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Thursday, April 1, 2010

The Relation Between SoilsTexture and Water Holding Capacity


Different soil textures have different water holding capacity as well. Fine soils, for example: clay soils, has a fine pore space more, so the ability to hold more water. While coarse-textured soil, eg sand-textured soil, has a fine pore space less, so the ability Manahan less water as well.
Soil Texture USDA


According Hardjowigeno (1992) that the water contained in the soil due to retained (absorbed) by the soil mass, muffled by the water impermeable layer, or because of poor drainage conditions. Water can be absorbed or retained by the soil due to the forces of adhesion, cohesion, and gravity. Because of these forces the water in the soil can be divided into:
(1) Water hidroskopik, is ground water that is absorbed so strongly that it can not be used in plants, this condition occurs because of the adhesion force between the soil with water. Water hidroskopik a blanket of water on the surface of soil grains.
(2) capillary water, is water in the ground where the power of cohesion (attractive force among the grains of water) and adhesion force (between water and land) is stronger than gravity. This water can move horizontally (sideways) or vertically (upwards) due to capillary forces. Most of the capillary water is water that is available (can be absorbed) for plants.

In determining the amount of water available to crops following several terms need to be understood, namely:
(1) Field Capacity: This is a fairly moist soil conditions which showed the highest amount of water that can be retained by the soil against the pull of gravity. Water to be held by such land continuously absorbed by the roots of the plants or evaporate so that the longer the dry soil. At one time the plant roots can no longer absorb water so the plants become wilted (permanent wilting point).
(2) permanent wilt point: is the water content of soil where the roots of the plants began to no longer able to absorb water from the soil, so plants wilt. Plants will continue to wither either at day or night.
(3) Water is available: is the amount of water available for plants, ie the difference between water content at field capacity minus the water content at permanent wilting point.

Water content at field capacity moisture content is indicated by the voltage 1 / 3 bar, whereas the water content at permanent wilting point is at 15 bars tension. Water available for plants is the water contained in the voltage between 1 / 3 bar up to 15 bar.

Number of water content in soil is closely linked to the amount of water stress (moisture tension) in the soil. The amount of water stress showed the amount of power needed to hold the water in the soil. Voltage is measured in cm bar or the atmosphere or water, or the logarithm of cm of water called pF. Units of the bar and the atmosphere is often considered the same as 1 atm = 1.0127 bar.

Soil water holding ability and influence by soil texture. Coarse-textured soils have lower water holding capacity than fine soils. Therefore, plants grown on sandy soil generally are easier to drought than the soil-clay or clay soils.
Conditions of water excess or shortage of water can interfere with plant growth.

Some functions of water for plant growth are:
(1) as a plant nutrient elements:
Plants require water from the soil along with the needs of CO2 from the air to form sugars and carbohydrates in the process of photosynthesis.
(2) as solvent nutrients:
Nutrient elements dissolved in the water absorbed by plant roots from the solution.
(3) as part of plant cells:
Water is part of the protoplasm of plant cells. Water availability in the soil is affected: (1) the number of rainfall or irrigation water, (2) the ability of soil to hold water, (3) the amount of evapotranspiration (evaporation directly through the ground and through vegetation), (4) high ground water, (5) content of soil organic matter, (6) chemical compounds or salts content, and (7) solum soil depth or soil layers.

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