جستجوی مقالات مرتبط با کلیدواژه "مواد آلی خاک" در نشریات گروه "کشاورزی"

The rangeland ecosystems of arid and semi-arid regions play the most important role in the distribution and density of vegetation in these areas due to the specific environmental conditions governing the soil, which is the bridge between living and non-living parts of ecosystems. Soil enzymes play important biochemical roles in the decomposition of organic matter at all stages in the soil system. These enzymes play an important role in the stability of the soil structure, the decomposition and formation of organic matter, the cycle of elements and the activity of soil microorganisms. Environmental stresses, such as drought, have negative impact on plant growth and soil microorganism's activity. Therefore, evaluating the effect of flood spreading on soil quality indicators can be a useful step in improving knowledge in this field. Therefore, this research was conducted during 2018 and 2019 to investigate the effect of flood spreading, plant types and characteristics on biological soil in the Kowsar floodplains located in Gareh-Bygone, Fasa.

Sampling of the soil around the roots of Artemisia sieberi Besser, Dendrostellera lessertii (Wikstr) Van Tiegh. and Heliantemum lippii (L) Pers, in two situations: with flood spreading and without flood spreading (control area) in spring and autumn from a depth of 0-20 cm and in three repetitions. After ensuring the normality and homogeneity of the variance of the data by the Shapiro–Wilk and Levene tests, the data were analyzed using the two-way variance method and mean comparison were made using Duncan's test at the 1% and 5% level and using the R software.

The results of soil fertility characteristics showed that there was no significant difference in the amount of phosphorus and potassium in the three pasture species studied under flood spreading and the control areas. However, the amount of carbon and nitrogen in all studied species was significantly higher in the flood spreading area (containing 0.3% organic matter) than the control area (with 0.15% organic matter). In addition, the results of this research indicated that the highest activity of acid phosphatase enzyme was observed in the rhizosphere of D. lessertii species and in the spring season, and on the contrary the lowest activity was observed in the rhizosphere of H. lippii species under the flood spreading condition. Alkaline phosphatase activity in all species was significantly higher in spring than in autumn season. The highest activity of this enzyme was observed for A. sieberi in the spring season with an average of 186 (µg p-nitrophenol g-1 soil h-1) in the flood spreading area and the lowest level was observed for H. lippii in the control area with an average of 57 (µg p-nitrophenol g-1 soil h-1) in the autumn season. In general, the level of phosphatase enzyme activity for the A. sieberi species in the spring season was approximately 89% higher in the flood spreading area than in the control area. The dehydrogenase enzyme activity was higher in spring than in autumn. Also, the highest activity of this enzyme was observed in the spring season for the D. lessertii  species with an average of 8.5 (µg TPFg-1 soil 24 h-1 ) in the control area, and the lowest level was observed in the autumn season for the A. sieberi species in the flood spreading area with an average amount of triphenol formazan was 1 (µg TPFg-1 soil 24 h-1 ) .In other words, the amount of dehydrogenase enzyme activity in the spring season was approximately 66% higher than that in the fall season in both areas (control and flood spreading). The results of this research showed that the activity of urease enzyme under flood spreading conditions in both seasons (autumn and spring), with an average of 270 and 300 (µg N/g.dm.2h) is more than the control area with an average of 173 and 250 (µg N/g.dm.2h). Also, the soil quality indices in all three studied species in the two (control and flood spreading) areas have a significant difference, so that the flood spreading operation has upgraded the value of these indices for the H. lippii species and the A. sieberi, while which has reduced the soil quality index of D. lessertii.

The results of this research showed that the flood spreading system is a desirable method for improving soil organic carbon, and its efficiency increases with the plant planting. The increase in moisture and the amount of organic matter in the flood spreading area can be a reason for increasing the activity of enzymes in the flood spreading area, so that in both autumn and spring, the activity of soil enzymes is more in the region. Considering the important role of organic matter in improving biological indicators and soil quality and health, the restoration of floodplains with native species can play an important role in providing these conditions. In addition, it is recommended that these tests be repeated with more samples and in different areas and the nitrogen, carbon, sulfur and phosphorus cycles and its relationship with the activity of other soil enzymes related to this cycle should be investigated.

