جستجوی مقالات مرتبط با کلیدواژه "تخلخل خاک" در نشریات گروه "آب و خاک"

Biochar is a carbon-rich organic compound that has recently been recommended for use as a soil conditioner. Little research has been done on the effect of biochar amount and elapsed time after biochar addition on soil physical properties. This research performed at Shahrekord University, in 2018. The aim of this study was to evaluate the long-term effects of different amount of rice straw biochar on soil bulk density (ρb), total porosity (n), mean weight diameter of dry (MWDdry) and wet (MWDwet) aggregates, air filled porosity (AFP) and capillary porosity (CP) of clay loam soil. This experiment was performed as a factorial experiment based on completely randomized design with three replications in a greenhouse. Biochar have four levels of zero as control (B0), 0.5 (B1), 1 (B2) and 2 (B3) weight percentage and the time have four levels of 2 (T1), 3 (T2), 6 (T3) and 9 (T4) months after biochar adding to the soil. The results indicated that two months after adding rice straw to the soil, ρb decreased by 6% compared to the control. At the same time, ‘n’, ‘MWDdry’ and ‘MWDwet’ increased by 3, 11 and 13%, respectively, compared to the control. Means comparison showed that the lowest ρb was obtained in B1T2, the highest ‘n’, ‘AFP’ and ‘CP’ were obtained in B1T2, B0T1 and B1T3, respectively, and the highest ‘MWDdry’ and ‘MWDwet’ were obtained in B3T4 and B0T4 respectively. Different times are needed for the effect of biochar on soil physical properties improvement. Based on the findings of this study, 1% of rice straw biochar can be used to durabil improvement of the physical properties of clay loam soil.

Extraction and exploitation of total petroleum hydrocarbons (TPHs) led to the contamination of soil and environment. Therefore, remediation of TPHs contaminated soils is necessary. The effects of biochar produced from bagasse and zeoplant as organic amendments on some physical properties of contaminated soils with TPHs were evaluated in Ahvaz, Khuzestan Province. Systematic soil sampling was performed based on the block with completely randomize design with three replications. The soil samples were transferred to the pots (7 kg) and treatments added to the soils in the 2, 4 and 6 % levels. Afterwards, the soil moisture was adjusted on 25 and 50% of field capacity (FC). All treatments were incubated for 100 days. After incubation, bulk density, porosity, FC, PWP, TPHs, water drop penetration time and the soil penetration class were measured. Meanwhile, the variation of hydrocarbons was analyzed using Gas Chromatography (GC). Based on the GC graph, approximately 50% of normal alkanes are C13-C20. Results showed that the application of biochar and zeoplant to the soil caused to decrease of bulk density and increase the total porosity, the permeability of soil, and water retention. Moreover, the efficiency of treatments was increased by increasing of treatment application. The highest efficiency was found with 6% of biochar with 25% of moisture content, also the 6% of zeoplant enhanced the PWP from 8% in the blank to 16%. So, the application of organic treatments improved soil properties; therefore, and have an important role on sustainable management.

< p >Peanut shell as a residual waste from peanut cultivation has a considerable volume and its compost can be used as an available source of nutrient elements for different plants. This study was carried out to investigate the use of peanut shell compost in field soil and soilless (peat-perlite ratio 2: 1) media and its effect on soil physical and chemical properties in Lahijan Ornamental Flower and Plant Research Station, in 2017. Control treatments consisted of field soil and peat-perlite (2:1) bedding, while peanut shell compost was used in values of 0, 25%, 50%, 75%, and 100% (by volume) to replace field soil and peat (2:1) in peat-perlite bedding. This study was conducted as a factorial experiment with two variables (type of media and compost levels) based on randomized complete block design with three replications using violet research model plant (Viola spp < /em>.). At the end of the experiment, physical properties of the substrates including total porosity, air fill porosity, water capacity, bulk density, and  nuterients content of the substrates including Ca, N, OC, P, K, Fe, Zn, Mn, Cu, and also pH and EC were measured. In soilless culture, application of 50% peanut compost (1 peat+1 perlite+1 compost), and in soil media, application of 75% peanut compost showed the best results for the research model plant. Peanut shell compost appears to have better results by reducing C/N ratios and increasing porosity and nutrient supply in these two substrates. Thus, peanut shell compost can be used to replace the expensive peats as well as improving soil properties for cultivation of this ornamental plant.

The effect of water quality on soil water retention, structure, and hydraulic conductivity in two soil textures was studied. Undisturbed soil samples were treated in 5 wetting and drying periods with 6 different types of water quality consisting of 2 levels of EC (0.2 and 10 dS m-1) and three levels of SAR (1, 5 and 12). Undisturbed soil samples were equilibrated on sand box apparatus to soil matric suctions of 0, 10, 20, 40 and 60 cm and on pressure plate apparatus to soil matric suctions of 100, 300, 1000, 2000, 4000 and 15000 cm. The van Genuchten-Mualem model was fitted to simulate the measured soil water characteristic curve. Soil physical quality index (S) and the inflection point of water retention curve (θINFL) were evaluated using fitted parameters. Also, the macro-porosity, meso-porosity, micro-porosity, available water content (AWC100 and AWC300), and saturated hydraulic conductivity were measured. The study was conducted in a completely randomized design with three replications. Results showed that increasing EC caused soil particles flocculation, by developing some new pores and, consequently, increasing water retention capacity. Although increase in SAR dispersed soil particles, alteration of some macro-pores and meso-pores to micro-pores enhanced water retention, especially at high matric suctions. But, the available water content did not change significantly. Also, increase in water EC enhanced water retention at all matric suctions and the highest moisture content at inflection point was seen at EC of 10 dSm-1. The increase in SAR and decrease in EC were directly related to decrease in saturated hydraulic conductivity. Soil physical quality index (S) decreased by sodium increment, which indicated the reduced soil physical quality.

