Soil Genesis and Classification
Mozhdeh Taghipour; Nafiseh Yaghmaeian Mahabadi; Mahmoud Shabanpour
Abstract
Introduction: Soil quality index is used as a quantitative tool for assessing the impact of land use and management practices on soil condition. Soil quality is a sensitive indicator for revealing the dynamics of soil conditions, and it may vary with different land use and ecological restoration measures. ...
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Introduction: Soil quality index is used as a quantitative tool for assessing the impact of land use and management practices on soil condition. Soil quality is a sensitive indicator for revealing the dynamics of soil conditions, and it may vary with different land use and ecological restoration measures. The land use affects the physical and chemical properties, biological processes, and land productivity, which lead to the change in soil quality. Land use change and agricultural development can lead to degradation, erosion and reduction of surface and subsurface soil quality. In most of the conducted studies, the surface soil quality has been evaluated; but these studies provide incomplete information because subsurface soil have the greatest impact on soil function and crop. In spite of various soil quality assessment methods developed in former researches, there are fewer attempts for selecting suitable and sensitive soil quality index, especially in different land uses. In this study, soil quality indicators were evaluated using multivariate analysis in three different land uses to select the most suitable and appropriate soil quality index in Tootkabon area of Guilan province.Materials and Methods: The study area is located in Tootkabon in Guilan province (latitude 36º 53' 21" N, longitude 49º 33' 44" E). Parent material is limestone and geomorphologic units that are comprised of hill land and plateau. In order to achieve the objectives of the research, 20 composite soil samples were taken from two depths of 0 to 15 and 15 to 30 cm from each of the land use, including forest, cropland and rangeland (60 soil samples in total) with the same parent material. The three land uses were located next to each other and at a close distance. In this research, using the principal component analysis (PCA) method, among 12 physical, chemical and biological soil indicators as total data set (TDS), clay percent, mean weight diameter, organic matter and available phosphorus were determined as the minimum data set. Then, the soil quality was evaluated by integrated quality index (IQI) and Nemoro quality index (NQI) using two linear and non-linear scoring methods (LS and NLS) and two soil indicator selection approaches, a total data set (TDS) and a minimum data set (MDS). Finally, to prioritize the soil quality indices based on sensitivity index (SI) and efficiency ratio (ER), the ranks of both criteria were summed and then made appropriate decision. All soil parameters were tested using one-way analysis of variance and the differences among means were analyzed using Duncan's significant difference test at the probability level of 0.05.Results and Discussion: The results of the present study showed that some soil properties including clay percentage, mean weight diameter, organic matter and available phosphorus had the greatest effect on soil quality in the study area. Most of the soil properties in rangeland and forest had a higher stratification ratio compared to cropland. The soil quality indices calculated using linear function for MDS indicated soil quality of forest and cropland were higher than rangeland. Maximum SI belonged to IQI-LS-TDS and IQI-LS-MDS with values of 1.56 and 1.40, respectively. Efficiency ratios (ER) were calculated to specify the power of each soil quality index being as representative index for whole soil parameters set. IQI-LS-MDS and IQI-NLS-MDS have the highest value of ER (75.0 %), it is obviously deducted that these developed soil quality indices correlate with much indicators than other indices. It has more efficiency ratio and therefore represents the soil overall condition highly. Finally prioritizing according to ranks of SI and ER showed that IQI-LS-MDS is the most suitable approach in soil quality assessment of study area. Conclusion: Minimum data set selection using principal component analysis as a multivariate statistical method could adequately represent total data set method. Therefore, it seems to be an appropriate approach for choosing more effective indicators with respect to saving time and money in the developing countries The linear soil quality indices showed higher capability than non-linear indices to differentiate soil quality among different land uses. Overall results of the prioritization soil quality indices imply that the IQI-LS-MDS has the most efficiency and sensitivity for variation in land uses, so it is suggested to use this quality index for further and comprehensive soil quality assessments plans.
Soil Genesis and Classification
Mahyar Moshtaghi; hasan ramezanpour; Nafiseh Yaghmaeian Mahabadi; Mahmoud Shabanpour
Abstract
Introduction: Soil classification categorizes soils into different classes on the basis of their distinguishing characteristics and provides a structured conceptual framework for describing and understanding soil properties. There are two soil classification schemes that are generally regarded as having ...