More than 80% of Iran's area is arid and semi-arid. Arid and semi-arid soils have various problems and limitations. One of the most important factors limiting soil fertility and crop production in these areas is the lack of soil organic matter (SOM). In more than 60% of Iran's agricultural lands, the amount of SOM is less than 1%; While its optimal level in soils should be 2-3%. SOM, as one of the most important indicators of soil health, plays a vital role in soil fertility and crop production; So, by increasing the amount of SOM, the physical, chemical, and biological characteristics of the soil and crop yield can be improved. However, the stability and residual effects of the fertilizers and organic wastes in the soil are low. Nowadays, converting organic wastes and residues into biochar and adding them to the soil is one of the new methods of increasing soil organic carbon, which enhance soil fertility and crop yield and has high residual effects due to its high stability. However, due to the specific characteristics of the soils of arid and semi-arid regions, using biochar in these regions is associated with challenges and has received less attention. In this review article, while reviewing the positive effects of biochar on soil quality indicators and crop production, the challenges of using biochar in the soils of arid and semi-arid areas, especially in drylands, and the solutions to overcome these challenges have been reviewed.

Application of chemical fertilizers since green revolution, make the crop production doubled or even tripled in some crops. However, long-term overuse of these fertilizers decreased soil quality. Thus to obtain the same yield, the rate of inorganic fertilizer application steadily increases from year to year. Recent studies revealed that in order to increase the chemical fertilizer efficiency, it needed to integrate organic resources with chemical fertilizers to soil. However, using organic manure in the soil will be decomposed very rapidly. Biochar is a source of high organic carbon which highly resistant to decomposition. It has a porous quality and large surface area which reduces leaching of nutrients. Biochar addition to soils can change microbial biomass, adsorb toxic compounds and improved soil water and pH status. The internal porosity of biochars may help soil microorganisms avoid grazers. Globally demands for plant- based medicines are growing. Black seed (Nigella sativa L.) is annual plant to Ranunculaceae family, is grown in arid and semi-arid regions of the world. Black seed considered as a spice, medicinal plant and used as seasoning in cooking and foodstuffs. Recently, there has been an increasing interest in integrated approaches in improving crop production to resist conditions of nutrient-poor soil, drought, and salinization. Since, a few attempt has been made to investigate the effects of biochar amendment on medicinal plants in semi-arid agricultural systems, the present study was initiated in agro ecological condition of Mashhad. A field experiment was conducted as split plots factorial layout based on a randomized complete block design with three factors and three replications at the Research Station, Faculty of Agriculture, Ferdowsi University of Mashhad, Iran during growing season of 2016. Three levels of irrigation (100, 70, and 40 percent of water irrigation requirement) were assigned as main plots and the combination of three levels of biochar (0, 10, and 20 ton ha-1) and two levels of chemical fertilizers (without and with chemical fertilizer) were allocated as sub plots. Recommended dose for nitrogen, phosphorus, and potassium was 150 kg ha-1, 75 kg ha-1 and 100 kg ha-1, respectively. The size of each experimental unit was 3×2 m2. Black seed thinning was performed after emergence to get a plant population density of 200 plants m-2. Post experimental soil which was amended with biochar and fertilizer were analyzed for total nitrogen, available phosphorus, potassium, soil organic matter, and microbial biomass carbon. Plant criteria which studied were such as grain yield (kg ha-1), straw yield (kg.ha-1) and water use efficiency (base of grain yield). Analysis of Variance (ANOVA) and Duncan multiple range test were used to compare the recoded data. Soil N, K, SOM, and Microbial biomass carbon were significantly affected by biochar application. Phosphorus was not affected by biochar. The highest biochar effect on soil characteristics was found under 20 ton ha-1 biochar application treatment. The results showed that application of 10 and 20 ton ha-1 of biochar improved soil nitrogen compared with control treatment. Soil organic matter was increased by 1.56% compared with 1.33% in control when 20 ton ha-1 biochar was used. It has been reported that the biochar may increase the organic matter of the poor soils. The soil microbial biomass carbon was increased by biochar and fertilizer application. It seems that the reason for increasing soil microbial biomass by adding biochar to the soil is enhancing available soil nutrients, adsorption of toxic compounds and improved soil water and pH status. The internal porosity of biochars may help soil microorganisms avoid grazers. Combine use of fertilizer and biochar were more affected on plants growth than biochar or fertilizer alone. The interaction between biochar, chemical fertilizer and water requirements significantly affected the seed and straw yield. The significant increase of grain yield, straw yield observed in I2B2F2 (70% water requirement+10 ton ha-1 biochar+ with chemical fertilizer) and I2B3F2 (70% water requirement+20 t.ha-1 biochar+ with chemical fertilizer) treatments. Biochar significantly increased water use efficiency which shows that under water deficiency, biochar can increase the uptake of water and nutrients. As a result, plants tolerance against water deficiency increase and more yields will be produced for a specific value of water. This means the water use efficiency can increase and the use of water will decrease.   This study confirmed that biochar application can help in increasing of black seed production through the improving some physical and chemical properties of the soil such as soil pH, soil nutrient availability, soil nutrient holding capacity, and soil microorganism conditions. Although the application of 20 ton ha-1 biochar improved soil properties compared with 10 ton ha-1, the difference was not significant.  Application of biochar with chemical fertilizers had better effects on seed and straw yield, compared with solely application of biochar and chemical fertilizers.  It may belong to the biochar ability to decrease nitrate and other elements leaching due to its high porosity and high water retention capacity which increased water use efficiency in the plant. This is important in particular, in arid and semi-arid areas, where reduces the amount of water consumed and increases water yields for plants that are under water stress. The seed production of black seed was not affected by reducing water requirements up to 70 % of its total water requirements when biochar was applied. This means that, by using the biochar in soil, only 70% water irrigation required. These results may use for water saving in agriculture in arid and semi-arid conditions.

