Soil science
M. Jafarian; A. Golkarian; H. Emami
Abstract
Introduction Changes in soil properties depend on factors such as climate, topography, landscape features, altitude, parent material, and vegetation. The quantity and quality of soils obtained from different rocks (igneous, sedimentary and metamorphic rocks) depend on the minerals that make up the ...
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Introduction Changes in soil properties depend on factors such as climate, topography, landscape features, altitude, parent material, and vegetation. The quantity and quality of soils obtained from different rocks (igneous, sedimentary and metamorphic rocks) depend on the minerals that make up the rock, as well as weather and other factors. Soil parent material is one of the primary and important issues in soil classification in terms of physical quality and also one of the most important effective factors in soil erodibility. The topographical factor of each region is one of the important and influential features on the soil quality of that region. The present research was conducted with the aim of understanding the spatial changes of soil properties in different slopes and different types of rocks. Material and Methods The studied area is located in Razavi Khorasan province in the cities of Mashhad, Chenaran, Sarakhs and Torbat-Haidarieh. The geographic location of the region ranges from 58 degrees and 52 minutes to 60 degrees and 40 minutes east longitude and 35 degrees and 38 minutes to 36 degrees and 25 minutes north latitude. This research was carried out on seven types of rocks: granite, Sarakhs paleogene limestone, Chenaran jurassic limestone, marl, shale, sandstone and ophiolite from relatively pure rocks of Razavi Khorasan province. In the present study, two factors of rock type and slope were investigated as effective factors of soil properties. Soil samples were taken from the surface layer (0-20 cm) and from three slope classes ie., less than 10%, 10-25% and more than 25%, as well as all soil samples from the southern slopes. Tree soil samples were taken from each slope and a total of 63 samples were taken and the samples were transfered to the laboratory for physical and chemical tests. In this study, the soil particle size distribution (texture) was measured by hydrometer method, organic carbon and calcium carbonate were determined by wet oxidation and titration with HCl 6 M, the mean weight diameter of soil aggregates and surface crust factor were calculated by related equations. To measure soil cohesion and penetration resistance were used pocket vane test and pocket penetrometer, respectively. Comparison of means was done through Duncan test in spss software. Results and Discussion The results showed that all the studied variables in different types of stones had a significant difference at the level of 1%. There was no significant difference in the variable of surface level in different slopes. Also, the variables of calcium carbonate percentage and saturated conductivity at 5% level had significant differences in different slopes. Other characteristics of soil, including percentage of organic matter, the mean weight diameter of soil aggregates, the number of drops impact, and soil cohesion and penetration resistance in different slopes had a significant difference at the level of 1%. Althoug the soil texture class was not significantly different in different slopes, the percentage changes of clay, silt and sand had a lot of difference along the slope. The highest and lowest parameters of organic matter percentage, Soil cohesion and penetration resistance were observed in granite and shale, respectively. The highest percentage of calcium carbonate was observed in Chenaran limestone (40.41%) and the lowest in granite (14.72 %). The mean weight diameter of soil aggregates was the highest in ophiolite (1.005 mm) and the lowest in marl (0.403 mm). The mean weight diameter of soil aggregates in the medium slope was significantly higher than the other two slopes. The parameter of the number of drops impact was the highest in granite (47.14 number) and the lowest in marl (27.70 number). The highest value of saturated conductivity variable was observed in marl rock and the lowest value was observed in Chenaran limestone. Conclusion The results showed that all the investigated variables had significant differences in different types of stones. Also, some of the investigated variables such as percentage of organic matter, percentage of equivalent calcium carbonate and the mean weight diameter of soil aggregates had significant changes along the hillside. As a general conclusion, given that the physical and chemical properties of the soil are partly under the influence of the parent material and the slope, and also with the presence of good geological information in the country, it can be suggested to provide suitable management solutions to prevent soil erosion and degradation by comprehensive examination of soil properties under different slope and types of stones.
ali baliani; Ali Reza Vaezi
Abstract
IntroductionRainfall erosion results from the expenditure of the energy of falling raindrops and flowing water when these two agents act either singly or together. Soil erosion by rainfall is a serious ongoing worldwide environmental issue that contributes to soil and water quality degradation. Understanding ...
