فهرست مطالب زهرا وارسته خانلری

To investigate the effect of biochars on the concentration of organic carbon, nitrogen, phosphorus and enzyme activity, an experiment was conducted. Biochars were used at 10%. The experimental treatments CS, PMB, GSB and NSB. The samples were incubated for two months and sampling was done on days of 5, 10, 30 and 60. The results showed that the application of PMB and GSB caused a significant increase in organic carbon, available phosphorus and ammonium in the soil compared to CS. The highest nitrate was observed in GSB. The concentration of available phosphorus and nitrate increased with increasing incubation time, and organic carbon and ammonium decreased with increasing incubation time. The results showed that the use of PMB and GSB caused a significant increase in organic carbon, available phosphorus and ammonium in the biochar-amended soils. The highest nitrate concentration was observed in GSB. Available phosphorus and nitrate increased with increasing incubation time, and organic carbon and ammonium decreased with increasing incubation time. The concentration of invertase in PMB and GSB was significantly different from CS. The peak of invertase activity was observed in PMB at 5 days of incubation. Adding GSB to the soil increased the activity of urease by 1.7 times compared to CS. GMEa and TEI were higher in GSB compared to other treatments. Rch was as follows: GSB > PMB > NSB. In cluster analysis, GSB and PMB were placed in one cluster. The results showed that GSB and PMB had the greatest effect on the measured factors.

To investigate the release of nitrogen. Phosphorus and potassium elements from biochar, an experiment was conducted in a completely randomized design in three replications. Biochars were used by 2% in weight (W/W). The experimental treatments included control soil (CS), Soil+ Grape waste biochar (GSB), Soil + wheat straw and stubble (WSB) + brown walnut shell biochar (NSB) and Soil. The samples were incubated for about four months and sampling was done at days of 0, 7, 14, 28, 42, 56, 88 and 120. The results showed that the biochar addition significantly increased the concentrations of nitrogen, phosphorus and potassium in all biochar-amended soils compared to the control soil. Nitrogen concentration ranged from 766.6 mg kg-1 in control (average of sampling times) to 1272.2, 1366.7, and 1488.9 mg kg-1 in GSB, WSB and NSB treatments, respectively. Phosphorus concentration enhanced from 44.5 mg kg-1 in control (time-average of sampling) to 79.1, 67.1, and 70.8 mg kg-1 in GSB, WSB and NSB, respectively, and the concentration of potassium in the control increased from 103 mg kg-1 to 656.5, 293.8, and 125.6 mg kg-1 in the GSB, WSB, and NSB treatments, respectively. The WSB and NSB treatments released an average of 52% and 50.5% of their nitrogen content, respectively during 120 days, increased while GSB released only 28.6% of its total nitrogen on average. The order of nitrogen release rates in biochar were as follows: WSB≥ NSB> GSB. Regarding the release of phosphorus, NSB was considered to be the most efficient biochar, which was able to release 5% of its phosphorus during 4 months, while, GSB was the lowest effective biochar releasing only 0.5% of its phosphorus during the corresponding time. The order of phosphorus release from biochar treatments was as follows: NSB > WSB > GSB. The amount of available potassium in GSB was 2.3 to 6.7 times higher than the other treatments. The order of potassium release from biochar treatments was as follows: GSB > WSB > NSB. The results of infrared spectroscopy showed that the dissolution of amides containing nitrogen is the main mechanism of N release. The decrease in pH caused by nitrification, probably facilitated Ca-P dissolution from biochar and led to a higher phosphorus release.

Human activities such as deforestation, conversion of natural ecosystems to farming, biomass burning, tillage and cultivation, grazing, fertilizer use have a significant and negative impact on soil organic carbon pool. In particular, the conversion of natural ecosystems to agriculture reduces soil organic carbon pools. Understanding the spatial distribution of organic carbon in soil is particularly important for understanding the role of soil in the global carbon system. Therefore, the purpose of the present study was to investigate the changes of total carbon and its components in different sizes of aggregates of a forest soil after conversion to paddy.

