نشریه تحقیقات کاربردی خاک
سال هشتم شماره 2 (تابستان 1399)

Biochar modification is performed to improve the structure of pores, increase the specific surface area, functional groups, and reduction of raw biochar limits in absorption of pollutants. This study was conducted to evaluate the efficiency of corn stover modified biochar in adsorption of nitrate from aqueous solution. For this purpose, corn stover biochar (BC) and chemically modified corn stover biochar with MgCl2 (Mg-BC) was prepared at 500°C and its physico-chemical characteristics were measured. Adsorption batch experiments were carried. Effects of initial concentration of nitrate, contact time and pH on adsorption capacity mechanism were studied. The study of the characteristics of the two types of biochar showed that by the chemical modification of corn stover, enhanced yields, pH, surface area, cation exchange capacity and anion exchange capacity, oxygen content, H/C and O/C ratio, while decreased carbon content and C/N ratio. Adsorption of nitrate by both biochar reached to equilibrium after 480. The optimal pH for removal of nitrate was 3. The results demonstrated that chemical modification of biochar enhanced nitrate adsorption and maximum nitrate adoption by BC and Mg-BC was 51.72 and 72.18, respectively. Langmuir isotherm showed the best fit for nitrate in both biochars. The pseudo second order kinetic model also provided a good description for the adsorption process nitrate.Generally, result of present study revealed that modification of biochar could improve physico-chemical and adsorption capacity of nitrate from aqueous solution. Therefore, MgCl2 modified biochar could be a suitable absorbent for purifying water resources which contaminated by inorganic pollutants, including nitrate.

 Deviation from the optimum percentage (DOP) is an important method for interpretation of the results of chemical analysis and diagnosis of nutritional status of plants. In order to evaluate the nutritional status of squash (Lagenaria Vulgaris) through DOP, 122 leaf samples were collected from squash fields of Khoy region and N, P, K, Ca, Mg, Fe, Mn, Zn, Cu and B were analyzed. The squash fields were divided into high and low yielding groups. The mean of nutrients concentration in high yielding-fields was selected as norms for the calculation of DOP indices. DOP indices showed that macro- and micro nutrients requirement as follow K>P>Mg>Ca>N and Zn>Fe>B>Cu>Mn respectively. So nitrogen had the most positive index but potassium and zinc had the most negative indices among nutrients. DOP nutritional balance index was much more than zero indicating nutritional imbalance in this region. Finally, it was concluded that K and Zn deficiencies are more critical in reduction of the squash yield and the application of their fertilizers can improve growth and yield of squash in the region.

The present study was designed to investigate the effect of Nano hydroxyapatite (nHAP) on some soil bioindicators and availability of cadmium in a polluted calcareous soil. This research was carried out in a factorial arrangement based on completely randomized design with three replications. Treatments included two levels of Cd (0 and 40 mg kg-1 soil), two levels of nHAP (0 and 1%) and two incubation times (14 and 28 days). The cadmium chloride solution was uniformly sprayed on the soil surface and equilibrated for a month, then nHAP was added to the soil at 0 and 1 w/w %. The activity of urease, dehydrogenase, and alkaline phosphatase enzymes, basal respiration and bioavilable Cd were measured after 14 and 28 days. Bioavilable Cd was extracted by DTPA. The results showed that the addition of nHAP in the Cd contaminated soil decreased bioavailable Cd by 2.3%, increased the activity of urease enzyme by 98% while had no effect on the activity of phosphatase, dehydrogenase and basal respiration. Investigation of changes of bioindicators in 14 and 28 days incubation in Cd contaminated soil showed that the activity of urease and dehydrogenase enzyme had a declining trend but the activity of phosphatase enzyme and basal respiration did not significantly change. It was also found that bioavailable Cd decreased with incubation time by 10.7%. In general, it may be concluded that nHAP influenced biological index in the calcareous soil differently, but it caused reduction effect on bioavailable cadmium in soil, although this reduction was not considerable.