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IntroductionRainfall erosion results from the expenditure of the energy of falling raindrops and flowing water when these two agents act either singly or together. Soil erosion by rainfall is a serious ongoing worldwide environmental issue that contributes to soil and water quality degradation. Understanding raindrop-impact-induced erosion processes are key to design and apply soil management techniques that minimize and control soil erosion risk. Water erosion and especially raindrop-impact-induced erosion is the primary agents that cause soil erosion-induced degradation and has been identified as one of the major processes contributing to the soil and water quality degradation. Soil degradation caused by rainfall raindrops impacts the soil surface disperses and splashes the soil, and displaces particles from their original position. Raindrops striking the soil surface develop a raindrop-soil particle momentum before releasing their energy in the form of the splash. Other causes of soil degradation are including compaction and penetration resistance.
Materials and Methods: This study was conducted to investigate the raindrop-impact-induced erosion in relation to slope gradient (0, 10, 20, and 30%) and antecedent moisture content or AMC (air dried, quarter saturation, semi saturation, and saturation). Toward this, six soil texture classes were exposed to simulated rainfalls with 40 mm h-1 in intensity for 15-min in four slope gradients and four antecedent moisture contents. Rainfall was simulated using rainfall simulator from soil erosion laboratory of the University of zanjan with 3-meter height and surface of 2 m2. A total of 288 experimental soil boxes with 25 cm × 35 cm dimensions and 5-cm depth were investigated using the completely randomized block design with three replications. Data of soil erosion processes include splash erosion particles amount caused raindrop impact, soil resistance ratio after rainfall using penetrometer, and compaction percent using bulk density after and before rainfall was measured and then compared using Duncan's test among the slope steepness and antecedent moisture content
Results and Discussion: Significant relationships were found between the splash erosion rate, soil resistance ratio and soil compaction means (P<0.01. (The results showed that silt soil carried the highest mean value in splash erosion rate with 1574.93 gm-2 h-1, soil resistance ratio with 10.53 and soil compaction with 17.43 percent, while sand soil carried the lowest mean value in splash rate with 437.37 gm-2 h-1, soil resistance ratio with 2.66 and soil compaction with 0.25 percent. Soil erosion processes were significantly affected by slope gradient and AMC. Soil erosion processes showed a decreasing rate in 0 slope degree and increasing rate in 30 slope degree and also decreasing rate in air dried and increasing rate in semi saturation AMC. Significant correlations (P< 0.01 and 00.05) were found between soil erosion processes and sand, silt, geometric mean particle diameter, bulk density, saturated hydraulic conductivity, and calcium bicarbonate equivalent. among the physical properties of the studied soils, the sand percentage, bulk density, and Geometric mean diameter showed a negative significant correlation with splash erosion, soil compaction, and soil resistance, and the percentage of silt and calcium carbonate content with splash erosion, soil compaction, and soil resistance were positive significant correlated. The cause of this negative and positive correlation might be dependent on particles size and more percent of coarse particles, the transfer of particles from the soil mass is reduced due to raindrops and degradation processes occur with less intensity. In addition, destruction processes with more intensity occurred with increasing silt and lime percent.
Conclusion: Increasing the slope gradient has an incremental effect on the amount of rainfall erosion processes i.e. sediment load, penetration ratio, and soil compaction value. However, antecedent moisture content in various soil textures has the different effect on the amount of rainfall erosion processes. Among the soil chemical properties, only calcium carbonate equivalent with splash erosion, density, and soil surface resistance was positively correlated and chemical properties such as a percentage of organic matter and exchangeable sodium percent no significant correlated with soil erosion processes. In other words, the physical nature of soil-forming particles such as particle size, as well as some of the chemical properties of soil particles such as organic matter, have a more effect on soil degradation, density, and soil resistance ratio. also the role of soil physical properties such as sand percent and calcium carbonate equivalent on the rainfall processes were more than soil chemical properties. In general, increasing the percent of silt and lime in the soil, unlike sand, was increased the sensitivity of the soil to the rainfall erosion and as a result increasing the splash erosion leads to increased soil compaction and soil resistance ratio.
D. Baharlooi; S. Ghorbani Dashtaki; B. Khalil Moghadam; Mahdi Naderi; P. Tahmasebi
Abstract
Introduction: The detachment process can be conceptually divided in two sub-processes included aggregate breakdown (Le Bissonnais, 1996) and movement initiation of breakdown products(Kinnell, 2005). soil detachment depends on raindrop size and mass(Elison, 1944; Bisal, 1960), drop velocity(Elison, 1944; ...
