Decomposition experiments of 14C-labelled sickle alfalfa in chao soils of different texture and these soils after removal of CaCO3 were carried out under field and laboratory conditions respectively. The amount of res...Decomposition experiments of 14C-labelled sickle alfalfa in chao soils of different texture and these soils after removal of CaCO3 were carried out under field and laboratory conditions respectively. The amount of residual 14C in, or 14CO2 evolved from, the soils at intervals after the beginning of decomposition were measured and the distribution of native and labelled C between particle size fractions isolated from these soils was edtermined. Results showed that contents of both labelled (14C) and non-labelled (12C) carbon decreased with increasing particle size. The enrichment factor for 14C was higher than that for 12C in the clay fraction, the reverse being true for the silt enrichment factors. The effect of soil texture on the decomposition of plant material could not be observed in chao soils when the clay content was lower than 270g kg-1, while it became obvious once CaCO3 was removed from these soils. The decomposition rate of plant material in the soil from which the native CaCO3 was removed was correlated significantly to both the clay content of the soil and the application rate of CaCO3. A preliminary correction equation describing the effect of clay and CaCO3 on the decomposition of organic material in chao soil was derived from the results obtained.展开更多
The supply of cadmium from soil to plant roots mainly depends on the diffusion process. This work was conducted tostudy the effect of some soil properties on cadmium diffusion coefficient (D) in soil. Measurements we...The supply of cadmium from soil to plant roots mainly depends on the diffusion process. This work was conducted tostudy the effect of some soil properties on cadmium diffusion coefficient (D) in soil. Measurements were made using the Shofield and Graham-Bryce's isotopic labelling method. Cadmium diffusion coefficients varied from 10￣(-7) to 10￣(-9) cm￣2s￣(-1),Higher values were observed in acid sandy soils and lower values in calcareous clay soils. Liming an acid soil resulted in a sub-stantial decrease of D. Addition of cadmium as nitrate salt generally increased D, while addition of sewage sludge and organ-ic matter resulted in a significant decrease of cadmium diffusion. The rhizospheric activity also induced a moderate reduction in D. The relationships between D 10￣(-9)cm￣2s￣(-1)) on the one hand and soil PH, moisture (Mc, g kg￣(-1)), organic matter (OM, gkg￣1 ), clay (Cy, g kg￣(-1)) and cadmium content (Cd, mg kg￣(-1)) on the other were obtained by the multigle regression:D=182. 1-29.g1 pH+0.210Mc-0.303OM+0.011Cy+1.64Cd (R￣2=0.859,n=22 ).展开更多
Constructed Technosols may be an alternative for creating urban green spaces. However, the hydro-structural properties emer- ging from the assembly of artefacts have never been documented. The soil shrinkage curve （...Constructed Technosols may be an alternative for creating urban green spaces. However, the hydro-structural properties emer- ging from the assembly of artefacts have never been documented. The soil shrinkage curve （SSC） could provide relevant structural information about constructed Technosols, such as the water holding capacity of each pore system （macropores and micropores）. The objectives of this study were （i） to evaluate the SSC and water retention curve （WRC） to describe the structure of constructed Tech- nosols and （ii） to understand the influence of organic matter content on soil hydro-structural properties. In this study, Technosols were obtained by mixing green waste compost （GWC） with the material excavated from deep horizons of soil （EDH）. The CWC was mixed with EDH in six different volumetric percentages from 0% to 50% （GWC/total）. The GWC and EDH exhibited highly divergent hydro-structural properties： the SSC was hyperbolic for GWC and sigmoid for EDH. All six mixture treatments （0%, 10%, 20%, 30%, 40% and 50% GWC） exhibited the classical sigmoid shape, revealing two embedded levels of pore systems. The 20% GWC treatment was hydro-structurally similar to the 30% and 40% GWC treatments; so, a large quantity of expansive GWC is unnecessary. The relation with the GWC percentage was a second-degree equation for volumetric available water in micropores, but was linear for volumetric available water in macropores and total volumetric available water. Total volumetric available water in the 50% GWC treatment was twice as high as that in the 0% GWC treatment. By combining SSCs and WRCs, increasing the GWC percentage increased water holding capacity by decreasing the maximum equivalent size of water-saturated micropores at the shrinkage limit and increasing the maximum equivalent size of water-saturated macropores, resulting in an increased range of pore diameter able to retain available water.展开更多
文摘Decomposition experiments of 14C-labelled sickle alfalfa in chao soils of different texture and these soils after removal of CaCO3 were carried out under field and laboratory conditions respectively. The amount of residual 14C in, or 14CO2 evolved from, the soils at intervals after the beginning of decomposition were measured and the distribution of native and labelled C between particle size fractions isolated from these soils was edtermined. Results showed that contents of both labelled (14C) and non-labelled (12C) carbon decreased with increasing particle size. The enrichment factor for 14C was higher than that for 12C in the clay fraction, the reverse being true for the silt enrichment factors. The effect of soil texture on the decomposition of plant material could not be observed in chao soils when the clay content was lower than 270g kg-1, while it became obvious once CaCO3 was removed from these soils. The decomposition rate of plant material in the soil from which the native CaCO3 was removed was correlated significantly to both the clay content of the soil and the application rate of CaCO3. A preliminary correction equation describing the effect of clay and CaCO3 on the decomposition of organic material in chao soil was derived from the results obtained.