Among various destruction factors affecting forests and grasslands, especially in arid and semi-arid regions, fire is considered the more dangerous factor and results in different physical, chemical, and biological changes in soil properties depending on the conditions. This study aimed to evaluate the residual effects of previously burned pastures on some soil chemical properties in Fereydan region of central Zagros. Fire in these areas was mainly due to human impacts. The experiment was conducted in a completely randomized design with unequal replicates. Calcium carbonate equivalent and organic matter contents, soluble sodium, potassium, calcium and magnesium, available phosphorus, iron, manganese and zinc were measured by standard methods. The results showed that fire had a significant effect on some of the measured soil chemical properties. Soil organic matter content, soluble potassium, calcium and magnesium, available phosphorus, iron and manganese were increased due to firing. Mean comparisons showed that soil organic matter increased from 2.10% in the unburned to 4.12% in the burned portion of pasture. The soluble potassium, calcium and magnesium increased from 0.45, 6.42, and 1.19 in the unburned to 0.95, 9.91, and 2.22 meq/l in the burned areas, respectively. The available phosphorus, iron, and manganese were increased from 31.30, 18.22, and 37.29 mg/kg in the unburned to 34.17, 20.39, and 55.64 mg/kg soil in the burned soil. The overall impact of burning on soil chemical properties was greater in the first year after the fire, and the effect decreased with time.

An option for improving soil physical, chemical and biological properties and carbon sequestration is by increasing organic carbon (OC) input through recycling of crop residues and organic manures. The objective of this study was to determine the degradation of some plant residues and the influence of application of plant residue on different chemical and biological forms of OC in soil. The sampled soil from the top 30-cm layer of an agricultural land treated with mild alfalfa, wheat and sawdust residues, at a rate of 20 g kg-1 (dry weight basis) and incubated in field capacity and lab temperature conditions. After 1, 20, 60 and 120 days of incubation a portion of each soil were taken for analysis. The experiment was considered a completely randomized design as factorial in three replicates. The factors were residues type and the passing time of incubation. Biomass C increased in all treatments significantly. Plant residue application increased cold water and hot water extractable OC significantly. They were relatively lower in sawdust treatment compared to alfalfa and wheat treatments in 1st day of soil incubation. Both of fulvic acid and humic acid in soil increased in plant residue treatments compared to those in control. However this increase was greater for humic acid especially in late stages of soil incubation. The study of changes of different chemical and biological fractions of OC during soil incubation and their correlations revealed that microbial secreted C and biomass C had coherence with cold water and hot water extractable OC.

Soil organic matter (SOM) is a key element in soil productivity and atmospheric carbon sequestration is sustainable approach for climate change mitigation. This research was conducted to determine the main factor controlling SOM in different land use, especially agricultural lands and evaluation the carbon sequestration potential in the Kermanshah province. For this means, artificial neural networks and decision tree was applied. For determining priority effects of physical and management factors sensitivity analysis was done. Results indicated that in agricultural lands, management related factors including, tillage related scenarios and straw management system dominantly controlled SOM contents. In rangelands and forest, by physical and management factors had equal effects on SOM variability. Analysis of the results indicated that by modifying tillage related factors especially avoid of moldboard plow and optimize straw management in agricultural lands, grazing control in rangelands and avoid deforestation in forests of the province, 30 8.2 and 7.1 million ton atmospheric carbon could be sequestered across the mentioned land uses.