For this study, Poplar Research Station in Guilan province was selected. Soil samples were collected from two uses of forest and adjacent paddy fields at two depths (0-20 and 20-40 cm). In the soil samples, aggregates of different sizes were separated and the amount of organic carbon in these aggregates was measured. Organic carbon was then fractionated into different sizes of these aggregates in both land use.

Investigation of organic carbon distribution in relation to aggregate size in two land uses showed that with increasing aggregate size, organic carbon content increased so that organic carbon content in Populus natural forest and rice fields were 4.5 and 3.3 times higher in aggregates larger than 2 mm (larger aggregates) than smaller aggregates 0.053 mm, respectively. The amount of organic carbon in the aggregates decreased with the change from natural forest to paddy fields. However, the decrease was greater in aggregates larger than 2 mm and lowest in aggregates (0.25–0.053 mm). Results of soil organic carbon fractionation showed that percentage of soil weight in fractions increased with increasing density in two land use. This situation was visible in two depths and in all the aggregate sizes. By increasing the density of fractions, the concentration of organic carbon in the fractions decreased. The organic carbon content of the fractions as a percentage of organic carbon content of whole soil, in all the aggregate sizes, and in the fractions with density < 2 g cm-3 was smaller than those of fractions with density > 2 g cm-3. In all of the aggregates, with increasing depth, organic carbon content of the fractions with density < 2 g cm-3 as a percentage of organic carbon content of whole soil decreased while those of the fractions with density of > 2 g cm-3 increased. By increasing the density of fractions, the C/N ratio of the fractions decreased. In all of the aggregate, due to the change of land use from natural forests to rice field, organic carbon content of the fractions as a percentage of organic carbon content of whole soil, decreased in the fractions with density < 2 g cm-3 and increased in the fractions with density > 2 g cm-3 and this was more pronounced in aggregates of larger size. The most sensitive and resistant fractions to land use change were fraction 2g/cm3 respectively. The ratio of carbon to nitrogen decreased as a result of land use change from natural forest to the rice field.

The change of land use and long-term cultivation in virgin forests and its transformation in rice field has changed organic carbon content of the fractions. The amount of free and occluded particulate organic matter in the aggregate (light fraction), which plays a very important role in the nutrition of the crop, was greatly reduced. This reduces the soil's health and the potential for carbon sequestration in the soil.

Vermicompost, as a nutrient-rich organic amendment, contains most nutrients in plant-available forms and can influence soil fertility and plant growth significantly. The objective of this study was to investigate the availability and release rate of potassium (K) in six vineyard topsoil (0-30 cm) with different textures (loam, clay loam, and sandy clay loam) treated with 2 % of cattle manure vermicompost (VC), through successive extractions with 0.01 mol L-1 CaCl2 over periods of 0.25-72 hours. The results showed that VC addition to soils increased the K availability. The average cumulative K released after 72 h from the control and treated soils was 526.9 and 547.9 mg kg−1, respectively. Due to the conformity of data to the Simple Elovich Equation it was suggested that process of K release from soils was affected by diffusion processes. Simple Elovich rate constant values in soils ranged from 34.9 to 132.1 mg kg−1h-1.The VC had different effects on K release rate in soils. In clay loam soils with high clay content, low organic matter and K fixation capacity, VC increased K release rate, while in loam and sandy clay loam soils with low clay, high organic matter, and low K fixation capacity, it decreased K release rate. Overall, VC had a balancing effect on K release rate. It could be related to VC interaction with soil particles, especially clays. Due to the importance of K in grape nutrition and K deficiency in some soils, the use of VC in vineyards is recommended.

