Relasi-relasi Lengas Tanah

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

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

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

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

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

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

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

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

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

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

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 Sew The masses can be obtained from: 1 soil Gsw Massa = Kerapatan x Volume volumes masses Diagram Fase Diunduh dari: Soil Water Phases - N. Sivakugan

Diunduh dari: Soil Water Phases - N. Sivakugan Hubungan Fase Dari definisi sebelumnya: soil air water 1 Gsw Sew Se e Phase Diagram Diunduh dari: Soil Water Phases - N. Sivakugan

Hubungan Fase soil air water 1 Gsw Sew Se e Diagram Fase Diunduh dari: Soil Water Phases - N. Sivakugan

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)

Sifat Hidraulik Tanah & Tekstur Tanah

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)

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

Gravity vs. Capillarity Horizontal movement due to capillarity Vertical movement due largely to gravity