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Showing 44 results for Ghorbani

M. Alikhani, G.r. Ghorbani,
Volume 3, Issue 3 (fall 1999)
Abstract

To determine the best ratios of alfalfa hay to corn silage with similar dietary NDF, cation-anion balance, energy and protein content in the lactating dairy cows, eight mid-lactating Holstein dairy cows with average body weight of 570 kg, and milk yield of 22 kg/d with 3.5% fat, were assigned to each of four experimental diets with alfalfa hay to corn silage ratios of 100:0, 67:33, 33:67 and 0:100., in a 4 × 4 Latin square design with two replicates. Dry matter intake, digestibility, rumen degradability of DM, fat percentage and total solids in milk for diets one to four were 19.09, 19.94, 20.94, 20.90 kg/d 69.07, 65.75, 71.78, 49.82% 52.8, 49.6, 50.4, 46.7% 3.47, 3.53, 3.79, 3.93% 12.17, 12.17, 12.48, 12.60%, respectively. Diets containing 67% silage showed the highest dry matter intake, 3.2% FCM and digestibility. Degradability in rumen were highest and lowest in diets containing 100% alfalfa hay or corn silage, respectively. Increased ratios of silage to alfalfa hay corresponded to increases in milk fat and protein yield, milk protein percentage and total solids in milk.
A. Alizadeh, A.g. Ghorbani, G.h. Haghnia,
Volume 4, Issue 4 (winter 2001)
Abstract

In order to compare the effect of drip and furrow irrigation methods with different quantities of water (50%, 75%, and 100% of the amount of water evaporated from class A pan evaporation during irrigation intervals) on yield and quality of tomato, an experiment was conducted on a silty loam soil in Mashhad Agricultural Research Station. The experimental design was a factorial trial with completely randomized blocks and. four replications.

The results showed that the highest yield (51 t/ha) was obtained from the treatment of drip irrigation with 100% water application. This amount was 4.5 tons higher than the yield from furrow irrigation treatment. Deficit irrigation by 25 and 50 percent decreased total yield by 34.7% and 67.95% in the drip irrigation method and by 27.57% and 64.29% in the furrow irrigation, respectively. Water use efficiency in drip irrigation was two times higher than that in the furrow treatment. Quality and chemical composition of the fruits were not significantly different in the two irrigation methods. Increasing the water deficit, however, increased the amount of soluble solids of the fruits.


A. Foroozandeh, A.h. Samie, G.r. Ghorbani,
Volume 5, Issue 1 (spring 2001)
Abstract

The objectives of this study include the determination of the growth potential of Naeini lambs when fed with diets varying in energy and protein concentrations and also an investigation of the influence of level of energy and/or protein intake on carcass characteristics and composition. Ninety Naeini weather lambs (initial live weight 29.89 ± 2.9 kg) were used in a 92-day feeding experiment. Animals were blocked to each of nine dietary treatments. Diets contained either 2, 2.25 or 2.5 Mcal ME/Kg DM and 11.7, 13.2 or 14.7% CP diets were fed in a 3 × 3 factorial arrangement in randomized complete blocks.

Lambs fed with high energy diets consumed significantly more feed (P<0.05) than lambs given the medium (ME) or low energy (LE) diets. The average final body weight and daily weight gain for lambs fed with HE, ME and LE diets were 41.4, 38.3, 34.5 Kg and 162, 124, 74 g/d, respectively, which were significantly different (P<0.05). Feed conversion ratio in HE group was significantly lower (8.3) than ME (10.4) or LE (14.3) groups. Energetic efficiencies and protein efficiencies were better for HE than for ME and LE diets. Increasing dietary energy significantly (P<0.05) improved energy and protein efficiencies of the diets. Dressing percentage, lean meat and eye muscle depth were significantly (P<0.05) improved with increasing levels of energy in the diet, but also increased dissectible fat. No significant changes were observed in bone percentage and body ash due to any changes in dietary energy. As the protein level of rations increased, feed conversion ratio and carcass meat percentage increased, but carcass protein percentage decreased.


