کریم شهبازی

One of the limiting factors in crop yield in calcareous soils of arid and semi-arid regions is the deficiency of micronutrients in these soils. This study was conducted to examine the effects of various commercial humic acids (HAs) and fulvic acids (FAs) on the release of manganese (Mn) in 15 calcareous soils. The results indicated that the application of all five different HAs used in this study had no significant effect (P<0.05) on the release of Mn, but the effects of FAs varied in different soils, the majority of them resulted in a significant increase (P<0.05) in Mn release. In 20% of the soils, either three or all five FAs, and in 26.7 % of the soils, either two or four of the FAs resulted in a significant increase in Mn release. In one soil, none of the FAs were effective in increasing Mn release. Two FA samples, FA1 and FA5, were much more efficient in releasing Mn, indicating that the effectiveness or ability of the marketed or commercial FAs to release Mn, on an equal weight basis, is not the same and varies greatly among them. The difference was, to some extent, due to the ability of these humic substances to form strong (multidentate) complexes with Mn or act as a chelating agent. The results also indicated that effectiveness was dependent on soil characteristics, which were related to the binding strength of Mn with surface functional groups of soils and the solubility of Mn minerals in the soil.

This study was conducted to investigate the effect of soil salinity on nitrogen mineralization in the presence and absence of wheat straw in three soils with textural classes of clay, loam and loamy sand under laboratory conditions as a factorial arrangement based on a completely randomized design with 3 replications. The studied factors were salinity (1, 10, 20 and 30 dS/m), wheat straw (0 and 2% by weight with C/N=89.5) and time (2, 5, 12, 20, 28, 37, 46, 53, 64, 73, 85 and 90 days). After investigation of different Iranian agricultural soils, three soils with low salinity (0.84-1.1 dS/m) and low organic carbon (0.22-0.98%) were selected. Considering the results, in the three soils, the amount of ammonium and nitrate in the treatment without straw was higher than those in the treatment with straw. In straw treatment, there was an initial descending trend in the amount of ammonium and nitrate for the three soils, but after a period of time, ammonium and nitrate content of the soil showed an ascending trend and returned to the initial value. With increasing soil salinity, the amount of soil ammonium increased in clay and loamy sand soils but decreased in the loamy soil. Nitrate content showed a descending trend for the three soils with increasing salinity. In general it is concluded that the presence of wheat straw in the soil can mitigate the negative effects of high concentrations of salt on nitrogen mineralization and reduce nitrogen losses.

In the process of conducting this research, 110 studies on monitoring nitrate content in agricultural products produced in Iran were gathered. These studies were published until March 20, 2023. The collected studies underwent evaluation for methodology, quality control, and quality assurance of results and were then assessed based on standard research criteria. The evaluation of the study's methodology revealed that only 27.3% of the studies adhered to standard methods for sampling, storage, and sample transfer. In 15.5% of the studies, the method of preparation and extraction followed standard procedures. Additionally, in 30% of the studies, the nitrate measurement method was conducted according to established standard procedures. The evaluation of quality control in the studies showed that only 20.9% reported some indicators of quality control and assurance. The assessment of nitrate concentration in agricultural products revealed the weighted mean concentrations of nitrate (mg kg-1 fresh weight) as follows: potato 98.7, cucumber 120.9, tomato 40.7, onion 39.6, watermelon 19.9, melon 62.9, carrot 151.1, eggplant 235.2, peppers 329, other root and tuber vegetables 542.4, lettuce 907.7, spinach 995.4, celery 1093.4, fresh edible legumes 37.7, parsley 596.5, cabbages 414.7, other leafy vegetables 635.6, apple 32.4, and orange 37.2. The findings of the present research reveal that the mean nitrate concentrations in Iran’s agricultural products fall below the maximum permissible levels outlined by both the Iranian national standard and international standards. As a result, it can be generally concluded that there is no significant cause for concern regarding residual nitrate concentration in Iran’s agricultural products.

