Soil Texture and Structure - carlisle.k12.ky.us

1 soil Texture and StructureHAVE YOU EVER made sand castles andmud pies? If so, think back at how thesand and mud were alike or different. Whatdid they feel like? What happened when theydried? Both had unique properties that will bediscussed in this : 1. Describe soil Texture and soilcharacteristics related to Explain soil Structure and vari-ous types of soil Terms: soil TextureThe inorganic material in soil is calledmineral matter. Mineral matter began as rock thatwas weathered into small particles . Most soils have different sizes of mineral particles . Theseparticles are called sand, silt, or clay, based on their the largest of the mineral particles . Sand particles create large pore spaces thatimprove aeration. Water flows through the large pore spaces quickly.

2 Soils with a high percent-age of sand are generally well-drained. Sandy soils lack the ability to hold nutrients and are notfertile. Sandy soils also feel gritty to the a mid-size soil particle. It has good water-holding ability and good fertility character-istics. Silt feels like flour when dry and smooth like velvet when : soil Texture and StructurePage by CAERT, Inc. Reproduction by subscription densityclayclodsmineral matterparticle densitypedspermeabilitysandsiltsoil structuresoil texturesoil workabilitytextural trianglewater-holding capacityClayis the smallest size soil particle. Clay has the ability to hold both nutrients and waterthat can be used by plants. It creates very small pore spaces, resulting in poor aeration and poorwater drainage.

3 Clay forms hard clumps when dry and is sticky when 1. Characteristics of Sand, Silt, and ClayCharacteristicsSandSiltClayLooseness GoodFairPoorAir SpaceGoodFair to GoodPoorDrainageGoodFair to GoodPoorTendency to Form ClodsPoorFairGoodEase of WorkingGoodFair to GoodPoorMoisture-Holding AbilityPoorFair to GoodGoodFertilityPoorFair to GoodFair to GoodE-unit: soil Texture and StructurePage by CAERT, Inc. Reproduction by subscription LoamSilty ClayLoamSandyClay LoamLoamSilt LoamSiltSandy LoamSandLoamy Sand102030405060708090100102030405060708 090100 PERCENT SANDPERCENT CLAYPERCENT SILT10203040506070809010035%clay30%silt3 5%sandExample: A soil with35% clay, 30% silt, and35% sand is a clay loam*FIGURE 1. The textural triangle can be used to differentiate the several classes of CLASSESSoil textureis the proportion ofthe three sizes of soil particles that arepresent and the fineness or coarsenessof a soil .

4 soil Texture may be determinedin one of two ways. The percentages ofsand, silt, and clay may be tested in thelab. Once tested, the textural class of thesoil can be determined by referring tothetextural triangle(a device usedto differentiate the several classes ofsoil). Soils with different amounts ofsand, silt, and clay are given differentnames. For instance, a soil containing40 percent sand, 20 percent clay, and 40percent silt is called loam soil . The rela-tive amounts of sand, silt, and clay mayalso be determined in the field using theribbon method. Five textural classesmay be determined using this A ribbon of soil forms easily and remains long and fine-textured A ribbon forms but breaks into pieces 3/4 to 1 inch No ribbon forms. The sample breaks into pieces less than 3/4 inchlong.

5 The soil feels smooth and coarse-textured No ribbon forms. The sample feels gritty and : soil Texture and StructurePage by CAERT, Inc. Reproduction by subscription 2. The ribbon method is used to determine five majortextural classes of CONNECTION: Sedimentation Test of soil TextureA simple activity can be performed to determine the percentages of sand, silt, and clay in agiven soil sample. Place about two cups of soil in a tall, straight-sided quart jar. Add five table-spoons of 8 percent water softening solution and enough water to almost fill the jar. Tighten thelid and shake vigorously for five minutes. After 40 seconds, measure the depth of the settled soiland record it as the sand depth. Do not shake the jar again. In 30 minutes, measure the depthof the settled soil .

