فهرست مطالب مهدی نجفی قیری

Water stress is one of the main factors in crop growth in arid and semi-arid regions of the world, which limits the grain yield of the safflower (Carthamus tinctorius L.). To increase the soil fertility and yield of crops, it is necessary to pay sufficient attention to the use of biomass of organic matter, especially crop residues, and its conversion to biochar. This research aims to evaluate the biochar application produced from cotton and wheat residues under late-season water stress in the south of Fars province (Darab) on photosynthetic pigments, enzyme activity, yield components, and yield of safflower.
In order to investigate the biochar application and water stress on the amount of photosynthetic pigments, enzyme activity, and yield of safflower, a field experiment was laid out as split plots in the form of randomized complete block design with 3 replications in the 2019-2020 growing season. The experimental factors include the irrigation regime as the main factor in two levels (optimal irrigation and cutting off irrigation after the flowering stage), and the secondary factors were fertilizer treatment as subplot including control (without fertilizer), consumption of 3 tons of biochar from wheat residues per hectare, consumption of 3 tons of biochar from cotton residues per hectare, consumption of 150 kg of urea per hectare + 50 kg of triple superphosphate per hectare, consumption of 112.5 kg of urea per hectare + 37.5 kg of triple superphosphate per hectare, consumption of 112.5 kg of urea + 37.5 kg of triple superphosphate + 3 tons wheat biomass per hectare, and 112.5 kg of urea + 37.5 kg of triple superphosphate + 3 tons of cotton biomass per hectare. In this research, chlorophyll a and b, total chlorophyll, catalase, and peroxidase activities, yield components, and yield of safflower were calculated.
The results of the experiment showed that the measured traits were significantly affected by the irrigation regime and fertilizer treatment. Under cutting-off irrigation after the flowering stage, the fertilizer treatment of 112.5 urea + 37.5 phosphate + 3 tons of wheat biochar per hectare increased 55 and 40% chlorophyll a and total chlorophyll compared to the control, respectively. Water stress increased the carotenoid content, catalase, and peroxidase enzymes. The highest amount of catalase and peroxidase enzyme activity was obtained in the control under cutting-off irrigation after the flowering stage, which increased by 48 and 38%, respectively, compared to the control under optimal irrigation. The number of seeds per capitule and the number of fertile capitules per plant in the treatment of 112.5 urea + 37.5 phosphate + 3 tons of cotton biochar under water stress conditions increased by 8.8 and 19.51%, respectively. Also, under water stress, the application of 112.5 urea + 37.5 phosphates + 3 tons of cotton biochar improved and increased the relative content of leaf water, biological capitules yield, and grain yield compared to the control by %53, %22, and %34, compared to control, respectively.
Results showed that in both of the irrigation regimes, application of 3 tons of cotton or wheat biochar alone can increase the biomass and grain yield compared to control. Overall, the application of 112.5 urea + 37.5 phosphate + 3 tons of cotton biochar under water stress conditions improved the relative water content of the leaves, the number of seeds per capitule, the number of fertile capitule per plant, and finally, biomass and yield of safflower. With respect to water shortage under late season in southern parts of Fars province, and in order to decrease the detrimental effects of water stress, farmers can use the biochar of cotton combined with reduced dosage of urea and triple superphosphate fertilizers.

Soil resources are important components of the ecosystem, and therefore, their quality should be considered. One of the important factors affecting the quality of soils is land use change. The present study was conducted to investigate the effects of land use change and deforestation on some soil fertility and biological characteristics in the forest area of the Yasouj region. In this area, four land uses of dense forest, sparse forest, deforested (degraded) lands, and rainfed agriculture were randomly sampled from two slope classes. In each land use 10 soil surface samples were taken. Fifteen soil fertility and biological characteristics were measured using routine methods. The results showed that dense forest and deforested (degraded) lands had the best and worst conditions, respectively, in terms of the measured parameters. Among the measured characteristics, the values of alkaline phosphate, exhaled respiration, nitrogen, basal respiration, acid phosphatase, manganese, and zinc showed the greatest decrease respectively, and the values of phosphorus and potassium exhibited the least decrease, as a result of land use change from dense forest to degraded lands. The findings showed that the conversion of ecosystems such as forests to agricultural lands or deforestation has led to a severe decrease in the fertility and biological indicators of soil quality. Therefore, the protection programs of these areas should be more considered.

Soil is a natural environment for plant growth and due to its importance, the study of heavy metal distribution for soil contamination monitoring and environmental quality maintaining is necessary. This investigation was performed to study the spatial variability of some heavy metals in some surface soils of the Shazand City. A total of 76 soil surface samples were randomly collected from a depth of 0-30 cm in the study area. After preparation of the samples, some physico-chemical characteristics and the total amount of, lead (Pb), cadmium (Cd), nikel (Ni), zinc (Zn) and copper (Cu) were measured. Mean concentrations of Pb, Cd, Ni, Zn and Cu were 31.20, 54.12, 23.11, 2.05 and 59.36 mgkg-1, respectively. Significant correlations were found between Ni with Cu (r= 0.41, p<0.01) and Zn (r= 0.5, p<0.01). Also, a significant correlation was obsrved between Cu and Zn (r= 0.4, p<0.01). The spatial variability of these variables was examined by variogram models and ordinary kriging. The results of geostatistical analysis showed that the spherical model was the best model for describing the spatial variability of all studied elements. Strong spatial dependence (the ratio of nugget to sill less than 0.25) was obtained for the lead element. According to the standard limits, Pb and Cd showed the highest pollution in rangeland and agricultural land use in the study area, respectively. It’s recommended to increasing soil quality and reduces it’s degradation from pollutants applied proper environmental proceeding.

Global observations have confirmed that in recent decades, forests have been converted into agricultural land at a swift pace; this is a major global concern. Forests around the world have also experienced severe disturbances due to other anthropogenic activities. The conversion of forests to cropland often results in soil degradation. Slope gradient and land use change are known to influence soil quality; therefore, the assessment of soil quality is important in determining sustainable land-use and soil-management practices. Magnetic susceptibility (χlf) measurements are widely used to study soil-forming processes. Many efforts have been made to correlate soil magnetic susceptibility with different soil properties, such as topography, parent material, Fe oxide forms, etc. The Yasouj area of Kohgilouye Province is one of the most densely forested areas in Zagros mountainous region. Parts of the area have been cultivated to feed the growing population, which has led to forest degradation. The objectives of this study were to assess some soil properties focusing on soil χlf and Fe- oxides forms in different land uses and slope positions.

