Soil Texture Factors Research Articles

High-risk driving factors of rain-induced flooding hazard events on the Loess Plateau and its ecological subregions

Rain-induced flooding hazards are prevalent on the Loess Plateau (LP). Descriptive statistics, kernel density estimation, and geographical detector methods were used to explore the spatial and temporal distribution, driving factors, and their high-risk intervals of rain-induced flooding hazard events (RFHEs) on the LP and whether they differ across the entire LP and its ecological subregions. The findings showed that 91 RFHEs occurred mainly in the south-central LP during 2004–2020. The daily rainfall, surface relief amplitude (SRA), elevation, normalized difference vegetation index (NDVI), soil texture, and gross domestic product (GDP) were identified as the driving factors of RFHEs on the LP. However, the driving factors of RFHEs in the Sandy and Agricultural Irrigation Regions (Subregion C), and Earth-rocky Mountainous Region and River Valley Plain Region (Subregion D) all had an added population factor compared to the entire LP, but they lacked NDVI and SRA factors, respectively. The driving factors for the Loess Plateau Gully Region (Subregion A) lacked SRA and soil texture factors. The Loess Hilly and Gully Region (Subregion B) lacked NDVI, soil texture, and population factors. There were also differences between high-risk intervals on the LP and its subregions. The high-risk daily rainfall for the entire LP was 64.5 mm, while it was 64.5, 82.3, 14.7, and 50.0 mm for subregions A, B, C, and D, respectively. Therefore, adopting uniform standards on the LP may over-estimate or under-estimate RFHE occurrence in ecological subregions. These findings contribute to guiding decision-makers involved in ecosystem management and hazard prevention.

A holistic analysis of Chinese sponge city cases by region: Using PLS-SEM models to understand key factors impacting LID performance

Sponge city is a national sustainable stormwater management program proposed by the Chinese government to deal with urban water issues (e.g., flooding, poor water quality) brought on by climate change and urbanization. Various strategies for sponge city construction are required since environmental constraints differ regionally across the country. To identify regional variations, reveal the inner links between externalities and design elements in sponge city construction, and offer practical suggestions, efforts in two directions are made based on the data of 68 sponge city cases around China: 1) discussing design parameters of four Low Impact Development (LID) facilities, including bioretention cell, permeable pavement, grass swale, and sunken green space, under four regionalization maps of hydrologic, climatic, landform and soil texture factors, and 2) building a holistic Partial Least Squares-Structural Equation Modelling (PLS-SEM) model illustrating the relationship between local characteristics, LID system design, and LID system performance in sponge city construction. The results show that: 1) rainfall and landform factors have great impact on LID facilities design, as their depths tend to be higher in water rich areas and coastal areas. 2) LID types and areas are positively influenced (+0.745) by the total area and permeable portion of a project, while the LID system performance (water quantity and quality control) is negatively impacted (−0.407) by the rainfall amount and clay fraction. 3) comprehensive LIDs choice instead of single LID facility shows more significant effect on improving LID system performance. It is recommended to establish different design standards and assessment indexing systems tailored to local environment when constructing sponge city projects.

Unraveling the significance of soil organic carbon-gravel parameterization: Insights into soil water and heat transport on the Tibetan Plateau

In the Tibetan Plateau (TP) soil water and heat transfer process, soil organic carbon (SOC) and gravel content are considered as the most influential soil texture factors. However, the issues of underestimating SOC and neglecting gravel effect affected the simulation performance of CLM5.0 on soil moisture (SM) and soil temperature (ST). This paper proposed a new parameterization scheme, the organic carbon-gravel (OC-G) scheme, to simulate ST and SM from 1990 to 2018. The results showed that correlation between the simulated and observed ST or SM was higher, and the error was smaller, after the modification of the parameterization scheme. This improvement justifies the applicability of the scheme for soil hydrothermal simulations on the TP. The experiment described that ST and SM were more sensitive to changes in SOC content. And changes in gravel or SOC content had the “Same-Frequency” effect in the northeast and southeast TP. When the SOC and gravel content changed at the same time, the effects on ST and SM were a “cumulative” effect. The change directly affected the memory time of ST and SM in summer. Specifically, when the SOC content was increased, the memory time of SM increased in the northwest and decreased in the southeast. When gravel content was increased, the memory time of SM decreased in the northwest but increased in the southeast, but the memory time of ST remained largely unchanged. Changes to the abnormal duration may alter summer weather and climate in Eastern China.

