Twenty five surface (0—20 cm) soil samples were collected from different locations in Egypt representing non polluted, moderately and highly polluted soils. The aim of this study was to evaluate total Co content ...Twenty five surface (0—20 cm) soil samples were collected from different locations in Egypt representing non polluted, moderately and highly polluted soils. The aim of this study was to evaluate total Co content in alluvial soils of Delta in Egypt using the delayed neturen activation analysis technique (DNAA). The two prominent gamma ray lines at 1173 2 and 1332 5 keV was efficiently used for 60 Co determination. Co content in non polluted soil samples ranged between 13 12 to 23 20 ppm Co with an average of 18 16±4.38 ppm. Cobalt content in moderately polluted soils ranged between 26 5 to 30 00 ppm with an average of 28 3±1.3 ppm. The highest Co levels (ranged from 36 to 64 69 ppm with an average of 51 9±9.5); were observed in soil samples collected from, either highly polluted agricultural soils due to prolonged irrigation with industrial wastewater or surface soil samples from industrial sites.展开更多
This study developed empirical-mathematical models to predict the California Bearing Ratio (CBR) using soil index properties in Ogbia-Nembe road in the Niger Delta region of Nigeria. The determination of CBR of soil i...This study developed empirical-mathematical models to predict the California Bearing Ratio (CBR) using soil index properties in Ogbia-Nembe road in the Niger Delta region of Nigeria. The determination of CBR of soil is a laborious operation that requires a longer time and materials leading to increased cost and schedule;this can be reduced by adopting an empirical-mathematical model that can predict the CBR using other simpler soil index properties such as Plastic Limit (PL), the Liquid Limit (LL), the Plasticity Index (PI) and the Moisture Content (MC), which are less laborious and take lesser time to obtain. Thirteen models were developed to understand the relationship between these soil index properties: the independent variable and the California Bearing Ratio (CBR): the dependent variable;Six linear, Six quadratic and One multiple linear regression models were developed for this relationship. Analysis of variance (ANOVA) on the thirteen models showed that the Optimum Moisture Content (OMC) and the Maximum Dry Density (MDD) are better independent variables for the prediction of the CBR value of Ogbia-Nembe soil generating a quadratic model and a multiple linear regression model having a better coefficient of determination R<sup>2</sup> = 0.96 and 0.94 respectively, mean square error (MSE) of 0.74 and 1.152 respectively with Root mean square errors of 0.861 and 1.073 accordingly. These models were used to predict the CBR of the soil. The CBR values predicted by the model were further compared with those of the actual experimental test and found to be relatively consistent with minimal variance. This establishes that CBR of any soil can be predicted from the Index Property of the soil and this is more economical and takes lesser time and can be universally adopted for soil investigation.展开更多
Phosphorus (P) and potassium (K) levels in southern Brazilian (Rio Grande do Sul, RS) soils are largely below the critical concentrations more than four decades after implementation of the officially recommended syste...Phosphorus (P) and potassium (K) levels in southern Brazilian (Rio Grande do Sul, RS) soils are largely below the critical concentrations more than four decades after implementation of the officially recommended system. This study aims to evaluate the increase in P and K levels in 0-10 and 0-20 cm deep samples from no-till soils using the Mehlich-1 (M1) and Mehlich-3 (M3) extractants as well as resin methods and to estimate the amount of P2O5 and K2O fertilizers necessary to increase the P and K soil levels by 1 mg·kg-1. The study was conducted in fields cultivated using a no-till system (direct planting) to grow soybeans, wheat, maize, pasture, and cover crops and fertilized with P2O5 and K2O. Soil samples were collected from the 0-10 and 0-20 cm soil layers and analyzed by the M1, M3, and resin methods. The results demonstrated that the P and K levels increased in the 0-10 and 0-20 cm layers. However, the amount of these levels increased depending on the source of phosphate fertilization and on the P and K extraction methods used. The amount of P2O5 fertilization needed to raise the P level by 1 mg·kg-1 was greater in the 0-20 cm layer than in the 0-10 cm layer, and the amount of K2O fertilization needed to raise the K level by 1 mg·kg-1 was higher in the 0-10 cm layer than in the 0-20 cm layer.展开更多
