-NRCS promotes the use of land within its capabilities and the treatment of land according to its needs for protection and improvement; 8 land use classes differentiate on the basis of limitations that restrict use or require special treatment

-Class I: Soils that have few or no limitations for cultivation; Class IV: Soils that have severe limitations that reduce choise of crops, require very intensive conservation practices, or both; Class VIII (highest): Soils and landforms that have very severe limitations that make them unsuitable for commercial purposes and restrict their use to wildlife, esthetics, recreation, and/or watersheds

-Subclasses: e: erosion hazards, w: wetness problems, s: soil limitations including excessive shallowness, extremely fine or coarse texture, stoniness, salinity, or sodicity, c: climatic limitations such as excessive coldness or dryness

-drainage is the removal of excess surface and subsurface water from the soil; how easily and effectively the soil is drained depends on the depth to bedrock, to a cemented pan, or to other layers that affect the rate of water movement, permeability, and susceptibility to flooding

-external drainage: "if area is in a low place, water can't get off it"

-internal drainage: moisture characteristics of soil; indicate whether potential crop growth is or is not limited by excess water

-areas occupied by a forest; usually have an index of productivity

-volume measure of lumber: board-feet

-tree species adaptation and relative growth rates depend on many factors, including soil depth through which roots may grow without physical or chemical hindrance, available water-holding capacity of the soil. soil texture, organic matter, aeration, and depth to the water table

-not used much anymore

-method of soil rating based on potential utilization and productive capacity 

-different species occupy different habitats; soil survey reports on the type of wildlife that can be found on the soil (based on original vegetation - woodland, openland, wetland, and now urban land...)

-also includes information on producing wildlife habitat elements (including grain and seed crops, grasses and legumes, wild herbaceous plants, hardwood trees and shrubs, coniferous trees, and wetland food and cover plants

-engineering index property

-depth to the bedrock/hardpan; depth to the upper and lower boundaries of each layer is indicated

-engineering index property

-texture is defined according to percentages of sand, silt, and clay in the fraction of the soil that is less than 2 mm in diameter

-"Loam," for example, is soil that is 7-27% clay, 28-50% silt, and less than 52% sand 

-Atterberg limits

-indicate the plasticity characteristics of a soil

-liquid limit: what water content level does the soil flow; the moisture content at which the soil passes from a plastic to a liquid state

-plasticity index: if you have dry soil, then add water, it becomes more plastic; plasticity index is the numerical difference btwn the liquid limit and the plastic limit; the range of moisture content within which the soil remains plastic

-the weight of soil (ovendry) per unit volume

-bulk density data are used to compute shrink-swell potential, available water capacity, total pore space, and other soil properties

-moist bulk density of a soil indicates the pore space available for water and roots

-moist bulk density is influenced by texture, kind of clay, content of organic matter, and soil structure

-permeability refers to the ability of a soil to transmit water or air

-tells the rate at which water will flow (in/hr

-estimates indicate the rate of downwared movement of water when the soil is saturated

-Available moisture content (or available water capacity): after a soil is saturated by rain, some water drains out and some is held by the soil through its cohesion and adhesion; water that can be held is the field capacity, compared to when moisture is so low and plants can no longer extract water, which causes them to wilt = wilting point

-field capacity to wilting point is the range for the available moisture content

-the range of pH of each major horizon is based on many field tests, tells how acidic or basic the soil is

-important for selecting crops and other plants, in evaluating soil amendments for fertility and stabilization, and in determining the risk of corrosion

-how salty the soil is

-problem because most plants don't like salt, and it is corrosive (the potential soil-induced chemical action that dissolves or weakens uncoated steel or concrete)

-the potential for volume change in a soil with a loss or gain of moisture

-volume change occurs mainly because of the interaction of clay minerals with water and varies with the amount and type of clay minerals in the soil

-wet = expand; dry = shrink

-if the shrink-swell potential is rated high, shrinking and swelling can cause damage to buildings, roads and other structures, and special engineering/construction measures are needed

-soils can be sources of roadfill, sand, gravel, and topsoil and are rated good, fair, or poor based on the soil properties and site features that affect the removal of the soil and its use as a construction material

-roadfill: is soil material that is excavated in one place and used in road embankments in another place

-topsoil: used to cover an area so that vegetation can be established or maintained; the upper 40 inches of a soil is evaluated for use as topsoil

-hydrologic soil groups are used to estimate runoff from precipitation and are grouped according to the intake of water when the soils are thoroughly wet and receive precipitation from long-duration storms