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Introduction: Soil classification categorizes soils into different classes on the basis of their distinguishing characteristics and provides a structured conceptual framework for describing and understanding soil properties. There are two soil classification schemes that are generally regarded as having worldwide application, the Soil Taxonomy (ST) and the World Reference Base (WRB) which are also popular in Iran. These systems of classification consider diagnostic horizons and factors of soil formation as the basis of classification. The aim of this study was to determine the classification of soils of tobacco farms in the Talesh County of Guilan Province based on ST (2022) and WRB (2022) according to the soil diagnostic characteristics, then comparing two systems for soils of tobacco farms to determine the ability of better description of soils by these two systems of soil classification.Materials and Methods: Talesh County is considered to be the most important tobacco production areas in Guilan Province and IRAN. The most extensive area of tobacco cultivation in Guilan Province is located in this County and in Jokundan and Mountain districts. The study area has a humid climate with cold winter and hot summer. The mean annual temperature is between 15.6 and 17.2 degrees Celsius and the annual rainfall is between 786 and 1370 mm. Based on the map of moisture and temperature regimes of Iran and with the help of jNSM software, the moisture and temperature regimes were determined as Udic and the Thermic respectively. In the study area twenty pedons (eight pedons for Mountain and twelve pedons for Jokandan) were described and the morphological characteristics of the pedons layers were studied in the field according to the Soil Survey Manual. Then, the soil of each horizon was collected, air-dried, and sieved by passing through a 2 mm sieve before analyzing the properties of the soil. Soil pH, Electrical Conductivity, Texture, Organic Carbon, Calcium Carbonate Equivalent, Cation Exchange Capacity and Base Saturation were determined in all the samples according to Methods of Soil Analysis. Soils were then classified according to classification criteria of ST (2022) and WRB (2022) systems. For showing changes of tobacco farms soils, eleven pedons were selected as representative pedons and the reference between ST (2022) and WRB (2022) was established for tobacco soils at the level of the subgroup or secondary classification unit.Results and Discussion: The results revealed that according to ST (2022), representative pedons of Mountain district were classified as Entisols, Inceptisols and Mollisols orders while, Jokandan had Entisols, Inceptisols, Mollisols and Vertisols pedons. WRB (2022) Reference Soil Groups (RSGs) for Mountain was Regosols, Umbrisols and Phaeozems and for Jokandan district were Fluvisols, Cambisols, Phaeozems and Vertisols. At lower levels of classification, ST (2022) uses climatic data as soil moisture regime whereas WRB (2022) does not use. Therefore, the suborders or great groups of all soils were separated based on the Udic moisture regime. Finally, representative pedons were classified as Typic Udorthents, Mollic Udifluvents, Oxyaquic Udifluvents, Typic Humudepts, Dystric Eutrudepts, Typic Hapludolls, Fluventic Hapludolls, Aquic Argiudolls, Typic Argiudolls and Aquic Hapluderts at great group level. In regard to the WRB (2022), in the secondary levels, each section had its own series of principal and supplementary qualifications. Among those, the principal qualifications were mainly Eutric, Cambic and so on, and the supplementary qualifications were mainly Clayic, Loamic, Siltic, Humic and so on. Conclusion: It was found that when compared with ST (2022), the WRB (2022) had stronger abilities to distinguish soil properties for tobacco cultivation which was mainly reflected in the following aspects: 1- The climate-related soil moisture regimes were generally used to classify the suborders in ST (2022). It was found that the soil moisture status of all pedons was Udic, as well as the fixed format of naming soils in ST (2022), Therefore, divisions were limited in the suborders, 2- The flexibility of WRB with the utilization of multiple qualifiers brings out more sensitivity in reflecting soil characteristics in the soil name if compared with Soil Taxonomy. Also, the emphasis put on soil morphology compared with laboratory data makes the system suitable for application in areas with rather modest facilities, 3- The existence of the Mollic or Umbric horizon in pedons is well defined by WRB (2022), while this issue is ambiguous in ST (2022), 4- WRB (2022) have not fixed naming formats, the number of secondary levels qualifiers of the WRB system could be increased or decreased with the number of diagnostic characteristics of the soil pedons. 5- Nomenculture is very complicated in both systems, nevertheless, it is inevitable to transfer information to non- specialist users in a more simpler language, in WRB (2022) this information can be extracted more easily from the soil name.