This study was performed to examine the separate and simultaneous influence of predictive models’choice alongside sample ratios selection in soil organic matter(SOM).The research was carried out in northern Morocco,c...This study was performed to examine the separate and simultaneous influence of predictive models’choice alongside sample ratios selection in soil organic matter(SOM).The research was carried out in northern Morocco,characterized by relatively cold weather and diverse geological conditions.The dataset herein used accounted for 1591 soil samples,which were randomly split into the following ratios:10%(∼150 sample ratio),20%(∼250 sample ratio),35%(∼450 sample ratio),50%(∼600 sample ratio)and 95%(∼1200 sample ratio).Models herein involved were ordinary kriging(OK),regression kriging(RK),multiple linear regression(MLR),random forest(RF),quantile regression forest(QRF),Gaussian process regression(GPR)and an ensemble model.The findings in the study showed that the accuracy of SOM prediction is sensitive to both predictive models and sample ratios.OK combined with 95%sample ratio performed equally to RF in conjunction with all the sample ratios,as the latter did not show much sensitivity to sample ratios.ANOVA results revealed that RF with a∼10%sample ratio could also be optimum for predicting SOM in the study area.In conclusion,the findings herein reported could be instrumental for producing cost-effective detailed and accurate spatial estimation of SOM in other sites.Furthermore,they could serve as a baseline study for future research in the region or elsewhere.Therefore,we recommend conducting series of simulation of all possible combinations between various predictive models and sample ratios as a preliminary step in soil organic matter prediction.展开更多
Background:Soil erosion is among the foremost causes of declining soil resources in Ethiopia,which in turn affect agricultural productivity.To limit this problem,for the last two decades in Gumara watershed,soil and w...Background:Soil erosion is among the foremost causes of declining soil resources in Ethiopia,which in turn affect agricultural productivity.To limit this problem,for the last two decades in Gumara watershed,soil and water conservation measures have been practiced through free labor community mass-mobilization.However,their effect on soil fertility has not been evaluated.This study investigated the impact of implemented soil and water conservation measures on fertility improvement in the Gumara watershed.Both composite and core soil samples were taken from upstream,midstream,and downstream adjacent conserved and non-conserved cultivated and grazing plots.Selected soil fertility indicators were analyzed using standard laboratory procedures.Results:Soil and water conservation practices have resulted in a statistically significantly higher mean values of total nitrogen,exchangeable Na+and Mg2+at p<0.01,and of soil organic carbon and organic matter at p<0.05 in the watershed.The clay content,soil reaction,cation exchange capacity,and exchangeable K+showed nonsignificant,but higher mean values in conserved plots.Furthermore,the effects of conservation practices on soil properties were found more effective in cultivated land uses as compared to that of grazing land uses.This is because conservation treatments had significant effects on organic carbon,total nitrogen,exchangeable Na+and Mg2+in cultivated land uses but only on exchangeable Na+in grazing land uses.The interaction effect of treatments and land uses did not reach a statistically significant result for any of the soil properties considered in this study.Conclusion:Conservation measures have important implications for improving soil fertility in the Gumara watershed.Therefore,proper guidance and follow-up,use of agro-forestry and grass strips,and maintenance are required for the watershed’s sustainability and good soil conditions.展开更多
Numerous scientific challenges arise when designing a soil monitoring network (SMN), especially when assessing large areas and several properties that are driven by numerous controlling factors of various origins and ...Numerous scientific challenges arise when designing a soil monitoring network (SMN), especially when assessing large areas and several properties that are driven by numerous controlling factors of various origins and scales. Different broad approaches to the establishment of SMNs are distinguished. It is essential to establish an adequate sampling protocol that can be applied rigorously at each sampling location and time. We make recommendations regarding the within-site sampling of soil. Different statistical methods should be associated with the different types of sampling design. We review new statistical methods that account for different sources of uncertainty. Except for those parameters for which a consensus exists, the question of testing method harmonisation remains a very difficult issue. The establishment of benchmark sites devoted to harmonisation and inter-calibration is advocated as a technical solution. However, to our present knowledge, no study has addressed crucial scientific issues such as how many calibration sites are necessary and how to locate them.展开更多
