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Home , Topsoil

COOPERATIVE EXTENSION SERVICE • UNIVERSITY OF KENTUCKY COLLEGE OF AGRICULTURE, LEXINGTON, KY, 40546

AGR-203 Improving the Productivity of Landscapes with Little or No Topsoil 100 90 10 Edwin L. Ritchey, Plant and Sciences 100

80 20 andscapes with little or no topsoil can 90 10 make it difficult to produce a , 70 30 Llawn, or other plants. Topsoil, dark in 80 20 color compared to the underlying soil, is 60 40 the part of a soil that is most biologically 70 30 active, nutrient rich, and easily managed. % clay It also is usually more easily worked than Y % 50 50 60 40 silty underlying soil, supplies most of the CLA clay

SILT % plant’s water and nutrients, and is gener- 40 sandy 60 Y % 50 50clay ally best for plant growth. silty CLA clay clay silty clay generally contains more 30 loam 70 clay and is usually more acidic than the 40 sandy 60 clay sandy clay loam topsoil. with high amounts of clay clay silty clay 20 loam 80 are generally sticky, cloddy, generally 30 loam 70 loam hard to work, and wetter (water may not sandy clay loam sandy loam silt loam infiltrate them quickly). Clayey soils will 10 loam 90 20 80 hold appreciable amounts of water, but loam y silt sand they hold it tightly, so that plants cannot silt loam sandy loam 100 readily use as much of it as they would in 10 loam 100 90 80 70 60 90 50 40 30 20 10 a more loamy or silty topsoil. The reason y sand silt sand SAND % to amend clay soils is to improve 100 • structure (you cannot easily change 100 90 80 70 60 50 40 30 20 10 the texture) Figure 1. triangle. SAND % • /drainage To determine a soil’s texture, 90 10 • plant-available water supply determine the percentages of sand, silt, and 90 10 • workability clay. The soil separates will sum to 100%. For of least two of those percentages, go to the 70 30 90 10 70 30 All these improvements will reduce side of the triangle for a least two of the sepa- 90 10 the tendency of clayey soils to form clods. rates and follow the gray line for the percent- SILT % Y % 50 50 poor age point to where70 the lines 30converge. 50 50 Soil Texture and Structure CLA 70 30 SILT % 30 70 30 medium 70 Y % poor Soil texture and structure are two 50 50 50 50 different soil properties, both often mis- CLA good understood. Soil texture is the relative 10 90 10 90 For example,30 a soil containing 30% sand,70 30 medium 70 proportions of sand, silt, and clay sepa- 60% silt, and 10% clay is classified as a silt 90 70 50 30 10 90 70 50 30 10 rates in the soil (Figure 1). Soil separates loam. good 10 90 are defined according to their size, with 10 SAND % 90 clay being the smallest separate (less than 90 70 50 30 10 90 70 50 30 10 0.002 mm), sand being the largest (2 to SAND % 0.05 mm), and silt in between (0.05 to if this change were feasible, you would slightly lower plant-available water, since 0.002 mm). Texture is hard to manipulate likely not be able to see any benefit. For sand does not hold as much water as clay. and rarely helps. An acre of soil to a depth example, adding sand to a clayey soil is the arrangement of of about 7 inches weighs about 2 million slightly reduces proportions of clay and the primary soil particles (sand, silt, and lb, so changing textural percentage by 1% silt but does not measurably change clay) into aggregates, or peds. It affects for one separate would require 20,000 infiltration or the tendency of clayey soil soil . Soil structure is influenced lb of material (1% of 2 million lb). Even to form clods. Adding sand also would by soil fauna, roots, , compost, ma-

