Chapter 6
Soil Air and Heat Regime
Section 1 Soil air
一,Composition of soil air
Atmosphere O
2 CO2 N2 Other
gases
Atmosphere
near soil
surface
20.94 0.03 78.05 0.95
Soil air 18.0-
20.03
0.15-
0.65
78.8-
80.24
－
Compare soil air with atmosphere（ Volume %）
Characteristics of soil air
1,The level of CO2 in soil is about eight times
higher than the normal atmospheric level.
2,The O2 level in soil air is slightly lower than
it is in atmospheric air.
3,Soil air usually is much higher in water vapor
than is the atmosphere.
4,Also,under waterlogged conditions,the
concentrations of gases such as methane（ CH4） and
hydrogen sulfide (H2S) are notably higher in soil air.
Depth
/cm
Plastic mulches Bare soil
05-01 07-29 05-01 07-29
CO2 O2 CO2 O2 CO2 O2 CO2 O2
0 － － 0.915 － － 0.056 0.056 －
5 0.158 20.497 1.006 20.439 0.70 20.649 0.211 20.653
10 0.420 20.397 1.060 20.275 0.104 20.513 0.279 20.668
15 0.250 20.486 0.865 19.953 0.134 20.857 0.385 20.506
20 0.483 20.478 1.348 20.060 0.150 20.121 0.406 20.634
30 0.573 19.865 1.159 20.005 0.313 20.181 1.157 20.362
50 0.922 19.929 1.520 19.698 0.402 20.198 1.281 19.873
Average 0.615 20.124 1.268 19.953 0.269 20.329 0.847 20.022
The soil air contents of the mulches and bare cotton
farmland in different growth stages (%)
二,The movement of soil air
（一）,Convection (Mass Flow)
Convection –The soil air is transferred from higher
pressure area to lower pressure area.
Where qv is the volume convective flux of air; k is the
permeability of the air-filled pore space; is the viscosity of soil
air; is the pressure gradient in soil air.
pkq v )/(?
（ 二 ）,Soil air diffusion
The process of diffusion can be represented by a flow equation
in which the driving force is the gas concentration gradient
(Fick’s Law).
dx
dcDq
d
where qd is the diffusive flux (mass diffusing across a unit area
per unit time),D is the gas diffusion coefficient,and dc/dx is the
concentration gradient of the gas.
A difference in the concentration of a particular gas in one zone
compared with any other zone in the soil can result in the
movement of that gas by a process called diffusion.
Soil respiration:
Section 2 Soil heat
一,The source of soil heat
（一） Solar radiation
Solar radiation is the
primary source of energy to
heat soils,But clouds ad dust
particles intercept the sun’s
rays and absorb,scatter,or
reflect most of the energy,H I Ea
（二） Biological heat
Organic matter is decomposed
by microorganism,
（三） Heat inside the earth
二,The radiation balance and
affect the factors in soil surface
（一） The radiation balance in soil surface
Little of the solar energy reaching the
earth actually results in soil warming,The
energy is used primarily to evaporate
water from the soil or leaf surfaces,or is
radiated or reflected back to sky,
Only about 10% is absorbed by the soil
and can be used to warm soil.
The radiation balance of a soil
surface can be written as:
R = [(I+H) – (I + H)× α] + (G – E)
= (I + H) (1 - α) – r
where R is the net radiation received per unit area,I is
the sun directly radiation,H is atmospheric radiation;
αis the albedo and represents the fraction of R which is
reflected by the soil surface,G is the incoming
longwave radiation,E is the longwave emission of the
surface.
（二） The affect factors of the radiation in
balance soil surface
1,Solar radiation capacity
2,Albedo in soil surface
3,Available radiation in soil surface
（ 1） Cloud,fog,water vapor and wind etc.
(2) Elevation and inclination of angle
of surface toward the sun
(3) Soil surface roughness
(4) Mulches of soil surface
三,Heat balance of soil
The heat balance of the soil can be described by:
S = Q? P? LE + R
where S is to obtain heat or to lose heat in
unit time;Q is balance of radiation; LE is
transpiration of water by the vegetative cover; P
is heating of the atmospheric air by conduction at
the soil surface; R is heating of the soil.