T. Ghoorchi, S. Rahimi, M. Rezaeian, G. R. Ghorbani,
Volume 7, Issue 2 (summer 2003)
Abstract

An experiment was carried out to estimate the potential activity of rumen anaerobic fungi in the degradation of dry matter and fiber of feeds. Samples of wheat bran, bagasse, cotton seed, alfalfa and corn silage were used as the substrates to culture rumen fungi which were isolated from a fistulated Shal sheep. Loss percentages of dry matter (DML), neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent (ADL), cellulose, and hemicellulose of samples were measured after 0, 3, 6 and 9 days of incubation. Dry matter and NDF loss of substrates varied from 10.6 % to 29.4% and 11.7% to 48.7% after 9 days of fungi growth. The highest and lowest DML and NDF were related to alfalfa and bagasses, respectively. The highest values for the ADF loss (39%), hemicellulose loss (65.6%) and cellulose loss (55.6%) were measured from alfalfa. The results indicated that rumen anaerobic fungi have the ability of degrading dry matter and fiber from different types of feed.
S. Dehghanian, M. Ghorbani,
Volume 7, Issue 3 (fall 2003)
Abstract

In this study, efficiency of apple producers in Khorasan Province was determined by a cross sectional data of 212 apple producers. Mean technical, allocative, and economic efficiencies were estimated to be around 31, 28, and 9 percent, respectively. A high potential was also detected for increasing these efficiencies. Apple producers’ age and education had positive effects and risk aversion had a negative effect on technical efficiency. Waste reduction, optimal use of inputs, introduction of technical-extension services, and apple insurance are suggested to increase efficiencies.
M. Alikhani, O. Fallahpour, G. Ghorbani,
Volume 8, Issue 1 (spring 2004)
Abstract

In order to determine the effects of using macaroni wastes instead of barley on dry matter intake (DMI), milk yield and composition, and nutrient digestibility, eight lactating Holstein cows (4 primiparous and 4 multiparous) in midlactation were used in a 44 Latin square design. The experimental periods were 21 d with 16 d for adjustment and 5 d for data collection. Treatments included a control diet (1) and diets 2, 3, and 4 containing 15, 30, and 45% macaroni wastes, respectively, which were fed three times a day as total mixed rations. During the last 5 days of each period, feed and fecal samples were taken for determination of DMI and apparent digestibilities and milk samples for fat, protein, lactose, and solids no fat (SNF). During the last day of collection period, urine samples were collected 3 and 5 h postfeeding for pH determination. The results showed no significant differences among experimental traits in either primiparous or multiparous, and across all cows. Milk yield and efficiency of feed conversion were nonsignificantly higher for diets 2, 3, and 4 compared with control cows. Compared to the control diet, DMI, fat, protein and SNF percentages did not significantly decrease in diets 3 and 4. From the results of this expriment, it may be concluded that replacing barley with macaroni wastes up to 45 percent could increase energy intake without any adverse effects on milk production and composition or on metabolic function in midlactating dairy cows.
N. Mehrdad, M. Alikhani, G. R. Ghorbani,
Volume 8, Issue 2 (summer 2004)
Abstract

In a completely randomized design with a factorial arrangement (3× 5× 3), three fistulated sheep with an average body weight of 47.5 ± 2.5 kg were used to determine the effect of cutting and growing stages (no bloom , early bloom and full bloom) on chemical composition and In situ degradability of alfalfa (Medicago sativa). Nylon bags (50 µm pore size) were filled with 3.5 g of each sample and suspended in the rumen before morning feeding and incubated for seven different times (0, 2, 4, 8, 16, 24 and 48 h). The results showed that alfalfa at no bloom stage had the highest crude protein and the lowest crude fiber content. The third – cut alfalfa had the highest degradability of dry matter and organic matter. Extent of degradability depended on crude fiber and solubility. During growth stage, the protein, soluble material and degradability levels decreased while crude fiber, neutral detergent insoluble crude protein (NDICP), and acid detergent insoluble crude protein (ADICP) increased. The amount of ADICP was an estimate of unavailable crude protein in the rumen. Although the rate of organic matter degradation was maximum in full bloom, no significant difference was observed between the three stages of growth. Effective degradability (ED) of crude protein was significantly different among stages the growth (p<0.05). Effective dry matter degradability (EDDM) with a passage rate of 6%/h was significantly higher in the third cutting of alfalfa. The results of this study showed that first cutting and full bloom alfalfa had the lowest and fifth cutting and no bloom had the highest CP levels. The effect of cutting and growing stages on degradability parameters was variable and did not allow any firm conclusions to be made.
A. Asadi Alamoti, M. Alikhani, Gh. Ghorbani, A. Samie,
Volume 8, Issue 3 (fall 2004)
Abstract