 Forty soil samples were taken from dense forest, sparse forest, eroded lands and dryland farming from different slops (0-15 and 15-30 percent) in Mokhtar Plain, west of Yasouj city. Soil samples were taken from the depth of 0–15 cm in a completely randomized design with five replications. Soil moisture and temperature regimes in the study area are xeric and thermic, respectively. Particle size distribution was determined by the hydrometer method and soil organic matter, CaCO3 equivalent and bulk density were determined using standard procedures. Fe (Feo) were extracted by acid ammonium oxalate, using a single 4-h extraction at pH 3 in the dark. Total free iron (Fed) was extracted with the CBD method. The total Fe contents (Fet) in the soil samples were determined after extraction with 5 mol L-1 HNO3. Magnetic susceptibility of the soils was measured at low (0.46 kHz; χlf) and high (4.6 kHz; χhf) frequencies, respectively; using a Bartington MS2 dual-frequency sensor, with approximately 10 g of air-dry soil in polyethylene vials. The percentage of frequency-dependent magnetic susceptibility (χfd%) was calculated to study the size of magnetic crystals in soils and the abundance of pedogenic ferrimagnetic in SP-SSD (~0.03 μm) boundary.

The results of this study showed that the land use and slope positions were among the important factors affecting the change of soil properties in this area. Land use change along with the reduction of organic matter reduced the stability of aggregates and increased land erosion. This process caused the loss of clay particles and magnetic minerals and affected many soil properties. Organic matter as an important indicator of soil quality, showed a decrease of about 3 times as a result of land use change from dense forest to eroded lands following by an increase in bulk density and a decrease in soil permeability and other soil quality indicators. Long-term afforestation and agricultural activities on sloping lands changed the soil texture from a class of silty loam in the forest to a lighter class of silty loam in agricultural use. Soil magnetic susceptibility, which is a function of soil magnetic particles was greatly affected by land use change and to a lesser extent by slope position. Due to the fact that magnetic susceptibility is influenced by factors such as soil texture, drainage class, erosion conditions, magnetic mineral contents, soil evolution conditions, land use changes from forest to other uses had significant effects (about 2 times) on χlf. Significant decrease in the amount of calcium carbonate in low slope positions was another reason for the increase in magnetic susceptibility in these positions. According to the measured values ​​of χfd (ranged from 1.9 to 7.2%), the magnetic particles of the soils had low to moderate amounts of superparamagnetic (SP) particles, which indicates the combined effect of pedogenic superparamagnetic ultrafine particles and  lithogenic (inherited) magnetic particles in χlf of the soils. The effect of slope on Fe forms (Feo, Fed and Fet) has been significant (p < 0.01) in almost all land uses. Due to the relatively high correlation of χlf with some soil properties such as Fe forms, soil clay, the amount of diamagnetic compounds including calcium carbonate in the studied soils, it is possible to estimate the value of these soil properties using χlf, which is a quick and cost-effective approach. Overall, it seems that magnetic susceptibility could be applied successfully to estimate some soil properties in hilly regions of Zagros Mountains of southwestern Iran, especially for monitoring the consequences of land use changes. It should also be noted that any change in the use of the area should be defined in accordance with the potential of the land in the long term to prevent a reduction in soil quality.

Astragalus fasciculifolius is one of the most distributed plant species in the arid and semiarid regions of southern Iran. It may be well grown on roadside. This investigation was carried out to study the effect of road and its traffic intensity on the soil physicochemical properties and plant nutrients availability of roadside and to monitor the concentration of nutrients in the aerial parts of Astragalus fasciculifolius. Thirty soil and plant samples from roadside and 100 m distance from road were randomly collected and some physicochemical soil properties and nutrients availability were determined. Concentrations of the nutrients in the aerial parts of the plants were also determined. The results indicated that roadside soils had more sand and calcium carbonate equivalent than the adjacent lands. Soils of the main roadside had less K and more Fe, Mn, Zn and Cu than the adjacent lands; this difference in local road was observed only for Fe and Cu. Nutrients concentration in the aerial parts of the plants was affected by road, and P, K, Mn and Zn showed significant increases in the roadside plants. Concentrations of P, Fe, Zn and Cu in plants grown in main roadside and concentrations of Fe and Zn in plants grown in the local roadside were correlated with their contents in the soils. The effect of roads on soil properties change and nutrients availability may be related to the addition of road bed and emission of vehicles. Generally, it could be concluded that roadside soils had more suitable water and nutrition conditions for the growth of Astragalus fasciculifolius, as compared to the soils of the adjacent lands.

Land use change from forest and pasture to Rosa damascena Mill orchard can affect many soil properties and fertility. Thirty-six surface soil samples from different land uses including forest, pasture and Rosa damascena Mill orchard were collected from Morvarid region (Darab, Fars province) to evaluate the effect of land use change on soil properties and fertility. Different soil properties, macro- and micronutrients availability and soil potassium forms were determined. Results showed that the content of organic matter, soil pH and cation exchange capacity in the orchard soil were significantly lower than those in the forest and pasture soils. The nitrogen content in the orchard soil was significantly lower than that in the other land uses, however the content of available P in the orchard soil was significantly higher than that in the forest and pasture soils (39 vs. 22 and 24 mg kg-1, respectively). The availability of manganese, zinc and copper in the orchard soil was significantly higher than those in the forest and pasture soils. The contents of exchangeable K in the forest soil (749 mg kg-1) and non- exchangeable K in the orchard soil (1344 mg kg-1) were significantly higher than those in the other land uses. Generally, farmers may change the soil properties and fertility with addition of chemical fertilizers, disturbing the soil and harvesting some aerial parts of plants. Changes in soil properties and nutrients availability must be considered in agricultural land management and the results of this research, for example the decrease in content of some macronutrients and organic matter due to the land use change from forest and rangeland to orchard, can be useful to predict the consequences of land use change in the studied region and other similar regions. It is recommended that in order to maintenance of nutrients balance in orchards, P fertilizers application should be done with more consideration and the decrease in the contents of organic matter and such macronutrients as N and K should be recompensed with organic and inorganic fertilizers application.

