air tanah lengas tanah soil water soil moisture

AIR TANAHLENGAS TANAH

Soil WaterSOIL MOISTURE

The importance of soil water ：1. Effect on soil formation,erosion, and structure stability

2. It is the major constituent of plant protoplasm.

3. It is essential for photosynthesis and conversion of starches to sugar .

4. It is the solvent in which nutrients move into and through plant parts.

SUMBER: jpkc.njau.edu.cn/land/ppt/5.soil%20water.ppt

The types and available of soil moisture Classification of soil water

• Adsorbed water• Membranous water• Capillary water• Gravitational water

• Numerical method

Soil adsorbed water ：1. held by strong electrical forces - low

energy2. little movement- held tight by soil 3. exists as a film4. unavailable to plants5. removed from soil by drying in an oven

Soil Membranous water ：1. held by hydrogen bonding 2. liquid state in water film3. major source of water for plants4. greater energy than adhesion water

Sketch map of membranous water

Air Kapiler = Soil capillary water ：Capillary water-The water held in the “capillary” or small pores of a soil, usually with a tension >60 cm of water.

Capillary water includes capillary hanging water and capillary rise water.

Capillarity ： 0.1-1mm

Capillarity obvious

0.05-0.1mm

Capillarity strong

0.05-0.005mm

Capillarity very strong

〈 0.001mm

Capillarity disappears

Air ditarik “naik” ke dalam tabung kapiler

Soil particle

Air kapiler dalam pori

Field capacity:The amount of water remaining in a soil after the free water has been allowed to drain away (a day or two) after the root zone had been previously saturated;

expressed as a percentage.

Kapasitas Lapang (KL) = Field capacity：

Soil particle

Air kapiler naik ke

atas melalui

pori kapiler dalam tanah

Groundwater Table

Ketinggian naiknya air kapiler :

h （ cm): the hight of capillary water rise ， d: the diameter of the capillary tube （ mm ）

Air Gravitasi = Gravitational water

Gravitational water Water which moves into, through, or out of the soil under the influence of

gravity.

二、 The express methods of soil water content

（二） The volume water content （ v ） Volume water content = volume of water/bulk volume of soil=(weight of water/ρW)/(weight of dry soil/ ρb)

（一） The mass water content （ m)

Percntage water = {[(wet soil weight)-(oven dry soil weight)]/

(oven dry soil weight)} ×100

( 三） Relative water content （ % ） Relative water content= soil water content/ field capacity

（三） Soil water-storage capcity

2 、 Water fang( 方 ) （ m3 ）whaFang DV 10/

VFang/mu( 亩 ) ＝ 2/3Dw

1 、 Water deepth （ DW ） DW=V·h or D hw

i,100 1

三、 Estimating water contents

• Gravimetric method: The soil sample is dried in an oven at 105°C and the mass of dry soil recorded.

• Neutron scattering method• Time Domain Reflectometry (TDR)

Soil Water Potential

Total soil water potential and individual potentials

Soil A:Sand Soil10%

Soil B:

Clay Soil15%

Where does water flow?SUMBER: jpkc.njau.edu.cn/land/ppt/5.soil%20water.ppt

Water moves from areas of high potential (wet soil : -2 or -4) to areas of low

potential (dry soil -8)

SoilSoilRoot

Soil water potential- The amount of work that must be done per unit of a specified quantity of pure water in order to transport reversibly and isothermally an infinitesimal quantity of water from a specified source to a specified destination.

The matric potential （ m ）This work is less than zero or negative work, thus reported in negative values.

The pressure potential （ p ）In saturated soil, the pressure potential is always positive. In an unsatrated field soil the pressure potential is always zero.

The solute (osmotic) potential （ S ）The amount of work an infinitesmal quantity of water will do in moving from a pool of free water the same composition as the soil water to a pool of pure water at the same location. The solute potential is usually very small and negative values.

The gravitational potential （ g ）The amount of work an infinitesmal amount of pure free water can do at the site of the soil solution as a result of the force of gravity.

g =±MgZ

Since soil matric and osmotic potentials are always negative they are often onsidered as ‘suction’ or ‘tensions’. Suction and tensions are however always expressed as positive values.

T＝ -m

How do you use suction and potentials to decide the direction of soil water movement?

Absolute positive valueSoil moisture suction

Soil water potential measurement

The popular unite of the soil water potential is : Pa

1 Pa=0.0102-cm column of water

1 atmospheres=1033-cm column of

water=1.0133bar

1 bar=0.9896atm=1020-cm column of water

1 bar=105 Pa

Kurva Karakteristik Air Tanah

The relationship between the soil-water content (by mass or volume) and the soil-water matric potential.

S=a(/s)b

S=A(s-)n/m

S: suction, Pa; θ:water content; a,b,A,n,m: experience constant.

0 10 20 30 40 50 60 70

SiltSand

Soil moisture content%

Affect the factors• Texture• Structure• Temperature• Phenomenon of

hysteresis

Soil moisture suction

SUMBER: http://www.tankonyvtar.hu/en/tartalom/tamop425/0032_talajtan/ch07s05.html

. Jumlah air dalam zona akar di antara FC dan WP , dan yang dapat digunakan oleh tanaman disebut “Air Tersedia”. (FC-WP = air tersedia). Untuk tanah-tanah pasir, lempung dan liat ,

nilai-nilai (air tersedia) adalah 6, 20 dan 17 persen volume.

