AIOBAS10-Intro-to-Land-Eval.pptx

Introduction to Land Evaluation Basic Soil Science Land Factors ◼There are Six land factors that are evaluated to determine the best use for an area of land. ◼Each factor must be evaluated based on criteria for that characteristic. www.OneLessThing.net 2 Land Factors ◼Slope: the steepness of t...

Introduction to Land Evaluation Basic Soil Science Land Factors ◼There are Six land factors that are evaluated to determine the best use for an area of land. ◼Each factor must be evaluated based on criteria for that characteristic. www.OneLessThing.net 2 Land Factors ◼Slope: the steepness of the area or field ◼Erosion: a percentage of the original topsoil which has suffered the harmful effects of water and wind ◼ Surface Texture: determined by the proportion of sand, silt, and clay in the topsoil (NOT the size of the sand particles) www.OneLessThing.net 3 Land Factors ◼Permeability of Subsoil: the ability of air and water to move through the subsoil ◼Drainage: the process of excess water being removed from the soil ◼Effective Depth: the depth to which plant roots can easily penetrate www.OneLessThing.net 4 Finding the Slope ◼Slope refers to the steepness of an area. ◼It is determined by estimating the number of feet the land rises or falls over 100 feet and expressed as a percent. ◼In other words, it is the change in vertical elevation over a given horizontal distance. ◼You can visually estimate slope by standing perpendicular to the stakes and sighting down your arm. www.OneLessThing.net 5 Finding the Slope ◼ To calculate slope, divide the amount of vertical change in elevation by the horizontal distance the change takes place over. ◼ Multiply that number by 100 to get a percentage. ◼ For example, if elevation changes 8 feet over a distance of 50 feet, then: 8 ft. / 50 ft. x 100% =16% slope. ◼ Also if the ground falls 12 feet over a distance of 100 feet then the slope is 12%. (12/100 x 100%) www.OneLessThing.net 6 Categories of Slope ⚫The category of slope will depend on your state and what area of the state you are in. ⚫Often slope is the main limiting factor for the land class of an area. www.OneLessThing.net 7 Categories of Slope ⚫For Texas, the categories are as follows. ◦ Nearly level — less than 1% slope. ◦ Gently sloping — 1 to 3% slope. ◦ Moderately sloping — 3 to 5% slope. ◦ Strongly sloping — 5 to 8% slope. ◦ Steep — 8 to 15 % slope. ◦ Very Steep — Land with over 15 % slope www.OneLessThing.net 8 Erosion ⚫Erosion is percentage of difference between the original topsoil and amount remaining. (amount lost/original thickness) x 100 ◦ None to slight - Less than 25% of the original layer present. ◦ Moderate - 25 to 75% of the original surface layer present. ◦ Severe - more than 75% of the original surface layer is removed. ◦ Very severe - more than 75% of surface soil removed. ● The plow layer exhibits characteristics similar to severely eroded soils with frequent uncrossable www.OneLessThing.net gullies and/or severe accumulations by wind. 9 Texture ⚫Topsoil Texture is determined by the proportion of sand, silt and clay. ◦ Fine means that the soil contains at least 35% clay. (feels like heavy flour) ◦ Medium is between Coarse and Fine. (feels like four and salt mixture) ◦ Coarse means that at least 70% of the soil is sand. (feels like salt) www.OneLessThing.net 10 Permeability ⚫Permeability is the rate of movement of water or air through the soil. ◦ Rapid: a sandy subsoil generally ◦ Moderate: medium-textured subsoil or a sandy clay subsoil that has bright red or yellow colors ◦ Slow: gray or gray mottled, fine, sticky, clay subsoil www.OneLessThing.net 11 Drainage ⚫Drainage refers to the surface and internal drainage and determines how quickly soil can be tilled following a good rainfall. ◦ Excessive: coarse, sandy materials, over 40 inches deep. ◦ Well-drained: no gray mottles in top 30 inches of soil profile ◦ Moderate: no gray mottles in top 20 inches, but present in 20-30 inch zone ◦ Somewhat poor: gray mottles in top 20 inches. ◦ Poorly drained: soil is usually gray to surface; subsoil is always predominately gray. ◦ Wet: surface water present www.OneLessThing.net 12 Effective Depth ⚫Effective Depth is the depth to which plant roots can easily penetrate. ◦ Deep: at least 40 inches ◦ Moderately Deep: at least 20, but less than 40 inches ◦ Shallow: