In recent years, economic boom in fast developing countries has been witnessed with spectacular progress in industri- alization and concurrent progress in modern agriculture. Such development is however not without an...In recent years, economic boom in fast developing countries has been witnessed with spectacular progress in industri- alization and concurrent progress in modern agriculture. Such development is however not without any socio-political and environmental side effects. A major concern has been the environmental pollution. If the current unabated disposal of various forms of wastes to agricultural lands is continued, the inherent capacity of soil to support agricultural pro- duction and sustain other ecosystem services will be in peril. Heavy metals with soil residence times of thousands of years present numerous health hazards to higher organisms. They are also known to decrease plant growth, ground cover and have a negative impact on soil biodiversity. Inorganic and organic contaminants typically found in urban areas are heavy metals and petroleum derived products. The presence of both types of contaminants on the same site presents technical and economic challenges for decontamination strategies. In this article we have reviewed the devel- opments to ameliorate the contaminated soils, with special emphasis on biological approaches, which have shown po- tential to low-cost remediation of soil pollution. Also the limitations of such approaches and direction of further re- search have been highlighted.展开更多
Crop yields in sandy soils can be increased by addition of clay-rich soil, but little is known about the effect of clay addition on nutrient availability after addition of plant residues with different C/N ratios. A l...Crop yields in sandy soils can be increased by addition of clay-rich soil, but little is known about the effect of clay addition on nutrient availability after addition of plant residues with different C/N ratios. A loamy sandy soil （7% clay） was amended with a clay-rich subsoil （73% clay） at low to high rates to achieve soil mixtures of 12%, 22%, and 30% clay, as compared to a control （sandy soil alone） with no clay addition. The sandy-clay soil mixtures were amended with finely ground plant residues at 10 g kg-l： mature wheat （Triticum aestivum L.） straw with a C/N ratio of 68, mature faba bean （Vicia faba L.） straw with a C/N ratio of 39, or their mixtures with different proportions （0% 100%, weight percentage） of each straw. Soil respiration was measured over days 0-45 and microbial biomass C （MBC）, available N, and pH on days 0, 15, 30, and 45. Cumulative respiration was not clearly related to the C/N ratio of the residues or their mixtures, but C use efficiency （cumulative respiration per unit of MBC on day 15） was greater with faba bean than with wheat and the differences among the residue mixtures were smaller at the highest clay addition rate. The MBC concentration was lowest in sole wheat and higher in residue mixtures with 50% of wheat and faba bean in the mixture or more faba bean. Soil N availability and soil pH were lower for the soil mixtures of 22% and 30% clay compared to the sandy soil alone. It could be concluded that soil cumulative respiration and MBC concentration were mainly influenced by residue addition, whereas available N and pH were influenced by clay addition to the sandy soil studied.展开更多
文摘In recent years, economic boom in fast developing countries has been witnessed with spectacular progress in industri- alization and concurrent progress in modern agriculture. Such development is however not without any socio-political and environmental side effects. A major concern has been the environmental pollution. If the current unabated disposal of various forms of wastes to agricultural lands is continued, the inherent capacity of soil to support agricultural pro- duction and sustain other ecosystem services will be in peril. Heavy metals with soil residence times of thousands of years present numerous health hazards to higher organisms. They are also known to decrease plant growth, ground cover and have a negative impact on soil biodiversity. Inorganic and organic contaminants typically found in urban areas are heavy metals and petroleum derived products. The presence of both types of contaminants on the same site presents technical and economic challenges for decontamination strategies. In this article we have reviewed the devel- opments to ameliorate the contaminated soils, with special emphasis on biological approaches, which have shown po- tential to low-cost remediation of soil pollution. Also the limitations of such approaches and direction of further re- search have been highlighted.
基金supported by a postdoctoral award of Australian Department of Education and Training Endeavour to S. Pal
文摘Crop yields in sandy soils can be increased by addition of clay-rich soil, but little is known about the effect of clay addition on nutrient availability after addition of plant residues with different C/N ratios. A loamy sandy soil （7% clay） was amended with a clay-rich subsoil （73% clay） at low to high rates to achieve soil mixtures of 12%, 22%, and 30% clay, as compared to a control （sandy soil alone） with no clay addition. The sandy-clay soil mixtures were amended with finely ground plant residues at 10 g kg-l： mature wheat （Triticum aestivum L.） straw with a C/N ratio of 68, mature faba bean （Vicia faba L.） straw with a C/N ratio of 39, or their mixtures with different proportions （0% 100%, weight percentage） of each straw. Soil respiration was measured over days 0-45 and microbial biomass C （MBC）, available N, and pH on days 0, 15, 30, and 45. Cumulative respiration was not clearly related to the C/N ratio of the residues or their mixtures, but C use efficiency （cumulative respiration per unit of MBC on day 15） was greater with faba bean than with wheat and the differences among the residue mixtures were smaller at the highest clay addition rate. The MBC concentration was lowest in sole wheat and higher in residue mixtures with 50% of wheat and faba bean in the mixture or more faba bean. Soil N availability and soil pH were lower for the soil mixtures of 22% and 30% clay compared to the sandy soil alone. It could be concluded that soil cumulative respiration and MBC concentration were mainly influenced by residue addition, whereas available N and pH were influenced by clay addition to the sandy soil studied.
