نشریه مدیریت خاک و تولید پایدار
سال سیزدهم شماره 4 (پیاپی 46، زمستان 1402)

Considering the two environmental problems that have plagued the northern provinces of the country in the recent years, they include a high volume of waste after harvesting rice and the excessive growth of azolla fern and the waste after collecting it from the surface waters. This research was carried out in the production of biological conditioners from these wastes and their effect on improving and strengthening the soil edge of the Anzali lagoon. Therefore, biochars have been prepared from azolla fern and rice husk and azolla compost was also prepared as biologicalal conditioners. The effect of these three conditioners on the chemical characteristics of the soil at the edge of the lagoon were investigated. This is the first time that two environmental problems (azolla fern and rice wastes) have been used as an opportunity to improve and strengthen the soils of the region.

For this research, at first, soil samples were taken from the edge of the lagoon. After producing the remedial treatments (rice husk biochar, azolla biochar and azolla compost), they were mixed with the soil sampled from the edge of the lagoon at three levels of 0 (control), 2 and 4% and the treatment was carried out. The samples were incubated in closed incubation containers of 1 kg for a period of six months and the treatments were prepared in 3 repetitions. At the end of the incubation period, the chemical characteristics of the soil including: acidity, electrical conductivity, cation exchange capacity, percentage of organic matter, percentage of organic carbon, and amount of: calcium, magnesium, sodium, potassium, phosphorus, and nitrogen, were measured. This research was conducted as a factorial experiment and in the form of a completely randomized design.

The results of the analysis of variance showed that the effect of the type of biochar and its level, as well as their mutual effect on all the examined characteristics, was significant at the 1% level compared to the control sample. Among the remedial treatments, biochar azolla treatment recorded the best result compared to other remedial treatments with the highest increasing performance on the available phosphorus, nitrogen, sodium, magnesium, organic matter percentage and pH. After that, azolla compost remedial treatment with high increase performance on available potassium, electrical conductivity and cation exchange capacity recorded a better result. The best performance of the modifying treatments was mainly observed at the level of 4 mass percent of the treatment mixed with the soil. By increasing the level of the modifier compound with soil, a significant increase was observed at the level of 5% in all the measured characteristics and elements.

The results of the analysis of variance of the effect of time, biochar type, level of polluted water and level of biochar on all the investigated parameters showed a significant effect at the 1% level compared to the control sample. According to the results of this research, by using biological conditioner such as biochar and compost, it can be seen reducing the amount of agricultural waste and the problems caused by them (depositing, burying and burning them), we can use these problems as an opportunity. Used to modify, strengthen and improve the chemical properties of soils.

Considering the high demand for tea in Iran and the insufficient local production, the use of chemical fertilizers to enhance production per unit area is increasing. The long-term use of chemical fertilizers, especially nitrogen fertilizers, in tea gardens has led to soil acidification which in turn impacted the soil quality and health. Therefore, searching for an alternative method that is as efficient as chemical fertilizers and compensates for the disadvantages caused by the excessive use of chemical fertilizers is essential in tea gardens nutrition

In this research, native nitrogen-fixing (Azospirillum) and phosphorus solubilizing rhizobacteria were isolated from the rhizosphere of tea plants and then used as biofertilizers for cultivation of Chinese hybrid tea seedlings at tea research center in 1400 under pot experiment. This experiment was conducted in a randomized complete block design with factorial arrangement and three replications. The factors include pH of soil at two levels (4.65 and 5.21), and fertilizer treatments at five levels including blank (B), control; where chemical fertilizer was applied based on soil analysis (C), nitrogen fixing bacteria was applied as biofertilizer (BN), phosphorus solubilizing bacteria was applied as biofertilizer (BP), and nitrogen fixing and phosphorus solubilizing bacteria were applied as biofertilizer (BNP). After three months of tea planting, the effect of applied biofertilizers on soil biochemical characteristics and yield of tea plant were investigated.

The soil pH values in all treatments that received biofertilizers were higher than that of the blank and control treatments. The highest and the lowest soil nitrogen (N) content were observed in BNP and B treatments, respectively. The highest content of soil phosphorus (P) was observed in BNP treatments, which P content in this treatment with BN was not significantly different. The soil available potassium content in treatments that receiving bio and chemical fertilizers did not show a statistically significant difference. The highest and the lowest values of fresh weight, dry weight and yield were observed in BNP and B treatments, respectively. The highest content of N and P in plant were observed in BNP (4.8%) and BP (0.24%) treatments, respectively. The potassium content of plant in treatments that received biofertilizers was lower than B, while the potassium content in all biofertilizer treatments were higher than that of the control.