The objective of this study was to evaluate the characteristics of millet silage prepared in laboratorial mini silos and to determine the effects of additives on its fermentation quality. Whole millet (Panicum milliaceum) was harvested at milk and soft-dough stages of maturity, left untreated or treated with ground barely, molasses, formic acid, lactic acid producing bacteria, and combination of molasses plus inoculant, and were ensiled in a completely randomized design in 2×6 factorial arrangement. Stage of maturity had no significant effect on NDF and ADF, buffering capacity, residual water soluble carbohydrate, acid detergent insoluble nitrogen, ammonia nitrogen and in vitro dry and organic matter digestibility however, values for dry matter, crude protein and pH were significantly different. Loss of dry matter, elevated NH3-N (24% of total nitrogen) and increased butyric and acetic acid levels (.2 and 1.33% DM, respectively) in control silage indicated clostridial fermentation. Between treatments, the lowest NH3-N was observed for silages treated with formic acid. Molasses and molasses plus inoculant produced higher lactic acid and lower butyric acid. Higher in vitro dry matter and organic matter digestibility showed positive effects of additive usage compared to control group. Addition of molasses and molasses plus inoculant resulted in higher in vitro dry matter digestibility (63.1 and 64.3 %, respectively), but no significant differences were observed between barely, formic acid and inoculant treated silages. Results of this study clearly showed the need for adding a source of water soluble carbohydrates to millet in order to obtain a good quality silage. Also inoculation of lactic acid bacteria does not necessarily promote homolactic fermentation if insufficient amounts of water soluble carbohydrates are presented.
M. Babashahi, Gh. Ghorbani, H. R. Rahmani,
Volume 8, Issue 3 (fall 2004)
Abstract

The purpose of this study was to evaluate nutritional status in Isfahan dairy herds and the relationship between milk urea nitrogen (MUN) and fertility in the first postpartum insemination. Blood and milk samples were collected from 170 and 290 Holstein cows from 9 dairy herds, respectively. Feed samples were also collected to quantify the relationship between MUN and protein and energy content of the ration. When simple linear regression was used, a close relationship was found to exist between blood and milk urea nitrogen. Regression equations indicated crude protein percentage and protein to energy ratio in the diet only explained 7 and 10 percent of milk urea nitrogen variations, respectively. The low correlation coefficient is probably due to incorrect nutritional management and variation in diet composition in different feeding days. Logistic regression was used to determine the relationship between MUN and fertility. A negative curvilinear relationship existed between MUN and rate of pregnancy at first insemination. Since cows with MUN concentrations of 16.5 to 19 mg/dl had a better chance for pregnancy than those having either below or above these values, it seems likely that pregnancy chances for those cows having this range of MUN concentration are 1.94 and 1.63 times more than cows with less than 14 mg/dl and between 14 - 16 mg/dl, respectively. The results of this study indicated that although MUN is a useful tool for nutritional management of dairy cows, it is not suitable for monitoring reproductive performance.
S. A. Hadj Heidari, Gh. Ghorbani, M. Alikhani,
Volume 9, Issue 2 (summer 2005)
Abstract

To compare the relative value of the fish meal and the cottonseed meal in highly fermentable diets (40% forage and 60% concentrate with), eight cows were assigned randomly to diets with 0, 1.5, 3 and 4.5 percent of the fish meal. In the first experiment, the degradability of dry matter and crude protein of the fish meal, the cottonseed meal and concentrate in diets was estimated with different incubation times (0, 4, 8, 12 and 24 h) with fistulated Ghezel sheep fed at maintenance level. The effective degradability of dry matter and the crude protein of fish meal was significantly lower than cottonseed meal (p<0.05). In different concentrates, there was no significant difference in effective degradability of dry matter but with the increase of fish meal the effective degradability of crude protein decreased significantly. In the second experiment, the eight multiparous Holstein cows with the similar milk production (25.37 ± 0.85) were examined in a replicated 4 × 4 Latin square design with the 21-day period. There were no significant differences between the treatments in digestibility of OM, OM and CP, the dry matter intake, 3.2 % FCM, milk fat (%), milk lactose (%), milk total solid (%), and the yield of the milk fat, feed efficiency and body weights. Diets containing fish meal, compared to the control group, significantly higher milk production, milk protein (%), the yield of milk protein and lactose (p < 0.1), but the different levels of fish meal had no significant effect on these factors. The urea pH decreased significantly with the increase of the fish meal but rumen pH and fecal pH were unaffected. The results of the experiment indicated that diets with the 1.5 or 3% fish meal in cows with less than 30 kg milk is recommended.
M. Alikhani, A. A. Alamooti, Gh. R. Ghorbani, N. Sadeghi,
Volume 9, Issue 3 (fall 2005)
Abstract