at least 10, but less than 20 inches ◦ Very Shallow: less than 10 inches www.OneLessThing.net 13 Land Capability Classes ⚫What are land capability classes? ◦ a system designed for classifying land according to its best use ◦ groups fields or areas with similar hazards/limitations www.OneLessThing.net 14 Land Capability Classes ⚫What are land capability classes? ◦ a system designed for classifying land according to its best use ◦ it groups fields or areas with similar hazards/limitations ⚫There are eight classes that have the same meaning in all parts of the U.S. (designated by Roman numerals) ⚫the higher the class number, the less the land is suitable for crop production (a.k.a. cultivation) www.OneLessThing.net 15 Land Capability Classes ⚫can be divided into two broad groups: ◦ land suited for crop production (Classes I, II, III, and IV) ◦ land suited only for permanent vegetation as pasture or forest (Classes V, VI, VII, and VIII) www.OneLessThing.net 16 Class I ⚫very good land with ideal soils; no limitations restricting it so it can be used for cultivated crop production ⚫Characteristics: ◦ Slope: level or very nearly level ◦ Topsoil Thickness: thick or moderately thick ◦ Erosion: none to slight ◦ Texture: coarse or medium ◦ Permeability: moderate ◦ Drainage: well drained and not subject to overflow ◦ Effective Depth: deep www.OneLessThing.net 17 Class II ⚫have some limitations that require moderate conservation practices but suitable for crop production ⚫Characteristics: ◦ Slope: nearly level or very gently sloping ◦ Topsoil Thickness: very thick, thick, moderately thick, or thin ◦ Erosion: slight or moderate ◦ Texture: coarse, medium, or fine ◦ Permeability: moderate or slow ◦ Drainage: well drained or moderately well drained ◦ Effective Depth: deep or moderately deep www.OneLessThing.net 18 Class III ⚫ may be used for crop production if certain conservation practices are followed; choice of crops is reduced due to limitations ⚫ Characteristics: ◦ Slope: nearly level, very gently sloping, or gently sloping ◦ Topsoil Thickness: extremely thick, very thick, thick, moderately thick, or thin ◦ Erosion: slight, moderate, or severe ◦ Texture: coarse, medium, or fine ◦ Permeability: moderate or slow ◦ Drainage: well drained, moderately well drained, somewhat poorly drained ◦ Effective Depth: deep, moderately deep, or shallow www.OneLessThing.net 19 Class IV ⚫ borderline cultivatable land; may be used for crop production if carefully managed; severe limitations that restrict crop choice and should be on a rotational basis ⚫ Characteristics: ◦ Slope: nearly level, very gently sloping, or sloping ◦ Topsoil Thickness: extremely thick, very thick, thick, moderately thick, or thin ◦ Erosion: slight, moderate, or severe ◦ Texture: coarse, medium, or fine ◦ Permeability: slow, moderate, or rapid ◦ Drainage: excessively drained, well drained, moderately well drained, somewhat poorly drained, or poorly drained ◦ Effective Depth: deep, moderately deep, shallow, or very shallow www.OneLessThing.net 20 Class V ⚫ these soils are very wet but may be used for pasture usually found in small and nearly level drainageways ⚫ not subject to erosion but do have drainage problems and frequent flooding the degree of wetness limits their use ⚫ unfit for cultivation ⚫ Characteristics: ◦ ◦ ◦ ◦ ◦ ◦ ◦ Slope: nearly level or very gently sloping Topsoil Thickness: moderately thick to thick Erosion: none to slight Texture: coarse or medium Permeability: slow Drainage: poorly drained to wet Effective Depth: deep to shallow www.OneLessThing.net 21 Class VI ⚫these soils unfit for cultivation and their severe limitations restrict use to pastures and forestry ⚫hazards include steep slopes, erosion, or shallow soils ⚫Characteristics: ◦ Slope: strongly sloping ◦ Erosion: severe ◦ Effective Depth: shallow www.OneLessThing.net 22 Class VII ⚫not suitable for crop production and has severe limitations for pasture or forestry use ⚫requires extensive management of conservation practices to control erosion ⚫major hazards are severe erosion and/or slope ⚫Characteristics: ◦ Slope: steep or very steep www.OneLessThing.net 23 Class VIII ⚫only suited for wildlife or recreation purposes ⚫Characteristics: ◦ usually extremely stony, sandy, or wet www.OneLessThing.net 24 “We make teaching Ag easier.” THANK YOU FOR LEARNING WITH ONE LESS THING.