Pergerakan Air dalam Tanah

1. The principle of water movement in soil2. Evaporation3. Infiltration4. Water redistribution

Pergerakan Jenuh Air tanah

The rate of water flow through soil can be described by Darcy’s Law which states that the flux of water q is proportional to the hydraulic gradient (the gravitational potential and the pressure potential )multiplied by the conductivity or permeability of the soil.

q KHLs

Saturated flow-The movement of water though a soil that is temporarily saturated. Most of the water moves downwards, and some move more slowly laterally.

The rate of flow through a given amount of soil in a given time equals the water quantity collected (Qw) divided by both the cross-sectional area of soil

used (A) and the time (t) of measurement.

Konduktivitas Hidraulik Jenuh (Ks)

The characteristics of the saturated hydraulic conductivity:

①The saturated hydraulic conductivity is a constant

② It is maximum in hydraulic conductivity

③ It is decided by the soil texture and the soil structure

The factors of affect the saturated hydraulic conductivity:

• The soil texture • The soil structure• The amount of organic matter• The clay mineral

Pergerakan Tidak-Jenuh Air tanah

The movement of water in soil in which the pores are not filled to capacity with water.

The unsaturted soil water flow is decided by the matric potential and the gravitational potential.

q Kddxm ( )

Darcy’s Law can be extended to describe unsaturated flow:

Konduktivitas Hydraulik Konduktivitas hidrolik merupakan fungsi dari

potensial air tanah.

Konduktivitas ini mengukur kemudahan air untuk

bergerak melalui massa tanah.

Penurunan konduktivitas kalau tanah mengering

terutama disebabkan oleh pergerakan udara ke dalam tanah untuk menggantikan

air tanah.

SUMBER: http://5e.plantphys.net/article.php?id=39

K(m) :unsaturated hydraulic conductivity

d/dx: water potential gradient

The unsaturated hydraulic conductivity is a function of soil matric potential.

Pergerakan uap air dalam tanah

Bentuk-bentuk gerapan uap air dalam tanah:

1. Difusi uap air dalam tanah

2. Koagolasi uap air

Vapor flow can be considered as a diffusion mechanism in which the driving force is the vapor

pressure gradient.

Infiltration , water redistribution and evaporation of soil surface

Soil water infiltration

The entry of water into soil.

Affect the factors ：Velocity of Supply water

Infiltration rate

SUMBER: http://croptechnology.unl.edu/pages/informationmodule.php?idinformationmodule=1130447123&topicorder=3&maxto=13&minto=1

The stable infiltration rate in several different texture soils ( millimeter/ hour)

Soil SandSandy loam Silt Clay Alkalized

Final infiltration

rate>20 10-20 5-10 1-5 <1

Redistribusi Air-Tanah Redistribution of soil water

The process of soil-water movement to achieve an equilibrium energy state of

water throughout the soil. Soil water redistribution is unsaturated flow of soil water.

Evaporasi (Penguapan) di permukaan tanah

Evaporation: Water lose as vapor from a soil or open water surface.

1.The keeping the stable stage of evaporation in soil surface

2.The stage of evaporate change with moisture content in soil surface

3.The stage of water vapor diffusion

Neraca Air Tanah di Lapangan

Soil water balance in the field can be written as: W=P+I+U-E-T-R-In-D

P: precipitation; I: irrigation;

E: evaporation; T: transpiration; R: runoff

Soil-plant-atmosphere continuum (SPAC)

Water moves from a relatively high potential energy level in the soil (-100 kPa) and flows down a potential gradient into the plant root (-500 kPa), plant stem (-800 kPa), and leaves (-1500 kPa), where it is eventually evaporated into the atmosphere (-10000 kPa).

Desert plants can live in -2×106 to -8×106 Pa.

Kontrol Air-Tanah

Air Tersedia:

The amount of water released between in situ field capacity and the permanent

wilting point (usually estimated by water content at soil matric potential of -1.5

Ketersediaan Air Tanah

SUMBER: http://www.tankonyvtar.hu/en/tartalom/tamop425/0032_talajtan/ch07s05.html

.Kurva Retensi Air Tanah

Kontrol Air Tanah1.Olah tanah : plow depth, intertillage, roll etc.

2.Mulsa: straw, plastic sheeting etc.

3.Irigasi: drip irrigation, sprinkler irrigation etc.

4.Biological save water .

air tanah lengas tanah soil water soil moisture

Documents

metode sisr storie index soil ratings penilaian indeks ...

“eco - soil septic tank (septic tank ramah tanah dan

ordo tanah mollisol menurut soil taxonomy 2014

universiti putra malaysia influence of soil...

gatra ekologi : air diperlukan dalam - ariyanto.staff.uns...

sesi akademik academic session 2014/2015 fakulti … ·...

potensi komoditas unggulan...

credits: 2 - soil science of uns...

pengelolaan lengas tanah lahan lebak hubungannya …

metode perbaikan tanah lunak dengan deep soil mixing

lengas tanah dan turguditas klon kopi...

mk. dasar ilmu tanah air tanah (soil moisture = soil water)...

repository.ung.ac.idrepository.ung.ac.id/get/kms/10211/pengembangan-sistem-usaha-tani... ·...

ketersediaan air untuk kebutuhan ... -...

laporan praktikum penetapan kadar lengas tanah€¦ ·...

acara 1 kadar lengas tanah

penyelidikan tanah (soil investigation)

penetapan kadar lengas tanah€¦ · air kapiler. air jenuh...

analisis karakteristik sifat kimia tanah pada lahan ... ·...

modul kesuburan tanah (soil fertility) · penggunaan...