In the last decade, the use of biochar as a soil amendment has been of interest to researchers. Many researchers have conducted studies on the effects of biochar on soil physical and chemical properties. The purpose of this study was to investigate the effect of rice husk biochar on some physical characteristics of soil and corn growth. For this purpose, experimental pots with three replicates were filled with a mixture of loamy soil and three levels of biochar: zero (control), 2% and 4 % (wt). The pots were planted to seed corn cv. Single Cross 704 and studied for three months. Rice husk biochar was produced at a temperature of 500 °C during the pyrolysis process in an electrical furnace. The physical properties of soils were measured after plant growth period. Data collection on plant height was done weekly. Root expansion was also evaluated at the end of the growth period. The results showed that biochar application improved soil physical properties by decreasing soil bulk density, increasing saturated hydraulic conductivity, increasing porosity, and increasing the amount of available water in soil. The height of the plant in the ninth week of growth period was 85 cm in the soil containing 4% biochar, significantly higher than 75 cm in the control soil. The shoot dry weight in 2% and 4% biochar was 154. 7 and 156. 8 g, respectively, which was significantly higher than the control (148. 8 g). No significant effect was observed in root surface, root dry weight, root diameter and root length. In general, it can be concluded that the addition of biochar causes changes in some physical properties of the soil such as bulk density, porosity, water content of the soil as well as saturated hydraulic conductivity. Also, the results showed that increasing the level of biochar application from 2% to 4% would have more potentially positive effects in the soil. Performing larger-scale experiments will definitely help to confirm the findings of this study. It is also necessary to investigate the effects of long-term biochar in soil.

Soil porosity plays the major role in relation with soil genesis, soil processes control and its interactions with the environmental factors and translocation of water and solutes. The heterogeneity of soil porosity components is simplified by considering some assumptions such as taking into accounr all of the pores do actively and are spherical. Micromorphological approaches by direct observation and determination of soil pores geometry prepares detailed characterization of soil pores. The aim of this study was quantifying soil pores geometric properties using flouerecent dye method. 39 undisturbed soil samples impregnated with a mixture of resin-acetone containing flouerecent dye, dryed out and cut. Then 40 digital images were taken from each sample under ultraviolet light. The images were thresholded until the soil pores distinguished as white from the matrix. The results of pores based on area, perimeter, elongation, compaction, roundness, ferret diameter, long and short axis diameters were classified visually. The quantitative results of pores area showed that the pores smaller than 100 μm2 in the plough layer (depth 29% in the plough pan due to compaction. Pores with > 100 μm2 area in plough layer increases > 80% of total porosity. The dominant compaction class was the (0.3-0.5 unit less) that its maximum percent was (56.94%) in the depth of 35-30 cm. According to the elongation index the most elongated pores (the class

Crisis of renewable water resources and rising demand for access to fresh water in arid and semi-arid countries is increasing. Therefore, it is indispensable to conserve water resources with high quality for urban purposes and drinking and use water resources with lower quality (such as treated wastewater) for other purposes such as agriculture and industry. In these conditions, having adequate information and local data in different parts of the world is essential. Thus, the main purpose of this study was to investigate the effects of two-year long-term irrigation with treated municipal wastewater in comparison with well water (as the control treatment) on the physical properties of soil. The soil physical properties were measured in three layers, each with three replications, and included saturation hydraulic conductivity (Ks), soil moisture characteristic curve, moisture content at field capacity (θFC) and permanent wilting point (θPWP) as well as “available water”, bulk and practical density, and porosity of the surface soil to depth of 90 cm . The study was conducted using a two-year split plot design. The rsults of statistical analysis showed that there was no uniform trend between various parameters and the influence of irrigation treatments at different depths of soil parameters were different. Results showed that the soil Ks in treatments irrigated with wastewater increased, compared to the control treatments, by 109%, 25%, and 75% in depths of 0-30, 30-60, and 60-90 cm, respectively. In addition, application of treated wastewater caused increase in the soil moisture content at θFC and θPWP point, but reduced the amount of total available water content. The effect of irrigation with treated wastewater decreased surface soil bulk density and increased its practical density. Also, the soil porosity in the 0-30 and 30-60 cm layers was lower compared to the control treatment, but was higher in 60-90 cm layer. Generally, it can be concluded that the use of treated wastewater improves soil physical conditions, but the application of untreated sewage water and TWW for irrigation is not recommended for edible crops.