Zeolite application to clayey soils may change potassium (K) pools distribution and its release rate. To test this hypothesis, two heavy-textured calcareous soils with different mineralogy (smectitic and mixed by XRD) from southern Iran were selected. Experiment was a completely randomized factorial arrangement. Treatments consisted of two soils and two zeolite levels (0 and 5%) and wetting-drying treatment. Soil samples were incubated in 50% of saturation percentage for 90 days. Then, three wetting-drying cycles were done on samples. Different forms of K and K release to 0.01 M CaCl2, HCl and CH3COOH by 12 successive 15 min extractions of soil samples were determined. Zeolite increased the content of different K forms in soil 1 (smectitic), while it increased soluble and exchangeable K and decreased non-exchangeable K in soil 2 (mixed mineralogy). This may be due to the high CEC (189 cmol(+)/kg) and K content (2.13% K2O) of the used zeolite. Wetting-drying cycles increased non-exchangeable K in soil 1 and exchangeable K in zeolite treated soils. CaCl2 extracted more K than HCl and CH3COOH solutions (682, 281 and 292 mg kg-1, respectively) because Ca ions are more efficient than H ions in replacing K from surface sites in the K-bearing minerals. Zeolite and wetting-drying had no effect on K release from soil 1 while they significantly decreased K release rate from soil 2.

Many factors including climate, type of rootstock, soil properties, geological factors, plant nutrition and irrigation affect the quantity and quality of orange fruit. In this study, the relations between citrus orchards conditions, their soil properties and leaf elements concentration and fruit quality were evaluated. The experiment was conducted as a randomized complete block design and soil, fruit and leaf samples were collected from six different regions of Darab, Fars, Iran. After fruit sampling, land properties such as physiographic features, slope, gravel, altitude and soil physical and chemical properties such as percent of sand, silt, clay, organic matter, calcium carbonate, pH and electrical conductivity and also N, P, K, Fe and Zn availability were determined. Several morphological and qualitative characteristics of fruit including, rind and flesh weight, rind thickness, length, diameter, fruit granulation, flavor, sugar and fruit juice acidity were determined. The contents of N, P, K, Fe and Zn in the collected leaves were determined. Three random samples were taken for each orchard and each replicate consisted of one tree. Results showed that fruit weight was correlated with the land slope, soil pH, electrical conductivity, soil organic matter content, soil N, P and K and leaf K content. Rind thickness showed a significant positive correlation with parameters such as land slope, electrical conductivity, organic matter, silt, clay and soil N, P and Zn and leaf N and K content. However, there was a significant negative correlation between rind thickness and soil gravel and sand contents. The relations between fruit granulation and soils calcium carbonate, gravel, organic matter content and soil K concentration were significant. TSS to TA ratio in fruit juices had significant negative correlation with land altitude, soils silt, calcium carbonate contents and leaf K content. Generally, many soil properties had significant effects on fruit quality but it seems that soil texture, organic matter, pH, P and K were more effective on fruit quality.

Little information is available regarding the effect of road on the adjacent vegetation and soil. The current investigation was done to study the effect of Darab-Bandar Abbas road on vegetation, soil properties and nutrient availability of the adjacent soils. For this purpose, eighteen soil samples in three different regions from the roadside and the adjacent land (50m from the road edge) were collected and the vegetation type and density were determined. Soil properties and the availability of N, P, K, Fe, Mn, Zn and Cu were also determined. Roadside soil had more organic matter and sand contents and less clay content and pH in comparison to the adjacent lands. The mean contents of N, Fe, Zn and Cu available in the roadside soils were 0.13%, 4.2, 3.2 and 0.7 mg kg-1, respectively; these were significantly more than those of the adjacent lands (0.06%, 2.8, 0.6 and 0.3 mg kg-1, respectively). Vegetation of roadside was more varied, consisting of Artemisia sieberi and Astragalus fasciculifolius. Vegetation cover in the roadside (13.8%) was significantly more than that of the adjacent lands (8.5%). Generally, it could be concluded that roadside soils had a suitable moisture condition and fertility for the vegetation development and this could be considered in the soil conservation management of the roadside soils.

Iron (Fe) deficiency in soil is a limiting factor for the growth of most plants. Fe availability in soil depends on distribution of Fe chemical forms among soil components which it is affected by physicochemical characteristics of soil. The aim of the present study was to investigate the distribution of Fe chemical fractions in some calcareous soils of orange orchards in Drab region (Fars province) and their relationships with some soil physicochemical properties and Fe concentration in leaves of orange trees. A sequential extraction procedure was used to fractionate Fe chemical forms in the studied soils. The results showed that the distribution of Fe chemical fractions in the studied soils were in the order: CFeOx > Fe-Res > AFeOx > Fe-WsEx > Fe-OM > Fe-Car > Fe-MnOx. There was about 98.2 percent of total soil-Fe in both CFeOx and Fe-Res fractions which it indicates the presence of Fe in unavailable forms for plant in the studied soils. Among the Fe chemical forms, AFeOx fraction only showed a significant and positive correlation with DTPA extractable Fe in soil and Fe concentration in leaves of orange trees. Also, among the soil properties, organic matter, calcium carbonate equivalent and cation exchange capacity were the effective characteristics of soil in determining the bioavailability of Fe and content of AFeOx form in soil. There were significant and positive correlations among some Fe chemical forms in soil that it represents a dynamic relationship between Fe chemical forms in soil. According to the results, it seems that the amount of soil organic matter can have an effective role on the availability of Fe in calcareous soils of orange orchards.

