Agronomy Horticulture Botany Soil Science Plant Pathology Entomology Extention Agril. Engineering Dairy Science Economics
 Current Category » Micro Irrigation and Drainage Engineering Drainage Pore Volume It represents the volume of water that can be drained from a unit available volume of soil when the soil moisture pressure is decreased from atmospheric pressure to some specific negative pressure. Q= Sh1          h2 f(h) dh Relationship between drainable porosity and capillary pressure. q= S h1 ah.dh = a/2 (h1square – h2 square)          h2 Where, a = slope of the line q= quality drained h1h2= hydraulic heads Example: It contains 35% moisture by dry weight when it is saturated and soil moisture pressure is equal to zero. When the soil moisture capillary pressure is increased to 100 cm of head the moisture content become 30% , bulk density of soil is 1.4, ( 1cc dry soil weights 1.4 gm). Calculate the drainable porosity of soil? At saturation 1cc soil contains 1.4 X 0.35 = 0.49 of water per cc of soil. Similarly at, 100cm capillary pressure Soil moisture concentration = 1.4 X 0.30 = 0.42 cc of water cc of soil.  :. Drainable porosity is 0.07 cc of water per cc of soil. Current Category » Micro Irrigation and Drainage Engineering