Whole plant sunflower and sunflower without head were ensiled in plastic containers using additives in a 2×2×2×2 factorial arrangement in a completely randomized design with three replicates. Additives were molasses, urea (at 4 and 0.5 percent wet basis respectively), and a bacterial inoculant (Agros 6gr/ton of forage as manufacture’s instruction). Compared with silages without head, ensiling sunflower as whole plant resulted in lower pH, neutral detergent fiber (NDF) and ash versus higher concentrations of crude protein and ether extract (EE). No significant effect of seed was observed on lactic acid concentration and dry matter degradability (P<0.05). With the addition of molasses, the cell wall components and the EE concentrations reduced, but dry matter content increased. Highest degradability of dry matter was also observed in molasses-treated silages (average 58.04, P<0.007). With the addition of urea a significant increase was seen in CP content of either whole plant or headless silages (P<0.0001) with no effect on other fermentation characteristics. Bacterial inoculation of silages elevated the levels of lactic acid (2.81% DM) with more pronounced effect on headless than whole plant silages. Regardless of type of additives, butyric acid concentrations were ideally minimal (near to 2%) indicating least clostridial damage. The qualitative visual evaluation of the silage on the basis of scale of 1-20 for the smel, colour and structure of the silage and giving number to the mold damage on the basis of 1-10 placed all the treatment in an acceptable quality, although the mold damage was highest in silages without molasses. Results of this experiment indicated that better quality of silalges could be provided by adding molasses and ensiling whole plant sunflower. Improving quality of silages contained molasses might necesitate the additiion of a source of water-soluble carbohydrate at ensiling.
S. A. Mir Mahdavi Chabok, M. P. Eskandari Nasab, A. A. Shadparvar, A. Ghorbani,
Volume 10, Issue 2 (summer 2006)
Abstract

Using a deterministic model for dairy herd according to milk pricing system in Iran, the economic weights of milk production, fat percentage, protein percentage and herd life with minimized cost were identified, while restricted total input and total costs were variable in animal unit. By data simulation and the data obtained from 3 different dairy herds in Iran, the sensitivity of economic values with the assumption of 20% change in forage and concentrate price, forage to concentrate ratio, feed-cost, non-feed cost, base price of milk, free-market price of milk, average milk production, fat percentage, protein percentage and herd life were estimated. In the base condition, the economic weights of milk production, fat and protein percentage and herd life in three herds were -0.55, -0.24, -0.54 -34, -20, -11 -34, -37, -33 -0.37, 0.67, -0.39, respectively. The effect of change in different factors of production system on economic weights of three farms was variable. The economic weights of milk production, fat percentage, protein percentage and herd life had the most sensitivity to change in the average milk productoin, base price of milk and herd life, respectively.
A. Jalalian, M. Amirpour Robat, B. Ghorbani, S.h. Ayoubi,
Volume 11, Issue 42 (winter 2008)
Abstract

  Soil erosion is one of the most threatening issues for crop production and environmental qualities, especially for soil and water resources. Appropriate knowledge about total soil loss and runoff is valuable in order to perform soil and water conservation practices in watersheds. EUROSEM, "a single event, dynamic and distributed model," was developed to simulate soil loss, sediment transportation and deposition by rill and interrill processes. This study was conducted to evaluate EUROSEM model in order to simulate soil loss and runoff in Sulijan sub-basin, which covered 20 ha, from Charmah-Bakhtari province. The sub-basin was divided in to 19 homogeneous elements using topographic, land use, plant cover, slope and channel properties throughout it. Soil, plant cover, land surface and climate characteristics were measured and evaluated by field observations and laboratory measurements. Actual soil loss and runoff for studied events were determined by direct measurement in the field. After sensitivity analysis, calibration and validation steps were carried out to simulate runoff and soil loss. The results of sensitivity analysis showed that the EUROSEM model for predicting runoff was more sensitive to hydraulic conductivity, capillary drive and initial soil moisture. On the other hand the model for predicting soil loss was more sensitive to Manning's coefficient and soil cohesion. The results showed that the EUROSEM model was able to simulate well the total runoff, peak of runoff discharge, total soil loss and time for the peak of soil loss discharge. But that could not simulate well the peak of soil loss discharge and time for the peak of runoff. Although it seems that EUROSEM is able to predict soil loss and runoff partially well in individual events, it is necessary to evaluate the efficiency of the models for different basins with varieties of soil, plant cover and climatic properties.


