Effects of soil water content and organic matter addition on the speciation and bioavailability of heavy metals

2012 ◽  
Vol 423 ◽  
pp. 55-61 ◽  
Author(s):  
Maria C. Hernandez-Soriano ◽  
Jose C. Jimenez-Lopez
Keyword(s):  
Heavy Metals ◽  
Organic Matter ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Organic Matter Addition

Effects of Ecological Projects on Grassland Soil Physicochemical Properties in Three-River Headwater

2013 ◽  
Vol 807-809 ◽  
pp. 843-847
Author(s):  
Xu Dong Zhao ◽  
De Gang Zhang ◽  
Li Na Shi ◽  
Yong Shun Yang
Keyword(s):  
Organic Matter ◽  
Physicochemical Properties ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Available Phosphorus ◽  
Soil Physicochemical Properties ◽  
Total N ◽  
Effective Measure ◽  
Artificial Grassland

The depth variations of soil physicochemical properties in the degraded native grasslands and the artificially restored grasslands were studied in the Three-river headwater areas of Qinghai-Tibetan plateau, China. The results showed: (1) With the increase of the gradient of restoration years, soil water content, total chemical properties, total potassium, phosphorus, available phosphorus and potassium were increased thereafter in the artificial grasslands. (2) With the increase of grassland degradation gradient, soil water content was gradually reduced, and the total N, K, the organic matter didnt gradually reduced also. (3) Both restoration years and degradation degree didnt influence the nutrient distribution in soil. (4) The organic matter, total N and K of degraded grassland were increased by artificial grassland construction. Therefore, artificial grassland construction canbe used as an effective measure of ecological projects in the Three-river headwater area.

Distribution of carbon and nutrients and fluxes of mineral nitrogen after clear-felling a Pinusradiata plantation

1990 ◽  
Vol 20 (9) ◽  
pp. 1490-1497 ◽  
Author(s):  
P. J. Smethurst ◽  
E. K. S. Nambiar
Keyword(s):  
Organic Matter ◽  
Soil Temperature ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
N Mineralization ◽  
Soil Depth ◽  
Mineral N ◽  
Southeastern Australia ◽  
Nutrients Fluxes

The effects of clear-felling and slash removal on the distribution of organic matter and nutrients, fluxes of mineral N, and soil water and temperature were studied in a 37-year-old Pinusradiata D. Don plantation, on a sandy Podzol in southeastern Australia. Slash, litter, and the top 30 cm of soil combined contained 1957 kg N•ha−1, of which slash and litter contained 12 and 25%, respectively. Therefore, loss of slash and litter due to burning or other intensive site preparation practices would substantially reduce the N capital at the site. During the first 18 months after clear-felling, soil water content in the clear-felled area was up to 50% higher than in the uncut plantation, but there were only minor differences in soil temperature. Slash removal decreased the water content of litter, but had little effect on the water content or temperature of the soil. In the uncut plantation, N mineralized in litter and soil was completely taken up by the trees. Following clear-felling, rates of N mineralization increased in litter after 4 months, and in soil after 12 months, but changes were less pronounced with slash removal. After clear-felling, increased mineralization and the absence of trees (no uptake) led to increased concentrations of mineral N in both litter and soil, 64–76% of which was leached below the 30 cm soil depth prior to replanting. Despite leaching, concentrations of mineral N after clear-felling remained higher than those in the uncut plantation for at least 3 years.

scholarly journals Evaluation of Improved Model to Accurately Monitor Soil Water Content

Water ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 3441
Author(s):  
Jingyu Ji ◽  
Junzeng Xu ◽  
Yixin Xiao ◽  
Yajun Luan
Keyword(s):  
Organic Matter ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Soil Texture ◽  
Irrigation Management ◽  
Clay Fraction ◽  
Organic Matter Content ◽  
Matter Content ◽  
Improved Model