文摘The supply of cadmium from soil to plant roots mainly depends on the diffusion process. This work was conducted tostudy the effect of some soil properties on cadmium diffusion coefficient (D) in soil. Measurements were made using the Shofield and Graham-Bryce's isotopic labelling method. Cadmium diffusion coefficients varied from 10￣(-7) to 10￣(-9) cm￣2s￣(-1),Higher values were observed in acid sandy soils and lower values in calcareous clay soils. Liming an acid soil resulted in a sub-stantial decrease of D. Addition of cadmium as nitrate salt generally increased D, while addition of sewage sludge and organ-ic matter resulted in a significant decrease of cadmium diffusion. The rhizospheric activity also induced a moderate reduction in D. The relationships between D 10￣(-9)cm￣2s￣(-1)) on the one hand and soil PH, moisture (Mc, g kg￣(-1)), organic matter (OM, gkg￣1 ), clay (Cy, g kg￣(-1)) and cadmium content (Cd, mg kg￣(-1)) on the other were obtained by the multigle regression:D=182. 1-29.g1 pH+0.210Mc-0.303OM+0.011Cy+1.64Cd (R￣2=0.859,n=22 ).
基金the University of Damascus, Syria, for financial support of the Ph.D.(No.1473)
文摘Constructed Technosols may be an alternative for creating urban green spaces. However, the hydro-structural properties emer- ging from the assembly of artefacts have never been documented. The soil shrinkage curve （SSC） could provide relevant structural information about constructed Technosols, such as the water holding capacity of each pore system （macropores and micropores）. The objectives of this study were （i） to evaluate the SSC and water retention curve （WRC） to describe the structure of constructed Tech- nosols and （ii） to understand the influence of organic matter content on soil hydro-structural properties. In this study, Technosols were obtained by mixing green waste compost （GWC） with the material excavated from deep horizons of soil （EDH）. The CWC was mixed with EDH in six different volumetric percentages from 0% to 50% （GWC/total）. The GWC and EDH exhibited highly divergent hydro-structural properties： the SSC was hyperbolic for GWC and sigmoid for EDH. All six mixture treatments （0%, 10%, 20%, 30%, 40% and 50% GWC） exhibited the classical sigmoid shape, revealing two embedded levels of pore systems. The 20% GWC treatment was hydro-structurally similar to the 30% and 40% GWC treatments; so, a large quantity of expansive GWC is unnecessary. The relation with the GWC percentage was a second-degree equation for volumetric available water in micropores, but was linear for volumetric available water in macropores and total volumetric available water. Total volumetric available water in the 50% GWC treatment was twice as high as that in the 0% GWC treatment. By combining SSCs and WRCs, increasing the GWC percentage increased water holding capacity by decreasing the maximum equivalent size of water-saturated micropores at the shrinkage limit and increasing the maximum equivalent size of water-saturated macropores, resulting in an increased range of pore diameter able to retain available water.