S.s. Hosseini, M. Ghorbani, M. Khaledi, E. Hassanpour,
Volume 12, Issue 43 (spring 2008)
Abstract

This paper analyzed the effect of transaction costs on supply response of rice producers in Iran. Some of these producers participate in market as sellers or buyers and others remain self-sufficient. Farmers have different responses based on fixed and proportional transaction costs. The data used in this research consisted of information about 260 rice producers in Mazandaran province in 2004. The results indicated that lowering transactions costs would increase output by both increasing market participation and increasing production for market participants. Given that transaction costs affect market participation, aggregate supply will respond to changes in the transaction cost structure through its effect on market participation. It is recommended that policies reducing transaction costs be applied as a complementary policy to price policies to affect supply response.
R Kowsar, Gh Ghorbani, M Alikhani, A Samie, M Khorvash,
Volume 13, Issue 47 (4-2009)
Abstract


M Hoseeini Ghafari, Gh Ghorbani, H Rahmani,
Volume 13, Issue 47 (4-2009)
Abstract

This study was conducted to determine the influence of two intermittent (1wk) and abrupt drying off methods on udder health index of dairy cows with 30d dry period. Eighteen multiparous dairy cows were dried off approximately 4 wk prior to the expected calving time in a completely randomized design. For intermittent milk cessation treatment, cows were dried off in the following manner. Milk samples were collected from front and rear quarters at 7d to 3d prior to drying off, at drying off, 14d, 7d prior to calving, at calving, and 7d post calving. Milk yield at drying off day was recorded. Lacteal secretion samples were stored at -18Ċ and used for lactoferrin quantitation. Other samples were stored at 4Ċ for somatic cell count, total bacteria count and other milk components. The results indicated that, there were no differences in fat, protein and lactose percentages and milk pH between two drying off methods (P>0.05). However, there was a significant effect of drying off methods on lactoferrin concentration it was higher in dairy cows dried off by intermittent milk cessation, applied in 2 and 1 wk prior to calving time (P<0.01). Total bacteria count was not different in the two drying off methods. Milk total bacteria counts was higher in rear quarters compared to front quarters (P<0.05). Milk somatic cell counts were higher in cows dried off by abrupt milk cessation (P<0.05). There was a positive correlation between milk somatic cell counts and total bacterial counts (r = 0.352, P<0.01). No significant difference was observed in colostrum and milk lactoferrin concentration, somatic cell counts, fat, protein and lactose percentages, between rear and front quarters. With respect to higher lactoferrin concentration in cows dried off by intermittent milk cessation and due to antibacterial action of lactoferrin against mastitis pathogens, it seem that intermittent milk cessation treatment is preferred for cows given short dry period.
N Nourmahnad, M Emamzadei, B Ghorbani, A.r Mohamdkhani,
Volume 13, Issue 50 (winter 2010)
Abstract

Water scarcity causes production losses in arid and semi arid regions. In this condition, deficit irrigation is one of the most important methods to minimize effects of water shortage. This research was conducted to evaluate the effects of two kinds of irrigation management (deficit irrigation and partial rootzone drying technique) on some of physiological and phenological characteristics and water use efficiency of tomato. The experiment was carried out in a completely randomized design with five treatments and four replications. The treatments consisted of DI75 and DI50 (supplying 75% and 50% water requirement) applied to the whole root system, PRD75 and PRD50 (supplying 75% and 50% water requirement) which was applied to one side of the root system, and alternated in every irrigation, and FI treatment, which supplied 100% water requirement, and was considered as control. The results showed that the highest water use efficiency was observed in PRD75 (6.28 kg/m3) and the lowest in DI50 (1.98 kg/m3). Water use efficiency was reduced 67% in DI50 and increased 4.6% in PRD75, as compared with full irrigation. Furthermore, plant water state showed that relative water content was higher in PRD treatments than DI treatments. The analysis of variance indicated that there was a significant difference in leaf diameter stomata among treatments at 5% level .The higher level of water increased stomata diameter. The opening of stomata in FI and DI treatments was higher than PRD treatments. FI had the highest numbers of stomata per unit of leaf area and PRD50 had the lowest (10509.04 and 6904.4, respectively). There was no difference among treatments in phenological characteristics in terms of growing degree-day to fruit yield and growing-degree day to harvesting.
Sh. Ghorbani Dashtaki, S. Dehghani Baniani, H. Khodaverdiloo, J. Mohammadi, B. Khalilmoghaddam,
Volume 16, Issue 60 (Summer 2012)
Abstract