Soil and plant contamination with heavy elements due to industrial activities has adversely affected human health and has received much attention in recent decades. Heavy metals can endanger soil, plant and human health by entering the soil cycle and food products. In order to reduce the harmful effects of heavy metals on the soil ecosystem and food pollution, a factorial experiment was conducted in three replications in a completely randomized design in a greenhouse. The aim of this study was to investigate the effect of different amounts of natural biochar and poultry manure on the fertility of zinc and cadmium elements in a contaminated soil.

In order to conduct this research, first different levels of poultry manure (zero, 0.5, 1, 2, 4 and 8% by weight) and natural biochar (zero, 2, 4, 6, 8 and 10% Weight) were added separately to a contaminated soil. Then, 4 levels of incubation were applied to the moisture capacity of the farm (1, 2, 3 and 4 months). At the intervals mentioned from the pots, sub-samples were prepared and transferred to the laboratory. After drying in the oven at a temperature of 50-55 ºC was taken pH, EC, the total and absorbable amount of zinc and cadmium elements in them.

Comparison of mean effects of incubation and poultry manure and biochar levels showed that with increasing consumption level and incubation, soil pH decreased by 3.9% and 1.4%, respectively, and EC amount by 36.5 and 10.4 percent increased. There was a statistically significant difference between the control treatment of the control or the zero level of poultry manure and biochar with the treatment of 8% of poultry manure and biochar (statistically 5% probability level). With increasing incubation and levels of poultry manure and natural biochar, the adsorbent concentration of zinc and soil cadmium decreased significantly (P <0.05), which decreased in treatments containing poultry manure for zinc and cadmium, respectively, 19.9 and 29.5 percent, and in treatments containing natural biochar, zinc and cadmium were measured as 28.4 percent and 22.7 percent, respectively. In poultry manure treatments, the lowest zinc and cadmium concentrations extracted with DTPA extract in the fourth month and the consumption level of 8% were 304.7 and 10.9 mg/kg, respectively, and the highest amount was observed in the first month. Witness treatment (zero percent level) was observed to be 380.2 and 20.0 mg/kg, respectively. In treatments containing natural biochar, the lowest amount of zinc and cadmium extracted with DTPA extract in the fourth month and 10% consumption level were 272.4 and 12.9 mg / kg, respectively, and the highest amount was treated in the first month. The control (zero percent level) was observed to be 380.3 and 20.7 mg/kg, respectively.

According to the results of this study, the use of biochar and manure fertilizer caused a decrease in the concentration of absorbable heavy metals studied in the soil. Although treatments containing biochar and manure reduced the adsorption concentration of metals in the soil, the concentration of adsorbent metals in the soil decreased further with increasing levels of poultry manure and biochar and the incubation of the soil. In general, it can be stated that the application of poultry manure and natural biochar in the soil is an effective method to reduce the toxicity and absorbable concentration of heavy metals in the soil and also increase the yield and quality of agricultural products.

Soil is one of the factors influencing the balance of the ecosystem and countless biological and biochemical processes take place in it. In all of these processes, enzymes act as catalysts. Their presence in different cycles of soil nutrients causes the release of elements needed by plants. Therefore, the measurement of some of these enzymes can be an important indicator and criterion for evaluating soil bioavailability and consequently ecosystem measurement. Therefore, in order to investigate the extent and effect of mineral nitrogen (ammonium nitrate) and mineral phosphorus (triple superphosphate) in soils to which wheat plant residues have been added, on the enzymatic activities of urease, invertase, cellulase, alkaline and acid phosphatase were performed by a factorial experiment in a completely randomized design with three replications in the laboratory. The purpose of this study was to investigate the effect of different levels of N and P and their interactions on some enzymatic activities of soil containing plant residues of wheat.