In this study biofertilizer treatments, Azospirillum and phosphorus solubilizing bacteria, increased the nitrogen and phosphorus contents in tea plant and soil, respectively. Since these bacteria improved plant growth and soil properties, it seems that native rhizobacteria isolated from tea rhizosphere have the potential to be used as biofertilizers in tea gardens in line with sustainable agriculture. Although, long term investigation during the several growth periods and different seasons of the year is needed for further evaluations.

Due to the low amount of rainfall and vegetation and the low use of organic fertilizers, Iran's soils have a low amount of organic matter, which affects the quantity and quality of agricultural products. Sewage sludge is an organic waste that is used as fertilizer in agriculture in some areas and can both improve the physical and chemical properties of the soil and increase the concentration of macro- and micro-nutrients that are essential for plant growth. Maize, Zea mays, is a tropical and subtropical four-carbon plant that is one of the most important grains in the world and has high nutritional requirements. Plant inoculation with symbiotic microorganisms, especially roots symbiotic fungi, could increases the ability of plants to better absorb water and nutrients, fight against environmental stresses, and improve plant growth and health. Therefore, in the present study, the effects of sewage sludge application adjust by inoculation with root endophytic fungi in maize cultivation on the uptake of some micronutrients and phosphorus was investigated.

A surface soil sample (0 to 30 cm) was prepared from the agricultural farm of Lorestan University. A factorial experiment in the form of a completely randomized design including soil microbial inoculation at three levels (no inoculation, inoculation with Rhizophagos intraradices, and inoculation with Serendipita indica) and sewage sludge (zero and 2 percent; w/w) was performed in three replicates under greenhouse conditions. Maize seeds were grown in 4 kg pots and after 3 months, the concentration of phosphorus, copper, zinc, iron and manganese elements in the shoot and root of the plant were measured. Also, some microbial characteristics (respiration, microbial carbon biomass, and acid and alkaline phosphatase activity) were measured in the soil.

The results showed the positive effect of both applications of sewage sludge and microbial inoculation on the concentration of elements in the plant. Biological parameters significantly increased (p< 0.05) with the application of 2 % sewage sludge: soil respiration (33 %), microbial carbon biomass (38 %), acid phosphatase (35 %), and alkaline phosphatase (6.5 %). Also, fungal inoculation significantly increased the concentration of phosphorus and micro-nutrients in the roots and shoots of the plant. There were no significant differences between the applications of the two symbiotic fungi; the only exception was the Zn concentration of root that was higher in treatments inoculated with R. intraradices than in treatments inoculated with S. indica. There was a positive correlation between available phosphorus with soil organic matter, plant biomass, and acid and alkaline phosphatase activity.

The results showed the positive effect of using purified sewage sludge at the level of two percent and inoculation of root endophytic fungi in the uptake of phosphorus and micronutrients by the plant, improving plant growth characteristics, and improving soil biological characteristics such as microbial carbon biomass and phosphatase enzyme activity. Inoculation with both symbiosis fungi was similar, but regarding this point that reproduction of S. indica is simpler, so it is recommended as a plant-promoting fungi that could reduce the application of P fertilizers and help the plant to uptake more P from soil. In this research, refined sewage sludge was used in low content (2 %), so it is essential to pay attention to the application of unrefined or higher amounts of sewage sludge that may result in microbial contamination or future problems.

During the Quaternary period mid to high-latitude areas were affected by loess deposition. In Iran's northern and northeastern regions, significant loess deposits are prevalent and distributed throughout the Iranian Loess Plateau and along the northern foothills of the Alborz Mountains. Intercalated within these loess deposits are paleosols, formed during warm and moist climatic conditions (interglacial period). These paleosols offer an opportunity to study the climatic and environmental changes that occurred during the Quaternary period. Understanding the relationship between loess deposition and paleosol formation can offer significant insights into the mechanisms that drive changes in global climate and how they affect the Earth's geology and ecosystems. Studies have shown that loess sediments and loess-derived soils contain different concentrations of iron minerals such as hematite, iron oxyhydroxide, and goethite. These minerals are highly sensitive to environmental changes, and evaluating the changes of these minerals in loess-paleosol sequences can be a valuable indicator for studying paleoenvironmental changes. The two main minerals that cause color and magnetic susceptibility changes in loess-paleosol sequences are goethite and hematite. Therefore, the assessment of loess-paleosol sequences from the aspect of magnetic and colorimetric parameters provides the possibility to identify paleoenvironmental and climatic changes. The main goal of this research is to investigate the changes in iron oxides in the loess-paleosol sequence in the east of Golestan province using colorimetric techniques and temperature-dependent magnetic susceptibility in order to provide enough information for reconstructing the paleoclimatic conditions during the formation of paleosols.