Saturated hydraulic conductivity (Kfs) and macroscopic capillary length of soil pores are important hydraulic properties for water flow and solute transport modeling. Measuring these parameters is tedious, time consuming and expensive. One way is using indirect methods such as Pedotransfer functions (PTFs). The objective of this research was to develop some PTFs for estimating saturated hydraulic conductivity and inverse of macroscopic capillary length parameters (*). Therefore, the coefficients, Kfs and * from 60 points of Azadegan plain in Shahrekord were measured using single ring and multiple constant head method. Also, some of the readily available soil parameters from the two first pedogenic layers of the soils were obtained. Then, the desired PTFs were developed using stepwise multiple linear regression. The accuracy and reliability of the derived PTFs were evaluated using root mean square error (RMSE), mean error (ME), relative error (RE) and Pearson correlation coefficient (r). The highest correlation coefficients of 0.92 and 0.72 were found between Kfs-bulk density and *-bulk density, respectively. There was no significant correlation between soil particle size distribution and Kfs and *. This can be related to the fact that most of the soil samples were similar in texture and macro pores. The most efficient PTFs in predicting Kfs and * could explain 85 and 66 percent of the variability of these parameters, respectively. All the derived PTFs underestimated the Kfs and * parameters.
M. Hamidpour, A. Jalalian, M. Afyuni, B. Ghorbani,
Volume 16, Issue 62 (Winte - 2013 2013)
Abstract

Models are helpful tools to predict runoff, sediment and soil erosion in watershed conservation practices. The objectives of this research were to investigate sensitivity analysis, calibration and validation of EUROSEM model in estimation of runoff in Tangh-e-Ravagh sub-basin of Karoun watershed. The model was tested in a one hectare experimental test site. The area was divided into nine elements according to EUROSEM user's manual. A triangular weir was installed at the outlet of the area to collect runoff in specified time periods for six rainfall events. Sensitivity analysis of the model was performed by a ±10% change in the dynamic parameters of the model and examining the outputs for a rainstorm. Sensitivity analysis showed that total runoff was sensitive to saturated hydraulic conductivity and insensitive to soil cohesion. Sensitivity analysis indicated that the model sensitivity depends on evaluation conditions and it is site-specific in nature. Calibration and validation of the model was performed on input parameters. Calibration of hydrographs was performed by decreasing saturated hydraulic conductivity and capillary drive and increasing initial soil moisture. Validation results showed that EUROSEM model simulated well the total runoff and peak of runoff discharge, but it could not simulate well the time of runoff, time to peak discharge
N. Ghorbani Ghahfarokhi, Z. Kiani Salmi, F. Raiesi, Sh. Ghorbani Dashtaki,
Volume 17, Issue 63 (Spring 2013)
Abstract

Free and uncontrolled pasture grazing by animals may decrease soil aggregate stability through reductions in plant cover and subsequent soil organic C, and trampling. This could expose the soil surface layer to degradation and erosion. The objective of this study was to determine the influence of pasture management (free grazing, controlled grazing and long-term non-grazing regimes) on aggregate-size distribution and aggregation parameters by wet and dry sieving methods in two native pastures, protected areas in Chaharmahal va Bakhtiari province. The studied pastures were 1) SabzKouh pastures protected from grazing for 20 years, and 2) Boroujen pastures protected from grazing for 25 years. Soil samples were collected from 0-15 cm depth during the grazing season in summer 2008. Samples (finer than 2 mm) were analyzed for aggregate-size distribution and aggregation parameters by wet and dry sieving methods. Results showed that pasture management had a significant influence on aggregate-size distribution and aggregation parameters in the two areas. The two methods indicated that macro-aggregates in non-grazing and controlled grazing regimes were higher than those in free grazing regime, whereas in free grazing management micro-aggregates showed an opposite trend, and were greater compared with the other grazing regimes. Similarly, soil aggregate stability indices (i.e. mean weight diameter, aggregate geometric and ratio mean diameter) were all improved by non-grazing regimes, suggesting that animal grazing and trampling break down large soil aggregates due largely to compaction and reduced plant coverage. However, the extent to which grazing affects soil aggregation depends in large part on grazing intensity and duration, and the area involved.

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