Adding organic amendments to the soil increases permeability, water-holding capacity, biological activity, and nutrient content, and consequently increases the soil fertility and the yield of plants. In order to evaluate the effects of municipal waste compost and sheep manure on yield and yield components of wheat, a three-year field experiment was conducted as a randomized complete block design with three treatments, including the application of sheep manure (17.3 kg m-2), compost (15.6 kg m-2), and control (no organic amendment) in three replications in Agricultural Research Station of Zarghan, Fars province, during 2015-2018. The results showed that organic amendments had a significant effect on the number of fertile tillers per area, plant height, ear length, grain number per ear, thousand-grain weight, grain yield, biological yield, and harvest index; however, straw weight was not significantly affected by organic amendments. In all three years of the experiment, sheep manure and compost significantly increased wheat grain yield compared to the control treatment. On average, compost and sheep manure increased wheat grain yield by 63.9% and 46.1% in the first year, 29.3 and 53.7% in the second year, and 37.4 and 26.9% in the third year, respectively, compared to the no-amendment treatment. However, in the most cases, no significant difference was observed between sheep manure and compost. Therefore, farmers can use any of the sheep manure or solid-waste compost to increase wheat yield, the amount of which should be determined based on the amount of organic carbon in the farm soil.

Potassium, as an essential element, which its role in plant metabolism and resistance to biological and environmental stresses has been proven many times, requires accurate extraction and measurement for optimal management. The present study was conducted to investigate the effect of soil/extractant ratio on measuring the amount of available potassium in the soil. For this purpose, in October 2021, 62 soil samples were taken from agricultural fields all over the country, and their potassium content was measured by three extractants: 1 M ammonium acetate (three ratios of 5:1, 10:1, and 20:1), ammonium bicarbonate-DTPA (2:1, 5:1, and 10:1), and Mahlic-3 (5:1, 10:1, and 20:1) in the Karaj soil and water research institute (SWRI). The results showed that the amount of available potassium measured by ammonium acetate and Mehlich-3 extractants had no significant difference, but these two extractants had a significant difference with ammonium bicarbonate-DTPA. Probably, this difference is due to replacing the 2:1 ratio with a 20:1 ratio in the extraction method by ammonium bicarbonate-DTPA. In all three extractants, the estimated soil available potassium increased by increasing the soil to extractant ratio. On average, the amount of extracted potassium in 20:1 ratio was 11.5% and 5.01% more than the ratio of 5:1 and 10:1 for ammonium acetate, and 8.79% and 6.84% more than the ratios of 10:1 and 5:1 for Mehlich-3, respectively. By using a 10:1 ratio, all three extractants measured the amount of soil-available potassium without any significant differences. Therefore, it is suggested that all three extractants be used to determine the amount of available potassium. In addition, it seems a 10:1 ratio is a suitable ratio for measuring the amount of available potassium with minimal difference between different extractants.

Direct use of rock phosphate is considered as one of the alternatives to superphosphate, however, its use in acidic soils in the north of Iran has received less attention.This experiment was conducted as randomized complete block design. The treatments included: 1) control, 2) triple superphosphate (Tsp) fertilizer (based on soil test), 3) rock phosphate (to the extent that P addition was the same as Tsp), 4) compost at the rate of 10 tons per hectare, 5) rock phosphate+phosphate solubilizing fungi, 6) rock phosphate+phosphate dissolving fungi (Glomos), 7) rock phosphate + 10 tons per hectare compost, 8) rock phosphate + compost + phosphate solubilizing fungi (Pseudomonas), 9) rock phosphate+phosphate solubilizing fungi +compost. The results indicated the possibility of substituing rock phosphate for Tsp  in acidic soils of tea plantations, and organic matter plays an important role in better dissolution of rock phosphate by microorganisms in acidic soils. Application of bacteria, fungi, and compost treatments along with rock phosphate significantly increased the yield of green tea leaves as well as soil available P, compared to the control. Also, the concentration of trace elements in treatments containing compost showed a significant increase. The use of rock phosphate alone significantly increased the soil available P compared to the control, but the highest amount of soil P was obtained by simultaneous application of rock phosphate with compost and microorganisms (biofertilizers).