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Introduction: The detachment process can be conceptually divided in two sub-processes included aggregate breakdown (Le Bissonnais, 1996) and movement initiation of breakdown products(Kinnell, 2005). soil detachment depends on raindrop size and mass(Elison, 1944; Bisal, 1960), drop velocity(Elison, 1944; Bisal, 1960), intensity rainfall (Ting et al, 2008), kinetic energy (Kinnell, 2003; Fernandez- Raga et al, 2010), runoff depth(Torri et al, 1987; Kinnell,1991 and 2005), crop covers(Bancy, 1994; Ghahremani et al, 2011), wind speed( Erpul et al, 2000) and experimental area (cup size) (Leguedois et al, 2005; Luk, 1979; Torri and poesen, 1988). Many of studies have been conducted to evaluate the relationship between splash and slope (Bryan, 1979; Torri and Poesen, 1992; Wan et al, 1996).Torri and Poesen (1992) expressed that in steep slope the gravity force adds to the drop detaching force and decreases of soil resistance, consequently increases splash erosion rate with increasing slope. Soil splash erosion is also strongly influenced by soil properties including soil particles size distribution (Mazurak and Mosher, 1968; Legout et al, 2005; fan and li, 1993), soil shear strength(Cruse and Larson, 1977; Al-Durrah and Bradford,1981; Ekwue and ohi; 1990 ), soil cohesion(Torri et al, 1987), soil organic matter content and aggregate size (Ekwue and Maiduguri, 1991; Qinjuan et al, 2008), soil aggregates stability(Qinjuan et al, 2008), surface crust (Qinjuan et al, 2008).
Fire, play an important role in splash erosion. The absence of vegetation cover in disturbed lands accelerates splash erosion rates by as much as several folds compared to undisturbed sites (Lal, 2001; Thomaz and luiz, 2012).The detachment of soil particles by splash depends on several raindrop characteristics, including raindrop size and mass, drop velocity, kinetic energy, and water drop impact angle (Sharma et al., 1993; Singer and Le Bissonnais, 1998; Cruse et al., 2000, Bhattacharyya et al., 2010). Detachment rate is strongly influenced by soil properties, including soil texture and thickness of the water layer at the soil surface (De Ploey and Savat, 1968; Moss and Green, 1983; Sharma et al., 1991; Kinnell, 1991, Jomaa et al., 2010), soil strength, bulk density, cohesion, soil organic matter content, moisture content, infiltration capacity (Nearing et al., 1988; Owoputi, 1994; Morgan et al., 1998, Planchon et al., 2000, Ghahramani et al., 2011), soil initial water content, surface compaction and roughness (Planchon et al., 2000), the nature of soil aggregates and crust, porosity, capacity of ionic interchange, and clay content (Poesen and Torri, 1988). Several studies have shown that splash detachment rate is mainly related to surface rock fragments in soils with sparse vegetation cover (Jomaa et al., 2012). The present study was conducted to investigate the effects of fire on splash erosion and some erosion depended properties in semi-steppe rangeland of Karsanak region in Chaharmahal and Bakhtiari province which affected by man-made fire during 2008, 2009, 2010 and 2011.
Materials and Methods: Soil samples were obtained on 2012 from the mentioned regions (8 samplesfrom the burned area and 8 samples as a control (unburned) in the adjacent burned area) from 0-7 cm depth. Splash erosion under simulated rainfall intensity of 2 mm per minute was measured using multivariate splash cup apparatus considering the slope of 5 and 25 degree. Soil pH, soil electrical conductivity, equivalent calcium carbonate, soil organic matter, sand size fraction particulate organic matter (SSF POM), mean weight diameter and, geometric mean diameter of aggregates, percent of macro and micro-aggregates, percent of clay, silt, sand, water dispersible clay and soil bulk density were measured. Statistical data analysis was performed by t-test at 5% level.
Results Discussion: The results showed that soil splashing increased significantly in treatment 1 year after the fire in both slope 5 and 25 degree and in treatment 2 year after the fire in slope 25 degree. The amounts of increase in soil splashing compared to control treatment were 22, 24 and 15 percent in treatment 1 year after fire in slope 5 and 25 degree and in treatment 2 years after the fire in slope of 25 degree respectively. Comparison of the total soil splash on slopes of 25 degree at 1, 2, 3 and 4 years after the fire, showed a significant increase in the level of five percent relative to the slope of 5 degree at 1, 2, 3 and 4 years after the fire. The other measured soil properties (except equivalent calcium carbonate) was affected by fire. Also, the differences between many of the mentioned properties in the first 2 years after the fire was significant compared with the control area, but they have been reached to the initial values in the third and fourth years after the fire.