一,Soil heat capacity (soil thermal capacity)
Soil heat capacity-The amount of heat energy required to raise the
temperature of 1 g or 1 cm3 of the soil,
C is mass heat capacity (Jg-1℃ -1) ; Cv is volume heat capacity（ Jcm-
3℃ -1）。
The volume heat capacity of soil（ Cv） can be described by
following equation:
Cv = mCv· Vm + oCv· Vo ＋ wCv· Vw+aCv· Va
As volume heat capacity of air is very small,it will be omitted,
therefore,the above equation will be becomed:
Cv = 1.9Vm + 2.5Vo + 4.2Vw (Jcm-3 ℃ -1)
Section 3 Thermal properties of soils
6 － 3 土壤不同组分的热容量土壤组成物质重量热容量
（ J g
- 1 °
c
- 1
）
容积热容量
( J cm
- 3 °
c
- 1
)
粗石英砂 0.745 2.163
高 岭 石 0.975 2.410
石 灰 0.895 2.435
Fe
2
O
3
0.682 －
Al
2
O
3
0.908 －
腐 殖 质 1.996 2.515
土壤空气 1.004 1.255 × 10
- 3
土壤水分 4.184 4.184
Table 6-3 Soil heat capacity of different soil composes
二,Soil heat conductivity
Heat moves through soil mainly by a process
called conduction.
Heat conductivity( thermal conductivity)
The heat conductivity,λ,of a soil is defined as the
heat flux density by conduction through the soil divided
by the temperature gradient,(在单位厚度（ 1厘米）土层，温差为 1℃ 时，每秒钟经单位断面（ 1厘米 2）通过的热量焦耳数（?）。其单位是 J.cm-2.s-1.℃ -1。 )
)(/)(
/
2121 ttAT
Qdor
dtt
ATQ
＝?
表 6 - 4 土壤不同组成分的导热率 （焦耳 / 厘米·秒·度）
土壤组成分 导热率石英 4,4 2 7 × 10
-2
湿砂粒 1,6 7 4 × 10
-2
干砂粒 1,6 7 4 × 10
-3
泥炭 6,2 7 6 × 10
-4
腐殖质 1,2 5 5 × 10
-2
土壤水 5,0 2 1 × 10
-3
土壤空气 2,0 9 2 × 10
-4
Table 6-4 Soil heat conductivity of different soil composes
三,Soil thermal diffusivity
The soil thermal diffusivity
represents the ratio of the thermal
conductivity (?) to the volumetric heat
capacity of the soil.(土壤热扩散率 是指在标准状况下，在土层垂直方向上每厘米距离内,1℃ 的温度梯度下，
每秒流入 1cm2土壤断面面积的热量，
使单位体积（ 1cm3）土壤所发生的温度变化。其大小等于土壤导热率 /容积热容量之比值。 )
)/( 2 scmCvD
Where? is the thermal conductivity,
and Cv。
Section 4 Soil temperature
一,Month temperature changes of the soil
Season temperature changes
二,Daily variations
三,Influence of topography,landform
and soil nature in soil temperature
(一） Elevation
（二） Slope and slope direction
（三） The soil constitutes and soil natures
土壤空气氧浓度临界值 (Vol%)
作 物 O2临界值 作 者大 麦 7%~10% Geisler
玉 米 14% Geisler
豌 豆 20% Ammore
Geisler
棉 花 10% Tacket
谷类胚芽
10% Gill
1,土 壤含水量 愈低,其热容量 越小,导热率愈 低土壤 升温越 快
( )
2,灌溉可降低土壤表层土的昼夜温差 。 ( )
3,中 耕松土,可降低 土壤表层 土的热 容量,而 促进表 土升温 。
( )
4,一日之内土壤上下各层温度变化是同步的 ( )
5,土壤热量全部来源是太阳辐射 。 ( )
6,土温的变化与土壤肥力的高低无关 。 ( )
7,土壤热容量随土壤容重和含水量的增加而增大 ( )。
8,土壤有机质含量越高,其热容量越大 ( )
9,土壤热扩散率随含水量的增加而增加,随热容量的增大而减小
( )。
10,热扩散率表示土壤升温的难易,导热率表示是热传导的快慢 。
( )
课堂测验 —— 快速判断！！
本章小结：
一、概念土壤呼吸 呼吸商 气体扩散 Eh 土壤通气性土壤热容量 土壤导热率 土壤热扩散率 土壤热状况二问答题
1,土壤空气的组成有何缺点?
2,土壤通气 性对土壤肥力有何影响?
3,土壤 Eh的意义是什么?
4,如何调节土壤的通气性?
