我国土壤资源的现状及特点 (1).ppt

1.1 The Concept of Soil 1.1 什么是土壤？1.1 What is soil?1.1 What is soil?I.The concept of soilspThe Rites of Zhou：The materials that all plants grow in are soils,The materials that are cultivated for planting crops and trees are also soilspScientists in agriculture and forestry:Soils is the medium for growing plants;pGeologists:fragmented rocks(or the soil is the surface weathered layer of the solid crust);pEnvironmental scientists:soil serves as a buffer zone and it can filter contaminants;pEngineers:the foundations that are strong enough to support buildings or sources of engineering materialspEcologists:Among the systems on the surface of Earth,soil is mostly abundant in biological diversity,and a biotic layer where active biogeochemical energy exchange and material cycling occur I.The concept of soils Soil scientists Soil scientistsSoil is formed under the synthetic influences of organisms,climate,parent materials,topography and time,which is composed of minerals,organic matter,water and air.Soils locate on the surface of Earth,they are unconsolidated and porous layers where green plants live,they are capable of sustaining environmental quality.1.1 What is soil?1.1 What is soil?I.The concept of soilsthe difference between soil and land Soil LandTheir relationship:In short,the land contains soil,and soil is merely the part in land which can grow green plants.II.The essential characteristics of soils What is soil?a.Soil is essentially characterized by its fertility.Williams()s from former Soviet:Soil fertility is the ability of soil to supply nutrient to plantsSoil fertility is the capability of continuously supplying plants with the greatest amount of available nutrients and water during the whole lifetime of plant growth.Soil scientists of western countries(represented by American scientists):1.1 What is soil?Chinese soil scientists:(1)Chinese Soils(1987):soil fertility is described as the essential characteristic of soil,and it refers to the capability of soil to supply and coordinate nutritional and environmental conditions for plants(2)It is generally recognized in the field of Soil Science in China that soil fertility is the comprehensive expression of four major factors of soil water,fertilizer,gas and heat.II.The essential characteristics of soils1.1 What is soil?The relationship between soil fertility and soil productivity:Soil fertility is the essential property of soil；Soil productivity is the ability of soil to produce plant products.土壤肥力和土壤生产力（productivitEcologists(from the perspectives of matter and energy):the matter and energy within the soil that can be transformed to plants II.The essential characteristics of soils1.1 What is soil？b.The composition of soil fertilityBased on its availability(1)Effective soil fertility：the fertility shown during the current crop season,i.e.economic fertility.(2)Potential soil fertility：the fertility that cannot be shown during the current crop season,i.e.potential productivity.There is no clear distinction between effective soil fertility and potential soil fertility.These two can be transformed into each other,and the transformational conditions are changes in environmental and anthropogenic variables.II.The essential characteristics of soils1.1 What is soil？(1)Natural fertility:the fertility formed under the comprehensive influences of natural factors,and it is the product of soil forming processes.Natural soils(2)Artificial fertility:the fertility developed from soil ripening due to human cultivation.Agricultural soils Whether a soil is fertile also depends on species of plants.II.The essential characteristics of soils b.The composition of soil fertilityAccording to the sources of fertility：1.1 What is soil？SoilSoid phaseIntergra-nular poreSolid soil particlesLiquid phaseMineral particleOrganic matterSoil organisms include soil fauna,plant roots and soil microorganisms.The species and number of soil microorganisms are the largest;there are about a billion of them per gram soil with extremely low mass and volume,They are usually taken as part of organic matter and usually compared to the digestive system of soil.Gaseous phaseOrganismsGasMoistureSoil minerals account for 95%-99%of the solid mass and 38%to 45%of the total soil volume.They are formed by rock weathering or in the process of soil formation.They are usually compared to the skeleton of soil.Organic matter accounts for 1%to 5%of the solid mass and 5%to 12%of total soil volume.It is composed of biological remains and their decomposition products.It is usually compared to the muscle of soil.Soil organic matterThe gas phase accounts for 15%-35%of soil volume.It is composed of two parts and often compared to the respiratory system of the soil.the nitrogen and oxygen from near-surface atmospherethe vapor and carbon dioxide produced from soil itselfThe liquid phase accounts for 15%-35%of soil volume.Most soil water comes from surface water.The soluble substances from both soil air and solid materials can enter into soil water.Therefore,soil water is indeed soil solution.It is often compared to soil blood.III.Soil compositionThank you谢谢