### soil | tillage:

Conservation tillage
* common practice that creates a mulch on the soil surface.
* group of practices that reduce the amount of tillage needed.
* has many environmental benefits but requires increased use of herbicides.
* helps reverse the process so that carbon is retained in organic matter
  - to reduce soil erosion and improve soil structure
* is an effective practice for conserving soil and improving water quality
  - important technology for creating more sustainable agriculture worldwide
  - one way in which moisture can be conserved
* strives to maintain crop residues on the soil surface at all times.

Deep tillage
* breaks up and rearranges the structural blocks that occur below the surface.
* causes rapid losses of stored soil moisture.
* is generally harmful to earthworms.
* tends to select for species with dormant, long-lived seed.

Excess tillage
* breaks down soil structure and destroys residue.
* can contribute to soil structure breakdown and increased erosion
  - the breakdown of soil
* reduces crop residues and exposes the soil to wind and water erosion.

Excessive tillage
* can break down soil structure, leading to compaction.
* reduces organic material in soil and depletes soil stability and structure.

Primary tillage
* can help reduce the rate at which certain perennials, such as hemp dogbane, spread
  - of spread of certain perennials such as hemp dogbane
* is the first soil tillage after the last harvest.

Top soil
* contains stores of seed from locally occurring plants and has high nutrient levels.
* is present supporting a diversity of prairie plants.

Tropical soil
* are highly anoxic, whereas soils from the boreal forest are aerobic
  - poor in nutrients, so plants compete strongly for what is available
* have low cation exchange and water retention capacities.

Troxel soil
* are in depressions on outwash plains, stream terraces, and glacial till plains.
* contain more sand in the lower part of the solum.

Udifluvent soil
* common type of soil to build homes on and other buildings.
* has very dark gray fine sand.

Unlimed soil
* are mildly alkaline to very strongly acid
  - strongly acid or very strongly acid
  - very strongly acid to moderately acid
* have subhorizons that are strongly acid through slightly acid.

Unsaturated soil
* acts like a sponge, absorbing some of the water from rain or snow melt.
* three-phase system comprised of liquid, gas and the solid soil particles.

Urban soil
* Many urban soils are shallow and of very poor quality.
* are usually very compact and lack air space and organic matter.
* is often quite different from the native soil.

Vulcan soil
* are on gently to steeply sloping mesa tops and sides.
* have fragmental layers.

Warm soil
* absorbs less heat.
* causes males, cool soil leads to females.
* is necessary for germination of seeds and proper growth of plants
  - seed germination and proper plant growth
  - vegetable happiness, especially for plants from southern climes
* permits faster heating and speeds germination.

Watchaug soil
* are moderately well drained and lack a dense substratum.
* have a seasonal high water table.

Waupecan soil
* are on nearly level to gently sloping glacial outwash plains and stream terraces.
* have a drier control section and formed in sandy and gravelly outwash.

Weingarten soil
* are on similar positions
  - upland ridgetops, back slopes and foot slopes
* have a layer in the series control section that has fragic soil properties.

Western soil
* Many western soils are deficient in micronutrients.
* Most western soils contain abundant calcium, but as very insoluble calcium carbonate.