Heavy metal (HM) contamination and accumulation in soil and water is a serious problem throghout the world due to the toxicity, abundant sources, non-biodegradable nature, and accumulative behavior of HMs in environment. A comprehensive understanding of the HM pollution in soil is essential in order to make informed decisions on the approaches to reduce contamination, minimize human exposure, and protect populations from the risk. Pollution indices widely considered as useful tools for evaluation of the degree of contamination. In this paper, geo-accumlation Index (Igeo), enrichment factor (EF); single pollution index (PI), contamination factor (Cf), eological risk factor (Eri), sum of pollution index (PIsum), Nemerow pollution index (PINemerow), pollution load index (PLI), vector modulus of pollution index (PIVector), background enrichment factor (PIN), multi-element contamination (MEC), contamination security index (CSI), the probability of toxicity (MERMQ), degree of contamination (Cdeg), modified degree of contamination (mCd), potential ecological risk (RI), exposure factor (ExF) were suggested to address the degree of HM pollution in soil. Finally, a method was proposed for non-dimensionalisation of the above-mentioned indices as well as for calculation of an integrated soil contamination index derived from the sum of the weighted-average scores of all individual indicators. Using these indicators is useful in quantitative evaluation and digital mapping of soil pollution for management purposes.

Considering the high cultivation area of pomegranate in Iran, it is necessary to pay attention to this plant nutrition in order to increase quantitative and qualitative of pomegranate fruit. Nutrition management is one of the most important factors for determining the yield and quality of fruit that there are a few studies to reach the optimal management of nutrition in pomegranate. Therefore, the present study was conducted to investigate the effect of different levels of organic component and chemical fertilizers on quantity and quality characteristics of Punica granatum fruit cv. KhazarBardaskanas a factorial design based on randomized complete blocks design with three replications. Treatments include vermicompost in three levels of 0, 12.5 and 18.75 (V1, V2, V3) kg tree-1 and humic acid in two levels of 0 and 5 g tree-1 (H1, H2) as the soil application and zinc chelate in the two levels of 0 and 0.005 (Zn1, Zn2) as foliar spray. The measured factors were yield, length and diameter of fruit and some qualitative characteristics of fruit juice such as total phenol, antioxidant activity, titratable acidity (TA), total soluble solids (TSS). Also, the concentration of nitrogen, phosphorus, potassium and zinc were determined in leaves. The results of present study showed that the effects of treatments were significant for more measured parameters. The maximum amount of yield 29.09 kg tree-1, antioxidant activity (39.79 %) and total phenol (863.12 mg GAE 100g-1) were observed in V2H2Zn2 treatment of 12.5 kg tree-1 vermicompost, 5 g tree-1 humic acid and 0.005 foliar sprayof zinc. Also, the level of nitrogen, potassium and zinc in the leaves were obtained from the above mentioned treatment (V2H2Zn2), which compared with the control treatment can be recommended as the superior treatment.

Phosphorus (P) is one of nutrient elements for plant growth. In most soils P has complex behavior and forms sparingly soluble and insoluble compounds with soil particles. Determination of forms of soil phosphorus influenced the activity of phosphate-solubilizing microorganisms (PSM) is important in the evaluation of soil phosphorus status. To evaluate the effects of PSM on P fractions distribution in a calcareous soil, an experiment was conducted in a factorial based on completely randomized design. The factors were including incubation time (0, 7, 21, 45 days) and microorganisms (Fungal strains including: Aspergillus niger, Aspergillus terreus, Penicellium sp. and control (without microbial inoculation)). Soil samples were incubated at 28 ° C for a period of 45 days. Then, different forms of inorganic phosphorus, organic phosphorus and Olsen phosphorus were determined by sequential extraction method. The results showed that the fungal inoculation caused significant changes in the amount of phosphorus, organic phosphorus and mineral phosphorus. At the end of incubation, amount of available phosphorus, organic phosphorus, mineral forms (Ca2-P) and (Ca10-P) in fungal inoculation compared to control treatment increased 1.53, 1.39, 4.05 and 1.07 times, respectively. However, the (Ca8-P) and (Al-P) forms in the treatment of fungi were reduced 23.76 and 35.95%, respectively. The amount of phosphorus in different forms and treatment control to a Ca10-P> OP> Ca8-P> Olsen-P>Al-P> Ca2-P respectively.The fungal treatment was observed, a negative correlation (r= -0.81**) between phosphorus Olsen-P and Organic-P (O-P), Ca10-P and significant positive correlation (r=0.83**) with Ca2-P ،Fe-P and Al-P. In general, using phosphate-solubilizing fungi in calcareous soils provides useful information for evaluation of phosphorous status in soil and understanding of soil fertility that influence plant nutrition.

