Arsalan Sadeghian; gholamabbas sayyad; Ahmad Farrokhian Firouzi; Mojtaba Norouzi Masir
Abstract
Introduction: Soil is one of the renewable natural resources that take a long time to get renewed; its destruction or conservation depends on how land is used and managed. Soil quality refers to soil capacity in maintaining biological fertility, sustainability in plant production and yield. Maintaining ...
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Introduction: Soil is one of the renewable natural resources that take a long time to get renewed; its destruction or conservation depends on how land is used and managed. Soil quality refers to soil capacity in maintaining biological fertility, sustainability in plant production and yield. Maintaining soil quality is essential for sustainable food production and decomposition of organic wastes. Different agronomic managements have various effects on soil quality indicators. There are few published researches about the effect of various agronomic managements on soil quality indices in arid and semi-arid regions (such as Iran). Therefore, this study was conducted to investigate and compare the effects of three different agronomic management including crop rotation-crop residue removal, monoculture-crop residue removal and monoculture-crop residue retention systems on some physical indicators of soil quality.
Materials and Methods: In this research, three farms with three crop management systems including crop rotation-crop residue removal, monoculture-crop residue removal and monoculture-crop residue retention (10 ton per hectare) systems were investigated. In the monoculture-crop residue removal treatment, wheat was continuously cultivated for 8 years. In the rotation-crop residue removal system, wheat - mung bean were cultivated in rotation for 2 years. For the monoculture-crop residue retention system, wheat was planted for 10 years, after which the post-harvest residues were mixed with topsoil (0-15 cm). One hundred twenty soil samples (40 samples from each field) were prepared by systematic sampling from 0 to 15 cm depth. In order to investigate the effect of different agronomic management on soil physical quality, some indicators including soil organic matter, total porosity, bulk density, mean weight diameter of aggregates, aggregate stability, available water capacity, penetration resistance, saturated hydraulic conductivity, and slope of retention curve at inflection point (S-index) were measured. The experiment was conducted in a randomized complete block design with four replications. Also, the mean comparison was performed using Duncan's multiple range test.
Results and Discussion: The results of analysis of variance showed that the type of crop management had a significant effect (p<0.01) on organic matter, total porosity, bulk density, mean weight diameter of aggregates, aggregate stability, available water capacity, penetration resistance, saturated hydraulic conductivity and S-index. The results of mean comparison indicated that the monoculture-crop residue removal system resulted in a significant increase in bulk density (1.31 g cm-3) and soil penetration resistance (0.4 MPa) than other systems, while the highest organic matter content (1.038 %), porosity (55.7%), mean weight diameter (1.04 mm), aggregate stability index (28%), available water capacity (0.15%), saturated hydraulic conductivity (46.17 cm h-1) and S-index (0.053) was observed in the monoculture-crop residue retention system. The most measured values for soil quality indicators were more in monoculture-crop residual retention system compared with the other treatments. The amount of S-index of soils under monoculture-crop residual retention, crop rotation-crop residues removal, and monoculture-crop residual removal systems were 0.053, 0.032 and 0.019, respectively. The high S-index value of soil under monoculture-crop residual retention system can be attributed to its suitable amount of soil organic carbon and better soil structural quality. By contrast, in monoculture-crop residue removal system, elimination of organic matter had undesirable effect on soil porosity, and aggregate stability. Furthermore, the S-index values of the soils under crop rotation-crop residues removal, and monoculture-crop residual removal systems are below the Dexter’s soil quality index threshold (0.035); therefore, the results indicated that the soils are degraded.
Conclusion: The results of this study showed that crop management plays an important role in changing soil physical quality indicators. Among the studied crop managements, monoculture-crop residue retention management system showed more positive effects on soil physical parameters than the others. Retention of crop residues on soil surface increases the soil organic matter which in turn has positive effects on soil properties such as aggregate stability, saturated hydraulic conductivity, available water content and slope of retention curve at the inflection point. On the other hand, the monoculture-crop reside removal treatment, with less soil organic matter, had more undesirable effects on agronomic soils than other treatments. Based on the results, the effect of different agronomic management systems on improving soil physical quality indexes was in the following order: monoculture-crop residue retention >crop rotation-crop residue removal > monoculture-crop residue removal. According to the results, it can be concluded that soil organic matter is the central index of soil quality, which is intensely influenced by crop management system. Therefore, in arid and semiarid areas such as Iran, monitoring of the long-time effect of agronomic management on status of soil organic matter and soil physical indices is urgent.
R. Beitlefteh; A. Landi; S. Hojati; Gh. Sayyad
Abstract
Introduction: Recently, air pollution due to the occurrence of dust storms is one of the worst environmental problems in Western and Southwestern Iran, especially the Khuzestan Province (12, 13). According to the reports of the Meteorological Organization of Iran the average number of dusty days in the ...