Conclusion: Time was shown to be effective factor inrecovering soil propertiesin Karsanak region of Chaharmahal and Bakhtiari province which affected by man-made fire during 2008, 2009, 2010 and 2011. Fire accelerates splash erosion rates by as much as several folds compared to control in this area.
F. Mahmoodi; R. Jafari; H. Karimzadeh; N. Ramezani
Abstract
Introduction: Use of remote sensing for soil assessment and monitoring started with the launch of the first Landsat satellite. Since then many other polar orbiting Earth-observation satellites such as the Landsat series, have been launched and their imagery have been used for a wide range of soil mapping. ...
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Introduction: Use of remote sensing for soil assessment and monitoring started with the launch of the first Landsat satellite. Since then many other polar orbiting Earth-observation satellites such as the Landsat series, have been launched and their imagery have been used for a wide range of soil mapping. The broad swaths and regular revisit frequencies of these multispectral satellites mean that they can be used to rapidly detect changes in soil properties. Arid and semi-arid lands cover more than 70 percent of Iran and are very prone to desertification. Due to the broadness, remoteness, and harsh condition of these lands, soil studies using ground-based techniques appear to be limited. Remote sensing imagery with its cost and time-effectiveness has been suggested and used as an alternative approach for more than four decades. Flood irrigation is one of the most common techniques in Isfahan province in which 70% of water is lost through evaporation. This system has increased soil salinization and desert-like conditions in the region. For principled decision making on agricultural product management, combating desertification and its consequences and better use of production resources to achieve sustainable development; understanding and knowledge of the origin, amount and area of salinity, the percentage of calcite, gypsum and other mineral of soil in each region is essential. Therefore, this study aimed to map the physical and chemical characteristics of soils in Vazaneh region of Isfahan province, Iran.
Materials and Methods : Varzaneh region with 75000 ha located in central Iran and lies between latitudes 3550234 N and 3594309 N and longitudes 626530 E to 658338 E. The climate in the study area is characterized by hot summers and cold winters. The mean daily maximum temperature ranges from 35°C in summer to approximately 17°C in winter and mean daily minimum temperature ranges from 5°C in summer to about -24.5°C in winter. The mean annual evaporation rate is 3265 mm. In this study, image processing techniquess including band combinations, Principal Component Analysis (PC1, PC2 and PC3), and classification were applied to a TM image to map different soil properties. In order to prepare the satellite image, geometric correction was performed. A 1:25,000 map (UTM 39) was used as a base to georegister the Landsat image. 40 Ground Control Points (GCPs) were selected throughout the map and image. Road intersections or other man-made features were appropriate targets for this purpose. The raw image was transformed to the georectified image using a first order polynomial, and then resampled using the nearest neighbour method to preserve radiometry. The final Root Mean Square (RMS) error for the selected points was 0.3 pixels. To establish relationships between image and field data, stratified random sampling techniques were used to collect 53 soil samples at the GPS (Global Positioning System) points. The continuous map of soil properties was achieved using simple and multiple linear regression models by averaging 9 image pixels around sampling sites. Different image spectral indices were used as independent variables and the dependent variables were field- based data.
Results and Discussion: The results of multiple regression analysis showed that the strongest relationships was between sandy soil and TM bands 1, 2, 3, 4, and 5, explaining up to 83% of variation in this component. The weakest relationship was found between CaCo3 and 3, 5, and 7 TM bands. In some cases, the multiple regressions was not an appropriate predicting model of soil properties, therefore, the TM and PC bands that had the highest relationship with field data (confidence level, 99%) based on simple regression were classified by the maximum likelihood algorithm. According to error matrix, the overall accuracy of classified maps was between 85 and 93% for chlorine (Cl) and silt componets, repectively.
Conclusions: The results indicated that the discretely classified maps had higher accuracy than regression models. Therefore, to have an overview of soil properties in the region, classification techniques appears to be more applicable than regression models. The findings of this study shows that the extracted maps of the physical and chemical characteristics of soils can be used as a suitable tool for field operations, cambating desertification and rehabilitation purposes and compared to maps that are created by traditional methods, our final maps have more economically and time saving advantages. Therefore, they can be used as an adjunct to field methods to aid the assessment and monitoring of soil condition in the arid regions of Isfahan province.
amir ranjbar; H. Emami; Ali reza Karimi; R. Khorassani
Abstract
Introduction: Saffron is one of the most important economic plants in the Khorasan province. Awareness of soil quality in agricultural lands is essential for the best management of lands and for obtaining maximum economic benefit. In general, plant growth is a function of environmental factors especially ...