In recent years, vast areas of Urmia Lake have dried up and that's why, saline sediments appeared on the surface of the earth, which are very susceptible to erosion. This study was conducted to investigation of wind erosion and its relationship with soil physicochemical properties in eastern land of Urmia Lake. In this research, 96 soil samples were collected from an area of 414000 hectares at a depth of 5 cm based on stratified random sampling method. To measure the wind erodibility, the samples were exposed to 5 different wind velocities (9.5, 11, 12.5, 14.1 and 15 m s-1 at the height of 20 cm) in wind tunnel and finally, its relationship with soil physicochemical properties was investigated. Based on results, soil wind erodibility varied within the range of 76.69-9.98, and with a mean of 10.21 and a coefficient of variation of 94.5% have a relatively high variation in studied area. Wind erosion is significantly affected by soil physical properties, including mean weight diameter, the percent of the size classes 2-4.75, 1.7-2 and 0.1-0.25 mm of soil secondary particles (P<0.001). Based on the results, the erodible fraction (secondary particles smaller than 0.85 mm) had the most appropriate relationship with soil wind erodibility (R2= 0.75, P<0.001) and by increasing it, the soil wind erodibility increased exponentially. Considering the less costly and time-consuming in measuring erodible fraction and also less costly and time-consuming compared with measurement of soil wind erodibility in the field and wind tunnel, this index can be used as a part of soil factor in wind erosion prediction models such as WEQ and RWEQ in the studied area.

Splash erosion is the first type of water erosion caused by the impact of rain drops on the soil surface. Rain drops can disperse and move soil particles. Particles which transfer is effected by raindrop splash depends on several factors, including the soil type and the slope conditions. Although information on the role of these two agents splash erosion is available, but the selectivity of particles in splash erosion is a subject that needs further investigation, especially in the semi-arid region soils. This study was conducted to investigate the effects of splash erosion and selectivity of particles in different soils under the influence of slope. For this purpose, experiments were carried out in three different soils (Loam, Clay loam, Sandy clay loam) on four slopes (0, 10, 20 and 30%) under a simulated rain with constant intensity of 30 mm.h-1 in three replications, with a total of 36 units in the form of a completely randomized design. According to the results, the highest and the lowest amount of splash erosion were in the clay loam soil (105.07 g.m-2.min-1) and the sandy clay loam soil (80.28 g.m-2.min-1), respectively. With increasing the gradients, the intensity of splash erosion increased. In general, the selectivity of particles in the splash erosion was affected by the soil texture, the slope of the surface, and the interaction between of them. Silt was the most sensitive particle to splash, accounting for almost 57% of the splashed particles, and against the sand with almost 6% contribution to the splash was the most resistive particle. In all textures (except the loam texture), the selectivity of the silt particles at different levels of the gradient was greater than the rest. In the loam soil, clay particles were more selective than the silt particles, most likely due to the lower amount of clay particles in the original soil samples.

Application of Mycorrhizal Fungi (MF) and biochar can increase water and nutrient uptake in the rooting zone and thus improve crop production. A factorial experiment with completely randomized design with three replications was conducted to investigate the effects of biochar (0, 2 and 4% w/w) and MF (non-inoculation and inoculation with MF) on the morphophysiological characteristics and concentration of elements in calendula (Calendula officinalis L.) in greenhouse condition. The biochar was passed through a sieve of 2 mm and mixed with soil. The application of mycorrhizal fungi was done by direct contact with the root of plant. After six months, the morphophysiological characteristics and the concentration of some macro and micro elements in shoot were measured. The results showed that with simultaneous application of 4% biochar and mycorrhizal fungi increased chlorophyll, flower diameter, plant height, leaf area, stem diameter, plant dry weight and concentration of P, K, Ca and Fe compared to control, significantly. Zn concentration increased in 4% biochar treatment and simultaneous use of 4% biochar and mycorrhizal fungui compared to the control significantly (13.7 and 19.5% respectively). The application of 4% biochar caused a significant increase in Mn concentration compared to the control (91.3 against 86.6 mg.kg-1), while the application of 2% biochar has not a significant difference with control and 4% biochar treatments. The results of the effect of adding biohar to soil after plant growth period showed that available K, Ca, Mg and Mn increased with addition of 4% biochar by 22.2, 18.2, 43.6 and 15.2%, respectively. However, 2% biochar treatment had no significant effect on these soil parameters compared to control. It seems that application of these materials can improve availability of nutrients and plant growth parameters by improving plant growth conditions and affect crop production.

