Percentage of Soil Saturation

Soil Saturation Factors

• The amount of water necessary to saturate a soil depends on the soil traits. Coarse sand has a higher capacity to hold water before reaching the saturation level. Compacted soil of any type requires less water as the spaces between the soil particles have been eliminated by the compression.

Measuring Soil Saturation

• Lab analysis of soil saturation percentages requires weighing the soil sample as it is taken from the field and when it water has been added to raise the sample to 100 percent saturation. The sample is the dried in an oven until all moisture is removed. The difference in the weight between the dry soil and the original sample is the amount of water in the soil sample. The weight as a percentage of the weight of the water in the saturated sample is the percentage of soil saturation.

Soil Saturation and Plants

• Plants bring in air through roots. Completely saturated soil can suffocate a plant. Ideally, the soil should include about 50 percent open spaces or voids that are filled with an equal mix of water and air. This provides the plant with both the air and water needed for growth. Combinations of high water content and soil compaction can produce situations where plants may fail.

Other Soil Measurements

• Soil scientists also measure gravitational water, defined as the water flowing through the soil, and field capacity, defined as the water held in the soil under normal circumstances. The most of the field capacity of a soil is available for plants through the root system. However, a small percentage remains in the soil and cannot be utilized by a plant. This is known as the wilting point.