Sampling was performed from the loess-paleosol sequence in the eastern Golestan province, for each loess and paleosol horizon. Initial colorimetric and magnetic susceptibility measurements were carried out respectively for 1345 and 24 samples at LIAG Institute in Germany. Color measurements were carried out with a spectrophotometer machine that covered the visible light range. The temperature magnetic susceptibility was carried out using in the 20–700°Ctemperature range in an argon atmosphere to minimize oxidation.

According to the results of this study, we can mention the identification of iron minerals in loess and paleosol samples using colorimetric analysis. Iron minerals such as hematite, goethite, and maghemite can be detected at wavelengths 565, 435, and 595 nm, respectively. Colorimetric results showed that the ratio of hematite to goethite of paleosols has increased compared to loess sediments in the study area, which indicates the increase in precipetation and soil moisture during the interglacial period. The heating curve (temperature-dependent magnetic susceptibility) of loess samples at 560-590 degrees Celsius showed a sharp decrease due to magnetite minerals in these samples. At the same time, this happens in paleosols at a temperature of 300-350 degrees Celsius, which is due to the loss of the maghemite mineral formed during the interglacial period. The results showed that the decrease in the heating curve in paleosols indicates the increase in the intensity of soil-forming processes.

The results of this study showed that iron minerals such as magnetite, maghemite, hematite, and goethite in loess and paleosols play an important role in magnetic properties and soil color. Also, the increase in the presence of hematite and maghemite in paleosols indicates the increase in the intensity of soil formation processes and humidity during the formation of paleosols. The results of this research showed that the colorimetric technique, along with temperature-dependent magnetic susceptibility, can be one of the fast and accurate methods in studying and identifying paleosols.

Mineralogical composition, soil morphological properties, and magnetic susceptibility were affected along soil evolution in soils. That is why micromorphology helps in performing soil classification and evolution studies, as well as making soil management practices much more efficient. Clay mineralogy is a useful tool that helps in better understanding soil forming factors and processes. Soil magnetic properties are complex reflections of chemical, geological, and biological soil characteristics. Thus, knowledge about factors affecting magnetic susceptibility can help in better understanding and interpreting the results obtained in an area. Assessment of soil magnetic behavior might be used in pedology, soil mapping, investigation of soil process variations, parent material composition, sedimentary processes, soil drainage conditions, soil pollution, and separation and identification of soil unit boundaries. The present study was performed to investigate the effects of magnetic susceptibility, clay mineralogy, and micromorphology on soil characteristics, genesis, and evolution.

Seven representative pedons were selected in sedimentary and igneous sections in uncultivated land use and physiographic units: hill, piedmont plain, alluvial plain, and lowland. Physicochemical properties measurements were performed on the collected samples from representative pedons using standard methods. The pedogenic (Fed) and amorphous (Feo) iron concentrations of the extracts were determined using a Vario Atomic Absorption Spectroscope (AAS) instrument. Undisturbed soil samples were selected for micromorphology studies and thin section preparation. Additionally, three soil samples were used for X-ray diffraction (XRD) analyses after carbonates, organic matter, and Fe were removed using Jackson (1965) and Kittrik and Hope (1963) procedures. Finally, the mass-specific magnetic susceptibility of soil samples was determined using a Bartington MS2 meter equipped with the MS2B Dual Frequency sensor, capable of taking measurements at both low (χlf at 0.46 kHz) and high (χhf at 4.6 kHz) frequencies.