The use of organic and inorganic amendments is one of the effective methods for reducing the deleterious effects of heavy metals in contaminated soils and their immobilization. Addition of biochar as an organic soil amendment may change some soil chemical properties and provides suitable condition for immobilization of heavy metals in soil. Also, zeolite is a porous alkali alumino-silicate mineral that its application as an inorganic modifier is developing particularly in stabilizing of heavy metals in soil. Therefore, the aim of this study was to evaluate the effectiveness of biochar (derived from different organic materials) and natural zeolite application and their interaction on immobilization of zinc in a Zn-contaminated calcareous soil.
The appropriate amount of soil from the surface horizon (0-30 cm) of a calcareous soil, was collected, air dried and passed through 2 mm sieve. Then, the amount of 400 mg kg-1 Zn supplied as ZnSO4, 7 H2O was added to each soil sample (200 g). A factorial experiment in a completely randomized design was done with three replications. Factors included zeolite at three levels (0 (Z0), 3 % (Z1) and 6 % (Z2) (w/w)) and biochar at six levels (without biochar application (C), wheat straw biochar (WSB), corn straw biochar (CSB), licorice root pulp biochar (LRB), rice husk biochar (RHB) and sheep manure biochar (SMB) each at 3 % (w/w)). Contaminated soil samples were treated according to the experimental design and were kept for 90 days at room temperature (22±2 ˚C) and about field capacity moisture with distilled water. To evaluate the effectiveness of applied amendment materials in soil for immobilization of zinc, the sequential extraction procedure (sing et al, 1988), mobility factor (salbu and kreckling, 1998) and the parameters of two-first order kinetic model (Q1, Q2 and Q3) (Santos et al, 2010) were used.
with increasing zeolite levels from Z0 to Z2, the concentration of soluble-exchangeable (WEx), carbonatic (Car), organic (Om) and FeMn-Oxides fractions were decreased significantly while residual (Res) form of Zn was significantly increased. Application of all biochars significantly caused the decrease of WEx, Car and MnOxides (MnOx) forms in soil while crystalline Fe oxides (CFeOx) fraction was significantly increased compared to control (C). Res fraction was also increased significantly as influenced by different biochars application compared to control, so that, the impact of WSB, CSB, RHB and SMB treatments were similar and more than LRB treatment. The mobility factor (MF) value in different biochar treatments were as: C > LRB > RHB > CSB > SMB > WSB. Combined treatment of WSB and Z2 (WSBZ2), had the lowest MF of Zn in soil. The Q1 parameter of the kinetic model had significant and positive correlations with WEx and Car forms of Zn while Q3 and Q2 parameters had a significant and positive correlation with MnOx, FeOx and Res fractions. Furthermore, with application of all five biochars and increasing zeolite percentage, Q1/Q3 and Q2/Q3 ratios were significantly decreased compared to control. The lowest values of Q1/Q3 and Q2/Q3 ratios were observed in CSBZ2 and WSBZ2 combined treatments respectively.
application of all biochars and zeolite levels, led to the redistribution of Zn in soil, so that, Zn was transformed from more available forms to more stable forms. According to the results, it seems that the combined application of WSB and zeolite (Z2) was the best treatment to stabilize Zn in the studied soil.

Halophytes may change different soil properties and nutrients availability by organic materials addition to soil and soil conservation against erosion agents. Destroying these lands and halophytes may have an undesirable effect on environment. To study the effects of physiographic position, plant variety and plant growth position (sole or under another plant) on soil properties of salt marshes, an investigation was carried out in Korsia region, Darab (Fars province). Soil samples were collected from the beneath of Tamarix aphylla and Salsola rigida (sole and under Tamarix) and between plants with triplicates in two different salt marshes with lowland and piedmont plain positions. Soil properties including particle size distribution, organic matter, pH, EC and equivalent calcium carbonates and nutrients availability including P, K, Fe, Mn, Cu and Zn were determined. Results indicated that lowland had more saline and heavier textured soil and shorter Tamarix aphylla as compared with piedmont plain. Tamarix aphylla increased organic matter, EC, P, K, Fe, Mn, Cu and Zn; however, it had no effect on soil texture and equivalent calcium carbonates. Salsola rigida increased organic matter and its effect on available Mn and Zn was more than other nutrients. Salsola rigida under short Tamarix aphylla did not change soil salinity; while Salsola rigida under long Tamarix aphylla decreased soil salinity. Generally, it seems that organic matter is the most important factor on different plant nutrients availability and soil fertility status of the soils studied. Organic matter affects mobility, precipitation or nutrient uptake by the effect on pH, chelating agent production, nutrient adsorption, and nutrient release due to decomposition and soil physical properties improvement.

Different soil potassium (K) pools including soluble, exchangeable and non-exchangeable in surface and subsurface soils may be totally used by canola roots at different growth stages under drought conditions. A field experiment was conducted for one growing season (2013-2014) to study K pools changes during growth stages of two rapeseed cultivars under drought. The experiment was arranged in a randomized complete block design with four factors including different stages of rapeseed growth (before planting, seedling, stem elongation, flowering, grain filling and harvesting), drought (full irrigation, drought from flowering and silique formation), rapeseed cultivars (Sarigol and RGS) and soil depths (0-15 and 15-30 cm). Soil samples were collected and soluble, exchangeable and non-exchangeable K were determined. Results showed that the contents of soluble and non-exchangeable K (NEK) decreased during the growth stages (22 and 198 mg kg-1, respectively) while the contents of exchangeable K increased until stem elongation (57 mg kg-1) and then remained constant. Decrease in the contents of HNO3-extractable K (sum of soluble, exchangeable and non-exchangeable K) in the topsoils was significantly more than that in the subsoils (198 vs. 142 mg kg-1). Drought also had a significant effect on K pools distribution. Drought from flowering decreased the contents of NEK and HNO3-extractable K; however, drought from silique formation had no significant effect on the contents of the different K forms. Type of rapeseed cultivar had no significant effect on K pools distribution. It is concluded that a severe decrease in HNO3-extractable K occurs at the flowering stage (170 mg kg-1) and it must be considered for K fertilizers management. Decrease in NEK during the rapeseed growth supports the hypothesis that this form of K may be released during a growth season and this large pool of K may be considered in K fertility management and fertilizer recommendations. Generally, K uptake by Sarigol cultivar was significantly higher than that by RGS cultivar (177.7 vs. 129.4 kg ha-1). Potassium uptake by rapeseed decreased by drought and this decrease was more pronounced by drought from silique formation (more than 40% decrease in K uptake).