The accurate monitoring of soil water content during the growth of crops is of great importance to improve agricultural water use efficiency. The Campbell model is one of the most widely used models for monitoring soil moisture content from soil thermal conductivities in farmland, which always needs to be calibrated due to the lack of adequate original data and the limitation of measurement methods. To precisely predict the water content of complex soils using the Campbell model, this model was evaluated by investigating several factors, including soil texture, bulk density and organic matter. The comparison of the R2 and the reduced Chi-Sqr values, which were calculated by Origin, was conducted to calibrate the Campbell model calculated. In addition, combining factors of parameters, a new parameter named m related to soil texture and the organic matter was firstly introduced and the original fitting parameter, E, was improved to an expression related to clay fraction and the organic matter content in the improved model. The soil data collected from both the laboratory and the previous literature were used to assess the revised model. The results show that most of the R2 values of the improved model are >0.95, and the reduced Chi-Sqr values are <0.01, which presents a better matching performance compared to the original. It is concluded that the improved model provides more accurate monitoring of soil water content for water irrigation management.

scholarly journals Long-Term Soil Water Content and Exchangeable Ca Interact to Stabilize Organic Matter

2020 ◽  
Author(s):  
Itamar Shabtai ◽  
Srabani Das ◽  
Thiago Inagaki ◽  
Johannes Lehmann
Keyword(s):  
Organic Matter ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Exchangeable Ca

Long-term soil water content and exchangeable Ca interact to stabilize organic matter

2020 ◽  
Author(s):  
Itamar Shabtai ◽  
Srabani Das ◽  
Thiago Inagaki ◽  
Ingrid Kogel-Knabner ◽  
Johannes Lehmann
Keyword(s):  
Organic Matter ◽  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Microbial Respiration ◽  
Plant Litter ◽  
Exchangeable Ca

&lt;p&gt;Organo-mineral interactions stabilize soil organic matter (SOM) by protecting from microbial enzymatic attack. Soil water content affects aggregation, mineral weathering, and microbial respiration, thus influencing the relative importance of SOM stabilization mechanisms. While the response of microbial respiration to momentary changes in water content is well established, it is unclear how microbial activity will impact stabilization mechanisms under different long-term moisture contents.&lt;/p&gt;&lt;p&gt;To understand how long-term soil moisture affects SOM stabilization mechanisms we studied fallow soils from upstate New York situated on a naturally occurring water content gradient. Wetter (but not saturated) soils contained more exchangeable Ca and had more strongly stabilized SOM, resulting in SOM accumulation. But it was not clear whether Ca-driven surface interactions or occlusion in micro-aggregates was more important, and if interactions with Fe and Al played a role in the Ca-poor soils. Also, the role of biotic drivers in SOM stabilization at different water contents was unknown.&lt;/p&gt;&lt;p&gt;We tested which mechanisms governed SOM stabilization by determining C and N contents and natural isotope abundances in particulate and mineral-associated organic matter fractions. We also extracted the C bound to Ca and to reactive Fe+Al phases. Wetter, Ca-rich soils had higher oPOM content, and in the heavy mineral fraction, higher relative concentrations of Ca-bound C, lower C:N values, and more oxidized C forms. In addition, wetter soils had greater microbial biomass. Together, these results showed that high long-term soil moisture increased microbial SOM cycling, and that processed SOM was better stabilized, in agreement with the recent notion that stable SOM consists of processed labile C. Additionally, higher soil moisture augmented the role of Ca in SOM stabilization over that of Al+Fe phases. We then manipulated the exchangeable Ca content and incubated soils with &lt;sup&gt;13&lt;/sup&gt;C&lt;sup&gt;15&lt;/sup&gt;N labeled plant litter. Ca-amended soils emitted less CO&lt;sub&gt;2 &lt;/sub&gt;while incubated with litter, confirming that Ca is instrumental in SOM stabilization. Tracing the labeled isotopes in the gaseous phase and soil fractions will allow us to gain a clearer understanding of how water content and soil Ca interact to stabilize SOM.&amp;#160;&amp;#160;&lt;/p&gt;

scholarly journals Soil Water Content Sensor Response to Organic Matter Content under Laboratory Conditions