Time-Lag Effect of Climate Conditions on Vegetation Productivity in a Temperate Forest–Grassland Ecotone

Climate conditions can significantly alter the vegetation net primary productivity (NPP) in many of Earth’s ecosystems, although specifics of NPP–climate condition interactions, especially time-lag responses on seasonal scales, remain unclear in ecologically sensitive forest–grassland ecotones. Based on the Moderate-Resolution Imaging Spectroradiometer (MODIS) and meteorological datasets, we analyzed the relationship between NPP and precipitation, temperature, and drought during the growing season (April–August), considering the time-lag effect (0–5 months) at the seasonal scale in Hulunbuir, Inner Mongolia, China from 2000 to 2018. The results revealed a delayed NPP response to precipitation and drought throughout the growing season. In April, the precipitation in the 4 months before (i.e., the winter of the previous year) explained the variation in NPP. In August, the NPP in some areas was influenced by the preceding 1~2 months of drought. The time-lag effect varied with vegetation type and soil texture at different spatial patterns. Compared to grass and crop, broadleaf forest and meadow exhibited a longer legacy of precipitation during the growing season. The length of the time-lag effects of drought on NPP increased with increasing soil clay content during the growing season. The interaction of vegetation types and soil textures can explain 37% of the change in the time-lag effect of the NPP response to PPT on spatial pattern. Our findings suggested that preceding precipitation influences vegetation growth at the early stages of growth, while preceding drought influences vegetation growth in the later stages of growth. The spatial pattern of the time lag was significantly influenced by interaction between vegetation type and soil texture factors. This study highlights the importance of considering the time-lag effects of climate conditions and underlying drivers in further improving the prediction accuracy of NPP and carbon sinks in temperate semiarid forest–grassland ecotones.

Spatial distribution dependency of soil organic carbon content to important environmental variables

Abstract Soil organic carbon (SOC) has a vital role in the physical, chemical and biological behavior of the soil, and therefore prediction of the amount and mapping spatial distribution of SOC is necessary for sustainable soil management. However, the relationship between SOC and remotely sensed and easily accessible variables have been rarely reported. The main objective of the present study is, therefore, to estimate SOC using the remote sensing of satellite images as well as some field variables for the Shazand Watershed, Iran. Towards that, 140 soil samples were taken from the top 30-cm of the soil from homogeneous units representing an area >1 km2 to measure SOC. The potential relationship between SOC and some remote sensing-based indices including Enhanced Vegetation Index (EVI), Difference vegetation index (DVI), Optimized Soil Adjusted Vegetation Index (OSAVI), Soil Adjusted Vegetation Index (SAVI), Modified Soil Adjusted Vegetation Index (MSAVI), Normalized Difference Vegetation Index (NDVI), Coloration Index (CI), Normalized Difference Moisture Index (NDMI), and some topographical and soil texture factors viz. elevation, slope, aspect, Topographical Wetness Index (TWI), clay and silt content of soil were assessed for the Shazand Watershed. In this regard, the relationships between SOC and environmental variables were analyzed using Ordinary Least Square (OLS), Geographically Weighted Regression (GWR), and Random Forest (RF) analyses. The results showed that none of the models indicated a good predictive performance due to low R2. However, CI was found as a better predictor (R2 = 0.258 for GWR and R2 = 0.040 for OLS; p-value

PRINCIPAL COMPONENT ANALYSIS OF FACTORS DETERMINING PHOSPHATE ROCK DISSOLUTION ON ACID SOILS

Many of the agricultural soils in Indonesia are acidic and low in both total and available phosphorus which severely limits their potential for crops production. These problems can be corrected by application of chemical fertilizers. However, these fertilizers are expensive, and cheaper alternatives such as phosphate rock (PR) have been considered. Several soil factors may influence the dissolution of PR in soils, including both chemical and physical properties. The study aimed to identify PR dissolution factors and evaluate their relative magnitude. The experiment was conducted in Soil Chemical Laboratory, Universiti Putra Malaysia and Indonesian Center for Agricultural Land Resources Research and Development from January to April 2002. The principal component analysis (PCA) was used to characterize acid soils in an incubation system into a number of factors that may affect PR dissolution. Three major factors selected were soil texture, soil acidity, and fertilization. Using the scores of individual factors as independent variables, stepwise regression analysis was performed to derive a PR dissolution function. The factors influencing PR dissolution in order of importance were soil texture, soil acidity, then fertilization. Soil texture factors including clay content and organic C, and soil acidity factor such as P retention capacity interacted positively with P dissolution and promoted PR dissolution effectively. Soil texture factors, such as sand and silt content, soil acidity factors such as pH, and exchangeable Ca decreased PR dissolution.

