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Home , Clay, Sand, Silt

UNDERSTANDING TURF MANAGEMENT The second in a series by R.W. Sheard, PhD., P.Ag.

SAND, and ny sample of soilis made up of responsible for the retention of sticky and is easily formed into a A a continuous array of many of the plant nutrients in the string. which may range from the very , such as calcium, , smallest clay particles to large potassium, trace elements and some SILT . In order to describe of the phosphorus. Clays react with The particles classifiedas silt are in- scientist have established a clas- the breakdown products of organic termediate in sizeand chemicaland sification system for ranges of matter to stabilize the in the physical properties between clay sizes; size ranges which soil.Asoilwithout clayparticles can and . The silt particles have reflect their role in many of the soil be a very infertile soil. limited ability to retain plant properties we are familiarwith. This Clays, because of their very small nutrients, or to release them to the classification system divides the size and very large surface area, are soil solution for plant uptake. Silt particles into four classes - gravel able to retain greater amounts of tends to have a spherical shape, and stone, sand, silt,and clay.Table than sandy soils.On the other giving a high silt soil a soapy or 1 lists the Canadian classification hand, as will be discussed in a latter slippery feeling when rubbed be- system for the size range ofparticles article, clays hold the water more tween the fingers when wet and is which may be found in a soil closelyand do not release the water more difficult to form into a string sample. as readily to grass roots as . than clays. Clay particles have a vastly greater Because of the spherical shape, silt CLAY tendency to stick together than alsoretains a large amount of water, sand, thus it is common farmer The scientists have assigned the but it releases the water readily to knowledge that soilshigh in clayare name clay to the finest particles and plants. While silt soils are generally difficult to .When a small sample not without reason. Clay size par- considered very fertile for the of a clay soil is wetted and rubbed ticles are the source of most of the growth of plants, largely due to between the fingers it will feel very chemicalproperties of soil.They are their water characteristics and ease of cultivation, engineers dread working with them due to their rela- Table 1: The classification system for soil particles; their sizes. surface tively easy release of water and lack area and visibility. of ability for the particles to stick together. Soli Separate Size Range Surface area Visibility SAND (rnrn) Sand particles are essentially small fragments, and as such, have Clay less than .002 23.000 electron microscope little or no ability to supply grass Silt .002 to .05 2.100 light microscope with nutrients or to retain them Very fine sand .05 to .10 light microscope against .Asrockfragments, sandy soils feel gritty between the Fine sand .10 to .25 210 human eye fingers. The sand grains have little Medium sand .25 to .50 human eye ability to stick together; thus sandy Course sand .50 to 1.0 21 human eye soils can not be rolled into a string Very coarse sand 1.0 to 2.0 human eye when wetted. Gravel 2.0 to 100 human eye It is known that sandy soilsare droughty soils because they retain larger than 100 human eye little water when wetted. Neverthe- less what water is retained is released to plants easily. When rain Fig. 1: The textural triangle used for assigning textural class names. (A or irrigation occurs the water readi- straight line drawn along the grid for the percentage clay and for the ly penetrates the soil surface, the percentage silt will intersect within a class name area. Try it using the excess moves through rapidly and numbers in Table 2.) the soil remains well aerated. These properties make sands a desirable medium for growing sports turf where there is no limitation in ap- pling water and nutrition, as needed, throughout the season. The analysis for the distribution of the various particles in a soil sample ( analysis) for the sand portion is done using a set of screens which have mesh sizes that retain the various ranges of sand particles. Estimating the silt and clay is more

complicated as it requires measur- \" ing the rate of settling of the particles in water. The analysis is based on a law of physics which says that small diameter particles settle more slowly in water than larger diameter particles. By dis- persing a sample of soil in a column of water so that all particles will set- tle independently of each other and taking samples at a set depth and .. time interval, the technician can cal- % sand culate how much silt and clay is in the sample. Because there can be an infinite array of percentages of sand, silt and clay in soils, scientist have devised a procedure for classifying the poten- tial combinations into 12 groups which reflect broad soil properties. These groups are called textural Table 2: Some typical particle size analysis and the corresponding class names and are obtained byap- class name. plying the particle size analysis to a textural triangle (Figure 1). Thus a Panicle size analysis soil which contains 40% sand, 40% Sand Slit Clay Textural class name silt and 20% sand would be called a soil. Table 2 lists several tex- - % by weight - tural class names and a typical particle size distribution for each. 92.5 5.5 2.0 Sand Some confusion occurs between the 61.0 28.0 11.0 Sandy loam use of these terms by many turf 40.0 41.0 19.0 Loam managers and the soil scientist. The 20.0 61.0 19.0 Silt loam soil scientist considers the name 3.5 89.0 7.5 Silt loam or clay to refer to a range of 28.5 42.0 31.0 Clay Loam particle sizes in a soil. The turf manager often refers to a loam as a 10.0 31.0 59.0 Clay soil which is easy to till or is not compacted whereas a clay is dif- Sand, Silt and Clay continued from page 5 The Sports Turf Association ficult to work, is compacted or may be a . extends a warm welcome In summary many chemical and to New Members ... physical properties of a soil can be assessed in rough terms from a knowledge of a particle size analysis ...who have joined since August of 1990. or the textural class name. For ex- ample in comparing a clay to a sandy loam it can be expected that Dennis Amott Hamilton Parks and Recreation 1) the clay will be relatively more Peter Booker Hamilton Parks and Recreation fertile, Tom Coffey .. Hamilton Parks and Recreation 2) the clay will have greater nutrient holding capacity for Dave Cowan Hamilton Parks and Recreation potassium, calcium and Joe Holmes. Hamilton Parks and Recreation magnesium, Darrell Pomfret Hamilton Parks and Recreation 3) the clay will have more organic matter, Gerry Companion York Region Board of Education 4) the clay will hold more plant Dan Ellis ... York Region Board of Education available water and be less Grant McKeich York Region Board of Education droughty, Ron Scheepers York Region Board of Education 5) the clay will have smaller pores resulting in slower air and Jane . . Oakville Parks and Recreation water movement within the Mike Gorman . . Town of Vaughan Parks Department soil, and Herman Krecher Town of Vaughan Parks Department 6) the clay will have greater Rick Reeves Town of Vaughan Parks Department stickiness, ability to be retain a shape when moulded and be Jeff Maslanka . Kitchener Parks Department harder when dry. Fred Williams City of Kingston Parks Ian Blundy .. Seneca College John Hopkins Lawrence Park Bowling Green Steve Pollard Green Thumb Horticultural Services Golf & Spans TURF Heather Kenny Green Cross Ltd. Magazine Marie Thorne . Green Cross Ltd. If you are not getting Golf & Larry . . Pickseed Canada Inc. SportsTURF Magazine, you are Richard Dwyer Pickseed Canada Inc. missing out on a well written Mark Bishop Bishop Seeds Ltd. and informative magazine ,- Paul Turner . . Bannerman Turf Equipment $50.00 U.S. funds. Karen Nesbitt . Nesbitt Aggregates Order your subscription by Bruce Sheppard United Agricultural Products sending in your name, address, city, province, postal code and Trent Baccardax Rain Bird Canada Ltd. payment to: Golf & SportsTURF P.O Box 8420, Van Nuys, Ca 91409 USA

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