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Introduction: Saffron is one of the most important economic plants in the Khorasan province. Awareness of soil quality in agricultural lands is essential for the best management of lands and for obtaining maximum economic benefit. In general, plant growth is a function of environmental factors especially chemical and physical properties of soil (20). It has been demonstrated that there was a positive and high correlation between soil organic matter and saffron yield. Increasing the yield of saffron due to organic matter is probably due to soil nutrient, especially phosphorous and nitrogen and also improvement of soil physical quality (6, 28, 29). The yield of saffron in soils with high nitrogen as a result of vegetative growth is high (8). Shahandeh (6) found that most of the variation of saffron yield depends on soil properties. Due to the economic importance of saffron and the role of soil properties on saffron yield, this research was conducted to find the relationship between saffron yield and some soil physical and chemical properties, and to determine the contribution of soil properties that have the greatest impact on saffron yield in the Ghayenat area.
Materials and Methods: This research was performed in 30 saffron fields (30 soil samples) of the Ghayenat area (longitude 59° 10΄ 10.37˝ - 59° 11΄ 38.41˝ and latitude 33° 43΄ 35.08˝ - 33΄ 44΄ 02.78˝), which is located in the Khrasan province of Iran. In this research, 21 soil properties were regarded as the total data set (TDS). Then the principal component analysis (PCA) was used to determine the most important soil properties affecting saffron yield as a minimum data set (MDS) and the stepwise regression to estimate saffron yield. To estimate the yield of saffron in stepwise regression method, saffron yield was considered as a dependent variable and soil physical and chemical properties were considered to be independent variables.
Results and Discussion: According to the PCA method, among the 21 studied properties, 7 out of them including calcium, iron, zinc contents, sand, calcium carbonate equivalent percent, mean weight diameter of aggregates (MWD) and manganese (Mn) had the higher Eigenvalues. Therefore, the above properties were introduced as the most important soil properties in saffron fields. Calcium carbonate had the negative effect on the availability of micro-nutrients (26). Christensen et al. (15) found that by increasing the calcium carbonate in soil due to high pH and formation of insoluble components, the uptake of micro-nutrients is especially limited.
The results of stepwise regression method (equation 1) showed that soil acidity (pH), zinc content, bulk density, MWD, iron content, salinity (EC), organic carbon and available potassium in soil were the most important properties that affect the yield of saffron, so that the determination coefficient (R2) of the regression model was high (Table 2) and it can explain 74% of the variation of saffron yield.
Y = 6924.51 – 1187.31 pH – 89.65 EC + 71.6 Fe – 826.02 Zn + 471.55 OC, + 5490.96 K + 1353.56 BD + 752.82 MWD (1)
where Y: saffron yield (kgha-1), pH: soil acidity, EC: electoral conductivity (dSm-1), Fe: iron concentration (mgkg-1), Zn: zinc concentration (mgkg-1), OC: organic carbon (%), K: soil potassium (%), BD: soil bulk density (Mgm-3), and MWD: mean weight diameter of aggregates (MM).
Based on the absolute values of standard ß in the regression model (Table 3), pH value and then after Zn concentration had the most effect on saffron yield. In general, responses of different plants to soil pH is varied, and saffron grows satisfactory in pH = 7.8 (5). Soil pH influences the uptake of soil nutrients by plants (15), so that this parameter had the most effect on saffron yield and by increasing the soil pH, the yield of saffron decreases. According to the regression model, Zn concentration was the second parameter in saffron yield. Zn has the important role in structure of plant enzymes (30). After these 2 parameters, Bd, MWD, Fe concentration, EC, Organic carbon and K concentration in soil had more effect on saffron yield (Table 3).
Conclusion: According to both PCA and regression methods, the concentration of iron and zinc and MWD were determined as the important and effective soil properties on saffron yield in the Ghayenat area. In addition, soil pH in stepwise regression method and calcium carbonate in PCA method were determined as the effective properties on saffron yield. Therefore, it is suggested that the parameters of Zn, Fe, and MWD along with soil pH and calcium carbonate which were regarded individually in two methods, were considered as the most soil properties in saffron yield.
