Author Topic: Introduction to Physical Characteristics of the Soil  (Read 1965 times)


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Introduction to Physical Characteristics of the Soil
« on: April 14, 2011, 04:15:04 PM »
Introduction to Physical Characteristics of the Soil

It is helpful to know the physical texture of the soil you are working with, as it affects water retention, drainage and compaction. The relative amounts of sand, silt and clay are used to classify soil types ranging from clay to loam to silt

Unfortunately, changing a topsoilís physical characteristics by adjusting the amount of sand, silt and clay requires a complete renovation of a  field or lawn and can be very expensive. One of the biggest challenges turf managers face is soil compaction. Soil becomes compacted due to excessive foot traffic and the use of maintenance vehicles such as lawn mowers. Compacted soil inhibits the movement of air and water in the soil. Roots need oxygen, and leaves get extra carbon dioxide from the decomposition of organic matter in the soil.

Compaction forces grass plants to grow short thick roots that canít absorb nutrients or water efficiently. As a result, the grass becomes thinner; the roots have fewer energy reserves; the plants become more susceptible to drought, weed infestations (particularly warm-season grasses such as crabgrass) and diseases; and other plants more tolerant of compaction (e.g., common plantain) can gain a foothold.

Where possible, limiting foot traffic will minimize compaction. The use of maintenance equipment with low ground pressure, such as small mowers or mowers with fat tires will also minimize compaction. Cultural practices that aerate the soil can reverse compaction; however, aeration may only provide temporary relief from compaction, and the resulting increase in the amount of oxygen in the soil speeds up the decomposition of organic matter.

Earthworms help to alleviate compaction by their constant movement and aeration of soil. An acre of soil can have as many as 500,000 earthworms digging up to 250 miles of tunnels per week. Earthworms can also generate as many as 120 tons of castings per acre per year. These castings can contain higher microbial populations and enzyme activity than the surrounding soil and they bring valuable minerals to the soil surface. The activity of earthworms promotes healthy, stress-resistant grass by improving the infiltration of oxygen and water to the roots and allowing the leaves easier access to carbon dioxide. Earthworm tunnels are coated with a sticky mucous that keeps them open for as long as a year. The mucous is rich in nutrients, and turf roots can grow in these tunnels and reach greater soil depths with less energy. Earthworms can be encouraged by maintaining sufficient organic matter in the soil and leaving the grass clippings on the lawn or turf.