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Relasi-relasi Lengas Tanah
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Menghitung masa (atau bobot) dan volume dari tiga fase yang berbeda
Va air Ma=0 Mt Vt Vv Notation M = mass or weight V = volume s = soil grains w = water a = air v = voids t = total Vw water Mw Vs soil Ms Diagram Fase Diunduh dari: Soil Water Phases - N. Sivakugan
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Definisi Kadar air (w) merupakan ukuran air yang ada dalam tanah. soil
water Vs Va Ma=0 Ms Mw Mt Vw Vv Vt X 100% Expressed as percentage. Range = 0 – 100+%. Phase Diagram Diunduh dari: Soil Water Phases - N. Sivakugan
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Diunduh dari: Soil Water Phases - N. Sivakugan
Definisi: Void ratio (e) is a measure of the void volume. soil air water Vs Va Ma=0 Ms Mw Mt Vw Vv Vt Phase Diagram Diunduh dari: Soil Water Phases - N. Sivakugan
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Diunduh dari: Soil Water Phases - N. Sivakugan
Definisi: Porosity (n) is also a measure of the void volume, expressed as a percentage. soil air water Vs Va Ma=0 Ms Mw Mt Vw Vv Vt X 100% Theoretical range: 0 – 100% Phase Diagram Diunduh dari: Soil Water Phases - N. Sivakugan
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Derajat kejenuhan (S): persentase pori yang terisi air .
Definisi Derajat kejenuhan (S): persentase pori yang terisi air . soil air water Vs Va Ma=0 Ms Mw Mt Vw Vv Vt X 100% Range: 0 – 100% Dry Saturated Phase Diagram Diunduh dari: Soil Water Phases - N. Sivakugan
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Diunduh dari: Soil Water Phases - N. Sivakugan
Contoh sederhana: Dalam ilustrasi ini: water air soil e = 1 n = 50% S = 50% Diunduh dari: Soil Water Phases - N. Sivakugan
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Bobot Isi (m) adalah kerapatan tanah dalam kondisi apa adanya.
Definisi Bobot Isi (m) adalah kerapatan tanah dalam kondisi apa adanya. soil air water Vs Va Ma=0 Ms Mw Mt Vw Vv Vt Units: t/m3, g/ml, kg/m3 Phase Diagram Diunduh dari: Soil Water Phases - N. Sivakugan
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Definisi Saturated density (sat) is the density of the soil when the voids are filled with water. Submerged density (’) is the effective density of the soil when it is submerged. ’ = sat - w Diunduh dari: Soil Water Phases - N. Sivakugan
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Kerapatan kering (d) : kerapatan tanah pada kondisi kering.
Definisi Kerapatan kering (d) : kerapatan tanah pada kondisi kering. soil air water Vs Va Ma=0 Ms Mw Mt Vw Vv Vt Units: t/m3, g/ml, kg/m3 Diagram Fase Diunduh dari: Soil Water Phases - N. Sivakugan
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Diunduh dari: Soil Water Phases - N. Sivakugan
Definisi Bulk, saturated, dry and submerged unit weights () are defined in a similar manner. Here, use weight (kN) instead of mass (kg). = g kg/m3 N/m3 m/s2 Berat jenis (kerapatan jenis) partikel tanah (Gs) biasanya berkisar antara 2.6 dan 2.8. Diunduh dari: Soil Water Phases - N. Sivakugan
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Massa = Kerapatan x Volume
Hubungan Fase Perhatikan fraksi tanah dimana Vs = 1. The other volumes can be obtained from the previous definitions. air e Se water Sew The masses can be obtained from: 1 soil Gsw Massa = Kerapatan x Volume volumes masses Diagram Fase Diunduh dari: Soil Water Phases - N. Sivakugan
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Diunduh dari: Soil Water Phases - N. Sivakugan
Hubungan Fase Dari definisi sebelumnya: soil air water 1 Gsw Sew Se e Phase Diagram Diunduh dari: Soil Water Phases - N. Sivakugan
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Hubungan Fase soil air water 1 Gsw Sew Se e Diagram Fase
Diunduh dari: Soil Water Phases - N. Sivakugan
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AIR TANAH TERSEDIA Definisi:
Water held in the soil between field capacity and permanent wilting point “Tersedia” untuk digunakan oleh tanaman Kapasitas Air Tersedia: Available Water Capacity (AWC) AWC = fc - wp Units: depth of available water per unit depth of soil, “unitless” (in/in, or mm/mm) Measured using field or laboratory methods (described in text)
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Sifat Hidraulik Tanah & Tekstur Tanah
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Fraksi air-tersedia yang hilanbg dari tanah (fd)
(fc - v) = soil water deficit (SWD) v = current soil volumetric water content Fraksi air-tersedia yang tertinggal (fr) (v - wp) = soil water balance (SWB)
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Total Air Tersedia: Total Available Water (TAW)
TAW = (AWC) (Rd) TAW = total available water capacity within the plant root zone, (inches) AWC = available water capacity of the soil, (inches of H2O/inch of soil) Rd = depth of the plant root zone, (inches) If different soil layers have different AWC’s, need to sum up the layer-by-layer TAW’s TAW = (AWC1) (L1) + (AWC2) (L2) (AWCN) (LN) - L = thickness of soil layer, (inches) - 1, 2, N: subscripts represent each successive soil layer
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Gravity vs. Capillarity
Horizontal movement due to capillarity Vertical movement due largely to gravity
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