There is a divergent of views about the relationship between vegetation and soil characteristics in different habitats. In addition, there are limited studies about the relationship between soil seed bank and soil characteristics. This study aimed to investigate the relationship between three edaphic factors (texture, EC and organic matter) with vegetation and of soil seed bank composition. Therefore, 50 plots (2 × 2m) were established on a salt-marsh site in spring. Soil samples were collected (from two different depths (0-5 and 5-10cm) to determine the composition of seed bank and perform soil chemical and physical analysis. In addition, the composition of above-ground vegetation was estimated in the growing season. Soil seed bank composition was determined in the greenhouse through a seed germination experiment. Multivariate analysis (ordination) and step-wise regression were performed to analyze the data. The results showed that EC and organic matter had a significant effect on the vegetation distribution, while these effects were less pronounced for soil seed bank composition. The cover of dominant species was affected by soil texture but edaphic factors had no significant effects on the soil seed composition and the seed density of dominant species.

Soil quality is the most suitable index to an assessment of the stability of terrestrial ecosystems, especially agro-ecosystems. To determine the effects of agricultural practices on soil organic matter, species richness and abundance of soil invertebrates, a study was conducted in three regions of Razavi and Northern Khorasan Provinces, Iran. Soil were taken from in each winter wheat field of the study area, and as well from some samples selected areas of the natural ecosystem. Soil texture, organic matter, diversity in and abundance of soil invertebrates were determined. The results showed that climate affects soil texture as well as organic matter, so that with increase in mean annual precipitation and a decrease in mean annual temperature, soil texture was finer and soil organic matter increased. Organic matter was affected by agricultural practices and followed increasing trend with in agricultural systems going on in each region. Also diversity and abundance of soil invertebrates increased with prevalence of agricultural systems. As a whole, we suggested that soil quality increased in agricultural systems.

Soil organic matter and its components are important factors in formation and stability of aggregates and subsequently soil structure. However data regarding organic matter distribution in soil aggregates is scarce, particularly in arid soils of Central Iran. The objective of this study was to investigate the distribution of organic carbon (OC), total nitrogen (TN), and carbohydrates in aggregates of different size classes (2–4, 1–2, 0.5–1, 0.25–0.5, 0.05–0.25 and

Soil carbohydrate, particulate organic carbon and distribution of organic matter in different aggregate fractions are factors affecting soil structure. This study was initiated in a clayey soil in Javanmardi plain (East Lordegan, central Zagros) to evaluate 1) the influence of conversion of degraded pasture to cropland (wheat fields) on total organic carbon (TOC), particulate organic carbon (POC), total nitrogen (Nt), dilute acid extractable carbohydrate (CHda), hot water extractable carbohydrate (CHhw), and 2) the amount of TOC, Nt and CHda inside of aggregates. Soils of degraded pasture and cropland were sampled in two depths of 0-5 and 5-15 cm. The results showed that carbohydrates and POC represent 3.6-6.5% and 39-52% of TOC in soils, respectively. Conversion of degraded pasture to cropland resulted in an increase in TOC, POC, Nt, CHda, and CHhw contents. For the degraded pasture, the amount of TOC, N and CHda were significantly different in aggregate size classes, and appeared to increase as size increased from 0.05 to 1 mm diameter. Nonetheless, there was no clear relationship between the size of aggregates and organic matter content for cropland. The POC/TOC ratio was higher in cropland compared to the degraded pasture, reflecting the coarser nature of organic inputs under cultivation. In general, results indicated that the OC contents in the macroaggregates were higher than those in the microaggregates fractions. This may resemble that the factors controlling the stability or destruction of macroaggegates can control the OC stocks in soils too.

