نشریه مدیریت خاک و تولید پایدار
سال دوازدهم شماره 1 (پیاپی 39، بهار 1401)

Rheological characteristics of soils (including their deformation and flow behaviors when subjected to external stress) can provide important information on microstructural and microaggregate stability. One of the newest methods of assessing the stability of aggregates is the use of rheometric discussions in this regard. In other words, rheometry can be used to evaluate the elastic behavior of soil versus its plastic behavior in a range of aggregate deformation and thus a more quantitative interpretation of aggregate formation or stability against stress. In the last decade, Amplitude sweep test (AST) has been used to evaluate the stability of soil microstructure and its elastic behaviors. The present study was designed to determine the aggregate stability and viscoelastic behavior of the soil using the rheometric method. In the present study, physical, chemical, clay mineralogical properties and classification of dominant soil orders in Chaharmahal-va-Bakhtiari Province were studied and compared in order to determine the stability of aggregates and viscoelastic behavior of soils using the rheometric method.

Five different soil orders were described and sampled in Shahrekord, Farsan, and Koohrang cities. After air-drying and sieving of soil samples taken from the genetic horizons, the physical and chemical properties were measured using standard methods. Besides, the type of clay minerals was determined by the X-ray diffraction method. AST was used to quantify the initial rheological parameter values, including the storage (G') and loss moduli (G"), deformation limit (γL: when the material begins to irreversibly deform), deformation at flow point (γf: when the material becomes viscous), loss factor (tan δ = G''/ G') and integral z (which summarizes the overall elasticity of the material) in order to study microstructural stability and microaggregates of the five soil orders. Finally, the correlation diagram was plotted among soil properties and rheological parameters using R software. Besides, the soil was classified based on the American Soil Taxonomy (2014) and WRB (2015).

The studied pedons classified based on the American Soil Taxonomy (2014) and WRB (2015) in five different soil orders and four reference soil groups, including Entisol (Cryosol in WRB), Vertisol, Mollisol (Kastanozem in WRB), Alfisol, and Inceptisol (Calcisol in WRB). Semi-quantitative analysis of clay minerals showed that the soils have different clay minerals assemblage including kaolinite, vermiculite, smectite, illite, chlorite, and quartz. The results of the AST indicated that the deformation limit was significantly higher in subsoil horizons than topsoil horizons and was also higher in the clayey soils compared to sandy soils. The soils with “vertic soil properties” showed the high range of linear viscoelastic region (LVE) that attributed to the samples with high elasticity behavior. Soils with higher clay contents and further evolution showed higher rheological parameters, implying that these soils had more rigid microstructures incomparable with other soil orders which in turn, indicated the higher microstructural and microaggregate stability. In contrast, the horizon, which had high sand content and little soil development, had the lowest values for all properties, thus indicating a lack of micro-aggregate stability. Pearson correlation coefficient analyses revealed that integral z was influenced by soil physicochemical properties, and was higher in soils with the clay fraction dominated by expansive clay minerals and higher cation exchange capacity.

Altogether, the rheological parameters indicated that more developed soils had greater microstructural stability than their less-developed counterparts. As a result, rheological measurements may be useful for identifying the major factors that affect soil aggregation. In addition, these parameters can be used as indicators to evaluate the relative amount of soil evolution in future studies.

Due to low efficiency of chemical fertilizers and high nitrogen demand for fruit trees at the first stage of growth, early spring growth, flowering and fruit set in fruit trees is heavily dependent on tree N reserves. Therefore, this experiment was performed to investigate the possibility of urea, zinc sulfate and boron uptake, as well as transmission of these materials from leaves to storage organs and from storage tissues to new developing tissues, in autumn foliar application. On the other hand, nitrogen application in early spring is more often devoted to the vegetative growth of the branches, while nitrogen uptake at the end of the season goes more to the storage organs such as root bark and tree trunks.

The experiment was conducted in a randomized complete block design with seven treatments and four replications for three years on 56 trees with the same age and size trees in the east of Mazandaran. The treatments included: 1. Control, 2. Urea (10 g.l-1), 3. Urea (10 g.l-1) + Zinc sulfate (5 g.i-1), 4. Urea (10 g.l-1) + Zinc sulfate (5 g.l-1) + Boric acid (4 g.l-1), 5. Urea (15 g.l-1) + Zinc sulfate (5 g.l-1) + Boric acid (4 g.l-1), 6. Urea (20 g.l-1) + Zinc sulfate (5 g.l-1) + Boric acid (4 g.l-1), 7. Urea (25 g.l-1) + Zinc sulfate (5 g.l-1) + Boric acid (4 g.l-1).