Fatemeh Samie; Nafiseh Yaghmaeian Mahabadi; Sepideh Abrishamkesh; Ataolah Maslahatjou
Abstract
Introduction Soil is one of the important parts of ecosystem. Land use change and developed agriculture can lead to soil loss and land degradation because they have damaging effects on soil properties including soil organic carbon, aggregate stability and soil erodibility factor. Soil erodibility factor ...
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Introduction Soil is one of the important parts of ecosystem. Land use change and developed agriculture can lead to soil loss and land degradation because they have damaging effects on soil properties including soil organic carbon, aggregate stability and soil erodibility factor. Soil erodibility factor can be measured by different methods including experimental plots. It shows that the problem should be dealt directly and it demands high amount of cost and time. The factor can be calculated by soil properties such as soil organic matter and particle size distribution. They play a crucial role for sustainable ecosystem and decreased soil erosion. Since a few decades ago, deforestation has caused increased soil degradation and it has had devastative effects on soil surface and subsurface properties. This study investigated soil erodibility factor by different methods in three land uses including forest, grassland, and cropland at two depths in Sidasht of Guilan province. Soil quality index was calculated for evaluation of effects of land use on soil quality degradation.Materials and Methods The study area is located in Tootkabon in Guilan province (latitude 36º 50' 10" N, longitude 49º 39' 15" E). Parent material is limestone and geomorphologic units that are comprised of hill land and plateau. The soil moisture and temperature regimes are xeric and thermic, respectively. In order to reach the goals of the study, samples were collected from three land uses of forest, grassland, and cropland at two depths of 0 to 10 and 10 to 20 cm in regards to parent material, slope class, and equal slope aspect. Soil samples were prepared in two categories: the disturbed soil and the undisturbed ones. After becoming air drying, the disturbed samples were sieved by a 2 mm sieve. Soil properties such as soil texture, bulk density, soil organic carbon, CaCO3, and soil stability were measured. Soil erodibility factor is calculated by nomograph, Vaezi and Ostovari methods. Also sensitivity index and stratification ratio were taken into account. Soil quality index was determined using linear and nonlinear scoring methods based on minimum data set. All soil parameters were tested using one-way analysis of variance and the differences among means were analyzed using Duncan's significant difference test at the probability level of 0.05.Results and Discussion Results showed that the effects of land use and soil depth on bulk density, soil texture and soil erodibility factor using nomograph method were non-significant (p ≤ 0.05). The amount of organic matter, soil structure stability index and soil erodibility factor of Vaezi method were significantly decreased by increasing the depth. MWD and GMD at forest were higher than cropland, and CaCO3 and soil erodibility factor of Ostovari method at forest were lower than cropland. In comparison with other methods, soil erodibility factor of Ostovari method demonstrated that the effect of land use was significant (p ≤ 0.05). Soil properties including bulk density, MWD, organic matter, and soil erodibility factor of Ostovari method were selected as the minimum data set. Results of nonlinear scoring method were better than linear scoring method because the linear scoring method just showed the effects of soil depth on soil quality index (p ≤ 0.05). The soil quality index using linear scoring method was decreased by increasing the depth. However, soil quality index using nonlinear scoring method in forest was higher than cropland, and it was decreased by increasing the soil depth. It was found that non linear scoring methods are superior to linear and soil quality index using the nonlinear scoring method showed better the soil quality among different land uses.Conclusion Sensitivity index and stratification ratio values showed that land use change and soil depth effect on soil properties including CaCO3, organic matter, structure stability index and MWD. The stratification ratio values more than 1.5 for organic matter and soil structure stability index can be stated that these properties can show the degradation of soil quality due to land use change. Soil quality evaluation showed that in relation to the effect of land use on soil quality index, nonlinear scoring method is superior to linear scoring, so that forest and agricultural land use had the highest and lowest soil quality index by nonlinear scoring method, respectively. Therefore, due to the high sensitivity of soil quality to land use change, preventing land use change is one of the necessary measures for sustainable soil management in the study area.