Improvement of soil properties through sustainable agriculture requires suitable management of plant residues. This study was conducted to investigate the effect of different types and managements of plant residue on soil physical properties in a field experiment as factorial based on RCBD with three replicates. The first factor was residue type including barley straw and alfalfa residue، and the second was different managements including 1) incorporating one percent of the plant residues with the soil (MIX1)، 2) incorporating 0. 5 percent of the plant residues with the soil (MIX0. 5)، 3) surface retention­­ of plant­ residues (SUR)، 4)، burning plant residues (BUR) and 5) control (C). The results showed that the applied managements of plant residue had significant effects on the selected soil properties. In comparison to the control، MIX1 application of barley straw resulted in the highest increases in organic carbon content (70%)، total porosity (23%) and final infiltration rate (82%)، and the highest reduction in bulk density (40%). In contrast، burning the alfalfa residue led to the highest reductions in organic carbon (200%)، total porosity (29. 5%)، the final infiltration rate (30%)، and the highest increase in bulk density (5. 5%). In addition، MIX0. 5 and SUR treatments improved the soil properties significantly. The highest and the least infiltration rates were found in MIX1 of barley straw (48. 6 mm/h) and BUR of alfalfa residue (4. 6 mm/h)، respectively. Overall، with respect to the improvement of soil properties، the managements of plant residue were prioritized as: MIX1>MIX0. 5>SUR>C>BUR.

Increase in soil bulk density and reduces in porosity and infiltration rate are the most common disturbances during timber harvesting and ground-base skidding. The present study was conducted to study soil physical properties e. g.، soil bulk density، moisture، porosity and soil hydrological properties e. g.، soil infiltration from ground-base skidding in twenty years since logging. After initial survey، four abandonment skid trails were selected with similar pedologic، climatic conditions and physiographic and different age in Necka-Zalemrod catchment in east of Mazandaran province. Results indicated that impacts of machinery traffices in high traffic intensity have remained yet 20 years since logging. Means soil bulk density، porosity and void ratio were 42. 4 greater، 24. 6 and 46. 7 percent، respectively، lower than the undisturbed areas. The least infiltration rate was recorded in 1-5 years old skid trail، so the reduction of water was not considerable within 18 minutes after experiment into soil in inner ring in this skid trail. Results in each skid trail firmed that in low traffic intensity soil physical and hydrologic properties was tent to “normal” recover in compare to the undisturbed areas.

This study was conducted to investigate the effect of water salinity and sodicity on pore size distribution and plant-available water of two clay and sandy clay loam calcareous soils. All combinations of water EC values of 0. 5، 2، 4 and 8 dS m-1 and SAR values of 1، 5، 13 and 18 (in total 16 solutions) were used to wet and dry the soil samples for five cycles. Then، water retention of the soil cores was measured at matric suctions of 0 (θs)، 10 (θ10) 100 or 300 cm (θFC) and 15000 cm (θPWP). The following quantities were calculated: the difference between θ100 or θ300 and θ15000 considered as available water contrent، the θs and θ10 as macrorosity، the θ10 and θ100 as mesoporosity، and the θ100 as microrosity. The initial porosity of both soils was similar، but the greater values of pore indices and θFC، θPWP and AWC were measured in the clay soil due to clay swelling. As water EC increased، mesopores were destructed and altered to macropores and micropores. Salinity altered the mesopores into macropores due to contraction of diffuse double layer and particle’s flocculation and consequently decreased the θFC، and created new micropores which were responsible for the higher value of θPWP. These trends ultimately diminished the AWC. As water SAR increased، mesopores were destructed and altered to micropores but it did not significantly affect the macropores. With increment of SAR، both θFC and θPWP increased due to structural distruption clay swelling and dispersion resulting in increased adsorptive and interlayer surfaces. The increasing effect of SAR on θPWP was greater and more distinct so that AWC was reduced. As a result، high values of SAR of irrigation water decreased the soil available water to plants besides its toxicity and hazardous effect on plants. With increment of irrigation water salinity، the destructive impacts of SAR diminished. The influence of water quality on water retention was pronounced for the clay soil. ‎

AbstractAgriculture is the largest consumer of water resources in Iran. One of the best options for increasing the irrigation efficiency and better application of precipitation in arid and semi-arid areas is employing of superabsorbent polymers to soil. Polymers can absorb rain and irrigation water, decrease deep percolation and increase water use efficiency. In order to investigate the effects of different rates of hydrophilic polymer superab A200 on water holding capacity and the porosity of soils with different salinity and textures, three factorial experiments were conducted using a completely randomized design with three replications. The polymers were applied to soils of different textures (sand, loam and clay) at the rates of 0.0, 0.2, 0.4 and 0.6 % w/w and salinity of the soils was adjusted at the levels of initial soil salinity (blank), 4 and 8 dS/m. The application of 0.6% w/w of polymer at the lowest salinity level increased available water content by 2.20 and 1.20 times greater than those of controls in the sandy and loamy soils, respectively. Thus application of polymers to soils especially in the sandy soils may increase water holding capacity, may decrease salinity and may help to improve irrigation projects in arid and semi-arid areas.