Agriculture and Natural Resources • Family and Consumer Sciences • 4-H Youth Development • Community and Economic Development EXTENSION nure, and cover crops. Structure is what When purchasing/obtaining usually needs to be modified to improve topsoil, make sure that the productivity where there is little or no material is of high quality: free topsoil. of trash (bottles, cans, plas- To increase productivity of lawns, tic, etc.), rocks, construction , and landscape plants in topsoil- debris, and problem weeds. deficient areas, here are some options for Be aware that Kentucky has improving soil structure and other soil no legal definition of topsoil. properties: Sometimes the material being sold as topsoil is actually less Soil Sampling and suitable for a lawn or garden Soil Testing than subsoil at the site. Adver- tising does not make any given Before amending soil, take a represen- material topsoil. Some materi- tative soil sample of the area as as als removed from the top layer any topsoil you might plan to place over of another soil might not be it. The soil should be sampled to a depth suitable as topsoil because the of 6 to 7 inches in about a dozen places soil from the other area was using a soil probe, auger, or spade (Figure disturbed previously and its 2). The sample should be hand crushed Figure 2. A soil auger (left), spade (center), or probe topsoil removed or eroded. may be used to sample soils. If you are using a spade, and well mixed, then submitted to the High-quality topsoil should the sample should be trimmed with a knife, as shown. local county extension office or a private be dark brown to reddish soil testing laboratory. brown in color, not cloddy, A sample submitted to your local and without excessive amounts of clay Another option is to add the desired extension office will be sent it to the UK or sand. Typically, Kentucky topsoil amount of topsoil to the existing lawn in Regulatory Services soil laboratory for contains 2% to 4% organic matter. Any- one application, smothering the lawn and analysis. The cost for the test will vary thing below 1.5% organic matter is only then reseeding. Use this method when depending on the extent of analysis marginally suitable as topsoil. Off-site you want a new grass lawn as well as requested. Results will be returned in topsoil should be tested, preferably before topsoil. Replacing topsoil is usually more one to two weeks and will provide infor- purchase, for levels of available nutrients expensive than improving it. For small mation about nutrient availability and and content of organic matter, which is areas, such as garden plots and home recommendations for lime and nutrient an indication of its quality. lots, replacement may be an economi- additions. Test results typically indicate Ideally, 6 inches of topsoil would be cally feasible choice, but it becomes cost how much phosphorus (P), potassium added, but any topsoil addition, even if prohibitive for large acreages or farms. (K), (calcium (Ca), magnesium (Mg), and less than 6 inches, would be beneficial. zinc (Zn) are available in the soil and the Before adding topsoil, check your site for Building Topsoil degree of soil acidity/alkalinity (soil pH). compaction with a tiling rod or penetrom- There is no for nitrogen (N), so Another option is to “build” topsoil, eter. If you suspect your site is compacted, nitrogen recommendations are based which will take several years but can your county extension agent can help you on the crop or plants to be grown and be accomplished with diligence and choose the best option to improve it. Deep whether the crop/plants are established patience. To build topsoil, the current soil disturbance may be necessary. The or a new planting. For an additional soil surface needs to be amended with or- best option is to add and then incorporate fee, (OM) content ganic materials. These materials include the first 2 inches of topsoil into the exist- can also be determined using the same manures as well as composts made from ing soil to prevent abrupt changes in soil sample. For more information regarding leaves, yard clippings, and kitchen wastes texture, then add and incorporate the re- soil sampling, see the UK Cooperative without the meat scraps that attract pests. maining topsoil. With a lawn, one option Extension Publication Taking Soil Test For more information on composting, is to spread layers of new topsoil over the Samples (AGR-16), online at http://www. consult University of Kentucky Coopera- existing grass, keeping those layers thin to ca.uky.edu/agc/pubs/agr/agr16/agr16.pdf. tive Extension Publication Home Com- avoid killing the lawn. Grass completely posting: A Guide to Managing Yard Waste Replacing Topsoil covered by soil will be “smothered” and (HO-75), found online at http://www. die. Multiple thin topsoil applications over ca.uky.edu/agc/pubs/ho/ho75/ho75.pdf. If topsoil has been removed during site time will slowly increase the yard’s topsoil Plant material generated in the gar- preparation and is still on the property, depth. It’s critical to spread added topsoil den or lawn should also be returned to move it back to the lawn and garden area. evenly to keep the yard from becoming the soil. Be careful, however. Disease Another option is to purchase/obtain too rough. Rake to smooth added soil if and insect buildup can occur when you topsoil, though buying it may be costly. an uneven spread occurs. return plant material to a garden if the