PRINCIPAL COMPONENT ANALYSIS OF FACTORS DETERMINING PHOSPHATE ROCK DISSOLUTION ON ACID SOILS

Many of the agricultural soils in Indonesia are acidic and low in both total and available phosphorus which severely limits their potential for crops production. These problems can be corrected by application of chemical fertilizers. However, these fertilizers are expensive, and cheaper alternatives such as phosphate rock (PR) have been considered. Several soil factors may influence the dissolution of PR in soils, including both chemical and physical properties. The study aimed to identify PR dissolution factors and evaluate their relative magnitude. The experiment was conducted in Soil Chemical Laboratory, Universiti Putra Malaysia and Indonesian Center for Agricultural Land Resources Research and Development from January to April 2002. The principal component analysis (PCA) was used to characterize acid soils in an incubation system into a number of factors that may affect PR dissolution. Three major factors selected were soil texture, soil acidity, and fertilization. Using the scores of individual factors as independent variables, stepwise regression analysis was performed to derive a PR dissolution function. The factors influencing PR dissolution in order of importance were soil texture, soil acidity, then fertilization. Soil texture factors including clay content and organic C, and soil acidity factor such as P retention capacity interacted positively with P dissolution and promoted PR dissolution effectively. Soil texture factors, such as sand and silt content, soil acidity factors such as pH, and exchangeable Ca decreased PR dissolution.

Evaluation of generic farming conditions in Eastern Lithuania

Agricultural experts’ perception and knowledge towards farming conditions and natural agro-environmental problems are important to develop a sustainable rural strategy and may serve when planning land use in sloping agricultural areas to avoid land abandonment. The objective of investigations was to analyze the attitudes of agricultural experts in the Eastern Lithuania region towards the state of the generic agrarian sector, soil erosion processes and natural handicaps. Replies of respondents indicated that the means (the Likert Scale) of the evaluation towards the items “Soil quality”, “Agricultural sector development” and “Land suitability for generic agricultural activity” were 2.68, 3.11 and 2.73, respectively. The evaluations indicating that the mean score perceived by respondents towards impact of soil erosion on common farming activity in the region was 2.63. A questionnaire study showed that respondents recognized that the impact of terrain and soil texture factors on the potential of soil erosion processes is the highest in the region, thus the factor of soil type has been evaluated as the least important. The most frequently noticed topographical parameter of the terrain influencing the intensity of soil erosion was slope steepness (63.1% of respondents), followed by slope aspect (21.1%) and length (15.8%). Hilly terrain and soil acidity constraints by frequency 24.5 and 18.9%, respectively, have showed the most important attitude of respondents, in the content of the natural handicaps limiting successful farming activity in the region. However, the study disclosed that unfavourable climate conditions and soil cover diversity were the two least crucial natural constraints for farming. These empirical findings intended to bring benefits and can help in decision-making framework in order to decide the best soil conservation measures and improving farming conditions in agricultural areas under natural handicaps.

Agroecological factors correlated to soil DNA concentrations of Rhizoctonia in dryland wheat production zones of Washington state, USA.

The necrotrophic soilborne fungal pathogens Rhizoctonia solani AG8 and R. oryzae are principal causal agents of Rhizoctonia root rot and bare patch of wheat in dryland cropping systems of the Pacific Northwest. A 3-year survey of 33 parcels at 11 growers' sites and 60 trial plots at 12 Washington State University cereal variety test locations was undertaken to understand the distribution of these pathogens. Pathogen DNA concentrations in soils, quantified using real-time polymerase chain reaction, were correlated with precipitation, temperature maxima and minima, and soil texture factors in a pathogen-specific manner. Specifically, R. solani AG8 DNA concentration was negatively correlated with precipitation and not correlated with temperature minima, whereas R. oryzae concentration was correlated with temperature minima but not with precipitation. However, both pathogens were more abundant in soils with higher sand and lower clay content. Principal component analysis also indicated that unique groups of meteorological and soil factors were associated with each pathogen. Furthermore, tillage did not affect R. oryzae but affected R. solani AG8 at P = 0.06. Lower soil concentrations of R. solani AG8 but not R. oryzae occurred when the previously planted crop was a broadleaf (P < 0.05). Our findings showed that R. solani AG8 concentrations were consistent with the general distribution of bare patch symptoms, based on field observations and surveys of other pathogens, but was present at many sites in which bare patch symptoms were not evident. Management of Rhizoctonia root rot and bare patch should account for the likelihood that each pathogen is affected by a unique group of agroecological variables.

Possibilities of the specification of the agricultural land evaluation according to the land texture

Presently the evaluation of agricultural land is given by categorization of agricultural soil, described via the system of soil ecological quality units (BPEJ) in the Czech Republic. This article is dealing with the possibilities of the soil value specifications based on conditions given by different soil texture. The basic is the model design of corresponding connections among indicators of soil fertility by means of statistical analysis of particular soil texture factors. The results show, that the strongest dependence is among factors of soil fertility with categories up to the 0.05 mm and up to the 2 mm in topsoil and also in the under soil. Average yield difference in terms of the main soil-climatic quality unit according to category of soil texture is 0.56 t of wheat per hectare and balances in intervals from 0.02 to 2.59 t per hectare. The average range of annual gross income changes is approximately 4,5 % respectively 3,8 % of land price in comparison with values without taking into account the distinction of the soil texture factors.