Addition of plant species residues to soils can add high amounts of potassium (K) as well as carbon sequestration. In the current investigation, residues of three plant species including Ziziphus spina Christi L., Phragmites australis and Atriplex halimus L. were collected from Darab plain and converted to biochars at 500 °C for 3 h under oxygen-limited condition. The soil used in the study was collected from a field in Darab at depth of 0-30 cm. Experiment was done using a completely randomized design with 7 treatments (plant residues, their biochars and control) and 3 replicates. Three percent of plant residues or biochars was added to the soil. Soil samples were incubated for 2 months at FC moisture and 22 °C temperature condition. Then, pH, EC, CEC and the contents of soluble, exchangeable, and non-exchangeable K of soil samples were determined. Results indicated that application of Ziziphus spina Christi biochar, Atriplex halimus leaves and Atriplex halimus biochar significantly increased soil pH. All residues and biochars increased EC from 0.43 (Ziziphus spina Christi biochar) to 3.57 dS m-1 (Atriplex halimus biochar). Biochars had more effect on soil EC than residues. Biochars had no effect on CEC, but Ziziphus spina Christi L. and Phragmites australis increased it significantly. Application of residues and biochars significantly increased soluble (144-937 mg kg-1), exchangeable (354-1430 mg kg-1), non-exchangeable (379-607 mg kg-1) and HNO3-extractable K (1030-2918 mg kg-1) and biochars had more effect than residues. Generally, Atriplex halimus leaves were more effective than Ziziphus spina Christi and Phragmites australis residues on soil properties and K forms contents. Residues and biochars application concentrated K in the exchangeable form (34-49 %). For application of these compounds, especially in the case of Atriplex halimus L., their effects on soil salinity and pH should be considered.

nowadays, application of organic and biological fertilizers in organic agriculture has become widespread due to their considerable benefits. Recently, the conversion of organic manures into biochar, as an alternative and stable organic fertilizer, has been paid attention by many researchers. Potassium is an essential nutrient for crop production. Application of various organic materials to the soil may effect on the content of potassium chemical fractions. The purpose of the present study was to investigate the effect of mycorrhizae fungi, animal fertilizers (sheep and chicken), and their biochar on the concentration of potassium chemical forms and the relationship between these forms with potassium content of maize plant in a calcareous soil.
Material and A factorial experiment as completely randomized design with three replication was done under greenhouse conditions. Treatments included five levels of organic fertilizer (without addition, sheep manure, poultry manure, sheep manure biochar, poultry manure biochar, each at 2 % w/w) and fungal inoculation in three levels (without inoculation, inoculation with Funneliformis mosseae and Glomus versiforme). Biochars were prepared under limited oxygen conditions at 500 0C for 4 hours. Appropriate amount of surface layer of a calcareous soil was collected and after passing through 2 mm sieve, were treated by organic fertilizers and arbuscular mycorrhizae fungous according to the experimental design. Then, 5 corn seeds (Zea mays L. 704) were planted at 2 cm depth in plastic pots. During plant growth, the soil moisture was maintained about 80 % field capacity level by distilled water. After 10 weeks, shoots were harvested and roots were separated from soils. After air drying and passing soil samples through 2 mm sieve, the concentration of potassium chemical forms (soluble, exchangeable and non-exchangeable) were measured. Also, the potassium uptake by shoots was also calculated by multiplying the potassium shoot concentration in dry matter yields.
Results indicated that organic manures and their biochars increased the contents of soluble, exchangeable and non-exchangeable K (8-65, 43-128 and 29-72 mg kg-1, respectively as compared to control). Generally, sheep manure and its biochar increased all K forms more than poultry manure and its biochar. Conversion of manures to biochar decreased soluble K and increased exchangeable and non-exchangeable K. Application of Funneliformis mosseae decreased soluble K and increased non-exchangeable K; while application of glomus versiforme decreased soluble K and increased exchangeable K. The amount of K extracted by HNO3 (sum of K forms) in treated soils with organic manures was lower than treated soil with biochars. Application of poultry manure biochar led to an increase in the effect of mycorrhiza species on the K content in soil while, application of sheep manure biochar caused a decrease in the effect of these fungous on three chemical forms of K. Organic materials and biofertilizers application significantly increased K uptake (16-217 and 14-36 mg pot-1, respectively as compared to control). Potassium concentration in shoot of maize plant had significant and positive relationships with all forms of K in soil.
applied organic manures (sheep and poultry) in increasing the soluble form of K were more effective than their biochars while, biochars increased the content of exchangeable and non-exchangeable forms of K more than raw materials. Also, application of each mycorrhizae species caused a decrease in soluble form of K. Generally, it can be concluded that organic materials and mycorrhizae fungi application may affect the K uptake or its leaching potential due to their effects on different forms of soil K.

Degree of soil evolution, type and amount of clay minerals are among the factors affecting potassium release from the soils. The release rate of non-exchangeable K (NEK) plays a significant role in supplying K for plants; particularly in soils that they are rich in K bearing minerals such as mica and feldespar. Kinetics of K release was studied by extraction with 0.01 M CaCl2 in 14 surface soils of different climatic regions of Kohgilouye and Boyerahmad Province, southwestern Iran. Mineralogical analyses revealed that smectite, illite, chlorite and palygroskite are major clay minerals of the soils studied. The release rate of NEK at the end of extraction (656h) was in the range of 38.1 (Typic Xerorthents) to 320 mgkg-1 (Calcic Haploxeralfs). In addition, the release rate of K showed higher correlation with the properties such as clay content, non-exchangeable K , CEC as well as illite and smectite contents. The amount of K release was in the sequence: Alfisols (222.3 mgkg-1) > Inceptisols (111.3 mgkg-1) > Entisols (105.0 mgkg-1). Power function, first order and parabulic diffusion equations could reasonably describe the K release kinetics. Fit of the data to these equations indicated that release of K is controlled mainly by diffusion process.

Different soil properties may affect the soil mineral nutrients availability, nutrients uptake by plant, plant growth and fruit quality. This study was carried out to investigate the nutrients status of soils and leaves of Washington Navel orange trees and their relationships with fruit quality of two orchards with similar nutrition management and different soil properties. Soils, leaves, and fruits of two orchards with similar management were collected and physical and chemical soil properties, soil nutrients availability, leaves nutrient contents and fruit quality were determined. Results indicated that the availability of all mineral nutrients was sufficient and P, Zn and Cu availability in orchard 1 was significantly higher than those of orchard 2; while this result was inverse for K. Orchard 1 had more K and Mn and less Fe. Fruits in orchard 1 had less peel thickness, more flesh ratio, more TSS, less total acidity and more TSS/TA. Positive and significant relationship was obtained between leaves K and P contents and fruit weight, peel thickness, TSS, TA, and TSS/TA.

