Types Of Soil Water PDF

TYPES OF SOIL WATER Physical Classification For. Jeshaiah Chen Mopheth B. Aguilar  TYPES OF SOIL WATER 1. Gravitational Water- free water that moves through the soil due to the force of gravity. is found in the macropores. It moves rapidly out of well- drained soil and is...

TYPES OF SOIL WATER Physical Classification For. Jeshaiah Chen Mopheth B. Aguilar  TYPES OF SOIL WATER 1. Gravitational Water- free water that moves through the soil due to the force of gravity. is found in the macropores. It moves rapidly out of well- drained soil and is not considered to be available to plants. It can cause upland plants to wilt and die because gravitational water occupies air space, which is necessary to supply oxygen to the roots. Drains out of the soil in 2-3 days  TYPES OF SOIL WATER 2. Capillary water- water in the micropores, the soil solution.  Most, but not all, of this water is available for plant growt  Capillary water is held in the soil. against the pull of gravity Forces Acting on Capillary Water micropores exert more force on water than do macropores Capillary water is held by cohesion (attraction of water molecules to each other) and adhesion (attraction of water molecule to the soil particle). The amount of water held is a function of the pore size (cross- sectional diameter) and pore space (total volume of all pores)  TYPES OF SOIL WATER 3. Hygroscopic water- this water forms very thin films around soil particles and is not available to the plant. The water is held so tightly by the soil that it cannot be taken up by roots.  not held in the pores, but on the particle surface. This means clay will contain much more of this type of water than sands because of surface area differences.  is held very tightly, by forces of adhesion. This water is not available to the plant.  However, the force of gravity is counteracted by forces of attraction between water molecules and soil particles and by the attraction of water molecules to each other.  SOIL MOISTURE CONSTANTS These are the terms most commonly used when working with soil water. Terms we will use when making soil moisture calculations. 1. Saturation - all soil pores are filled with water. This condition occurs right after a rain. 2. Field capacity - moisture content of the soil after gravity has removed all the water it can. 3. Wilting point - soil moisture percentage at which plants cannot obtain enough moisture to continue growing.  SOIL MOISTURE CONSTANTS 4. Hygroscopic water - when the soil is about air dry - Water held at water potential less than -31 bar. This water is not available to plants. 5. Oven dry - soil that has been dried in an oven at 105 degrees C for 12 hours. All soil moisture has been removed. This point is not important for plant growth but is important for calculations since soil moisture percentage is always based on oven-dry weight. 6. Plant available water is that held in the soil at a water potential between -1/3 and -15 bar. WATER AND SOIL CONDITIONS WATER AND SOIL CONDITIONS WATER AND SOIL CONDITIONS -fin-