Understanding the factors and processes affecting soil erosion and sedimentation in an area is an essential for providing a suitable strategy for soil conservation. In this research, the effect of soil characteristics on runoff and sediment yield was reviewed using a rain simulator in Ardabil plain. Principle component analysis (PCA) was used to show the effect of soil properties. Surface soil sampling was carried out at 77 points in the form of 3500 × 3500 m regular grids and runoff and sediment sampling using 40-point rain simulator. Some physical and chemical properties of soils (texture, saturation moisture, organic carbon, electrical conductivity, acidity, total nitrogen and potassium) were measured in the laboratory. In addition, the vegetation cover percentage was measured by plot at sampling points. Simulation of rain (intensity of 23.9 mm h-1 in 10 minutes) was carried out at 40 sampling points and runoff and sediment samples were taken and transferred to the laboratory. The representative soil profiles descriped to suborder level using Soil Taxonomy. The principal component analysis (PCA) results showed that nine factors of 13 investigated factors were located in first three principle component that contribute of 57.1% of total variation in erosion changes. According to the results, the highest amount of runoff (4.8 l m-2) and sediment (58 g m-2) was measured in Psamments because of low organic carbon content (0.78%) in this suborder which reduced soil permeability and amount of generated runoff increases. The lowest amount of runoff (2.4 l m-2) and sediment (21.84 g m-2) were observed at Xeralfs, where the amount of organic carbon (3.21%) and aggregate stability (6.59%) are high that increases permeability and reduces soil losses.

Due to the relationship between crop yield, and soil characteristics and land topography, knowledge and awareness of these characteristics is necessary to achieve sustainable development in agriculture. This study was performed to evaluate and determine the relationships between Rose yield (Rosa Damasceneea Mill) with soil properties and land topography by using Multivariate Linear Regression models (MLR), Artificial Neural Network (ANN) and Structural Equation Modeling (SEM) in Bardsir City, Kerman Province. For this purpose, soil sampling and crop yield were performed in the form of a regular grid pattern. Besides, some topographic features of the land were calculated using digital elevation model (DEM) of the region, and to implement the conceptual models, three theoretical models were designed and tested. The results showed that MLR and ANN models were able to justify 68 and 87 % of the yield variability, respectively, which indicates the higher accuracy of ANN model than MLR in yield estimation. The results of SEM illustrated that Rose yield is mainly controlled by soil chemical properties, topographic features, and soil physical properties, respectively. Different scenarios for SEM showed that simpler models with fewer hidden structures could have a better fitting. Therefore, the first conceptual model of this method with the values of root mean square error, goodness of fit index and comparative fit index of 0.033, 0.88 and 0.94, respectively, was selected as the best model. The overall results showed that the ANN model was more efficient than MLR in yield prediction due to consideration of the nonlinear relationship between crop yield and the factors affecting it. In addition to the ability of the ANN model to estimate crop yield, the SEM also showed that the latter method can provide more explanations about the relationships and simultaneous interactions between variables. In general, the application of SEM method, relying on the capabilities of this method, can improve the yield of various crops.

Soil quality (SQ) index is used as a quantitative tool for assessing the impact of land use and management systems on soil condition. The aim of this study was to quantify SQ under agricultural ecosystems in Zanjan province using multivariate analyses. 154 soil samples were collected from 77 farms in Zanjan province (27 sites under irrigated and 50 sites under rain-fed land use) at 0-30 and 30-60 cm depths. 24 soil physical, chemical and biological properties were measured. Principal component analysis was used to identify minimum data set (MDS) for assessing SQ. Two groups of MDS were determined by considering physical, chemical and biological properties separately (MDS1), and by using all measured soil properties (MDS2). The capability of linear or non-linear approaches to develop SQ index was investigated. Four SQ indices were calculated using MDS1 and MDS2, linear and non-linear scoring methods. Total nitrogen, available phosphorus, sodium, zinc and copper, microbial biomass carbon, microbial quotient index, aggregate stability and bulk density were determined as the MDS1. Soil organic carbon, available phosphorus, sodium, zinc and copper, microbial quotient index, aggregate stability and sorptivity were identified as the MDS2. Both methods had enough efficiency to identify MDS for assessing SQ. The linear SQ indices (p˂0.001) showed higher capability than non-linear indices (p˂0.01) to differentiate SQ between rain-fed and irrigated land uses. The SQ index calculated using linear function and MDS1 indicated SQ of irrigated land use (0.524) had a better condition compared to rainfed land use (0.433). The SQ index calculated using MDS2 also indicated a similar trend between irrigated (0.551) and rainfed land use (0.433).