The End
Soil Air and Heat Regime
Section 1 Soil air
一,Composition of soil air
Atmosphere O
2 CO2 N2 Other
gases
Atmosphere
near soil
surface
20.94 0.03 78.05 0.95
Soil air 18.0-
20.03
0.15-
0.65
78.8-
80.24
－
Compare soil air with atmosphere（ Volume %）
Characteristics of soil air
1,The level of CO2 in soil is about eight times
higher than the normal atmospheric level.
2,The O2 level in soil air is slightly lower than
it is in atmospheric air.
3,Soil air usually is much higher in water vapor
than is the atmosphere.
4,Also,under waterlogged conditions,the
concentrations of gases such as methane（ CH4） and
hydrogen sulfide (H2S) are notably higher in soil air.
Depth
/cm
Plastic mulches Bare soil
05-01 07-29 05-01 07-29
CO2 O2 CO2 O2 CO2 O2 CO2 O2
0 － － 0.915 － － 0.056 0.056 －
5 0.158 20.497 1.006 20.439 0.70 20.649 0.211 20.653
10 0.420 20.397 1.060 20.275 0.104 20.513 0.279 20.668
15 0.250 20.486 0.865 19.953 0.134 20.857 0.385 20.506
20 0.483 20.478 1.348 20.060 0.150 20.121 0.406 20.634
30 0.573 19.865 1.159 20.005 0.313 20.181 1.157 20.362
50 0.922 19.929 1.520 19.698 0.402 20.198 1.281 19.873
Average 0.615 20.124 1.268 19.953 0.269 20.329 0.847 20.022
The soil air contents of the mulches and bare cotton
farmland in different growth stages (%)
二,The movement of soil air
（一）,Convection (Mass Flow)
Convection –The soil air is transferred from higher
pressure area to lower pressure area.
Where qv is the volume convective flux of air; k is the
permeability of the air-filled pore space; is the viscosity of soil
air; is the pressure gradient in soil air.
pkq v )/(?
（ 二 ）,Soil air diffusion
The process of diffusion can be represented by a flow equation
in which the driving force is the gas concentration gradient
(Fick’s Law).
dx
dcDq
d
where qd is the diffusive flux (mass diffusing across a unit area
per unit time),D is the gas diffusion coefficient,and dc/dx is the
concentration gradient of the gas.
A difference in the concentration of a particular gas in one zone
compared with any other zone in the soil can result in the
movement of that gas by a process called diffusion.
Soil respiration:
Section 2 Soil heat
一,The source of soil heat
（一） Solar radiation
Solar radiation is the
primary source of energy to
heat soils,But clouds ad dust
particles intercept the sun’s
rays and absorb,scatter,or
reflect most of the energy,H I Ea
（二） Biological heat
Organic matter is decomposed
by microorganism,
（三） Heat inside the earth
二,The radiation balance and
affect the factors in soil surface
（一） The radiation balance in soil surface
Little of the solar energy reaching the
earth actually results in soil warming,The
energy is used primarily to evaporate
water from the soil or leaf surfaces,or is
radiated or reflected back to sky,
Only about 10% is absorbed by the soil
and can be used to warm soil.
The radiation balance of a soil
surface can be written as:
R = [(I+H) – (I + H)× α] + (G – E)
= (I + H) (1 - α) – r
where R is the net radiation received per unit area,I is
the sun directly radiation,H is atmospheric radiation;
αis the albedo and represents the fraction of R which is
reflected by the soil surface,G is the incoming
longwave radiation,E is the longwave emission of the
surface.
（二） The affect factors of the radiation in
balance soil surface
1,Solar radiation capacity
2,Albedo in soil surface
3,Available radiation in soil surface
（ 1） Cloud,fog,water vapor and wind etc.
(2) Elevation and inclination of angle
of surface toward the sun
(3) Soil surface roughness
(4) Mulches of soil surface
三,Heat balance of soil
The heat balance of the soil can be described by:
S = Q? P? LE + R
where S is to obtain heat or to lose heat in
unit time;Q is balance of radiation; LE is
transpiration of water by the vegetative cover; P
is heating of the atmospheric air by conduction at
the soil surface; R is heating of the soil.