In the world, attention to the content of heavy metals in the soil has increased due to their potential risks to the environment and human health. In recent decades, many studies have been reported on soil contamination by heavy metals in Iran, but most studies do not show heavy metal status in soils on a national scale. On the other hand, despite the importance of background concentration of heavy metals for the assessment of pollution and environmental risks of these metals, no study has yet been published for soils of Iran at the national scale. In this study, an attempt was made to provide a comprehensive understanding of the status of heavy metals in soils of Iran on a national scale based on quantitative and qualitative analysis of the results of studies reported. To conduct this research, a total of 247 studies (both articles and final reports of research projects on field monitoring of heavy metals in soils of Iran that were published until November 2021 were collected. The required information (analysis results of about 21,400 soil samples) were extracted from the studies and first evaluated in terms of quality assurance and quality control criteria. Then, studies were classified into agricultural, urban and industrial based on the type of land use, and after screening and selecting studies that had the minimums required in terms of quality control, various statistics such as weighted average, median, background concentration and pollution index for heavy metals As, Pb, Cd, Cr, Co, Ni, Cu and Zn were calculated and analyzed....

Gypsum is spread in soils of arid and semi-arid regions and controls the soil physiochemical properties when it exists as the main soil component. Due to the undesired effects of gypsum in agriculture and plant growth, the accurate determination of its concentration is very important for soil classification and land use management. In this study, the parameters affecting the gypsum determination by the acetone method, namely contact time, extractant to soil ratio, and different extractants were investigated. Results revealed that the gypsum dissolution reaction was fast and most of the gypsum was dissolved in less than 0.5 h. Gypsum extracting with high extractant to soil ratios (1:200) had led to underestimation in the gypsum concentration. So that, the measured gypsum at 0.5 h extraction in soils with 10, 20, 30, 40, 50, 60, 70, 80, and 100% gypsum was underestimated by -1, 3.5, 9.6, 11.0, 22.4, 29.3, 39.6, 47.5, and 87.8% (according to the actual content) respectively. Decreasing the extractant to soil ratio to 1:400, overestimated (10 to 50%) the gypsum in the samples containing less than 50% gypsum. NaCl, KCl and MgCl2 solutions increased the gypsum solubility eliminated the underestimation in gypsum determination especially in 1:200 ratio. However, the use of salt solutions as extractants in the natural soils had led to overestimate at the higher extractant to soil ratios (1:400). The critical electrical conductivity (EC) in the measuring of gypsum by the Acetone method was 1000 µS/cm. According to the results, use of deionized water as the extractant, 0.5 h contact time, and variable soil to water ratio according to the soil gypsum content and to reach the EC of lower than 1000 µS/cm were the optimum condition for determination of soil gypsum by the acetone method which is recommended.

Many factors are involved in the production of healthy crop products and their monitoring requires a process-based and systemic approach at all stages from site selection to consumption. The present paper draws upon national and international experiences reflected in reviews in order to identify the most important factors affecting crop quality; the results will be expectedly exploited toward designing future studies and developing measures to improve crop qulity. Soil is the medium in which agricultural production takes place. Although geological formations with high concentrations of pollutants (especially heavy metals) might pollute soil resources, human activities inlcuding polluting industrial activities, improper application of agricultural inputs such as pesticides, chemical and organic fertilizers (especially phosphate fertilizers and non-standard sewage sludge), undertreated effluents, and atmospheric deposits (especially in urban and peri-urban areas) are some of the factors that expose soil and agricultural production more severely to the adverse of effects of such pollutants. Water pollution cannot be divorced from that of soil as they are closely related. While certain reports attribute soil pollution in parts of Iran solely to heavy metals with geohydrological origins, long-time crop irrigation using wastewater with high pollutant loads should not be ignored as a serious source of soil pollution. It should be noted that management plays a pivotal role in growing healthy products via using healthy inputs while maintaining biodiversity but that this cannot be achieved in the absence of such healthy basic resources as: a) soil, b) water, and c) air. In other words, unhealthy crops with pollutant loads result from both production processes and the environmental factors affecting them. A review of some domestic studies revealed that extensive background experience is required in the various sampling, measurement, and reporting skills, given the high sensitivity of these processes, to arrive at sound interpretations of the results of nitrate and heavy metals concentrations reported in some domestic journals. These studies have reported high concentrations of nitrate in spinach, lettuce, and celery but lower concentrations in such fruits as tomatoes, watermelon, and cantaloupe. Crops such as cucumbers, celery, and potatoes reportedly accounted for the highest nitrate concentration exceeding the allowable nitrate limits but minimum levels in tomatoes, watermelons, and cantaloupes. This is while heavy metal contaminations in plants have not been extensively reported on. Production of crops with allowable limits of pollutants presupposes due consideration of the factors outlined above. The approach proposed in this article requires soil fertility management, proper selection of crop species and cultivars, prohibited farming in contaminated lands, and avoidance of soil exposure to atmospheric deposition and polluted waters. These goals, in turn, may be achieved through accurate monitoring of agricultural product quality and identification of high-risk farming regions.