Addition of organic residues to soil in organic farming may change soil K status and subsequently its availability and cycling. For this purpose, an experiment was done as factorial in completely randomized design with application of 11 organic materials (alfalfa, barley, pea and broad bean residues and sheep, cow, camel, poultry, pigeon and quail manures and vermicompost) in two clayey soils of Darab and Sepidan (Fars province) under two moisture conditions (field capacity and saturation) with three replicates. First, 2 g of organic materials was added to 100 g of soil samples and incubated for two months under field capacity and saturation conditions and laboratory condition (22±2˚C) and then the contents of soluble, exchangeable and non-exchangeable K were determined. Results indicated that all organic materials, except for vermicompost, alfalfa residue and camel manure increased soluble K and the highest increase was related to sheep manure up to 228 mg kg-1. The content of exchangeable K was increased with all organic residues application from 70 to 730 mg kg-1. The content of non-exchangeable K was also increased with organic residues application and the highest and lowest increases were found for poultry manure and camel manure, respectively. Generally, the contents of soluble and exchangeable K of Darab soil and non-exchangeable K of Sepidan soil were more affected by organic materials application. The saturation condition increased exchangeable K and decreased soluble and non-exchangeable K. Increase in the content of soluble K and soil salinity should be considered for organic amendments application to soils with high leaching potential and for salt sensitive plants.

Application of different organic materials in organic agriculture may change the status of plant nutrients in deficient soils. Arid soils of Iran may have a considerable content of potassium (K); but their K content is decreasing due to intensive agriculture. This K deficiency may be alleviated by different organic materials application in organic agriculture.
In the current investigation, a completely randomized experiment was done with application of four plant residues and their produced biochars to a calcareous soil and their effect on different forms of K. Three grams of wheat straw, corn straw, rice bran and licorice root residue and their produced biochars was added to 100 g of a clay loam calcareous soil and incubated for 90 days at 22±2 °C and 50 % of saturation moisture content. The soil samples were air-dried and sieved and pH, electrical conductivity and contents of soluble, exchangeable, non-exchangeable, HNO3-extractable K and K release rate from soil minerals were determined.
Results indicated that plant residues had no effect on soil pH, but all biochars increased soil pH (mean of 0.07). Soil EC was increased with application of wheat and corn straws and conversion of plant residues to biochars had more effect on soil salinity. Licorice root residue and its biochar had no effect on the content of different K forms; but other plant residues and their biochars increased soluble, exchangeable and HNO3-extractable K in the order of wheat residue > corn residue > rice bran. On average, biochars had more effect than plant residues on the content of soluble, exchangeable and HNO3-extractable K (212, 269 and 286 mg kg-1, respectively). The content of HNO3-extractable K was not affected with plant residues and their biochars (except for corn straw). Wheat and corn straws and rice bran released 286, 217 and 146 mg K kg-1, respectively; and their biochars released 637, 429 and 290 mg K kg-1, respectively from K-bearing minerals and this may be due to the effect of organic molecules and non-organic cations of organic materials on mineral weathering and K release.
It is concluded that application of plant residues and their biochars may have significant effects on soil K status and alleviation of K deficiency and the role of biochar is more important than primary plant residues. On the other hand, increase in soil salinity and pH especially in calcareous soils of arid land should be take into consideration.

Potassium and nitrogen are two major nutrients, have important role in increasing rice quantity and quality. Potassium like nitrogen is taken up in large amount by rice. Evaluation of nutrient status in soil is important from nutritional, environmental and economical aspects. This study was conducted in order to evaluate 11 different chemical extractants for determining suitable extractants for estimation of available potassium of rice in 11 selected soils of Kohgiluyeh Province. Rice seeds were cultivated in 1.5 kg pots in three replications and harvested after 10 weeks. Plant potassium was extracted with 1N HCl. Soil available potassium was extracted using 1M NH4OAC, 1 and 2M sodium chloride, 0.025 M sulfuric acid, 0.1M barium chloride, 0.01M calcium chloride, Morgan-Wolf, AB-DTPA, 1N NaOAC, 1M magnesium acetate and 2M Hydrochloric acid. The amount of K extracted by 1N NaOAC and 1N NH4OAC, was significantly (r=0.85** and 0.73**, respectively) correlated with K concentration, followed by Morgan and 2N NaCl. The lowest correlation is belonged to 1N HCl. Therefore, due to the simplicity and economy, the rate of extraction and the high correlation, extractants of 1N NaOAC and 1N NH4OAC are recommended as suitable extractants for determining the available K uptake by rice in the soil studied.