-A = most permeable (high infiltration rate, low runoff potential) when thoroughly wet; have a high rate of water transmission and consist mainly of deep, well drained sands 

-D = least permeable (los infiltration rate, high runoff potential) that consist chiefly of clays that have a high shrink-swell potential, soils that have a permanent high water table, soils that have a clay layer at the surface, and soils that are shallow over neraly impervious material;  these soils have a very slow rate of water transmission

-pond reservoir areas hold water behind a dam or embankment; soils best suited to this use have low seepage potential in the upper 60 inches and seepage is determined by the permeability of the soil and the depth to fractured bedrock or other permeable material

-farm ponds: water stock, used for irrigation and recreation

-suitability for irrigation: some soils have minerals so when you irrigate, the minerals come to the surface and can be a problem if they are heavy metals (ex. selenium)

-depth of soil, soil permeability, seasonal wetness (high water tables) all affect the ability to construct a septic tank

-the high water table indicates that that soil is alluvium (stream deposited, stream could come back at some point) and is a "quick and dirty way" to determine the flood risk

-recreation includes the construction of camp areas, picnic areas, playgrounds, paths and trails, and golf fairways

-soil survey rates soils based on restrictive features such as wetness, slope, and texture of the surface layer and susceptibility to flooding is considered

-the degree of soil limitation is expressed as slight, moderate or severe; some soils are so fragile they shouldn't be used for recreation

-most crops can be classified into four groups:

1) row crops- (cotton, corn, soybeans, sorghum, sugar beets, most biofuel crops) usually produce the most profit and the most exposure to erosion; wide enough rows for people and machinery to get through but have maximum amount of bare Earth exposed! Why not plant grass? Competition for water and nutrients, needs to be cleared of weeds

2) small grain crops - (oats, wheat, rye, barley) can be grown in rows or broadcast, also can be used as cover crops; give more protection because the plants grow fast and are usually close together; sclerophyllic plants: mediterranean climate, presence of oils that can cutrail effects of drought

3) forage crops - (grown to be fed to animals through either pasture or harvested and then fed); produce still thicker cover and provide excellent erosion control; legumes have bacteria in the roots that have nitrogen-fixing capabilities (clover, alfalfa); can be tilled under as green manure; great amount of biomass under the soil, which cuts down on leaching, loosens the soil, decreases bulk density, creates more pore space (greater ability to take in air, water, roots...)

4) tree crops - forest = extensive, orchards & vineyards = intensive; with undergrowth and a litter layer on the surface almost eliminate erosion 

-improves condition of soil

-different crops have different demands, thus rotating crops depletes soil less (varied nutrients are absorbed by different plants)

-break weed, insect, disease cycles

-rotate conservative crop with depleting crop (ex. plant grass after years of corn, plant corn third year, plant grass again after 2-3 years)

-based partly on soil, partly on climate

-range site conditions indicate the vegetation and wildlife that a particular site can support; range sites of the same type of classification should be treated/managed similarly

-strip cropping resembles a widely spaced version of intercropping; it divides a field into long, narrow bands that cross the path of the erosive force of water or wind

-strips with more vegetative cover slow runoff, reduce wind velocity, and catch soil eroded from the more exposed strips (inexpensive way to reduce erosion)

-contour strip cropping is one of the most effective means of controlling water erosion while growing crops in rotation; it works well where the slopes are long and smooth; one of the most important design factors of contour strip cropping is the width of the strips, which must be limited in width to avoid excessive runoff and erosion

why till?

1) prepare for seed and rootbed (tilling makes it easier for roots to establish)

2) control weeds

3) promote air and water infiltration, can even help with erosion control

also... (not included in book, but stated by Trimble): 4) allows for the soil to warm up (exposes soil to the air, not as insulated)

downside: oxidation of organic materials that are exposed to the foil; soil fauna (earthworms, ants, spiders, mice, moles...) are greatly affected by tillage!