In the present work, switchable hydrophilic solvent-based extraction (SHSE) followed by high performance liquid chromatography with UV detection (HPLC-UV) was used to determine free amino acids in fertilizer samples. During the phase transformation of SHSE, the organic phase appeared to effectively capture the target analytes. In this extraction technique, 200 μL of a water-immiscible solvent (dipropylamine) is used, which can be solubilized in the acidic aqueous phase. Phase separation is then brought about by the addition of sodium hydroxide. The variables affecting this method were optimized to achieve the best extraction efficiency. The optimized conditions included: volume of sample 25 mL, volume of extraction solvent 200 μL, and extraction time 2 min. Under the optimal experimental conditions, good detection limits (0.0006-0.0021 µmol ml-1), linearities (R2 > 0.997), and precision (relative standard deviation less than 5.0%) were obtained. Finally, the developed method was successfully applied to the determination of target analytes in different types of fertilizer samples and acceptable recoveries (> 97.2%) were obtained.

We investigated the produced wheat of Iran in terms of heavy metal cadmium and lead, and also to measure the extent of zinc.

The amount of the mentioned metals in 419 wheat samples, after preparation and extraction, was analyzed by atomic absorption spectrometry.

The amount of cadmium in the 8.59 percent of wheat was higher than permissible limit in national standard index of Iran (0.03 mg/kg). In all provinces, the average amount of cadmium was less that the permissible limit, except Gilan. The findings showed that the amount of lead in 0.72 percent of analyzed samples was higher than permissible limit in the national index (0.15 mg/kg). In all provinces, the average amount of lead was less than national index of Iran. Analysis of concentration of zinc, a useful element, showed that in much of samples (about 79 percent), the concentration of this element less than acceptable level (30 mg/kg).

The analysis of frequency distribution of heavy metals in different provinces of Iran showed that in Gilan province, the concentration of cadmium is more than permissible limit. Since that the permissible concentration of cadmium in the national standard of Iran is unreasonably exigent. It is suggested that the maximum tolerance limit for cadmium in wheat grain should be reviewed. If the Codex standard is considered as an indicator of the pollution of heavy wheat production in Iran, in relation to cadmium, none of the analyzed samples cadmium concentration has not exceeded the Codex limit. In addition, the results of zinc measurement in wheat samples indicate zinc deficiency in most of the samples. Therefore, regarding the share of bread in the food basket of Iranian society, increasing the concentration of zinc in the wheat of Iran should be taken into consideration.

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

In this study, the concentration of effective amino acids in plant metabolism was measured in different soil and fertilizer samples by high performance liquid chromatography. First, the amino acids of the sample were extracted with 0.1 N hydrochloric acid. Then they were derivatized with phenyl isothiocyanate (PITC). Finally, the phenylthiocarbamyl-amino acid derivatives were isolated in the reverse phase column using gradient elution with sodium acetate trihydrate and acetonitrile-water (40:60), and detected by a UV detector at 254 nm. Several parameters related to the separation of amino acid peaks, including pH and temperature of the mobile phase, buffer concentration and modifier (triethylamine) in the mobile phase were studied. By changing each of the existing conditions, the amount of resolution for amino acid peaks was optimized. Under optimal conditions, a good linear range (0.0312-0.125 µmol / ml) was obtained for 17 amino acids with a detection limit of 0.0094 µmol / ml and acceptable reproducibility for each amino acid (RSD ≤6.1%). Finally, the percentage of free amino acids was measured in different soil and fertilizer samples by this method.