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Introduction: Recently, air pollution due to the occurrence of dust storms is one of the worst environmental problems in Western and Southwestern Iran, especially the Khuzestan Province (12, 13). According to the reports of the Meteorological Organization of Iran the average number of dusty days in the cities of Ahvaz and Abadan in the Khuzestan Province reaches 68 and 76 days each year, respectively (6). Previous studies have shown that the yearly damage costs of wind erosion and occurrence of dust storms in the Khuzestan Province reach about 30 Billion Rials (5). However, very few studies have been conducted on the characterization of dust particles and also the identification of their origins in Iran, especially the Khuzestan Province. Hojati et al. (10) reported that dust deposition rate, mean particle diameter, and concentration of soluble ions in samples taken from Isfahan and Chaharmahal and Bakhtiari Province decrease with altitude, with a significantly lower gradient in periods with dust storms. They reported three factors that control the rate and characteristics of dust deposited across the study transect: 1) climatic conditions at the deposition sites, 2) distance from the dust source, and 3) differences between local and transboundary sources of dust.Therefore, this study was conducted to investigate the effects of dust storms on deposition rate, mineralogy and size distribution patterns of dust particles from twelve localities around the Houralazim lagoon.
Materials and Methods: Dust samples were collected monthly during a 6 month experiment from August 2011 to February 2012. In order to differentiate between the contribution of dust production by local soils and other sources, surface soils were also sampled from the vicinity of the dust sampling sites. The collection trays were made of a glass surface (100 × 100 cm) covered with a 2 mm-sized PVC mesh on the top to form a rough area for trapping the saltating particles (Fig. 2). Dust samples were collected by scraping materials adhered to the glass trays using a spatula. All the trays were wet cleaned before the next collection. The collected dust and soil samples were examined for their grain size distribution using a Malvern Hydro 2000g laser particle size analyzer, as well as their mineral compositions by a Philips PW1840 X-ray diffractometer and a LEO 906 E transmission electron microscope (TEM).
Results and Discussion: The results showed that wind speed and direction patterns during the periods with dust storms and those without dust storms were different. Accordingly, in periods with dust storms (3, 5 and 6) the contribution of winds with speeds greater than 11.1 m/sec, especially from the Northwest direction, increased when compared with those from the periods without dust storms (1, 2 and 4). Besides, the direction of prevailing winds in periods without dust storms were mainly from the West and the Northwest. However, in periods with dust storms East-directed winds were also observed (Fig. 3). These show that the source areas of dust particles in these periods are probably different. The results also illustrated that the average amount of deposited particles in the periods with dust storms (12.5 g m-2 month-1) was considerably more than that of the periods without dust storms (7.5 g m-2 month-1) (Figs. 4 and 5). The difference in dust deposition rate between periods having dust storms and those without dust storms seems to be due to dust input from a source outside the study area. Particle size distribution analysis showed that dust particles collected from the study area in both periods (with and without dust storms) are mainly silt-sized particles. This fraction contributes to 60 to 76 % of the particles collected from periods without dust storms and 66 to 82 % of particles affected by dust storms (Table 2). The results also imply that in both periods (with and without dust storms), dust particles collected from the study area had a bimodal distribution pattern which suggests mixing of settled particles from different sources and/or deposition processes (Fig. 6). Mineralogical composition of dust particles were collected from both periods (with and without dust storms) and those from the soils contained quartz, calcite, feldspar, halite, dolomite and palygorskite (Figs. 7 and 8). Moreover, the TEM images of dust particles collected in periods with dust storms showed higher amounts of palygorskite than in periods without dust storms (Fig. 9).
Conclusion: The similarity in the physical properties of local soils and deposited particles of the periods with and without dust storms implies that the contribution of local soils and sediments in producing dust particles is high. However, it seems that in periods with dust storms the contribution of a transboundary origin such as Iraqi arid lands in producing dust particles increases.
N. Ramezani; G. Sayyad; A.R. Barzegar; Gh. Haghnia; Y. Mansuri
Abstract
AbstractCompaction developed by agricultural practices may change water conducting soil pores. Compacted soil pores results in destruction of soil structure, reduces pore connection and hence reduction of soil quality which in turn affects the population of microorganisms in soils. A research was performed ...
