Sedimentation Test of Soil Texture Description: The sedimentation test is an easy way to measure the percent sand, silt, and clay in a soil sample. It is based on the fact that large heavy particles will settle most rapidly in water, while small light particles will settle most slowly. The Calgon laundry powder is used to dissolve the soil aggregates and keep the individual particles separated. Materials: Soil sample One quart fruit jar with lid 8% Calgon solution—mix 6 tablespoons of Calgon (a laundry powder available in stores) pre quart of water Metric ruler Measuring cup Tablespoon Procedure: 1. Place about ½ cup of soil in the jar. Add 3 ½ cups of water and 5 tablespoons of the Calgon solution. * NOTE: In general, I fill the jar about half full, and then add water almost to the top, along with about 1Tbsp. of the Calgon. Either way works fine. 2. Cap the jar and shake for 5 minutes. Leave the jar on the desk and let settle for 24 hours. 3. After 24 hours, measure the depth of settled soil. All soil particles have settled so this is the Total Depth. Write it down and label it. * NOTE: Some of the smallest particles may not have settled in 24 hours. Some clays may take as long as a week. 4. Shake for another 5 minutes. Let stand 40 seconds. This allows sand to settle out. Measure the depth of the settled soil and record as Sand Depth. 5. Do not shake again. Let the jar stand for another 30 minutes. Measure the depth, and subtract the sand depth to get the Silt Depth. 6. The remaining unsettled particles are clay. Calculate clay by subtracting silt and sand depth from total depth to get Clay Depth 7. Now calculate the percentage of each soil separate using these formulas: % sand =

sand depth X 100 total depth

% silt =

silt depth X 100 total depth

% clay =

clay depth X 100 total depth

SOIL TEXTURE: RIBBON TEST Since facilities are not always available for determination of soil texture by mechanical analysis, it is useful to be able to estimate the texture by feel. With considerable practice it is possible to become quite proficient with this method. This method is particularly important to people working on soil surveys and land appraisal, since they have neither the time nor the equipment to conduct a mechanical analysis of the soil in the field.

Procedure: A. Moisten a small sample of soil in the palm of the hand and work it until it has a consistency about like workable putty. Then hold the sample between the thumb and forefinger and press the thumb forward to form the sample into a ribbon. If the ribbon forms easily and remains as a long plastic ribbon the sample probably has 40 % or more of clay and is basically a clay texture. If a ribbon forms but breaks easily it is about 27 to 40% clay and is basically a clay loam texture. If the ribbon does not form, the sample probably contains less than 27% clay and is basically a loam. B. Thus we have decided whether the sample is basically a clay, clay loam, or loam. Next we must decide if there is a predominance of either sand or silt. Sand has a very gritty feeling so, for example, a soil that was found to be basically a clay but yet contained much gritty sand would be called a "sandy clay". Silt has a very smooth talclike feel and a lack of gritty feel so, for example, a soil that was basically a loam but had a smooth silt feel would be called a "silt loam". A soil that had neither a predominance of silt nor of sand would simply be a clay, clay loam, or loam. The feel of a soil is modified by: 1. the amount of moisture present. 2. the amount of organic matter. This especially affects clayey soils. Very high amounts cause the soil to be "chaffy". 3. the type of clay. In tropic and sub-tropic regions different types of clay predominate and give a different feel to soils.