The salt–affected lands in arid regions of central Iran are characterized by low rainfall, low fertility, high evaporation and salinity. The cultivation of salt–affected lands may have a major influence on soil quality. The aim of this study was to determine the response of soil quality indicators to reclamation and cultivation of salt–affected lands occurring in Abarkooh plain, central Iran. Soil quality indicators were evaluated in three land use systems including salt-affected land, wheat, and alfalfa fields. Composite soil samples were collected at 0–10, 10–20, 20–30, and 30–40 cm layers and analyzed for soil organic carbon, total nitrogen, carbohydrate, particulate organic carbon in macro-aggregates (POCmac) and micro-aggregates (POCmic), organic carbon mineralization and wet aggregate stability. The cultivation of salt–affected land caused a significant decrease in electrical conductivity at all layers and increased the amount of soil organic carbon, total nitrogen, carbohydrate, POCmac, POCmic, and organic carbon mineralization. At all layers, the POCmac/POCmic ratio in the alfalfa fields was higher than that in the wheat fields. The cultivation of salt-affected land caused a significant increase in soil aggregate stability (MWD) at all layers. In most cases, the amounts of soil organic matter and MWD were greater in alfalfa than in the wheat fields, reflecting a better soil quality and thus higher potential for increasing soil organic carbon sequestration in the alfalfa fields.

As a part of soil biodiversity, mycorrhiza has an important role on soil function. For assessment of agricultural practices on spore density and diversity of mycorrhiza, a study was conducted in winter wheat fields on Shirvan, Mashhad and Gonabad, three regions of Khorasan. In each region, high and low input fields of winter wheat and a natural system for comparison were selected. Use of agricultural inputs was criteria for selection of low and high input fields in each region. Soil sampling was done on fields and natural systems. Organic matter and spore density of mycorrhiza were measured in soil samples. Percent of soil organic matter in all systems was low, but in agroecosystems was greater than in natural system. Mean spore density of mycorrhiza in the soil of Shirvan, Mashhad and Gonabad was 118, 99 and 76 per gram dry soil, respectively and was affected by region and soil organic matter. Soil spore density in agroecosystems was greater than natural systems and was affected by soil organic matter and plant production. Species richness of mycorrhiza in high input and natural systems of Gonabad was 4 and in other systems were 5. Results showed that agroecosystems improved conditions for mycorrhiza and efficient use of these services.

Adopting proper agricultural management and conserving soil organic matter are important components of sustainable agriculture. Soil organic matter content is a key attribute in soil quality. Labile organic matter pools can be considered as suitable indicators of soil quality that are very sensitive to changes in soil management practices. This research was carried out to investigate some organic carbon labile pools as an indicator evaluating the effects of different managements on some quality parameters of two calcareous soils. The study was conducted in 2 locations: 1- plots that receiving 0 (C1), 25 (C2), 50 (C3) and 100 (C4) Mg/ha of manure for five years successively with a cropping rotation of wheat –corn every year and plots under three cropping rotations (C5, C6 and C7) at Lavark experimental farm and 2- inquiry research station of Fozveh at different plots with three different cropping rotations (C8, C9 and C10) with a given cropping history recorded for the last 5 years. Soil samples were taken from the center of each plot and the depths of 0-5 cm and 5-15 cm. Their organic carbon, hot water soluble carbohydrate, particulate organic matter (POM), organic carbon and hot water soluble carbohydrate of POM, mean weight diameter of water stable aggregates were determined. Different managements consisting of different levels of manure and types of cropping rotation had significant effects on the soil characteristics measured. The greateast amount of carbohydrate and aggregate stability was obtained in the plots of 100 Mg/ha of manure in Lavak and in alfalfa plots in Fozveh station. Also, the results showed that aggregate stability has a better correlation with hot water soluble carbohydrate in comparison with other soil organic pools. Therefore, the carbohydrate extracted by hot water may be used as an index to assess the impacts of different agricultural management systems on soil quality.

The general characteristics of salt-affected soils and soil structure degradation process are partially known, but the effects of saline and sodic conditions on mechanical properties of soils are not well recognized. In this study, the effects of electrical conductivity (EC) and sodium adsorption ratio (SAR) on tensile strength of soils with different organic carbon contents were assessed under laboratory conditions. The soil samples were collected from Dasht-E-Naz, at Sari region in the North of Iran. The samples had the same clay mineral (Illitic) and the main difference between them was the organic carbon content, subjected to different cropping systems. The tensile strength was determined on soil samples which had been treated by solutions having defined EC (0.5 and 4 dS/m) and SAR (0, 5, 15). The tensile strength was positively related to organic carbon content, but negatively to SAR. With increasing SAR, tensile strength decreased, and at a given SAR, the treatments with higher EC showed higher tensile strength. The analysis of variance showed significant differences (at 0.01) between soil samples (four levels), soil sampling depth (two levels), EC (two levels), and SAR (three levels) for all variables under investigation. For soil factor, the order of averages were: Virgin soil > Permanent pasture (Festuca) > Intensive cropping > Permanent pasture (Agropyron).