Evaluation of the nutrient status in soil is important from the nutritional, environmental, and economical aspects. Potassium is an essential element for plant growth and is a dynamic ion in the soil system. Soil testing is a useful tool that can help to ensure the efficient use of applied plant nutrients. Soil tests measure the quantity of a nutrient element that is extracted from a soil by a particular chemi¬cal extracting solution. The measured quantity of extractable nutrient in soil is then used to predict the crop yield response to application of the nutri¬ent as fertilizer, manure, or other amendments. Over the years, many different soil testing pro¬cedures and extracting solutions were evaluated in an effort to identify a method that provides the most reliable prediction of crop yield response to nutrient application. It was determined that some soil testing procedures are best suited for particular soil types and climatic regions, whereas other soil testing procedures are better suited for different soil types and climates. Olive is a strategic and economic product in Iran. Fars province is the second largest olive producer in Iran. There is no general information about K status in the soils and olive trees of the Fars province as well as no introduced appropriate K extractants for theses soils. Therefore, the objectives of this study were: i) evaluating potassium status of some soils of olive orchards of Fars province and ii) introducing appropriate k extractants for extracting available K in these soils.
Fars province, with an area of 122000 km2 is located in southern Iran. The elevation varies from 500 m to 4400 m above mean sea level. Based on the information regarding olive orchards of Fars province, 13 typical olive orchards were selected. 26 surface (0-30 cm) and subsurface (30-60 cm) soil samples were taken. Physiochemical properties of the soil samples were determined based on standard methods. Soil reaction, texture, electrical conductivity, calcium carbonate, organic carbon, and cation exchange capacity were identified. The 12 K extracting solutions were 1M NaCl, 2M NaCl, 0.01M CaCl2, Morgan, AB-DTPA, 1M NH4OAC, 0.25M NH4OAC, 1M NaOAC, 2M HCl, 0.1M HNO3, 1M HNO3, and 0.025M H2SO4. The K contents of leaf samples were determined in 1g of each sample. The samples were dried and then ashed in 450°C for 4 h. 2M HCl was used to digest the samples. Potassium in all the filtrated extracts were then analyzed using flame photometer.
The all soils were calcareous (average of 48.7 and 50.2% calcium carbonate equivalent in surface and subsurface, respectively) with pH in range of 7.05-7.8. The textural classes were loam, clay loam, and sandy loam. The results showed that the concentrations of K extracted varied widely with the used method, because each extractant remove different portions of K. Among the 12 tested methods, boiling 1 mol/L HNO3 extracted highest amount of K (mean 696.1 mg/kg and range of 203.3-1893 mg/kg) which extracted soluble, exchangeable, and non-exchangeable potassium forms due to its high concentration of H and 2mol/L HCl removed the lowest amount of K (mean 32.7 mg/kg and range of 2.6-148.5 mg/kg). Correlation coefficients between K extracted by 12 extractants were de¬termined. The correlation between potassium extracted by all the chemical methods was positive and significant except for boiling 1M HNO3. Between all tested extractants, 0.25M NH4OAC and 1M NH4OAC had the highest correlation (p≤0.01, r= 0.999). The relationship between soil potassium and potassium concentration in olive leaves were evaluated. Maximum correlation between leaf K and extracted soil K were noticed in 2M NaCl, 0.25M NH4OAC, 1M NaOAC, and AB-DTPA (r=0.721, 0.718, 0.717, and 0.714, respectively) and the minimum correlation was noticed in 1M HNO3 (r= 0.661).
The concentrations of K extracted varied widely with applied method, because of desorbing different portions of K by each method, different concentrations of each extracting solution, and the different times of equilibration. On average, the quantity of extracted K by 12 methods were in the following order: boiling 1M HNO3> 1M NH4OAC> 0.25M NH4OAC> AB-DTPA> morgan> 0.1 HNO3> 0.025M H2SO4> 0.01M CaCl2> 1M NaCl> 1M NaOAC> 2M NaCl> 2M HCl. This study showed that 2M NaCl, 0.25M NH4OAC and 1M NaOAC would be suitable as soil testing methods for determining available K for olive in the soils of Fars province. These extractants were the best because of high correla¬tion with plants potassium. In addition, advantages of these extractants are low cost and simplicity. As a recommendation, using of K fertilizers in most olive orchards of the province will improve quantity and quality of the yield.

In situ immobilization procedures concern the reduction of heavy metals bioavailability in contaminated soils using the materials which are compatible with the environment. In recent years, biochars effectively have been used to minimize the heavy metals uptake by agricultural crops in polluted sites using the immobilization process. Also, zeolite is a porous alkali alumino-silicate mineral that its application as an inorganic modifier is developing particularly in stabilizing the soil heavy metals. Accordingly, the aim of this study was to investigate the copper (Cu) stabilization as influenced by biochars (derived from different organic materials) and natural zeolite application and their interactions in a Cu-polluted calcareous soil.
The appropriate amount of soil from the surface horizon (0-30 cm) of a calcareous soil, was collected, air dried and passed through 2 mm sieve. Then, the amount of 500 mg kg-1 Cu supplied as CuSO4, 5 H2O was added to each soil sample (200 g). A factorial experiment in a completely randomized design was done with three replications. Factors included zeolite at three levels (0 (Z0), 3 % (Z1) and 6 % (Z2) (w/w)) and biochar at six levels (without biochar application (C), wheat straw biochar (WSB), corn straw biochar (CSB), licorice root pulp biochar (LRB), rice husk biochar (RHB) and sheep manure biochar (SMB) each at 3 % (w/w)). Contaminated soil samples were treated according to the experimental design and were kept for 90 days at room temperature (22±2 ˚C) and about field capacity moisture with distilled water. To assess the efficiency of applied amendment materials in soil for stabilization of Cu, the sequential extraction procedure, reduced partitioning index (IR) and the parameters of two-first order kinetic model using EDTA extractant (Q1, Q2 and Q3) were used.
Relative percentage of Cu chemical fractions in different treatments in soil were as: carbonatic (Car) > residual (Res) > organic (OM) > adsorbed (Ads) > soluble笗Ⅺ砞榹 (WsEx). With increasing the application of zeolite levels from Z0 to Z2, the concentration of WsEx, Ads, OM and Car fractions were significantly reduced by 5.46, 7.80, 10.40 and 15.30 percent respectively while, the Res form of Cu was increased. Application of all biochars except RHB, significantly caused the decrease of WsEx fraction compared to control. Use of all biochars led to reduction of the concentration of OM and Car fractions of Cu significantly while, Res fraction was significantly increased compared to control. Also, IR value was significantly increased as affected by zeolite levels and biochars application. The SMBZ2 combined treatment had the highest IR value. Soil pH showed a significant and positive correlation with Res fraction and IR value of Cu, which it indicates the important role of pH enhancement in stabilization of Cu in tested soil as affected by applied treatments. Copper desorption by EDTA extractant in all treatments was initially rapid, then continued at a slower rate, which probably indicating the incorporation of several sites with different bond energy in Cu desorption from soil. The Q1/Q3 and Q2/Q3 ratios were significantly decreased by application of all biochars and zeolite levels. The lowest of these ratios was observed in WSBZ2 combined treatment. There was a significant and positive correlation between the Q1 and Q2 parameters with Car fraction and the Q3 parameter with Res fraction of Cu in soil.
Application of all biochars and zeolite levels caused the transformation of Cu chemical fractions from more bioavailable and mobile forms to more stable forms. According to the results, it seems that SMBZ2 and WSBZ2 combined treatments were more effective to stabilize Cu in soil than other treatments.

The status of soil K forms and its relationship with K content in wheat grain at harvest period may be important for nutrient fertility management. For this purpose, 40 surface (0-20 cm) and subsurface (20-40 cm) soil samples and also grain samples from wheat fields of Darab region were randomly sampled in 2014. Then physicochemical properties of the soils and the contents of soluble, exchangeable and non-exchangeable K and contents of K in wheat grains were determined. Results indicated that content of soluble, exchangeable and non-exchangeable K in the studied soils ranged 15-70, 91-443 and 396-1182 mg kg-1, respectively. Significant relationships were obtained between soil K forms and clay, calcium carbonate and CEC. Although it is expected that content of easily available K (soluble and exchangeable K) was low at late stage of wheat growth, most soils had sufficient K content. The positive and significant relationship among different K forms was indicative of the K forms equilibration at the time of wheat harvesting. Although there is not a relationship between K content in wheat grain and soil K forms, it was shown that K content of wheat grain was correlated with soil exchangeable K and clay content in fine-textured soils (clay > 30%). It means that ammonium acetate may be a suitable extractant for estimation of soil K status and plant available K of heavy-textured soils in the studied region.