Soils are the outermost layer of the earth's crust, and they are closely interrelated with the formation of the land on which they are formed and developed. Therefore, any change in the geomorphic processes affects the soil-forming processes. "Soil geomorphology" is an assessment of the genetic relationships between soils and landforms. Although the relationships between landforms and soils have been investigated by researchers, a quantitative evaluation of the relationship between soil and geomorphic surface has been less considered. However, the soil-geomorphology relationship is a two-way relationship, and a question arises here is that how an observed soil can indicate geomorphic surfaces or landforms? Accordingly, the current research tries to examine this issue with the use of statistics and conditional probability. For this purpose, the geomorphic units of the central region of Isfahan were delineated using geopedology approach (Zinck method) and 344 soil profiles were analyzed, and the conditional probability of the existence of each geomorphic unit was obtained on condition of observation of different soils. The findings quantitatively showed that there is a strong and close relationship between soil development and formation and the geomorphic condition, so that some soils can be found only in certain geomorphic unit. In other words, the soil is an indicator/unique soil for the geomorphic unit. Due to the similar relationship between the geomorphical levels and the soil taxonomical levels, the diversity increased as the taxonomical levels increased from orders to the families. Also, the findings showed slightly in the study area that the effect of "landforms and topography" on the development and formation of soils is more than parent material.

Due to the calcareous nature of our country's soils, the plant phosphorus availability is low.  In order to study the effects of soil microorganisms and biochar application on the phosphorous availability, growth and yield of sorghum and some soil chemical characteristics, a pot experiment as factorial in completely randomized design were conducted. In this research, effects of two treatments of inoculation and non-inoculation of phosphate solubilizing bacteria and two biochar consumption treatments (0 and 1.5% by weight) on the four levels of zero, 25, 50 and 75 mg .kg-1 of P2O5 as triple superphosphate source, in three replications were studied. The results showed that phosphate solubilizing bacteria inoculation and biochar application had a significant increase on the volumes, fresh and dry weight of roots, fresh forage yield and phosphorous, nitrogen, potassium and zinc uptake. Using phosphorus increased the forage weight by increasing the height and diameter of the stems. Phosphorus application also increased soil salinity and decreased soil organic carbon, but bacteria inoculation increased the amounts of organic carbon and decreased soil salinity while biochar application increased both of organic carbon and salinity amounts. None of them had a significant effect on soil acidity. Data showed that although single application of the biochar and or bacteria had significant effects on the phosphorus uptake increases, but combined use of biochar and phosphorus and bacteria with phosphorus and also combination of these three treatments caused sorghum yield increases by increasing of phosphorus uptake. In other words, biochar or bacterial had a positive effect on the phosphorus effectiveness so that the highest plant height, fresh and dry forage, and the highest phosphorus, nitrogen, potassium and zinc uptake were obtained from the combined use of phosphorus solubilizing bacteria, biochar and 50 mg P2O5 per kg of soil.

Agricultural activities, especially rainfed wheat, is one of the main reason of the destruction of natural rangeland in the west of Iran. This study aimed to investigate the effect of changing natural rangeland to rainfed wheat for 40 years on some soil properties at the Saral Agricultural Research Station in Kurdistan province. Soil samples were collected from 0–25 cm depth randomly. Some soil properties such as soil texture, bulk density, mean weight diameter, cation exchange capacity, electrical conductivity, pH, calcium carbonate equivalent, total nitrogen, total organic carbon and available amount of Mg, Ca, K, P, NO3 and NH4 were measured. The results showed that land use change from rangeland to rainfed wheat significantly reduces soil quality with regard to all investigated properties except bulk density, calcium carbonate equivalent, P, K, NO3 and NH4. Determination of soil quality index (SQI) using Principal Component Analysis (PCA) showed that total organic carbon, total nitrogen, clay and silt almost justify more than 90% of the variance, which were selected as the minimum data set in the SQI calculation. The results of SQI showed that the index was significantly higher in rangeland (1.58) than in cropland (0.72), indicating degradation of soil quality by cultivating operations.