-discs and tractors are selected to minimize the number of passes; powerful discs allow for just one pass

-minimize number of passes to reduce expenses of: 1) fuel; 2) tires compact soil with each pass; 3) time of the farmer doing the tilling

-conservation tillage is a term that is applied to a variety of systems that leave the soil surface trashy, cloddy, and ridged

-water and wind erosion are reduced by tillage systems that leave more crop residue on the soil surface and make the soil more permeable (examples: stubble mulch tillage, reduced tillage, and no-till)

-stubble mulch tillage: method of farming with undercutting implements and associated equipment so that crop residues remain on the soil surface at seeding time to control erosion until the new crop procides its own protection; benefits: saves water in soil, prevents erosion, keeps water from evaporating, more organic material in the soil; problems: insolates soil (cold soil) and clogs up conventional equipment

-no-till farming: no tillage for seedbed preparation or weed control except for the action of the driller, which is dropped into the soil and "come along and zap it with herbicides"; benefits: increases infiltration, structure improves, macrofauna spared, soil is a carbon sink, saves fuel; problems: cost of herbicides and potential environmental and health costs

-work in moderate rainfall

-semi-arid Mediterranean climates

-western Europe b/c very steep slopes

-farmers forced to cultivate on steep slopes due to population living on not so steep ones

Problems: riser contains animal, plant pests & to keep level, rise must be the same all around (slope) 

-developed in U.S. & extensively used

-rework soil 

-enough slant to hold water

-machinery can still go over it b/c slope is not too steep

-reduce the length of slope, reduces erosion

-increase in avg. slope, decrease length of slope

-terraces have very gentle slope (4/10 of 1% OR 5in/100ft.)

-run water on either side of field into waterways on each side

-must get rid of water just kike contour b/c of overland flow

-over time, you cut the troughs but can easily be replaced by farmer himself

-when you cannot use bench or mangum b/c the land is too steep

-cannot use machinery

-must have VERY valuable land and crop to use this b/c it is very expensive, so must be worth it

-pipes in the ground take water away

-where there is vegetation to catch water, lose productive land for crops

-how high can rise be?

-given location, what can the vertical interval be?

VI= S(slope)*X(geoographic factor)

-North U.S. -0.8 vs South U.S.- 0.4 (means that N. U.S. can have terrace risers that are twice as high & wide if compared to S. U.S.) this is due to the erosive power of rainfall b/c climate plays a huge role

-mild slope= wide trail, steep slope= narrow trail 

get water down in a way that is best

-grassed waterways are the cheapest & most used way

-three basic designs (triangle, trapezoid, parabolic) 

-easy to build, however not recommended

-channel erosion: slope, depth, & velocity (want to minimize these)

-maximize resistence & minimize force by reducing these factors

-flat & level bottom

-machinery can make keeping this difficult 

-broad parabolic crossection (this minimizes depth which minimizes velocity, but stuck with slope) 

-most effcient of all

-the smoother, the better

-more difficult with machinery

-best controller of water velocity

-need grass for protection 

-determine velocity

-V= (1.5/n)(R^2/3)(S^1/2) 

-depends on depth (hydraulic radius), roughness factor, & slope

-ex) Bermuda grass @ 5-10% slope can handle velocity 2.4m/s but @ >10%, it can only handle 1.8 m/s b/c more power

-density of water

-velocity

-depth

-slope

(minimize last 3 to minimize stream power) 

-rock barriers like rip-rap

-drop structures

-build dams

Rock barriers like Rip-rap

-stones-water flows over rocks, but energy becomes concentrated below rock, so need something like concrete to absorb energy

-Rip rap: permeable fabric to catch water flowing thru rocks, so it does not erode the soil

-It can also be expensive, so use grassed waterways if possible  

-rocks are hand laid, labor cost

-pond up water 

-manmade structure, typically small and built on minor streams, or as part of a dam's spillway, to pass water to a lower elevation while controlling the energy and velocity of the water as it passes over

-Unlike most dams, drop structures are usually not built for water impoundment, diversion or raising the water level.

-Mostly built on watercourses with steep gradients, they serve other purposes such as water oxygenation and erosion prevention.

-trap sediment

-help stabilize drainage ways using drop structures (control erosion, to even out flow as well by mitigating channel flow) 

-stores floodwater temporarily for irrigation, livestock, recreation

Class A: rural, no damage if broken

Class B: rural, damage can occur if broken

Class C: urban, serious damage

-build dams

-control floods & watersheds

-better land-use practices

-manage streams 

-placement of berm (best)

-build dam

-subsurface/surface flume

-grazing of animals (animals are allowed to go into streambanks)

-objects like trees can cause organic debris which can cut channels

-turbulence in water 

-streambanks need grass which creates biomass 

-rip-rap by bulldoze cut bank

-add woody vegetation

-keep animals off

-make it grassed 

-wind barriers

-prevent soil erosion/ wind erosion

-to be effective, fields must be small

-field becomes infested with pests

-shade is created making cold climate

-trees can take away water from crops

-trees may encroach onto cropland, affecting crops