Arsenic adsorption on soils plays an important role in controlling mobility, bioavailability and toxicity of arsenic in the environment. Kinetic studies on arsenic adsorption are often done at soil to water ratios of 1:10 to 1:50, which generally make the conditions of the study different from the prevailing field situations. In this study, kinetics of arsenic adsorption were investigated in five arsenic-uncontaminated agricultural soils at saturation moisture content of 50% over long periods of time (2 minutes to 20 days). Six kinetic models were fitted to the data. The kinetics of arsenic adsorption on soils were nonlinear and biphasic. Arsenic adsorption rates were initially rapid, but gradually decreased with time and reached a plateau after 72 hours. The cumulative amount of arsenic adsorbed by soils ranged from 158 to 210 mg/kg, 47-67% of it was adsorbed in the first two minutes (the first measurement time) and 68-86% of it was adsorbed in the first hour of the reaction. Cumulative adsorption of arsenic on different soils was reduced by 1.9-16% in the presence of 100 mM phosphate, 0.7-9% in the presence of 100 mM citrate and 0.6-9% in the presence of 10 mM phosphate as compared to arsenic adsorption alone. The simplified Elovich model with the higher coefficients of determination ( ) values (0.93-0.96) and lower standard errors of the estimate values (5.1-6.5 mg/kg) best described arsenic adsorption data in all soils compared to zero-, first-, and second-order, power function and parabolic diffusion models.

Different methods are used for determination of the primary particle size distribution (PSD) in Iranian soils laboratories, which in many situations makes it difficult to compare results and their precision. This research was conducted to achieve an easy and inexpensive strategy with acceptable accuracy. First, 112 soil samples from 16 different provinces of Iran with a wide range of soils were taken from different climates and land uses. Soil PSD was measured by hydrometer with and without cement removal. The results showed that the common reading method of 40 seconds and 2 hours (Bouyoucos, 1962) measures the clay fraction with an average absolute error of 9.5% as compared to the complete record method. This error was more than 10% in 40.5% of the proposed soils and more than 5% in 94.2% of the soils. The deviation of this method from the actual value is increased as the soil becomes finer. Two four-reading methods with the classification of International Soil Science Association (ISSS) including: a) 2 and 10 minute readings (to measure silt fraction) and 6 and 8 hours (to measure clay fraction), and b) readings of 2 and 10 minutes (to measure silt fraction) and 6 and 24 hours (to measure clay fraction) were suggested to determine the soil texture. The two later methods show the soil texture correctly in 97.1 and 94.2% of the soils, respectively. The error of these two methods for determination of clay fraction is less than % in more than 90 and 81% of the proposed soils, respectively.

Because the range between boron (B) deficiency and toxicity thresholds in soils for many plants is very short, accurate evaluation of available soil B status by soil testing is necessary for proper use of B fertilizer. This study was conducted to compare ICARDA and Soil Science Society of America (SSSA) procedures as the most commonly used methods to determine available soil B. A total of 20 surface soils with different physical and chemical properties were selected and their available B concentration was measured by ICP method and the colorimetric procedures proposed by ICARDA and SSSA. The effect of activated carbon application and the presence of suspended colloids on B concentration was also investigated. Mean available B concentration in the soils for ICARDA and SSSA methods by ICP were 2.59 and 2.86 mg/kg, whereas those by azomethine-H were 2.43 and 2.69 mg/kg, respectively. The relationship between B measured by ICP and azomethine-H for SSSA indicated a higher correlation ( ) and a better fit to 1:1 line than ICARDA ( ). Mean B concentrations were 2.86 mg/kg using hot 0.02 M  and 2.84 mg/kg using hot water. The use of activated carbon decreased B in extracts significantly. The mean of available B extracted from the soils using hot water with carbon was 2.59 mg/kg, whereas it was 2.84 mg/kg without carbon. Use of 0.2, 0.4 and 0.6 g carbon per 40 ml of B solutions with different initial concentrations yielded the mean B recovery of 104.9, 100.4 and 97.6%, respectively. Because of suspended colloids, B concentrations in extracts filtered through Whatman 40 filter-paper were higher than those filtered through Whatman 42. Without the use of carbon, predicted error in B determination due to color in extract ranged from 0 to 0.88 mg kg-1. Generally, the SSSA method measured available soil B more accurate than ICARDA and it is therefore recommended to use.