Houra Fayyaz; Nafiseh Yaghmaeian; Atefeh Sabouri; Ahmad Shirinfekr
Abstract
The rapid growth of population demands higher land use efficiency to ensure food security. The most appropriate way to reach this goal is to increase yield per unit area. In this regard, the assessment of soil fertility and productivity is a prerequisite for developing sustainable agriculture. Soil fertility ...
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The rapid growth of population demands higher land use efficiency to ensure food security. The most appropriate way to reach this goal is to increase yield per unit area. In this regard, the assessment of soil fertility and productivity is a prerequisite for developing sustainable agriculture. Soil fertility indicates the soil capability to provide optimum conditions for plant growth. Assessing soil fertility is an essential need to identify environmental-friendly strategies leading to more sustainability in agricultural systems. Soil fertility directly and indirectly affects the yield and crop quality. In order for food security and increased food production to be achieved, the development of a useful method for assessing soil fertility and productivity is fundamental. Various modeling techniques have been proposed as a useful tool to determine soil fertility. An assessment of the soil fertility status by using a soil index could provide key information to improve strategies and effective techniques for the future to achieve sustainable agriculture. The present study was conducted: (1) to determine the soil fertility index (SFI) using two methods which are conceptually different from each other including: Fuzzy-AHP and parametric methods; (2) to identify the main soil limiting factors for tea production; and (3) to compare two methods of quantitative assessment of soil fertility in relation to tea yield in tea cultivation with different productivities in west Guilan province.Materials and Methods Based on the mean annual tea yield, the selected tea cultivation were divided into low, medium, and high productivity. Sixty-six soil samples were collected from 0 to 30 cm depth. The green tea leaves were harvested at a 2 m2 plot at each site. In this research, clay, silt, and sand content, mean weight diameter of soil aggregates, bulk density, soil pH, electrical conductivity, soil organic carbon, total nitrogen, available phosphorus, available potassium, available copper, and zinc were measured by conventional methods. Then, the soil fertility indices of tea cultivation with different productivities were determined by fuzzy-analytical hierarchy process (SFI-Fuzzy AHP) and Parametric (SFI-Parametric) analyses. The Fuzzy analytical hierarchy process is a combination of factor weights of AHP with the fuzzy values of each parameter. The product of values generated from individual fuzzification of parameters with their corresponding factor weights. All soil parameters were tested using one-way analysis of variance and the differences among means were analyzed using Tukey's significant difference test at the probability level of 0.05.The coefficients of determination for the linear regression between the two SFI values and tea yields were conducted.Results and Discussion Results indicated that the effect of pH, available potassium and copper, mean weight diameter, and bulk density on tea yield was significant (p <0.01). The highest of organic carbon, mean weight diameter, available potassium and copper were obtained in high productivity. The highest of soil pH and bulk density were related to low productivity. The main soil limiting factors for tea production were soil organic carbon, available potassium, and soil pH. The results showed that for both SFI-Fuzzy AHP and SFI-Parametric methods, the highest and lowest soil fertility indices were related to high and low productivity, respectively. The mean SFI- Fuzzy AHP of the high productivity tea were significantly higher than low productivity tea cultivation. It was found that SFI- Fuzzy AHP is superior to SFI-Parametric to evaluation of soil fertility for tea production .So that, the correlations between crop yields and SFI- Fuzzy AHP (R2= 0.63) is higher than SFI-Parametric (R2= 0.50).Conclusion Understanding the soil fertility status is one of the important aspects of sustainable soil management in order to optimal crop production and prevent environmental degradation. Considering the importance of yield as an important indicator in the sustainable management of agricultural ecosystems, it is expected that there is great potential for increasing crop yield by improving soil fertility. The SFI- Fuzzy AHP of the high productivity tea were significantly higher than low productivity tea cultivation and created more differentiation between various soil fertility classes in tea cultivation. Therefore, determining the soil fertility index by Fuzzy-AHP method to evaluate the soil fertility of tea cultivation is superior to the parametric method. Based on the obtained results, it is suggested that for the optimal tea production, in addition to the application of potassium fertilizer, the exact amount of which should be estimated based on the soil test results, the organic matter application should also be considered.
