Hydrology, environment and water resources 2015 / Soil water. Rodrigo Proença de Oliveira

Rodrigo Proença de Oliveira

Hydrology, environment and water resources

2015 / 2016

Soil, pedosphere and lithosphere

• Rock >> regolith >>

soil

• Soil:

Superficial layear (1-2 m) of the geologic substract (pedosphere),

that holds:

– Minerals:

Sand, silt and clay - mineral nutrients

– Humus:

provides nutrients, as well as the soil structure and its

ability to hold water and nutrients;

– Air:

source of oxygen and CO2 requited by micro organisms

– Water:

provides the environment where the chemical reactions

that hold life can occur

Hydrology, environment and water resources 2015/16: @Rodrigo Proença de Oliveira 2015/16 2

desagregation + water

+ organic matter

Solo Li to sf er a P ed os fe ra ~ 20 0 m ~2 m

Regolith

Hydrology, environment and water resources 2015/16: @Rodrigo Proença de Oliveira 2015/16 3

<Earth

Moon>

Elements that condition soil production

• Parent rock

• Time

–

allows for the parent rock desegregation and for the adding and mixing of

water, organic matter, and for the degradation of organic matter:

– More time leads to thicker soils with distinctive characteristics from the parent rock

• Climate

–

determines the physical and chemical processes that act over the

primary rock, its reaction times, as well as the types of plants and animals that

interact with the soil:

– Precipitation enables parent rock desegregation and provide conditions for the

movement of oils particles by percolation. Excessive precipitation may carry all minerals to inferiors layers, leaving only insoluble material in the upper layers.

– High temperatures facilitates chemical desegregation of the parent rock and provides conditions for a faster degradation of the organic matter.

• Plants and animals

– provides the organic matter to the soil (mainly

plants) and the microorganisms required for its degradation.

Topography

–

determines the erosion and conditions the amount of water and

solar energy available to the soil:

– Steep slopes lead the thinner and less developed soils

– Gentle slopes lead to humid soils with a high percentage of organic matter

Soil characterization

• Texture:

related to the sediment particles dimension distribution /

Textura : diz respeito à distribuição da dimensão das partículas

• Structure:

related to the geometric organization of the sediment

particles /

Estrutura: diz respeito à disposição geométrica das partículas

• Chemical composition (including pH)

/

Composição química (incluindo acidez)

• Depth of soil

/

Profundidade

• Porosity

/

Porosidade

• Soil usage capacity

/

Capacidade de uso

• A fertile soil has /

Um solo fértil tem:

– Organic matter to provide nutrients and water retention capacity

/ Humus (matéria orgânica) para proporcionar nutrientes e capacidade de retenção de água

– Clay to retain water and nutrients /

Argila para reter água e nutrientes

– Nutrients (N, C, K, P and Ca) /

Nutrientes (N, C, K, P e Ca)

– Good drainage /

Boa drenagem

– Good porosity /

Boa porosidade para facilitar o arejamento e crescimento de plantas

Soil texture

1 3 4 9 8 7 11 10 12 2 5 6

Zona USDA Name Nome

1 Clay Argiloso

2 Sandy Clay Argilo-arenoso

3 Silty Clay Argilo-siltoso

4 Sandy Clay Loam Franco-argiloso-arenoso

5 Clay Loam Franco-argiloso

6 Silty Clay Loam Franco-argiloso-siltoso

7 Sandy Loam Franco-arenoso

8 Loam Franco

9 Silt Loam Franco-siltoso

10 Sand Arenoso

11 Loamy Sand Arenoso-franco

12 Silt Siltoso

Particle size (

mm)

/

Tamanho das partículas (mm)

Standard Padrão Clay Argila Silt Silt Sand Areia Gravel

Seixo Calhau Pedra

International Society of Soil Science < 2 < 20 < 2000 US Dep. of Agricuture < 2 < 50 < 2000

British Standards Institution < 2 < 60 < 2000 < 60000 < 150000 DIN < 2 < 60 < 2000

Soil texture

Hydrology, environment and water resources 2015/16: @Rodrigo Proença de Oliveira 2015/16 9

Loam

(Solo franco)

- 20% of clay

(argila)

- 40% of silt

(silt)

- 40% of sand

(areia)

Good soils for plant growth because they can hold water and nutrients and provide them to plants;

Bons para suportar plantas porque tem a capacidade de disponibilizar água e nutrientes em quantidades adequadas.

Argila – Clay

Silt – Silt

Areia – Sand

Loam - Franco

Soil structure

It conditions the capacity to farm the soil and its

susceptibility to erosion /

Condiciona a facilidade de cultivo do solo e a sua susceptibilidade à erosão.

Basic structures /

Estruturas básicas:

• Granular /

Granular

• Prismatic /

Prismatica

• Massive /

Massiva

• Single grain /

Esferoidal

• Blocky /

Blocos

Soil density

• Solids density /

Massa volúmica dos sólidos

:

• Wet or bulk density /

Massa volúmica aparente do solo:

• Dry density /

Massa volúmica aparente do solo seco:

• Water density /

Massa volúmica da água:

Hydrology, environment and water resources 2015/16: @Rodrigo Proença de Oliveira 2015/16 11

Soil particle

Partícula de solo

Air

/ Ar

Water

/ Água

Soil

particles

Water

Air

V_t

V

_f

V

_s V_w V_a

M

_t M_s M_w M_a  0 s s s

V

M





t t t

V

M





t s d

V

M





w w w

V

M





22-10-2015

Porosity, water content and degree of saturation

• Porosity

Porosidade

• Water content (in volume)

Teor volúmico de humidade

• Degree of saturation

Grau de saturação

• Water content (in mass)

Teor mássico de humidade

t f

V

V

n



t w

V

V





f w

V

V

S



s w M M w  s d

n







 1

d w

w









w d t













Sólidos

Água

Ar

V_t

V

_f

V

_s V_w V_a

M

_t M_s M_w M_a  0

S

n







Field capacity and wilting point

• Field capacity:

Ratio between the water volume in soil after

draining by gravity and total void volume

/

Capacidade de campo: relação entre o volume de vazios ocupados pela água e o volume total de vazios, depois de um longo periodo de drenagem

.