For the purpose of this study, different levels of inorganic nitrogen were: control, 10, 25, 50 and 75 mg Nitrogen per kg soil (N, N10, N25, N50 and N75) and different levels of phosphorus including: control, 15, 30 and 45 mg phosphorous per kg soil (P, P15, P30 and P45) into a P and N poor soil. The soil was added to this soil by 5 wt.% Of crushed wheat residue, transferred to FC moisture and incubated at laboratory (relatively constant) temperature for 6 months. At the end of the incubated, the activities of urease, invertase, cellulase and alkaline and acid phosphatase were measured.

The interaction of different levels of phosphorus and inorganic nitrogen on some enzymatic activities showed that urease enzyme was highest in P30N25, P30N50, P15N25, P30N10, P30N75 and P45N10 and lowest in control treatment. Urease activity in these treatments was about 2.3 times that of the control. The highest activity of invertase was observed in P15N10, P15N25, P15N50 and lowest in P30N75. The activity of this enzyme was about 21% higher in the treatments containing phosphorus 15 and nitrogen 10 (mg/kg soil) than in the treatments containing phosphorus 30 and nitrogen 75 (mg/kg soil). The highest cellulase activity was observed in P15N10, P15N25 and the lowest activity in P45N25. Alkaline phosphatase had the highest activity in P30N10, P15N10, P30N25, P15N25 and P30N50 and lowest in phosphorus 45 and inorganic nitrogen 75 (mg/kg soil). The enzyme activity in these treatments was about 1.2 times that of P45N75. Acid phosphatase activity was highest in P15N50 and P15N25 and lowest in phosphorus 45 and inorganic nitrogen 10 (mg/kg soil) and in phosphorus 45 and mineral nitrogen 75 (mg/kg soil), respectively.

In general, application of mineral fertilizers to soil containing wheat residues increased some of the enzymatic activities according to the results of experiments for maintaining soil fertility and also balance in the rate of decomposition and emission of greenhouse gases and enzyme activity. Inorganic fertilizers at low concentrations are recommended as the catalysts for the reaction. Therefore, farmers are advised not to remove plant residues from the soil after the end of the growing season, but to balance the residual decomposition rate by adding appropriate levels of mineral fertilizers to gradually improve plant nutrition and characteristics while gradually decomposing. Physically improve the soil as well.

In this study, the effects of land use change (conversion of natural forest to paddy fields) and regeneration of deforested land on some qualitative and enzymatic properties of the soil were investigated. For this study, Populus Research Station in Guilan province, Astana Ashrafieh city was selected. Soil samples were collected from 5 land uses (natural forest, populus, Alnus and Taxodium and paddy forests) and two depths (0-20 and 20-40 cm). The data were analyzed as a factorial experiment in a completely randomized design with three replications. The factors included land use type at five levels and soil depth at two levels that were studied in three replications. Therefore, the number of treatments were 5 * 2 = 10, totally 30 units accounting replications. In total, there were 30 samples of disturbed soil and 30 samples of undisturbed soil that constituted the statistical data of the experiment. Some physical, chemical and biological properties of the samples were measured. The results showed that the mean weight diameter (75%), saturated hydraulic conductivity (95%), water repellency (53%), organic carbon (52%), total nitrogen (52%) and microbial biomass carbon (53%) in the natural forest were higher than the ones in the paddy field. Also, the activity of urease and arylsulfatase in the paddy soil was significantly lower than the one in the natural forest soil. However, the activity of dehydrogenase in the paddy soil was higher than the one in natural forest soil, indicating oxygen availability and moisture affect the activity of dehydrogenase and its activity increases as the soil moisture increases. Reclamation of some deforested lands by hand planted forest showed that Populus vegetation was more effective than the other vegetation covers in increasing aggregate stability, hydraulic conductivity, and microbial biomass carbon. While Taxodium cover increased the activities of urease, arylsulfatase and acid phosphatase more than the ones in other vegetation covers. The specific activity of enzymes (enzyme activity per unit of organic carbon), in dehydrogenase was significantly higher in the paddy soil than in the soil under natural forest. This indicates that the activity of this enzyme is independent of soil organic carbon changes and is dependent on soil moisture. Overall, it can be concluded that, in comparison with the qualitative and enzymatic activity, Taxodium coating improved these properties better than populus and Alnus coating.