FIELD DETERMINATION OF PHYSICAL PROPERTIES For most horticulturists, engineering accuracy is not needed. Time is also usually of the essence and a two day or two week delay for a laboratory report severely hinders work progress. Soil texture analysis by feel is more practical. It is a skill that is easily mastered with practice and confidence. Since it is not perfect name identification of each texture class, but a knowledge of how this texture effects plant growth, good estimates are as valuable as scientific analysis. The following are "hints" on detecting and estimating soil separates. It is most desirable to examine the soil first as a clod (dry), then as a powder, and finally slightly moistened as a "mud ball". SAND Clod - Dry clods are very soft or non-existent. Dry - Large grains or a high percentage of sand can be seen with the naked eye. Moist - Rubbed between the thumb and forefinger it feels gritty. You can often hear the grating of the large grains if it is held near the ear and rubbed. If less than 50% of the particles in the sample are sand the sound is usually not audible. Wet the sample slightly more and rub it in the palm of your hand with your forefinger. This is a very sensitive test for the presence of sand. Soils strong in these characteristics are usually sand, loamy sand, or sandy loam. CLAY Clod - Dry clods are difficult or impossible to break. Dry - Like silt, the small particles feel smooth. Moist - Large amounts of clay feel very slick, slippery , slimy, or greasy. They are very plastic; squeezing a wet ball between the thumb and forefinger may produce a ribbon up to 3 inches long. Loams will produce only very small ribbons. Clay balls are exceedingly stiff. On soils with small amounts of clay, pressing the ball with the thumb will leave a slight cast. The more distinct the cast the higher the percentage of clay. Clay leaves a stain on the hands that is difficult to wash off. This group includes clay, silty clay, and sandy clay. SILT Clod - The clod is often relatively difficult to break because the fine silt is often mixed with clay. If the percentage of clay is very low, the clod will break as easily as sand. The clod will "explode" leaving a fine dust on the fingers. Dry - Powdery like dry clay. Moist - Moist silt is velvety smooth without being sticky. Soils high in silt will not make as stiff a ball or as long a ribbon as clay soils. Silt and silt loam are two members of this category. LOAM This is the combination category and the group containing our best soils. It can be very difficult to define since it is an intermediate. This group includes sandy loam, silty clay loam, and sandy clay loam. Look at the soil textural triangle. It is far less likely under normal conditions that you will have soils in the corners or outer edges than it is that you will have soils toward the inner portion of the triangle.

Soil Texture Classification Classification is the naming of a soil. The soil triangle has been developed as a means of determining a name. After the amount of sand, silt and clay have been determined by mechanical analysis, the weights are converted to percentages by dividing the total weight of a sample into the portion of each of these separates. The three added together should equal 100%. By taking the percentage of any two of the three and following the corresponding lines on the soil triangle, you can determine the soil's classification. (See Triangle). Soil Structure In most soils which are still in a natural state, individual particles cohere into larger units called peds. These form different structures. Why they form is not really understood although it is known that organic matter, calcium carbonate, calcium sulfate, and iron and aluminum oxides act to cement the structures together. In many of our glacial soils which are of very recent origin little or no structural development is found. The same is true of areas that have been deeply or regularly tilled.

Characteristics of Soil Structure Classes ________________________________________________________________________ Very Fine The smallest size of peds Fine Medium Coarse Very Coarse The largest size of peds ________________________________________________________________________

Characteristics of Soil Structure Grades Grade Description ______________________________________________________________ Structureless No aggregation or orderly arrangement of particles or orderly arrangement of natural lines of weakness. Weak

Strong

Poorly formed, indistinct peds barely observable in place.

Durable peds quite evident in place and adhering only weakly to one another. ________________________________________________________________________

Soil Consistence Consistence is a term used to describe how soil reacts to external pressures. Special terms have been developed to describe soil consistency. Wet Consistence ( Field Capacity or above) Stickiness - adhering to other objects. Plasticity - ability to change shape when under stress and to retain that shape when the stress is removed. Moist Consistence Loose - not holding together. Friable - easily crumbled in the hand. Firm - distinctly resistant to crushing. Very firm - difficult to crush between thumb and forefinger. Dry Consistence ( Air Dry) Loose - not holding together. Soft - barely holding together. Slightly hard - slightly resistant to crushing. Hard - barely broken between the thumb and forefinger. Very hard - cannot be broken between the thumb and forefingers. Extremely hard - cannot be broken in the hands. Cementation Weakly cemented - can be broken in the hands. Strongly cemented - can be broken with hammer. Indurated - resistant to breaking with hammer.