• Wilting point:

ratio between the water volume in soil when

plants cannot abstract more water from the soil and total void

volume

Ponto de emurchecimento permanente: relação entre volume de vazios ocupados pela água e o volume total do solo, quando as plantas não podem retirar mais água do solo.

• Efective porosity

:

ratio between voids volume that may be

ocuppied by water and the soil volume

/

Porosidade efectiva: relação entre o volume de vazios ocupáveis pela água que circula por gravidade e o volume total do solo.

• Available water capacity

/

Capacidade utilizável:

• Minimum water content /

Máxima dessecação do solo:

Hydrology, environment and water resources 2015/16: @Rodrigo Proença de Oliveira 2015/16 13

t cc cc

_V

V

w





t e e

V

V

n



f ep cc u











22-10-2015 t r r

V

V

w





𝜃

_𝑤𝑝

=

𝑉

𝑡

𝑤𝑝

𝑉

_𝑡

Available water capacity

Field capacity <Saturated water content / Capacidade de campo < Teor de saturação

Wilting point > 0 (depends on suction capacity of plants) /Ponto de emurchecimento (depende da capacidade de sucção das plantas)

Available water capacity:In thory is equal to field capacity minus wilting points / Volume utilizável (teórica)/ Capacidade de campo – Ponto de emurchecimento

Useful soil depth = root depth (from 0,5 m (shrubs) to 2.5 m (large trees))/ Profundidade útil =

Profundidade radicular / que é a profundidade atingida pelas raízes das plantes que varia entre 0,5 m (herbáceas) e

Precipitation

Saturated soil

Saturated soil Soil at field

capacity Soil at field _capacity

Percolation

Soil at field capacity Soil at wilting

Average water content values

Hydrology, environment and water resources 2015/16: @Rodrigo Proença de Oliveira 2015/16 23-10-2015 15 s



_

_cc

_

_ep

_

_r

_

_cc

_

_

_ep

(adaptado de Rawls et al, 1993; citado por Hipólito e Vaz, 2011) Sand

Sandy Loam Loamy Sand

Loamy Clay Sand Loam

Silt

Loamy clay Loamy silt Clay Sandy Loamy Clay Silt Clay Silt

Clay

Saturation Field

capacity Wilting point

Moisture content at

Available soil capacity Minimum

Exercise

Consider a soil with a bulk dry density of1750 kg m

-3

_{and a solid density}

of 2500 kg m

-3

_{. Determine the soil porosity and the bulk density when}

saturated.

A massa volúmica aparente de um solo seco é 1750 kg m-3 _{e a massa volúmica dos sólidos é}

2500 kg m-3_{. Determine a porosidade do solo e a sua massa volúmica aparente quando}

Exercise

Consider a soil sample in a cylinder with 5 cm of radius and 10 cm of

height. Knowing that the wet and dry masses of the sample are 331,8 g

and 302,4 g, respectively and that the solid density is 2650 kg/m

3

_,

determine the sample water content (in volume) and saturated sample

water content (in volume).

Uma amostra de solo ocupa um cilindro de 5 cm de diâmetro e 10 cm de altura. Sabendo que as massas húmidas e secas são, respetivamente, 331,8 g e 302,4 g e que a massa volúmica dos sedimentos é 2650 kg/m3_{, determine o teor volúmico de saturação e o teor}

volúmico de humidade da amostra.

Exercise

A contained with a hole at the bottom contains 5 l of a soil with a water

content (in volume) of 0.15. Knowing that the soild filed capacity is

0.28, compute the water quantity that drains through the bottom hole

when 1 liter of water is added to the container.

Um vaso, munido de um orifício no fundo, contém 5 l de um solo com um teor volúmico de humidade de 0.15. Sabendo que a capacidade de campo do solo é 0.28, calcule a quantidade de água que sairá pelo orifício quando se deitar no vaso 1 l de água.

Exercise

An agricultural field with 1 ha is planted with a crop with a root depth of

0.5 m. Assuming the field capacity of the soil is 0.45 and that minimum

soil water content for crop production is 0.24, compute the water

requirements to raise the water content from that minimum to the field

capacity. Assuming the average evapotranspiration is 3 mm/day,

estimate the maximum time interval between irrigation.

Num terreno com 1 ha encontra-se instalada uma cultura agrícola com a profundidade radicular de 0.5 m. Sabendo que o solo tem uma capacidade de campo de 0.45 e que o mínimo teor volúmico de humidade admissível para produção é 0.24, estime o volume de água de rega para passar desse mínimo à capacidade de campo. Sabendo que a evapotranspiração média é de 3 mm/d estime também o intervalo de tempo entre duas regas sucessivas.

Exercise

An agricultural field with 1 ha has a soil with 30% sand, 60% silt and 10%

clay. Knowing that the optimal crop production requires that the soil

water content is kept higher than 50% of the available water capacity,

compute the irrigation volume, in m

3

_{, to raise the water content from its}

minimum to field capacity.

Num terreno com 1 ha, o solo é fundamentalmente constituído por 30% de areia, 60% de silte e 10% de argila e a cultura instalada tem uma profundidade radicular de 0,5 m. Sabendo que para uma produção ótima o teor de humidade não deve baixar de 50% da água total utilizável pelas plantas, estime o volume de rega em m3 _{necessário para passar do}