N. Yaghmaeian Mahabadi; N. Nobahar Deylami; M. Rahimi Mashkaleh; A. Fatemi Chookami
Abstract
Introduction As one of the pedogenic factors, topography can be an important and effective factor on yield and quality of crop performance through affecting water distribution and soil properties in different landscape positions. This factor affects soil properties by changing the altitude, steepness ...
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Introduction As one of the pedogenic factors, topography can be an important and effective factor on yield and quality of crop performance through affecting water distribution and soil properties in different landscape positions. This factor affects soil properties by changing the altitude, steepness and slope direction of lands. Understanding the soil limiting factors for the production of crop would help policy makers for the sustainable planning and management of the soils. Among many landscape parameters, effect of slope position and aspect on the variability of soil quality attributes and yield were little studied. This study aims to investigate the effect of topography on soil properties, yield and quality of tea in Lahijan, Guilan province. Materials and Methods Four slope positions were selected from one transect in the northern slope and one transect in the southern slope of tea gardens in Lahijan, Guilan province. In each slope position, one profile was drilled. Soil samples (0 to 30 cm depth) and green tea leaves were collected from in three plots (2 m2) around each profile. Physicochemical soil properties, yield and quality of tea were determined according to standard methods. So, this study was carried out in a factorial arrangement based on the completely randomized design with two factors, including slope position (summit, shoulder, backslope and toeslope) and slope aspect (northern and southern) with four replications. The data were analyzed by using SAS and graphs were plotted with the help of Excel program. Qualitative land suitability was also determined using simple limitation and parametric methods for tea production in this hilly region. Results and Discussion The results showed that slope position significantly affected some soil physical and chemical properties including silt content, electrical conductivity, total nitrogen, organic matter, available potassium and phosphorus. The highest content of organic matter, nitrogen and phosphorus in the soil of toeslope position can be attributed to soil erosion and transferred from top of the slope and their accumulation in this situation. The highest values of clay was found in the in the northern-toeslope position. The saturated water content in soil of the northern aspect was significantly higher than the southern aspect. The analysis of data showed that the interaction effect of slope positions and aspects on the yield and qualitative characteristics of tea, including the theaflavin, thearubigin, total color and brightness was statistically significant. Yield was the highest (3112 kg/ha) and the lowest (1762 kg/ha) in the northern-toeslope and southern-shoulder positions, respectively. The highest amount of theaflavin, thearubigin, total color and brightness were related to the northern-toeslope position. The northern aspect of all slope positions had more yield than the southern aspect that have contributed to higher amount of organic matter and saturated water content in northern aspect. Correlation analysis revealed that tea yield, thearubigin and brightness were significantly positively correlated with soil organic matter (P value < 0.05) also tea yield, theaeflavin and total color positively correlated with soil nitrogen (P value < 0.05). Also, theaflavin was significantly and positively correlated with thearubigin (P value < 0.05). This correlation is probably due to the presence of common chemical precursors for the formation of two substances as well as the transformation of theaflavin to thearubigin as one of the path for the thearubigin formation. According to the land suitability evaluation, the climatic factors especially the minimum temperature during the coldest month of the year is the most important limiting factor for tea cultivation in the study area. Another limiting factor was related to the topography (slope), which caused the lowest suitability class (N) in the shoulder and backslope positions. Conclusion Overall, the results showed that higher soil quality in northern-toeslope aspect lead to an increase in yield and quality of tea. The correlation results showed that soil nitrogen and organic matter are two important and effective parameters on the yield and quality of tea. This findings showed that the need to consider physiological characteristics of specific variety and the soil moisture and nutrients status in requirements tables for tea cultivation. Investigations on the soil-landscape relationship revealed that there is a strong link between the soil properties and the slope positions and aspects. More detailed studies would be helpful for the management of the sloping geomorphic surfaces.