为探究SHAW(Simultaneous heat and water)模型中输入参数不确定性在模拟积雪覆盖条件下土壤热过程中对输出结果造成的影响以及关键影响因素,以松嫩平原黑土区东北农业大学试验场为研究区域,运用SHAW模型模拟积雪覆盖条件下6个不同深度...为探究SHAW(Simultaneous heat and water)模型中输入参数不确定性在模拟积雪覆盖条件下土壤热过程中对输出结果造成的影响以及关键影响因素,以松嫩平原黑土区东北农业大学试验场为研究区域,运用SHAW模型模拟积雪覆盖条件下6个不同深度土层热过程动态变化情况,并结合拉丁超立方取样(Latin hypercube sampling,LHS)方法,采用标准秩逐步回归探究参数不确定性对土壤冻结深度和温度输出不确定性的影响。结果表明:SHAW模型能够反映土壤冻融规律,6个深度土层温度的模拟值与实测值平均绝对误差小于2℃,选取的参数对土壤温度的输出敏感性较弱,而初始积雪厚度对土壤冻结深度的输出起主导作用。总体而言,SHAW模型基于LHS抽样和标准秩逐步回归方法可用于模拟积雪覆盖条件下土壤热过程模拟研究。展开更多
文摘Twenty five surface (0—20 cm) soil samples were collected from different locations in Egypt representing non polluted, moderately and highly polluted soils. The aim of this study was to evaluate total Co content in alluvial soils of Delta in Egypt using the delayed neturen activation analysis technique (DNAA). The two prominent gamma ray lines at 1173 2 and 1332 5 keV was efficiently used for 60 Co determination. Co content in non polluted soil samples ranged between 13 12 to 23 20 ppm Co with an average of 18 16±4.38 ppm. Cobalt content in moderately polluted soils ranged between 26 5 to 30 00 ppm with an average of 28 3±1.3 ppm. The highest Co levels (ranged from 36 to 64 69 ppm with an average of 51 9±9.5); were observed in soil samples collected from, either highly polluted agricultural soils due to prolonged irrigation with industrial wastewater or surface soil samples from industrial sites.
文摘This study developed empirical-mathematical models to predict the California Bearing Ratio (CBR) using soil index properties in Ogbia-Nembe road in the Niger Delta region of Nigeria. The determination of CBR of soil is a laborious operation that requires a longer time and materials leading to increased cost and schedule;this can be reduced by adopting an empirical-mathematical model that can predict the CBR using other simpler soil index properties such as Plastic Limit (PL), the Liquid Limit (LL), the Plasticity Index (PI) and the Moisture Content (MC), which are less laborious and take lesser time to obtain. Thirteen models were developed to understand the relationship between these soil index properties: the independent variable and the California Bearing Ratio (CBR): the dependent variable;Six linear, Six quadratic and One multiple linear regression models were developed for this relationship. Analysis of variance (ANOVA) on the thirteen models showed that the Optimum Moisture Content (OMC) and the Maximum Dry Density (MDD) are better independent variables for the prediction of the CBR value of Ogbia-Nembe soil generating a quadratic model and a multiple linear regression model having a better coefficient of determination R<sup>2</sup> = 0.96 and 0.94 respectively, mean square error (MSE) of 0.74 and 1.152 respectively with Root mean square errors of 0.861 and 1.073 accordingly. These models were used to predict the CBR of the soil. The CBR values predicted by the model were further compared with those of the actual experimental test and found to be relatively consistent with minimal variance. This establishes that CBR of any soil can be predicted from the Index Property of the soil and this is more economical and takes lesser time and can be universally adopted for soil investigation.
基金Authors are thankfully to all Universities and agricultural extensions programs from Rio Grande do Sul State that kindly support this work allowing access in their experiments to collect informationto support us with crop yield and crop biomass data.
文摘Phosphorus (P) and potassium (K) levels in southern Brazilian (Rio Grande do Sul, RS) soils are largely below the critical concentrations more than four decades after implementation of the officially recommended system. This study aims to evaluate the increase in P and K levels in 0-10 and 0-20 cm deep samples from no-till soils using the Mehlich-1 (M1) and Mehlich-3 (M3) extractants as well as resin methods and to estimate the amount of P2O5 and K2O fertilizers necessary to increase the P and K soil levels by 1 mg·kg-1. The study was conducted in fields cultivated using a no-till system (direct planting) to grow soybeans, wheat, maize, pasture, and cover crops and fertilized with P2O5 and K2O. Soil samples were collected from the 0-10 and 0-20 cm soil layers and analyzed by the M1, M3, and resin methods. The results demonstrated that the P and K levels increased in the 0-10 and 0-20 cm layers. However, the amount of these levels increased depending on the source of phosphate fertilization and on the P and K extraction methods used. The amount of P2O5 fertilization needed to raise the P level by 1 mg·kg-1 was greater in the 0-20 cm layer than in the 0-10 cm layer, and the amount of K2O fertilization needed to raise the K level by 1 mg·kg-1 was higher in the 0-10 cm layer than in the 0-20 cm layer.