A.R. Vaezi; H. Gharehdaghlii
Abstract
Soil erosion prediction models are of great significance for soil and water conservation management. Rill erosion is the most important component of hillslope soil erosion processes. Therefore, predicting hillslope erosion requires that rill erosion is well understood and predictable. The study was conducted ...
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Soil erosion prediction models are of great significance for soil and water conservation management. Rill erosion is the most important component of hillslope soil erosion processes. Therefore, predicting hillslope erosion requires that rill erosion is well understood and predictable. The study was conducted to empirical quantification of rill development in the hillslopes. Rill characteristics consist of width, depth, cross section area, length, volume and soil loss, density of the rills and soil erosion rate along with slope characteristics (steepness and length) and soil properties were determined in 27 rills occurred on 9 hillslopes in marl formations of the Zanjanroud watershed, north west of Zanjan, Iran. All rill characteristics except the length showed significant correlation with both slope steepness and some soil properties including particle size distribution, sodium adsorption ratio, aggregate stability and saturated hydraulic conductivity. Rill depth as compared to other rill characteristics was reliably quantified in the hillslopes. This parameter had the highest relationship with slope steepness and saturated hydraulic conductivity (R2= 0.67, p< 0.001). Rill erosion rate contrary to the slope characteristics significantly related to clay content (R2= 0.56). This result revealed that in order to develop a model to predict rill erosion, it is vital that investigate all hillslope characteristics a long with soil properties in the watershed surface.
M.R. Rahimi Ashjerdi; shamsollah Ayoubi
Abstract
Conversion of forest and pasture lands into agricultural lands, which is triggered by the rapid population growth, causes serious soil degradation, especially in the hilly regions with undulating topography. The objective of this study was to explore the slope position and land use change effects on ...
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Conversion of forest and pasture lands into agricultural lands, which is triggered by the rapid population growth, causes serious soil degradation, especially in the hilly regions with undulating topography. The objective of this study was to explore the slope position and land use change effects on some soil properties in hilly region of west of Isfahan province, Feryduhahr district. In the two mentioned dominant ecosystems, four slope positions including summit, shoulder, backs lope and foot slope were identified and in each land use and slope position, three cores were selected to collect 72 soil samples from three depths (0–10, 10–20, 20–30 cm). The results showed that soil organic matter (SOM) in pasture land (2.1%) was approximately 40% higher than cu1tivated land (1.2%). Overall, SOM, total nitrogen, available potassium, clay and sand content significantly in pasture land were higher than cu1tivated land. In consequence of land use change from pasture to cultivated land, some soil properties in surface soils including calcium carbonate, bulk density and soil acidity showed increasing tendency as compared to pasture soils. The pasture soil with lower soil erosion and higher fine materials (clay), indicated higher magnetic susceptibility as compared to cultivated land. Variability of most of measured soil properties showed significant differences in different slope positions. Improper management practices and consequently water soil erosion was identified as the most possible process which has affected soil properties in different slope positions. In overall, it is conc1uded that slope positions and land use significantly influenced soil physical, chemical and magnetic properties in steep slopes of the study area.
M. Ghaemi; A. Astaraei; M. Nassiri Mahalati; S.H. Sanaeinejad; H. Emami
Abstract
Successful implementation of soil and crop management program requires quantitative knowledge of site characteristics and interactions that affect crop yield. Soil properties are one of the most important site variables affecting within- field yield variability. The objective of this research was to ...
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Successful implementation of soil and crop management program requires quantitative knowledge of site characteristics and interactions that affect crop yield. Soil properties are one of the most important site variables affecting within- field yield variability. The objective of this research was to identify intercorrelations among soil properties (chemical, physical and biological) using principal component analysis (PCA) and their relationships with maize yield variability in field. Site variables (18) and maize yield were measured in selected parts of Astan Quds agricultural fields in Mashhad city. The principal component analysis was used to reduce the site variables numbers and remove multicollinearity among variables. The first four PCs with eigenvalues>1 accounted for > 67% of variability in measured soil properties. Soil properties were grouped in four PCs as: (PC1) Soil highly descriptive fertility potential, (PC2) Soil moderately descriptive fertility potential, (PC3) Soil permeability potential, (PC4) Soil aggregation potential. The results showed that the factor of soil highly descriptive fertility potential explained 43% of variance and accounted for 77% of the yield variability in the field. Principal component analysis allows explaining a major part of crop yield variability by removing the multicollinearity.