Sensors ◽  
2016 ◽  
Vol 16 (8) ◽  
pp. 1239 ◽  
Author(s):  
Ali Fares ◽  
Ripendra Awal ◽  
Haimanote Bayabil
Keyword(s):  
Organic Matter ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Organic Matter Content ◽  
Matter Content ◽  
Sensor Response ◽  
Laboratory Conditions

The relations between soil water retention characteristics, particle size distributions, bulk densities and calcium carbonate contents for Danish soils

2005 ◽  
Vol 36 (3) ◽  
pp. 235-244 ◽  
Author(s):  
Niels Henrik Jensen ◽  
Thomas Balstrøm ◽  
Henrik Breuning-Madsen
Keyword(s):  
Particle Size ◽  
Organic Matter ◽  
Particle Size Distribution ◽  
Water Content ◽  
Bulk Density ◽  
Soil Water ◽  
Soil Water Content ◽  
Pressure Head ◽  
Pedotransfer Functions ◽  
Regression Equations

A database containing about 800 soil profiles located in a 7-km grid covering Denmark has been used to develop a set of regression equations of soil water content at pressure heads −1, −10, −100 and −1500 kPa versus particle size distribution, organic matter, CaCO3 and bulk density. One purpose was to elaborate equations based on soil parameters available in the Danish Soil Classification's texture database of particle size distribution and organic matter. It was also tested to see if inclusion of bulk density or CaCO3 content (in CaCO3-containing samples) as predictors or grouping in surface and subsurface horizons or textural classes improved the regression equations. Compared to existing Danish equations based on much fewer observations the accuracies of the new equations were better. The equations also predicted the soil water content at the measured pressure heads more accurately than the pedotransfer functions developed in HYPRES (Hydraulic Properties of European Soils). Introducing bulk density as a predictor improved the equation for the pressure head of −1 kPa but not for the lower ones. The grouping of data sets in surface and subsurface horizons or in textural classes did not improve the equations. Based on the equations a set of van Genuchten parameters for soil types in the Danish Soil Classification was elaborated. The prediction of soil water content, especially at pressure head −1 kPa, is more accurate using these van Genuchten parameters than using the pedotransfer functions developed in relation to the HYPRES database from a broad range of European soils.

A numerical approach for understanding the main parameters and processes influencing the soil organic matter decay in wildfire events

2020 ◽  
Author(s):  
Sebastián A. Aedo ◽  
Carlos A. Bonilla
Keyword(s):  
Thermal Conductivity ◽  
Organic Matter ◽  
Soil Organic Matter ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
High Temperatures ◽  
Pore Radius ◽  
Radiative Energy ◽  
Soil Response

&lt;p&gt;High temperatures reached at topsoil during wildfires can induce changes in physical, chemical, and biological soil properties. In the end, these changes are related to the loss of soil organic matter (SOM) and control the post-fire soil management decision. Therefore, the objectives of this study were: (1) to develop a numerical model to predict the SOM decay during wildfires, and (2) to study which are the main parameters that control the soil response. The model couples the energy balance for soil heating, and the species conservation for water and SOM using high temperature-induced vaporization and combustion kinetics. Fluid flow was neglected; however, radiative energy conducted through pores was included as a function of the volumetric pore radius. The soil thermal evolution showed values of r&lt;sup&gt;2&lt;/sup&gt;&gt;0.92 when the radiative term in the thermal conductivity was neglected, and r&lt;sup&gt;2&lt;/sup&gt;&gt;0.98 when the volumetric pore radius was adjusted. The results showed that the main parameters that control the soil response were soil texture, soil water content, volumetric pore radius, and oxygen availability. Also, soil response depends on the surface temperature and exposure time. Soil water content enhances the thermal properties and determines the amount of heat consumed during vaporization because of the high enthalpy of this endothermic reaction. On the other hand, neglecting oxygen flux leads to restricted oxidation, limiting the SOM decay. In terms of texture, silty soils showed the lower soil response, clay and loamy soils an intermediate response, and sandy soils had a higher response. Also, the volumetric pore radius enhances the soil thermal conductivity at high temperatures, leading to higher temperatures near the soil surface. These results suggest that the normalized SOM decay does not depend on the initial SOM content.&lt;/p&gt;

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