Urea foliar application increased the nitrogen concentration of leaves in autumn and also increased the concentration of nitrogen in bark and wood in various organs. Foliar application of zinc sulfate and boric acid also increased the concentration of zinc and boron in the leaves. Measuring the concentration of nitrogen, zinc and boron in the leaf tissue of young shoots in the spring showed that in foliar spraying treatments, the nitrogen concentration of young leaves increased compared to the control. Measurement of nitrogen concentration in leaves of young shoots, bark and wood of annual shoots as well as flower and flower buds showed that foliar spraying treatments had a significant effect on nitrogen concentration of bark and wood of these shoots. Thus, the nitrogen concentration increased from 0.53% in the control treatment to 0.92% in the treatment 25 gl-1 urea + 5 gl-1 zinc sulfate + 4 gl-1 boric acid.

According to the results of this experiment, in order to increase the storage of nitrogen, increase the fruit set, and reduce the flower and fruitlets drops, it is strongly recommended to do foliar application of urea at 20 to 25 gl-1 + zinc sulfate at 5 gl-1 + boric acid at 4 gl-1 in autumn, when 10 to 15 percent of the leaves are yellow.

Soil water repellency reduces soil infiltrability, water availability for plants, and can increase surface runoff, soil erosion and preferential flows, and reduces environmental fertility. Land use is one of the factors affecting soil water repellency. Soil water repellency can increase runoff in areas where land use change occurs. Thus, knowledge about the soil water repellency properties is necessary for effective environmental management. Changing the soil properties upon reduction of soil wettability can affect crop growth and yield, and water use efficiency. However, relations between soil water repellency and physical and chemical properties among different land uses in the large scale have not been studied yet. Therefore, the objectives of this study were: i) to investigate the persistence and severity of soil water repellency in different land uses, and ii) to develope regression relations between the water repellency indices and soil physical and chemical properties in the central part of Mazandaran province.

In this study, the persistence and severity of soil water repellency were investigated in the paddy fields located in the plains to mountainous areas consisting of four land uses of pasture, citrus garden, paddy field, and forest located in Amol city in the central part of Mazandaran province. Ninety-two soil samples were collected to determine soil water repellency and physical and chemical properties in the dry season of the year. The persistence of soil water repellency was determined using the water droplet penetration time (WDPT) test, and water repellency index (RI) and soil-water contact angle (β) were measured using the intrinsic sorptivity test in the laboratory. Correlation between water repellency indices and soil properties was studied. Relations between the water repellency indices and soil properties were derived by multiple regression.

Soil water repellency in all the land uses was sub-critical and all of the soil-water contact angle values were less than 90°. The highest mean values of soil water repellency indices in all methods were found in the forest land use, so that Log WDPT value was significantly different from paddy field land use. Log WDPT showed positive and significant correlations (r = 0.33**) with RI, indicating that the water repellency persistence (i.e., Log WDPT) and water repellency severity (RI) are directly related in the studied soils. The correlation between soil organic matter content and calculated β in the citrus garden land use was positive and significant (r = 0.42*). There was also a positive and significant correlation between Log WDPT and soil organic matter content (r = 0.36***). Negative and significant correlations were found between calcium carbonate equivalent (CCE( and Log WDPT in the whole study area (r = -0.28**) and in the paddy field land use (r = -0.29*)

The results showed that the land use through the effect on the soil organic matter content can induce and intensify water repellency in the studied soils. Moreover, the derived regression relations indicated that soil organic matter content, total nitrogen and CCE are important properties affecting water repellency in the studied soils.

Contamination of agricultural soils with heavy metals is one of the major challenges worldwide. Heavy metal stress can affect soil living community and, consequently, different soil processes. The aim of this study was to evaluate the effect of chitosan application levels and soil contamination with Pb on soil biological activity.