Potassium is an essential element for plant growth and exists as four forms in soils: soluble, exchangeable, non-exchangeable, and mineral. Soluble and exchangeable K are considered as readily available and non-exchangeable K as slowly available. Organic matters and acids play an important role in increasing the bioavailability of nutrients especially potassium in the soils. Organic acids are low-molecular weight CHO containing compounds which are found in all organisms and which are characterized by the possession of one or more carboxyl groups. Depending on the dissociation properties and number of these carboxylic groups, organic acids can carry varying negative charge, thereby allowing the complexation of metal cations in solution and the displacement of anions from the soil matrix.The ability of an organic acid to release K from soils depends on some factors such as: diffusion rate of the organic acid in soil, the diffusion capability of organic acid-element complexes, the contact time of the organic acid on a mineral surface, the ionization of the organic acid, the functional group of the organic acid and its position, and the chemical affinity between the organic acid and the mineral elements. This study was conducted in order to evaluate the effect of organic acids and vermicompost on transformation of K in some selected soils of Fars Province, southern Iran.
In this study, nine soils with enough diversity were selected from different parts of Fars Province. The experiment was done as a completely randomized design with three replications, consisting of three incubation times (5, 15 and 60 days) and four organic compounds (including 2% vermicompost, three acids of citric, malic and oxalic acid eachat a concentration of 250 mmolkg-1and one control). The samples were incubated at 50% of saturation moisture at 22°C. Routine physicochemical analyses and clay mineralogy were performed on soil samples. Soil reaction, texture, electrical conductivity, calcium carbonate, and gypsum were identified. Soluble, exchangeable, non-exchangeable and mineral potassium were measured. The amounts of K forms in each sample were determined. Total K was determined following digestion of soil (110°C) with 48 % HF and 6 M HCl. Water soluble K was measured in the saturated extract. Exchangeable K was extracted with 20 ml 1.0 M NH4OAc (pH 7.0) for 5 min. Nitric acid-extractable K was measured by extraction of a soil sample with boiling 1.0 M HNO3 for 1 h. Potassium was measured on all filtrated extracts by flame photometer. The content of clay minerals was determined semi-quantitatively, using peak areas on the diffractograms of ethylene glycol solvated specimens. Statistical analysis was accomplished using the SPSS 16.0 software and the comparison of mean values was done using the Duncan test at the 5% level of significance.
The amount of different forms of K including water soluble, exchangeable, HNO3-extractable, and mineral K are relatively high in the studied soils. Mineralogical analysis indicated that smectite, illite, palygorskite and chlorite were the major minerals in the clay fractions. The results also showed that exchangeable, non-exchangeable and total potassium were in the range of 166 to 378, 282 to 1694, and 2312 to 8437 mg/kg-1, respectively.Organic acids and vermicompostwere led toa significant increase in soluble K at all times compared to control and vermicompost treatment exhibited greater effect. These treatments also significantly increased exchangeable potassium compared to control. Significant differences between exchangeable potassium of organic acids and vermicompost treatments were not observed at 5 and 15 days, but significant differences were observed between treatments of mallic and oxalic acids at 60 days. Compared to the control, the non exchancheable K showed significant increase in all three organic acid treatments and vermicompost at 15 and 60 days.
Based on the results, while exchangeable and non-exchangeable (NEK) potassium showed a clear trend in treatments, solution potassium was first increased and then showed a decreasing trend due to the rapid changes in liquid phase compared to the solid phase. All treatments significantly increased soluble potassium in each 3 times. The greatest potassium increase associated with vermicompost. In general, oxalic acid> malic acid>vermicompost> citric acid, were increased exchangeable potassium, while the trend for NEK was in the order of oxalic acid> malic acid> citric acid>vermicompost, respectively. All treatments at all times (except for treatment 5 days of NEK), showed a significant increase in the exchange and NEK potassium compared to the control. The results also reflect the effect of the dominant soil clay mineral on transformation of exchangeable and NEK, so that the highest and lowest rate of increase was related to the soils with dominant palygorskite and illite, respectively. In general, it seems that the use of organic acids and organic matter leads to a rapid increase of potassium, which must be properly managed in the soils with high leaching. Due to the complexity of soil environment in terms of soil physical, chemical and biological aspects and the role of these factors on potassium transformation, repeating of this experiment in other soils is recommended.

Changes in soil potassium pools including soluble, exchangeable and non-exchangeable forms at various growth stages of wheat (Triticum aestivum L.) may be important in management of this macronutrient and knowledge of its dynamic process. To study that issue, an experiment was done in a completely randomized design on a 9-ha field during 2012-2013. Soil samples were taken from depths of 0-15 and 15-30 cm before sowing wheat, and at its various growth stages until ripening. Also, at various growth stages, plant samples were collected and different K forms in soil including soluble, exchangeable and non-exchangeable, and total plant K were determined. Results indicated that soluble K in surface soil decreased severely during early growth stages until stem elongation, and thereafter continued constantly. But, changes in subsurface soil were slower. Significant decreases in exchangeable K in surface soil occurred at stem elongation and ripening stages, but this reduction in subsurface soil occurred at grain milk stage. Non-exchangeable K changes in surface soil were observed at ripening stage, while changes in subsurface soil were not significant. Sum of soluble, exchangeable and non-exchangeable decreased from759 mg kg-1 to 720 and 680 mg kg-1 at stem elongation and ripening stages, respectively. Generally, HNO3-extractable K decreased in surface soil five times more than subsurface soil. Potassium concentration in shoots increased at tillering stage and reached 6.8 %, followed by a decrease to 1.1% and 0.8 % in shoot and seed, respectively, at ripening stage. Generally, results indicated a maximum K uptake by wheat at stem elongation stage that may be considered as a key tool in K fertilizer management. On the other hand, the role of non-exchangeable K and K in subsurface soil may be considered in available K estimation.