Agricultural activity, especially cultivating rice, is one of the main reason of the destruction of natural forests in the north of Iran. This study was performed to investigate the effects of changing natural forest to Paddy Field on some physical and chemical properties of the soil and to determine the most sensitive indices to the disturbance of an ecosystem. Moreover, in this study, the Principal Component Analysis (PCA) method was used to create a minimum set of data from measured physical and chemical parameters. Accordingly, two land uses (natural forest and paddy field) were selected in Gilan province and soil samples were collected from five different depths (0-20, 20-40, 40-60, 60-80, and 80-100) three times. Soil texture, density, field capacity, dispersible clay, mean weight diameter (MWD), pH, electrical conductivity, calcium carbonate, organic carbon, total nitrogen, cation exchange capacity, extractable carbohydrates with acid and extractable carbohydrates with hot water at each depth were measured and the results were analyzed as factorial in a completely randomized design. The results indicated that by changing the land use from forest to paddy field, the average apparent density of the soil profile (15%) and dispersible clay (33%) were increased. However, the MWD (76%), organic carbon content (57%), total nitrogen (53%), and cation exchange capacity (31%) were reduced. The sensitivity index (SI) showed that among the physical and chemical parameters, MWD and organic carbon content were respectively more sensitive than the other parameters to land use change. The results of PCA revealed that the four factors could almost justify more than 90% of the variance in MWD, organic Carbone, density, moisture content in field capacity, extractable carbohydrates with acid, and extractable carbohydrates with hot water. These parameters showed the highest commonality and the clay percentage had the minimum relative importance among the estimation of commonality values.

The evaluation of biologic parameters of soil quality plays an important role in assessing the land management and sustainability of agricultural systems. For this purpose, the biological properties of soil quality, which are sensitive to farming are measured and investigated. The aim of the present study is to evaluate the biological changes forest soil quality after converting to the paddy field and determining the most sensitive properties to disturbance of an ecosystem and the creating a minimum set of data from these parameters using the factor analysis method.

The present study was performed in Poplar research station in Gilan Province. The soil sample collection was done in both natural forest and closest paddy field from five different depth (0-20, 20-40, 40-60, 60-80, and 80-100 cm). The data were analyzed as a factorial test in a completely randomized design with three replications. The factors including the type of land use in two levels and soil depth in five levels were studies in three replications. Therefore, the statistic population of the present study was 10 treatments (5 × 2 =10) with three replications (totally 30 test units). In the study, the microbial respiration, the mineralization percentage of carbon, the microbial biomass carbon, microbial fraction, and the metabolic coefficient of the samples were measured and the sensitivity index to each feature was calculated. The data were analyzed using SAS software. Mean comparison of parameters of Duncan’s test and factor analysis using principal component analysis method were performed.

The results of the study showed that any land use changes from forest to paddy field led to increasing the mineralization percentage of carbon and the metabolic coefficient by 28 and 21% respectively. However, microbial biomass C (61%), microbial respiration (31%), and basal respiration (49%) were reduced. Sensitivity index (SI) indicated that microbial biomass is more sensitive than other parameters to land use. The use of principal component analysis (PCA) showed that two factors could explain more than 70% of the variance in microbial biomass and carbon mineralization percentage and more than 60% of the variance in the amount of carbon mineralization, basal respiration, and a metabolic fraction (quotient). These parameters represent the maximum communality estimation, and the microbial fraction showed the minimum relative importance among the estimates of the total communality values.

The change in land use from forests to the paddy fields had an adverse effect on the biological parameters of soil quality, which led to reducing the soil health and carbon sequestration potential in soil. Therefore, cultivation in these lands exacerbates soil degradation and stopping the process results in longer recovery and resilience time.