The increased levels of Arsenic, a poison element, in the soils and waters of Hashtrood city have caused different health issues for the people. Due to the lack of information about the arsenic content of the soils, the present study was conducted to survey the soil arsenic distribution and the possibility of reducing arsenic release from the soils. For this purpose, 53 soil samples from the top layer were collected and the arsenic concentration and distribution map was determined. Additionally, in order to evaluate the effect of iron hydroxide and gypsum as soil amendments, five polluted soil samples were selected and treated with the proposed amendments; each at three levels. The results revealed that the agricultural soils of the studied area are polluted by arsenic, as its average concentration was 49.36 mg/kg, but more than 80 percent of the studied soils had a lower concentration than the standard level. The agricultural soils of Ghopoz and Ghezellou showed the highest arsenic contamination. Application of iron hydroxide reduced the arsenic releasement in different soils significantly, as 10 ton/hectare iron hydroxide application reduced arsenic solution 64.5, 82.4, 83.7, 98.9, and 100 percent in the soils of 1, 2, 3, 4, and 5, respectively. Increasing the level of iron hydroxide application decreased arsenic release more intensively. Similarly, the gypsum decreased the arsenic release significantly and its reduction was more by increasing gypsum application In comparison to gypsum, the iron hydroxide was much more effective in controlling the arsenic releasement.

In soil laboratories of Iran to determine the initial soil particle size distribution (PSD) curve, different methods and strategies and pretreatments are used to remove soil cement materials, which in many cases make it difficult to compare the results and also evaluate their accuracy. The current research was performed to achieve an economical, simple and accurate protocol to mesure the soil PSD analysis. First, 112 soil samples from the top and sub soils were collected from 16 provinces. Then 91 soil samples were selected based on hydrometer method and they were analyzed mechanically with and without removal of different cement agents; such as Organic matter, lime, iron and aluminum oxides and combined removal of organic matter and iron oxide. Results showed that the removal of cement agent increases the clay fraction and reduces the silt and sand fractions. The removal of cement agents should be conducted where i) organic matter content is more than %4 or ii) iron oxides is more than %2 or iii) the amount of  organic matter + iron oxides is more than %5. In average, the removal of organic matter and iron oxide increases clay fraction 7%. Since the carbonates are often exist as the primary particles in the Iranian soils, the removal of carbonates is not suggested from the soils with more than %10 carbonates. Finally it is concluded that the cement agent in some soils may cause incorrect determination of soil texture class.

Animal manures are valuable organic sources for soil organic matter and crop nutrition. To evaluate the residual effects of two sources of animal manure on growth and yield of winter wheat (Triticum aestivum L) Zarin variety, a field experiment was conducted at Miandoab Research Station, Agricultural and Natural Resource Research and Educational Center of West Azerbaijan, Iran. Manures were used in 2014. In the next three years, no animal manure was applied. Residual effects of manures were determined during winter growing season of 2017-19. The treatments included T1= control, T2= 50 t ha-1 cow manure, T3= 100 t ha-1 cow manure, T4= 50 t ha-1 sheep manure, and T5= 100 t ha-1 sheep manure and were used in a randomized complete block design (RCBD) with three replications. None of the plots received mineral fertilizers. The results showed that the sheep manure was more efficient than the cow manure. Plots receiving 50 t ha-1 sheep manure showed higher grain yield and harvesting index of 36% and 17%, respectively, compared to control plots, whereas, 100 t ha-1 sheep manure did not show significant yield increase compared to the T4. Significantly higher nitrogen (1.84%), potassium (0.41%), magnesium (0.12%), iron (126.40 mg.kg-1), copper (16.4 mg.kg-1), zinc (45.7 mg.kg-1) and manganese (33.35 mg.kg-1) content in grain and highest potassium (1.76%), iron (269.3 mg.kg-1), zinc (9.16 mg.kg-1) and manganese (24.08 mg.kg-1) content in wheat straw were recorded under treatment T4. The overall results indicate that organic carbon and availability of nutrients, particularly P, Zn, and Fe in the soil surface layer were significantly higher in plots receiving manures compared to the control. Before the experiment, soil organic carbon (SOC) was 0.88%. After harvest, SOC in treatments of 50 and 100 t ha-1  of cow manure increased to 0.99% and 1.36%, and in treatments of 50 and 100 t ha-1 of sheep manure, it increased to 0.94% and 1.26%, respectively. The Results demonstrated that manure application, due to its role in soil fertility improvement, is an effective strategy for efficient production of wheat and enrichment of its grain.

