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Presentation on theme: "AIR TANAH LENGAS TANAH Soil Water SOIL MOISTURE."— Presentation transcript:


The importance of soil water: Effect on soil formation,erosion, and structure stability It is the major constituent of plant protoplasm. It is essential for photosynthesis and conversion of starches to sugar . It is the solvent in which nutrients move into and through plant parts. SUMBER:‎

The types and available of soil moisture Classification of soil water Adsorbed water Membranous water Capillary water Gravitational water Numerical method SUMBER:‎

Soil adsorbed water : held by strong electrical forces - low energy little movement- held tight by soil exists as a film unavailable to plants removed from soil by drying in an oven SUMBER:‎

5 Soil Membranous water :
held by hydrogen bonding liquid state in water film major source of water for plants greater energy than adhesion water SUMBER:‎

6 Sketch map of membranous water

7 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. SUMBER:‎

8 Air ditarik “naik” ke dalam tabung kapiler
Capillarity: 0.1-1mm Capillarity obvious mm Capillarity strong mm Capillarity very strong 〈0.001mm Capillarity disappears SUMBER:‎

9 Air kapiler dalam pori tanah
Soil particle SUMBER:‎

10 Kapasitas Lapang (KL) = 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. SUMBER:‎

11 Air kapiler naik ke atas melalui pori kapiler dalam tanah
Soil particle Groundwater Table SUMBER:‎

12 Ketinggian naiknya air kapiler :
h(cm): the hight of capillary water rise ,d: the diameter of the capillary tube(mm) SUMBER:‎

13 Air Gravitasi = Gravitational water
Water which moves into, through, or out of the soil under the influence of gravity. SUMBER:‎

二、 The express methods of soil water content (一)The mass water content(m) Percntage water = {[(wet soil weight)-(oven dry soil weight)]/ (oven dry soil weight)} ×100 (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) V=m· (三)Relative water content(%) Relative water content= soil water content/ field capacity SUMBER:‎

(三)Soil water-storage capcity 1、Water deepth(DW) DW=V·h or mm 2、Water fang(方)( m3) VFang/mu(亩)=2/3Dw SUMBER:‎

16 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) SUMBER:‎

Soil Water Potential Total soil water potential and individual potentials Soil A: Sand Soil 10% Soil B: Clay Soil 15% Where does water flow? SUMBER:‎

18 Water moves from areas of high potential
(wet soil : -2 or -4) to areas of low potential (dry soil -8) -.4 -3 -7 -8 -2 Root Soil Soil SUMBER:‎

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. SUMBER:‎

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. p=wgh SUMBER:‎

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 SUMBER:‎

22 Absolute positive value
Soil moisture suction 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? SUMBER:‎

23 Soil water potential measurement
The popular unite of the soil water potential is : Pa 1 Pa= 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 SUMBER:‎

24 Kurva Karakteristik Air Tanah
The relationship between the soil-water content (by mass or volume) and the soil-water matric potential. S=ab S=a(/s)b S=A(s-)n/m S: suction, Pa; θ:water content; a,b,A,n,m: experience constant. SUMBER:‎

Affect the factors Texture Structure Temperature Phenomenon of hysteresis Soil moisture suction Clay Silt Sand Soil moisture content% SUMBER:‎

26 . 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. ‎ SUMBER: ‎

27 Pergerakan Air dalam Tanah
The principle of water movement in soil Evaporation Infiltration Water redistribution SUMBER:‎

28 Pergerakan Jenuh Air tanah
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 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. SUMBER:‎

29 Konduktivitas Hidraulik Jenuh (Ks)
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. The characteristics of the saturated hydraulic conductivity: ①The saturated hydraulic conductivity is a constant It is maximum in hydraulic conductivity 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 SUMBER:‎

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

31 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: ‎

32 K(m) :unsaturated hydraulic conductivity
d/dx: water potential gradient The unsaturated hydraulic conductivity is a function of soil matric potential. SUMBER:‎

33 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. SUMBER:‎

34 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: ‎

35 The stable infiltration rate
in several different texture soils ( millimeter/ hour) Soil Sand Sandy loam Silt Clay Alkalized clay Final infiltration rate >20 10-20 5-10 1-5 <1 SUMBER:‎

36 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. SUMBER:‎

37 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 SUMBER:‎

38 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 SUMBER:‎

39 Soil-plant-atmosphere continuum (SPAC) Desert plants can live in
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 ( kPa). Desert plants can live in -2×106 to -8×106 Pa. SUMBER:‎

40 Ketersediaan Air Tanah
Kontrol Air-Tanah Ketersediaan 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 MPa). SUMBER:‎

41 .Kurva Retensi Air Tanah

Kontrol Air Tanah 1.Olah tanah : plow depth, intertillage, roll etc. 2.Mulsa: straw, plastic sheeting etc. 3.Irigasi: drip irrigation, sprinkler irrigation etc. 4.Biological save water . SUMBER:‎


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