6 Subtract the depth of sand from the measurement to get the silt depth. Thenext day measure the soil depth and subtract the sand and silt depths to get the clay , measure the total depth of the settled soil . Determine the percentage of each soil particleby dividing the particle depth by the total soil depth and multiplying by No ribbon forms. The sample is composed almost entirely of grittymaterial and leaves little or no 2. soil Textural ClassesSandDry Loose and single grained; feels Will form very easily crumbled ballSand: 85-100%, Silt: 0-15%, Clay: 0-10%Loamy SandDry Silt and clay may mask sand; feels loose, Feels gritty; forms easily crumbled ball; stains fingers : 70-90%, Silt: 0-30%, Clay: 0-15%Sandy LoamDry Clods easily broken; sand can be seen and Moderately gritty; forms ball that can stand careful handling; definitely stains : 43-85%, Silt: 0-50%, Clay: 0-20%LoamDry Clods moderately difficult to break; somewhat Neither very gritty nor very smooth; forms a ball; stains : 23-52%, Silt: 28-50%, Clay: 7-27%Silt LoamDry Clods difficult to break; when pulverized feels smooth, soft, and floury, shows Has smooth or slick buttery feel.

7 Stains : 0-50%, Silt: 50-88%, Clay: 0-27%Clay LoamDry Clods very difficult to break with Has slight gritty feel; stains fingers; ribbons fairly : 20-45%, Silt: 15-53%, Clay: 27-40%Silty Clay LoamSame as above, but very : 0-20%, Silt: 40-73%, Clay: 27-40%Sandy Clay LoamSame as for Clay : 45-80%, Silt: 0-28%, Clay: 20-35%ClayDry Clods cannot be broken with fingers without extreme Quite plastic and usually sticky when wet; stains fingers. (A silty clay feels smooth, a sandyclay feels gritty.)Sand: 0-45%, Silt: 0-40%, Clay: 40-100% soil CHARACTERISTICS RELATED TO TEXTUREThe Texture of a soil is important because it determines soil characteristics that affect plantgrowth. A few of these characteristics are water-holding capacity, permeability, and capacityis the ability of a soil to retain water.

8 Most plantsrequire a steady supply of water, and it is obtained from the soil . While plants need water, theyalso need air in the root zone. The ease with which air and water may pass through the soil workabilityis the ease with which soil may be tilled and the tim-ing of the with a larger percentage of sand are easier to work than soils with a larger percentageof clay. Clay soil tends to be tighter, making it more difficult to break up or cultivate, whereassandy soil is looser. It also takes longer for a clay soil to dry after a rain than a sandy : soil Texture and StructurePage by CAERT, Inc. Reproduction by subscription of the better drainage, a sandy soil can be worked sooner. In the case of wet clay soil ,the producer or gardener must wait longer for the soil to dry Texture may limit which crops can be grown.

9 For example, root crops, such as carrotsand onions, perform best in a sandy soil because it is loose and allows the plant to , growth of some plants is stunted when growing in sandy soils because they lack thewater- and nutrient-holding StructureSand, silt, clay, and organic matter particles in a soil combine with one another to formlarger particles of various shapes and sizes and are often referred to asaggregates, or structureis the arrangement of the soil particles into aggregates of various sizes andshapes. Aggregates that occur naturally in the soil are referred to aspeds, while clumps of soilcaused by tillage are are created through a number of ways, including freezing and thawing, wettingand drying, fungal activity, tillage, and by plant roots that surround the soil and separate theclumps.

10 Weak aggregates are cemented to make them distinct and strong. Clay, iron oxides,E-unit: soil Texture and StructurePage by CAERT, Inc. Reproduction by subscription with high organic mattercontent and good structurepermits water layer prevents waterfrom soaking deeply surface soilplus impermeable subsoilprevents 3. soil with good permeability allows water to be easily organic matter often act as cements. When soil microorganisms break down plant residues,gums are produced that glue peds STRUCTURAL CATEGORIEST here are eight primary types of soil Structure , including blocky, columnar, crumb, granu-lar, massive, platy, prismatic, and single The units are block-like. They consist of six or more flat or slightly The units are similar to prisms and are bounded by flat or slightly roundedvertical faces.