一,Soil heat capacity (soil thermal capacity)
Soil heat capacity-The amount of heat energy required to raise the
temperature of 1 g or 1 cm3 of the soil,
C is mass heat capacity (Jg-1℃ -1) ; Cv is volume heat capacity（ Jcm-
3℃ -1）。
The volume heat capacity of soil（ Cv） can be described by
following equation:
Cv = mCv· Vm + oCv· Vo ＋ wCv· Vw+aCv· Va
As volume heat capacity of air is very small,it will be omitted,
therefore,the above equation will be becomed:
Cv = 1.9Vm + 2.5Vo + 4.2Vw (Jcm-3 ℃ -1)
Section 3 Thermal properties of soils
6 － 3 土壤不同组分的热容量土壤组成物质重量热容量
（ J g
- 1 °
c
- 1
）
容积热容量
( J cm
- 3 °
c
- 1
)
粗石英砂 0.745 2.163
高 岭 石 0.975 2.410
石 灰 0.895 2.435
Fe
2
O
3
0.682 －
Al
2
O
3
0.908 －
腐 殖 质 1.996 2.515
土壤空气 1.004 1.255 × 10
- 3
土壤水分 4.184 4.184
Table 6-3 Soil heat capacity of different soil composes
二,Soil heat conductivity
Heat moves through soil mainly by a process
called conduction.
Heat conductivity( thermal conductivity)
The heat conductivity,λ,of a soil is defined as the
heat flux density by conduction through the soil divided
by the temperature gradient,(在单位厚度（ 1厘米）土层，温差为 1℃ 时，每秒钟经单位断面（ 1厘米 2）通过的热量焦耳数（?）。其单位是 J.cm-2.s-1.℃ -1。 )
)(/)(
/
2121 ttAT
Qdor
dtt
ATQ
＝?
表 6 - 4 土壤不同组成分的导热率 （焦耳 / 厘米·秒·度）
土壤组成分 导热率石英 4,4 2 7 × 10
-2
湿砂粒 1,6 7 4 × 10
-2
干砂粒 1,6 7 4 × 10
-3
泥炭 6,2 7 6 × 10
-4
腐殖质 1,2 5 5 × 10
-2
土壤水 5,0 2 1 × 10
-3
土壤空气 2,0 9 2 × 10
-4
Table 6-4 Soil heat conductivity of different soil composes
三,Soil thermal diffusivity
The soil thermal diffusivity
represents the ratio of the thermal
conductivity (?) to the volumetric heat
capacity of the soil.(土壤热扩散率 是指在标准状况下，在土层垂直方向上每厘米距离内,1℃ 的温度梯度下，
每秒流入 1cm2土壤断面面积的热量，
使单位体积（ 1cm3）土壤所发生的温度变化。其大小等于土壤导热率 /容积热容量之比值。 )
)/( 2 scmCvD
Where? is the thermal conductivity,
and Cv。
Section 4 Soil temperature
一,Month temperature changes of the soil
Season temperature changes
二,Daily variations
三,Influence of topography,landform
and soil nature in soil temperature
(一） Elevation
（二） Slope and slope direction
（三） The soil constitutes and soil natures
土壤空气氧浓度临界值 (Vol%)
作 物 O2临界值 作 者大 麦 7%~10% Geisler
玉 米 14% Geisler
豌 豆 20% Ammore
Geisler
棉 花 10% Tacket
谷类胚芽
10% Gill
1,土 壤含水量 愈低,其热容量 越小,导热率愈 低土壤 升温越 快
( )
2,灌溉可降低土壤表层土的昼夜温差 。 ( )
3,中 耕松土,可降低 土壤表层 土的热 容量,而 促进表 土升温 。
( )
4,一日之内土壤上下各层温度变化是同步的 ( )
5,土壤热量全部来源是太阳辐射 。 ( )
6,土温的变化与土壤肥力的高低无关 。 ( )
7,土壤热容量随土壤容重和含水量的增加而增大 ( )。
8,土壤有机质含量越高,其热容量越大 ( )
9,土壤热扩散率随含水量的增加而增加,随热容量的增大而减小
( )。
10,热扩散率表示土壤升温的难易,导热率表示是热传导的快慢 。
( )
课堂测验 —— 快速判断！！
本章小结：
一、概念土壤呼吸 呼吸商 气体扩散 Eh 土壤通气性土壤热容量 土壤导热率 土壤热扩散率 土壤热状况二问答题
1,土壤空气的组成有何缺点?
2,土壤通气 性对土壤肥力有何影响?
3,土壤 Eh的意义是什么?
4,如何调节土壤的通气性?
The End
