Selected farms included 15 tomato and 15 potatoes fields. Irrigation method in all fields was furrow irrigation. During the growing season, the amount of water and nitrogen were measured in all fields. At the beginning and end of the growing season, the amount of nitrate in the soil (two depths of zero to 30 and 30 to 60 cm) and at the end of the growing season, the content of nitrate in both potato and tomato crops were measured. The measurement method was spectrophotometry (spectroscopy) at 540 nm. Results showed that the amount of water and fertilizer consumed in potato fields were higher than required. But, in tomato fields, water consumption was more than the required amount and, in some fields, the fertilizer was higher, and in some less than the recommended amount. With increasing water, nitrate decreased in two depth 0-30 and 60-30 cm whereas with the increase in fertilizer urea, soil residual nitrate increased at the end of the season. With increase in fertilizer application, nitrate residue in the plants increased. Thus, effects of excessive water on nitrate leaching and creating environmental problems are serious. To avoid such problems, crops water requirement must be estimated with great care. Also, fertilizer application should be balanced and in accordance with the type of plant and its yield.‎

In recent years, floods and waterlogging conditions in the northern and southern provinces of Iran have become important challenges, which directly and indirectly affect the solubility and availability of most of the soil nutrients. To investigate the effects of waterlogging, seven soils were selected from the orchards of different regions of East Mazandaran (Ghaemshahr, Sari, and Neka). In a pot experiment, the soils were placed under continuous waterlogging conditions for 70 consecutive days, and the trend of changes in oxidation-reduction potential (Eh), electrical conductivity (EC), pH, concentrations of Ca2+, K+, Na+ and iron (Fe2+ and Fe3+) of these soils were studied. The results showed that the mean Eh values of soils dropped within 2 days of waterlogging, then increased slightly in the third day, and then began to drop again, and this drop trend continued until the end of the period, from 552 mV at the beginning of waterlogging and reached -99 mV at the end of the period. The average soil pH decreased from 7.8 to 6.88 after 10 days of waterlogging, and then increased and reached a relatively stable equilibrium (about 7.05). The average EC values of soils, increased after the first day of waterlogging, then, declined to 2.13 dS/m, and again increased to the maximum value (about 3.09 dS/m) after 10 days. The concentration of Ca2+, K+, and Na+ in the soil solution increased after waterlogging and reached the maximum within 2 days, then gradually decreased and reached a relatively constant amount. The concentration of Fe within the first days after waterlogging was 1.95 mg/L, increased to 6.67 mg/L after 10 days, then decreased to 4.27 mg/L after 20 days, and eventually increased to 9.98 mg/L at the end of the period (70 days). Based on the results of this study and considering the trend of EC changes and concentrations of nutrients in soil solution, application of chemical fertilizers to soils should be avoided after waterlogging occurrence. Also, due to the changes in soil Eh, the continuation of waterlogging for more than 5 days can lead to relatively anaerobic conditions in the soil and damage to fruit trees, therefore, drainage of excess water is recommended.

Information on soil pollution assessment and suitable extractants to determine the available amounts of heavy metals in calcareous and saline soils of Iran are limited. Therefore, this study aimed to compare EDTA pH 4.65, EDTA pH 8.6 and, DTPA pH 7.3 extractants to characterize availability of heavy metals including copper, cadmium, lead, and nickel in calcareous and saline soils of Khuzestan Province. To this end, 63 soil samples were collected from wheat fields of the province and wheat was planted under greenhouse conditions using randomized complete design with three replications. Due to salinity limitation, sequential leaching by two pore volumes of each soil was applied. Plant available amounts of copper, cadmium, lead and nickel in soils were measured with the extractants before and after leaching. Result demonstrated that DTPA pH 7.3 and EDTA pH 4.65 extracted the lowest and the highest amounts of heavy metals, respectively. Salinity reduction had different impacts on the heavy metals extraction based on the type of the metal and extractants, such that uniform and similar trends were not observed for the extracted metals. There was a significant positive correlation between the extracted copper of all three extractants and wheat copper content. This correlation for DTPA pH 7.3 extractant (r = 0.32, P ≤ 0.01) was higher than EDTA pH 4.65 (r = 0.27, P ≤ 0.05) and EDTA pH 8.6 (r = 0.25, P ≤ 0.05) extractants. For cadmium and lead, only positive and significant correlations (r = 0.33, P ≤ 0.01 and r = 0.28, P ≤ 0.05, respectively) were obtained between DTPA extract and their concentrations in wheat. No significant correlation was recorded between wheat nickel content with any of the extractants. Based on the results, it seems that the DTPA may be introduced as the most suitable extractant to determine the available copper of wheat in the calcareous and saline soils of Khuzestan. However, by considering the soil salinity, leaching requirement, and the weak correlations between the studied extractants and the plant available soil cadmium, lead, and nickel, further studies are recommended for assessment of these heavy metals.

Fluorine (F) is a necessary element for human and plant, however, high concentration of this element poses a risk to grazing animals and plants. Soil ingestion has been highlighted as a pathway for causing possible F toxicity in grazing animals. In this paper, total and soluble F concentrations and their relationships with selected soil properties in soils around Ahar City, East Azarbayjan Province, were studied. For this purpose, 21 composite soil samples were taken from around Ahar City and their major characteristics, total F concentration, and soluble F were measured. Results showed that the Ft and FCaCl2 concentrations ranged from 204.7- 574.3 and 0.7- 5.9 mg F kg-1soil with means of 334.8 and 4.1 mg F kg-1soil, respectively. These values were well within the range of non-polluted soils. Total fluorine showed significant correlation with total P concentrations, organic matter, and Al oxides contents of the studied soils; whereas such correlations were observed for total and free soluble fluorine concentrations with organic matter and pH, respectively. Concentration of F species in soil solution was much less than the critical concentrations of F for plants (0.3-0.5 µg/mL for oat and 32 µg/mL for tomato). In general, it seems that at normal soil ingestion rates, the soils are unlikely to cause F toxicity to grazing animals.