Nitrate is one of the most important pollutants that is accumulated mainly due to unbalanced fertilizer use and excessive use of nitrogen fertilizers in plant organs. Most of the nitrate in our body comes from vegetables. In Iran, tomatoes and cucumbers are consumed vegetables in the food basket of people. Therefore, the study of nitrate pollution in these products and the identification of the sources of pollutants and providing appropriate solutions for the relative reduction of contamination is necessary. In this study, we randomly collected samples of tomatoes and cucumbers from Alborz province for 16 months each week. Samples were washed with distilled water and moisture content and their nitrate content was measured by micro-Kajledal method. The results showed that nitrate content in the cucumbers Distribution the Alborz province with an average of 212.25 mg / kg fresh weight was higher than the World Health Organization (WHO) (150 mg / kg) and Iranian National Standardization Organization (INSO) (90 mg / kg of fresh weight). The range of nitrate content in fresh cucumber samples was 15.18-1221 mg / kg and according to the World Health Organization and National Iranian Standards Organization, 58.76% and 74% of cucumber samples had more nitrate content above the limit, respectively. The results of this study showed that the mean concentration of nitrate in tomato samples was 20.22 mg / kg, which was below the World Health Organization (300 mg / kg) and Iranian National Standardization Organization (120 mg / kg fresh weight) was less. The range of nitrate content in tomato samples was 3.4-121.3 mg / kg, and according to the Iranian National Standardization Organization index, only one tomato sample had nitrate content higher than the limit.
Conclusion and The results showed that mean nitrate concentration in autumn winter spring summer. In cucumber, the amount of nitrate in the skin is more than other parts of cucumber.

Humic substances (HS) are complex and heterogeneous materials with different sizes produced through decomposition and transformation of plant and microbial residues by chemical and biochemical processes. HS producers, consumers and also regulators have a great interest to find a precise and accurate method for quantification of HS due to increasing use of them in agriculture.  Since there is no distinct definition and consistent chemical structure for HA, an accurate quantification method has not been developed. There are four laboratory methods for determination of HA, FA, humates, and HA derivations (e.g. humate extracts) in commercial fertilizers. These methods include; ISO 5073 titrimetric method that has been published as national standard 11094, a colorimetric method that has been developed according to Mehlich method (1984), and two gravimetric methods that one of them has been developed by California Department of Food and Agriculture (CDFA) and other one is called New Standardized Method (NSM). All of these methods are based on the solubility of HS in dilute alkali solutions.  Moreover, FA and other alkali soluble materials e. g. amino acids, proteins, sugars and fatty acids are extracted and measured in colorimetric and titrimetric methods as HA, hence these methods overestimate HA content. The NSM method has obtained by modification of classical method and is based on extraction of HA and FA from natural substances. In this method the separation of FA from other strong base extractable substances such as polysaccharides, amino acids, proteins, and lipids is possible. Also, the NSM method has been accepted by International Humic Substances Society (IHSS) and Humic Products Trade Association (HPTA) and it is the base of standard method that has been developed by International Organization for Standardization (ISO 19822). Therefore, the NSM method is recommended as a reference method.