Salinization, leaching, and illuviation processes of gypsum and carbonates were observed in the studied pedons. The soils were classified as Aridisols (Soil Taxonomy system) and Solonchacks, Solonetz, Gypsisols, and Calcisols RSGs (WRB system) due to the presence of calcic, gypsic, salic, argillic, and natric diagnostic horizons. The presence of gypsum, carbonates, salt, clay accumulation, and argillic horizon reduces χlf values. The calcite coating located on the clay coating could probably be attributed to the presence of a climate with more available humidity in the past. The range of soil magnetic susceptibility was from 4.3×10-8 to 1264×10-8 m3kg-1. Gypsum infillings, different forms of gypsum, clay accumulation and coatings, and weathered calcite crystals were among the dominant micromorphological features observed in the studied pedons. Montmorillonite, chlorite, illite, kaolinite, quartz, and vermiculite minerals were observed in the studied pedons. Chlorite and illite minerals were dominant in the clay fraction of the studied soils, whereas a portion of these minerals was probably converted to vermiculite. Discontinuities observed in pedon 2 could be accounted for as proof of more available humidity in the past compared to the present time periods. Moisture has caused the removal of potassium and transformation of illite and chlorite to vermiculite. The dominance of illite and chlorite can be proof of initial weathering and evolution in the other studied pedons.

The χlf variations was related to depth trend and physicochemical properties. The χlf values showed a noticeable negative correlation with argillic horizon, gypsum content, carbonate calcium, and salinity. It seems that most of the clay minerals originated from the parent material in the present study, and pedogenic source has rarely taken place. Besides, the χlf and Fe contents were directly correlated. In general, the results indicated young soils with primary development stages in the area under study. Pedon 2 with buried polygenetic soils is an exception.

Due to the lack of suitable water resources and poor soil quality (high salinity, low organic matter, and plant nutrient deficiency), the increase of arable lands in arid and semi-arid regions has faced severe challenges. The use of organic amendments is recognized as a critical strategy for plant production in such soils. Nowadays, humic acid (HA) is known as one of the eco-friendly fertilizers that not only preserves soil quality but also plays a significant role in increasing the production of high-quality agricultural yields. The present study was conducted to extract humic acid from two sources of cattle and sheep manures and compare their effect on maize growth characteristics and inorganic phosphorus (Pi) forms in a calcareous soil compared to the commercial HA.

25 kg of sheep and cattle manure were collected from the farm of Shahid Bahonar University in Kerman and composted separately under controlled conditions for three months. Humic acid was extracted from composted manure using 0.5 N NaOH (1:10 material: extractant) in a dark environment under no oxygen conditions. The extracted HA's chemical and structural features, such as pH, EC, elemental composition, and functional groups, were determined. To investigate the effect of extracted humic acid on the growth of maize and soil inorganic P forms, a completely randomized design with seven treatments, including 0.1 and 0.2% of cattle manure extracted humic acid (CM-HA), 0.1 and 0.2% of sheep manure extracted humic acid (SM-HA), and 0.1% and 0.2% levels of commercial humic acid (HA), and a control treatment was designed in four replicates. The seedlings of maize were planted in treated pots and kept for 70 days under greenhouse-controlled conditions. At harvest time, the fresh and dry weights of the shoot and roots were measured. Soil Pi fractions, including H2O-extractable P, NaHCO3-extractable P, NaOH-extractable P, and HCl-extractable P, were also determined after maize harvesting.

The results showed that commercial humic acid had the highest pH and the lowest EC compared to the extracted acids. In contrast, humic acid extracted from cattle and sheep manure was more acidic than the commercial HA. The results of FTIR indicated the presence of phenolic hydroxyl, carboxyl, and aromatic rings in the extracted and commercial humic acids. The results showed that only 0.1% of commercial humic acid had no significant effect on maize's shoot fresh and dry weight. In contrast, other extracted acids, especially SMHA, significantly increased both growth characteristics of maize. In all treatments, the overall distribution of Pi forms was HCl-P > NaHCO3-P > NaOH-P> H2O-P. The results showed that HA application at the rates of 0.1% and 0.2%, mainly extracted HA from sheep manure, increased the contribution of more labile forms of inorganic phosphorus, including H2O-P and NaHCO3-P in the soil.

Since extracted HA from sheep manure and cattle manure have better quality than commercial HA and more effectively affect the growth of maize and labile forms of Pi, these resources can be used as an alternative for HA extraction and HA-based fertilizer production. In general, 0.2% of extracted humic acid from sheep manure had a more influential role in increasing the labile P forms in the soil and the growth of maize plants compared to other treatments.