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AbstractCompaction developed by agricultural practices may change water conducting soil pores. Compacted soil pores results in destruction of soil structure, reduces pore connection and hence reduction of soil quality which in turn affects the population of microorganisms in soils. A research was performed to study the pathways of water through the soil and quantify infiltration based on colored area at different levels of compaction in a loamy soil at Ahwaz University Compus in southern Iran. A completely randomized block design was used with five treatments: (blank with no passing, once, twice, three times, four times and eight times of tractor passings) with three replications. In the field, Brilliant blue CFC solution was used as a dye tracer and added uniformally to each treatment with a rate of 5 mm h-1 for a period of 8 hours using a custom designed rain simulator. Colored flow paths were photographed by a digital camera. Digital pictures were analyzed with image processing techniques and surface distribution of dye tracer was quantitatively determined for each treatment. Our results showed that physical and hydraulic characteristics of soil was significantly affected by compaction. The highest impaction was observed at 0-20 cm. From this depth downward, no change was seen in soil physical characteristics due to compaction. The results of image processing also revealed that dye infiltration (as an index of water infiltration) had a 77.5 percent reduction at the highest compaction level (8 times tractor passing) when compared to blank. Dye tracer pattern was uniform in blank while in 4 and 8 times teraffic surface infiltration was little where as in lower depths dye transter was observed due to preferential flow. Although laboratory measurements indicated the compaction levels at different depths, it was not detected by dye tracer results. On the other hand, flow patterns show compaction effects and informations regarding changes developed in soil water infiltration. Keywords: Brilliant blue CFC, Flow patterns, Rain simulator
M. Shariaty; Gh. Sayyad; A. Barzegar; Z. Darvishpasand
Abstract
Abstract
Disc infiltrometer is one of those devices that used in recent years in measurement of hydraulic conductivity of entire soil. In order to analyze the data taken by Disc infiltrometer a variety of methods based on Wooding’s base analyze have been introduced. The objective of this study was ...
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Abstract
Disc infiltrometer is one of those devices that used in recent years in measurement of hydraulic conductivity of entire soil. In order to analyze the data taken by Disc infiltrometer a variety of methods based on Wooding’s base analyze have been introduced. The objective of this study was to compare the performances of Ankeny and Weir methods for predicting soil hydraulic properties using disc data. The study was conducted using a 10 cm radius disc infiltrometer in three different soil texture. The water infiltration was measured for silty loam soil using 15, 10, 7, 3, 1 cm tensions, for loamy sand using 10, 7, 5, 3, 1 cm tensions, and for sandy soil using 30, 25, 21, 17 cm tensions, respectively. The average calculated sorptive number was 0.065, 0.175, and 0.192 cm-1 for loamy sand, sandy, and silty loam soils, respectively. All the unsaturated- saturated hydraulic conductivity coefficients obtained for three soil textures using Ankeny analyze were bigger than the values obtained using modified Weir equation so that the predicted saturated hydraulic conductivity coefficients using Ankeny analyze for sandy loam soil 7.5%, for silty loam soil 29%, and for sandy soil 45% were greated than Weir estimates.
Keywords: Equations Ankeny, Equations Weir, Unsaturated and Saturated Hhydraulic Conductivity,
Disc infiltrometer
N. Ramezani; Gh.A. Sayyad; A.R. Barzegar; Y. Mansuri; Gh. Haghnia; S. Taherizadeh
Abstract
AbstractCompaction developed by agricultural practices may change water conducting soil pores. Compacted soil pores results in destruction of soil structure, reduces pore connection and hence reduction of soil quality which in turn affects the population of microorganisms in soils. A research was performed ...
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AbstractCompaction developed by agricultural practices may change water conducting soil pores. Compacted soil pores results in destruction of soil structure, reduces pore connection and hence reduction of soil quality which in turn affects the population of microorganisms in soils. A research was performed to study the pathways of water through the soil and quantify infiltration based on colored area at different levels of compaction in a loamy soil at Ahwaz University Compus in southern Iran. A completely randomized block design was used with five treatments: (blank with no passing, once, twice, three times, four times and eight times of tractor passings) with three replications. In the field, Brilliant blue CFC solution was used as a dye tracer and added uniformally to each treatment with a rate of 5 mm h-1 for a period of 8 hours using a custom designed rain simulator. Colored flow paths were photographed by a digital camera. Digital pictures were analyzed with image processing techniques and surface distribution of dye tracer was quantitatively determined for each treatment. Our results showed that physical and hydraulic characteristics of soil was significantly affected by compaction. The highest impaction was observed at 0-20 cm. From this depth downward, no change was seen in soil physical characteristics due to compaction. The results of image processing also revealed that dye infiltration (as an index of water infiltration) had a 77.5 percent reduction at the highest compaction level (8 times tractor passing) when compared to blank. Dye tracer pattern was uniform in blank while in 4 and 8 times teraffic surface infiltration was little where as in lower depths dye transter was observed due to preferential flow. Although laboratory measurements indicated the compaction levels at different depths, it was not detected by dye tracer results. On the other hand, flow patterns show compaction effects and informations regarding changes developed in soil water infiltration. Keywords: Brilliant blue CFC, Flow patterns, Rain simulator