In order to investigate the effects of different levels of Pb (non-contaminated (Pb0), 250 (Pb250) and 500 (Pb500) mg kg-1 of soil) and chitosan application (without chitosan (Ch0), 0.6% (Ch0.6) and 1.2 % (Ch1.2)) on the available Pb (DTPA-extractable Pb) and some biological properties in soil, a factorial experiment was conducted in a completely randomized design. Different levels of lead and chitosan were added in pots containing 400 g of soil in three replications and and soil moisture was maintained at 70% field capacity for 45 days. At the end of the incubation period, DTPA-extractable Pb and the population of microbial groups including heterotrophic bacteria, fungi, spore-forming bacteria and actinomycetes were determined. Moreover, microbial biomass of C (MBC) and N (MBN), basal respiration (BR) and substrate-induced respiration (SIR) were measured and some ecophysiological characteristics including microbial metabolic quotient (qCO2), microbial respiration quotient (QR) and MBC: MBN ratio were calculated.

The results showed that Pb250 treatment did not show a significant effect on the population of the studied microbial groups compared to the control. Application of Pb500 treatment significantly reduced the population of spore-forming bacteria and actinomycetes but did not lead to a significant change in the faungi/bacteria ratio. BR, SIR, MBC and MBN were significantly reduced by Pb500 treatment. Under Pb500 treatment, qCO2, QR and MBC:MBN ratio increased. Application of chitosan at both levels decreased the available Pb concentration of lead in the soil so that application of 1.2% chitosan reduced DTPA-extractable Pb by 42% in Pb250 treatment and by 12% in Pb500 treatment. Application of chitosan increased BR, especially under Pb500 treatment, and caused a decrease in qCO2 (p ≤ 0.05).

It can be stated that the use of chitosan at low levels of soil pollution was more effective in reducing the Pb bioavailability. It also seems that the positive effects of the application of this biopolymer on the biological properties of the soil have been partly due to its biodegradation in the studied soil. In general, the results indicate the importance of chitosan application as a biodegradable adsorbent to reduce available Pb in soil and its potential to enhance biological activity in Pb-contaminated soil.

The main reason for soil loss in arid and semiarid regions is wind erosion. About 40 percent of lands have potential to wind erosion. In Iran due to the drying of a large area of the Lake Urmia and creating the salt marshes and abundant salt plains, it has recently been one of the main problem in this region. Due to the location of this lake, it will become one of the main sources of dust and wind erosion in northwestern of Iran. Determination of the wind erosion flux and its components will be useful for choosing appropriate solutions for this problem. Reliable field measurement of the amount of soil loss will not be possible if there is no satisfactory equipment. Several wind erosion samplers have been developed so far. But the most recommendable one is the BSNE (Big Spring Number Eight) sampler that was made and used by Donald Fryrear to gather the suspended particles.

In order to trap the suspension and saltation particles from the wind erosion, 14 poles with four BSNE samplers installed on each of them at height of 0.15, 0.5, 1 and 2 m above the soil surface were installed in a circular pattern with a 100 m radius on a land area of 3.14 ha. Also, in order to trap the creeping particles, 14 sediment traps which the opening of them was in the same level with ground were installed at a radial distance of 20 cm from each BSNE pole. For 6 months (from March - August 2017) the eroded particles were collected and weighed. Then the suspension (Isus), saltation (Isal) and creeping (Ic) fluxes were calculated.Meteorological information was obtained from Khosroshahr Weather Agency during the research period, which was at the closest distance from the study area. In order to investigate the effect of sampling time on suspension, saltation and creeping fluxes, a completely randomized experiment was designed with three replications. Duncan's test was used to compare the means. Statistical analysis was performed by SPSS software and charts drawn by EXCEL software. In order to determine the vertical profile of the suspension flux, the data obtained from the BSNE samplers at four heights (0.15, 0.5, 1 and 2 m ) was used.

Findings of this study showed that the effect of sampling time was significant on Ic, Isal and Isus (p≤0.01) and on total flux (It)(p≤0.05). The results of mean comparing showed that the highest of It was obtained in March and July (2.091 and 2.0153 ton.h-1.mon-1, respectively) due to the high speed of strongest wind (16 and 18 m.s-1, respectively) and lack of plant cover in March and dry soil surface in July (Monthly rainfall was zero). The lowest of It was obtained in April (0.1007 ton.h-1.mon-1) due to high monthly rainfall (78.3 mm) and high moisture of soil surface. Totally, the wind erosion in the study area was 11.028 ton.h-1.y-1. The Isus decreased with increasing the height of soil surface and the power equation was the best one to explain these profile.

There was a negative correlation between Ic (wind erosion section), Isus and It fluxes with monthly rainfall and positive correlation with speed of strongest wind. The mean It was maximum in March and July and minimum in April. The results showed that a large part of the particles were moving at a height of less than 15 cm above the soil surface.