基金the support from the Ministry of Education,Youth and Sports of the Czech Republic(project No.CZ.02.1.01/0.0/0.0/16_019/0000845)is also acknowledged.
文摘This study was performed to examine the separate and simultaneous influence of predictive models’choice alongside sample ratios selection in soil organic matter(SOM).The research was carried out in northern Morocco,characterized by relatively cold weather and diverse geological conditions.The dataset herein used accounted for 1591 soil samples,which were randomly split into the following ratios:10%(∼150 sample ratio),20%(∼250 sample ratio),35%(∼450 sample ratio),50%(∼600 sample ratio)and 95%(∼1200 sample ratio).Models herein involved were ordinary kriging(OK),regression kriging(RK),multiple linear regression(MLR),random forest(RF),quantile regression forest(QRF),Gaussian process regression(GPR)and an ensemble model.The findings in the study showed that the accuracy of SOM prediction is sensitive to both predictive models and sample ratios.OK combined with 95%sample ratio performed equally to RF in conjunction with all the sample ratios,as the latter did not show much sensitivity to sample ratios.ANOVA results revealed that RF with a∼10%sample ratio could also be optimum for predicting SOM in the study area.In conclusion,the findings herein reported could be instrumental for producing cost-effective detailed and accurate spatial estimation of SOM in other sites.Furthermore,they could serve as a baseline study for future research in the region or elsewhere.Therefore,we recommend conducting series of simulation of all possible combinations between various predictive models and sample ratios as a preliminary step in soil organic matter prediction.
文摘Background:Soil erosion is among the foremost causes of declining soil resources in Ethiopia,which in turn affect agricultural productivity.To limit this problem,for the last two decades in Gumara watershed,soil and water conservation measures have been practiced through free labor community mass-mobilization.However,their effect on soil fertility has not been evaluated.This study investigated the impact of implemented soil and water conservation measures on fertility improvement in the Gumara watershed.Both composite and core soil samples were taken from upstream,midstream,and downstream adjacent conserved and non-conserved cultivated and grazing plots.Selected soil fertility indicators were analyzed using standard laboratory procedures.Results:Soil and water conservation practices have resulted in a statistically significantly higher mean values of total nitrogen,exchangeable Na+and Mg2+at p<0.01,and of soil organic carbon and organic matter at p<0.05 in the watershed.The clay content,soil reaction,cation exchange capacity,and exchangeable K+showed nonsignificant,but higher mean values in conserved plots.Furthermore,the effects of conservation practices on soil properties were found more effective in cultivated land uses as compared to that of grazing land uses.This is because conservation treatments had significant effects on organic carbon,total nitrogen,exchangeable Na+and Mg2+in cultivated land uses but only on exchangeable Na+in grazing land uses.The interaction effect of treatments and land uses did not reach a statistically significant result for any of the soil properties considered in this study.Conclusion:Conservation measures have important implications for improving soil fertility in the Gumara watershed.Therefore,proper guidance and follow-up,use of agro-forestry and grass strips,and maintenance are required for the watershed’s sustainability and good soil conditions.
文摘Numerous scientific challenges arise when designing a soil monitoring network (SMN), especially when assessing large areas and several properties that are driven by numerous controlling factors of various origins and scales. Different broad approaches to the establishment of SMNs are distinguished. It is essential to establish an adequate sampling protocol that can be applied rigorously at each sampling location and time. We make recommendations regarding the within-site sampling of soil. Different statistical methods should be associated with the different types of sampling design. We review new statistical methods that account for different sources of uncertainty. Except for those parameters for which a consensus exists, the question of testing method harmonisation remains a very difficult issue. The establishment of benchmark sites devoted to harmonisation and inter-calibration is advocated as a technical solution. However, to our present knowledge, no study has addressed crucial scientific issues such as how many calibration sites are necessary and how to locate them.