文档介绍：Chapter 4
Soil texture and structure
Section 1
Soil three phases Constitution
一、Soil density and bulk density
(一) Soil density ( or Particle density)
Soil density is the density of the solid soil particles only; the measurement does not include water weight or pore (air) space. The dominant soil minerals- quartz, feldspars, micas, and clay minerals-average approximately g/cm3, the “standard” value used in calculations if particle density is not measured.
Individual minerals have densities from g/cm3 for bauxite (aluminum ore) to for hematite (iron ore) or for galena (lead ore).
(二)Soil bulk density
1. Bulk density, the density for a volume of soil as it exists naturally, includes any air space anic materials in the soil volume.
ρb = (mass of dry soil)/(total volume of soil) = Ms/Vt
= Ms/(Vs + Vw +Va)
A recently cultivated topsoil is likely to have a bulk density in the range from to g/cm3, while pact subsoil may have a bulk density of g/cm3 or even more.
Uses of soil bulk density:
①To calculate soil porosity(p0):
② To calculate soil weight
③ To calculate storage of positions
④ To calculate total water storage capacity and irrigation (or drainage) quota.
2. Bulk density in water
= (soil mass over-dry)/(precipitation volume)
3. Affect the factors of soil bulk density:
Texture, structure, content anic matter, and various nature factors and anthropogenic factors.
P0 = 1- (Bulk density/soil density)
(一)、Soil three phases constitution and porosity
二. Soil three phases constitution and pore
小
孔
隙
大
孔
隙
1、 Index three phases constitution
Solid phase (%) =(solid volume /soil body volume) ×100
Liquid phase (%) =(liquid volume /soil body volume) ×100
Gas phase (%) =(air volume /soil body volume) ×100
2、Soil porosity:
Soil porosity is the percentage of the volume of pores to the total volume of soil.
Soil porosity =1- Solid phase (%)
= Liquid phase (%) + Gas phase (%)
The void ratio is the ratio of the volume of p