Sugarcane is widely cultivated in Khuzestan province. After each harvest, a ratooning operation is performed to remove the impact of compaction due to traffic on the harvesting machines and recelennce furrow. This experiment was conducted to investigate the effect of machine type and forward speed on the quality of sugarcane ratooning operations.

Research treatments included conventional ratooning device (4-shanks subsoil + reshaper) and combined ratooning device (4-shanks subsoil + reshape disk and 10-shanks subsoil) and three- rates speeds (5, 6 and 7 km / h). The experimental design was a split plot design based on randomized complete block design with three replications in the cultivation industry of Amir Kabir farm ALC 408 with clay loam texture, 15% moisture, crop variety 1069-69CP and first year ratoon. The physical properties of interest in this study were Mean Weight Diameter (MWD) of clods, bulk density, soil surface uniformity, and water infiltration in soil. ANOVA and Duncan tests were used to compare the treatments.

There was a significant difference between the two types of ratooning machine and the three forward speeds in the mean weight diameter of clods, bulk density, surface uniformity and soil water infiltration. Comparison of means showed that the ratooning treatment with the combined machine at the speed of 7 km / h had the smallest mean weight diameter of clods. The use of an integrated device also significantly reduced the bulk density of the soil. The mean soil bulk density in the ratooning operation was reduced to 1.33 g / cm3. The lowest coefficient of variation of surface uniformity in ratoon treatment with combined machine at 7 km / hwas obtained equal to 16%. Also, the water infiltration rate in soil was significantly different between the conventional and combined ratooning machine treatments. Soil water infiltration rate was 1.6 and 2.3 cm / h, respectively, after the ratooning operation with a conventional ratooning machine and combined ratooning machine treatments. The effect of forwarding speed on soil water infiltration rate also showed that the highest water infiltration rate occurred at 5 km / h, equal to 1/2 cm per hour.

Finally, due to the significant difference between conventional and combined ratooning treatments, sugarcane ratooning combined machine had the greatest impact on soil physical parameters. This is due to the movement of the 10-shanks subsoil during the ratooning operation and the greater turbulence of the soil.

The leaching is an effective method for the removal of heavy metals using water or any other fluid. However, it is vital to identify the environmentally friendly leaching agent. The effectiveness of this technique depends on several factors. The researchers are looking for substances that have the least harmful impact on the environment. There is no reported study on the effects of dissolved organic carbon extract from poultry manure and sugarcane bagasse on leaching of Pb from contaminated soil. Therefore, the objective of this study was to investigate the leaching of Pb from mine contaminated soil as affected by dissolved organic carbon derived from poultry manure and sugarcane bagasse. .

In this study, an experiment was conducted to evaluate the efficiency of dissolved organic carbon derived by poultry manure and sugarcane bagasse to remove Pb from contaminated soil. For this purpose, the leaching and batch equilibrium experiments with the ratio of 1:20 (soil:extract) and different concentrations of dissolved organic carbon (50, 100, 200, 400, 800, 1000, 2000 mg/l), pH (4, 6, 7 , 8, 10) and time (0.5, 1, 2, 4 hours) were carried out. The best results of soil Pb leaching and batch equilibrium experiments were chosen for the leaching column (continuous and intermittent leaching) experiment. In both of continuous and intermittent leaching experiments, the Pb leaching with two types of extracts was investigated.

The results showed that the application of dissolved organic carbon derived from poultry manure initiated highest Pb leaching from mine contaminated soil in the both of continuous and intermittent leaching experiments. The intermittent leaching, resulted in the highest amount of Pb leaching from the contaminated soil (135.65 mg/kg) compare to continuous leaching experiments. In leaching experiment, the content of Pb leaching by dissolved organic carbon derived from bagasse did not change considerably. In the batch equilibrium experiment, the highest Pb leaching (55 mg/kg) was related to the application of 2000 mg/l dissolved organic carbon derived from poultry manure at pH 8. The amount of Pb leaching with the application of 400 mg/l of dissolved organic carbon derived from sugarcane bagasse at pH 7 was 20 mg/kg.

According to the results, the application of dissolved organic carbon derived from poultry manure removed a significant content of Pb from mine contaminated soil. However, the application of dissolved organic carbon from this type of sugarcane bagasse for Pb leaching was not effective.