Study has shown that the soil available-P content in 71.8% of the agricultural lands in Iran falls below 15 mg. kg-1. Moreover, excessive use of P-fertilizers in calcareous soils not only increases costs but also leads to P-accumulation and reduced uptake of micronutrients, especially Zinc, to pose serious threats to public health. Generally, only a small percentage (15‒20%) of P-fertilizers used each year may be absorbed by plants while the remaining portion precipitates to increase soil total-P in lands with high pH levels. This process can cause environmental problems in areas close to lakes or those near surface waters used to supply drinking water. These observations warrant the quest for indicators that address both plant requirements and adverse environmental effect. It is worth noting that P is far more easily released in calcareous soils than in acidic ones because the bond between phosphate ions and calcium is by five times weaker than that between phosphate ions and iron or aluminum. It may, therefore, be concluded that application of P fertilizers should be based on local soil analysis and that P fertilizers should be recommended in soils whose available phosphorus concentration is below a critical level. Thus, such appropriate practices as applying P- fertilizers with due consideration of soil analysis results, increasing soil organic matter, and using P solubilizing bio-fertilizers may be recommended in order not only to enhance uptake of soil non-available P but to meet plant requirements, optimize fertilizer consumption, and prevent environmental hazards as well.

Application of phosphorous (P) fertilizers to calcareous soils has some problems, because only 10-25% of P- fertilizers added to the soil are absorbed by the plant and the rest (75 to 90 %) is precipitated as calcium phosphate. Research has shown that P accumulates in soils where P-fertilizer has been used for a long time. Accumulation of P has caused a number of environmental problems including reduction of surface water quality. In some parts of Iran, such as Pars Abad-e- Moghan, which are considered as agricultural pole, study of total P by environmental indicators is necessary. For this purpose, this experiment was conducted in 2016. At first, sampling grid was drawn (at 3 * 3 km intervals) for agricultural lands, then soil sampling was done by GPS. Soil texture, organic carbon, pH, T. N. V, total P and available P were analyzed in all soil samples. Also, Environmental Performance Index (EPI) was estimated by Bolster (et al. 2014) method. SPSS (version 16) and GS+ software were used to determine the spatial correlation of total P, available P and Phosphorus Environmental Index [H1]  . The results revealed that the range of available P varied from 7 to 40 mg. kg-1 and total P ranged from 718 to 2315 mg. kg-1. The minimum, maximum and average environmental indicators were 40, 72, and 55, respectively, indicating that almost all of the farms in this area were at medium risk. Increasing the environmental index is more severe in soils in which total P exceeds 1200 mg kg-1 [H2]  .

The presence of heavy metals in the environment is causing ever-growing concern due to their toxicity, carcinogenicity and non-biodegradability. Nickel may enter and accumulate in agricultural soils through various ways. One of the most important chemical processes which affects the behavior and bioavailability of heavy metals is sorption of metals from liquid phase on the solid phase. This process controls the concentration of metal ions and complexes in the soil solution and can influence their uptake by plant roots. Sorption isotherm is a useful method to study metals retention in soils as it gives much useful information about sorption capacity of soils. The aim of the present study was to investigate the sorption properties of Ni by calcareous soils of Iran and its relation with some soil properties to better understand the fate of this metal in calcareous soils. Nickel (Ni) sorption characteristics in 20 calcareous soils of Iran were investigated in a range from 5.87 to 751.23 mgL-1 Ni concentration in solution using sorption isotherms of Langmuir, Freundlich and Redlich–Peterson. The “Curve Expert” software was used to fit the models of sorption isotherms. The high coefficient of determination (r2) and low standard error of estimate (SEE) were used as a criterion for selecting the best model. The Ni sorption isotherms could be fitted by the Freundlich model (r2=0.92-1.00; mean 0.99). The dimensionless parameter n that may indicate the sorption site energy distribution for different soils was between 2.07 and 3.15 and average of 2.46. Also the coefficient of determination and standard error of estimate showed that adsorbed behavior of Ni by calcareous soils can be described by Langmuir adsorption equation (r2=0.94-0.99; mean 0.98). The maximum sorption of studied soils for Ni ranged from 1369 to 5378, with average of 360 mg/kg. The coefficient of bonding energy (KL) in different soils was between 0.008 and 0.029 with an average of 0.015 L/mg that indicate narrow range of this parameter among the studied soils. The distribution coefficient (Kd) ranged from 22.6 to 122.5 with average of 54.8 L/kg. According to the coefficient of determination (r2=0.94-1.00; mean 0.99) and standard error of estimate (SEE= 47.9-163.3; mean 96.9), the Redlich–Peterson equation achieved the best fit to the data of Ni sorption in studied soils. The maximum Ni sorption (qmax) correlated with organic matter (r2=0.50, P