2 newly planted crops are similar to what Careful use of can also help used appropriately, their use will lower was there before. Rotate crop families to build topsoil and generally improve soil total fertilizer costs. For more informa- minimize this potential. These organic quality. Properly fertilized plants don’t tion regarding fertilizer application rates, materials can be surface applied. They have nutrient deficiencies, grow better, consult Fertilizer Calculations. don’t have to be incorporated, but mixing and produce more of the biomass that im- them into the soil is preferable because proves soil structure and quality when it’s Cover Crops, Green it will combine them and accelerate returned to the soil. A soil test will show Manures, and Mulch decomposition and formation of soil what nutrients your soil needs and pro- Another way to increase soil organic organic matter. The incorporation will vide recommended application rates so matter is to use cover crops and green also dilute added fresh manures, which you will be better able to choose the best manure. Cover crops are planted during will reduce odors, dilute manure salts, fertilizer source. For example, if the soil the off season to protect the soil from and encourage death of pathogens. Stabi- has an adequate supply of phosphorus, . When the is killed lized or composted manure is sometimes a nitrogen source such as urea (46-0-0) and incorporated into the soil, it becomes preferred to fresh manure. If you’re using would be preferred over DAP (18-46-0) a “green manure” that helps maintain or fresh manure in a vegetable garden, it is since DAP contains unneeded phospho- increase soil organic matter. Decaying best to apply it 120 days before harvesting. rus. Oftentimes, fertilizer products are roots leave behind soil pores for future For lawns, topsoil can be built by sold as “complete ” containing aeration, water infiltration, and root returning grass clippings and adding nitrogen, phosphorus, and potassium but penetration by new plants. Wheat is composts made from manure, yard with a low analysis (nutrient concentra- commonly used as a cover crop, but it waste, and other organic materials. Add- tion in percent N , P O , and K O, such 2 5 2 should be incorporated (killed) in early ing fresh manure is not recommended in as 5-5-5, 5-10-15, and 10-10-10). Gener- April before its size becomes unmanage- residential settings because of odor and ally, the lower the product’s fertilizer able. Legume cover crops like crimson pathogen concerns. Wood ash can also be analysis, the higher the unit price ($/lb) clover or winter pea will also supply added to gardens and lawns to raise soil of the desired nutrients. Purchase of such the soil with additional nitrogen. Crops nutrient (Ca, Mg, K) levels and neutralize products makes more likely the addition such as mustard greens and turnips are soil acidity (by raising soil pH), but wood of nutrients not required for optimal edible cover crops that also have deep ash does not increase soil organic matter. plant growth. tap roots that can penetrate moderately Generally, the more organic material you If specific fertilizer products are not compacted soil and improve water infil- can add and incorporate into the soil the readily available, add the amount of prod- tration. The main goal of cover cropping better, but there are limits. A good rule is uct that delivers the amount of nutrient is to keep the soil covered with living to apply no more than about a half-inch of most needed by the plants to be grown. vegetation throughout the year. organic material into the top 5 inches of Be aware that soil concentrations of other During the growing season, mulch soil. If too much material high in carbon nutrients will likely increase with time, so can be added between plant rows in the (leaves, straw, or grass clippings) is added, that at some point only nitrogen fertilizer garden to help reduce weed pressure and there’s a greater chance that nitrogen will will be required based on plant need; water lost through evaporation and also be immobilized and you will have to add other nutrients won’t be needed. Prod- to lessen potential . Mulches more nitrogen to help the residue break ucts containing only nitrogen should can either be organic (plant-based) down. be available at fertilizer retailers, and if

Fertilizer Calculations verted to lb/100 ft2 or lb/1,000 ft2 (or any analysis must be known and, by law, that other area you choose). One acre equals will be reported somewhere on the label. On the fertilizer label, nutrients concentra- 43,560 ft2. The recommendation conver- Using the 5-5-5 fertilizer to provide the tions are expressed in percent (%) lb of N- sion can be made by simply cross multiply- needed 1.15 lb N/1,000 ft2, we know the ing and then solving for the desired rate for 5-5-5 contains 5 lb of N/100 lb of fertil- P2O5-K2O/100 lb of fertilizer. For example, a fertilizer with an analysis of 5-5-5 contains the desired area, as follows: izer. Using the conversion shown below we determine that 23 lb of 5-5-5 will be 5 lb of N, 5 lb of P2O5, and 5 lb of K2O in each 100 lb of fertilizer. Ammonium nitrate 50 lb N ? lb N needed for each 1,000 ft2 of area to be 50 lb N per acre = 2 x 2 (34-0-0) contains 34 lb of N/100 lb of fertil- 43,560 ft 1,000 ft fertilized. Only 3.4 lb of 34-0-0 would be izer, or about 7 times more fertilizer/100 lb needed/1,000 ft2. 50 x 1,000 than 5-5-5. That means it would take about = 43,560 (1.15 lb N) x (100 lb 5-5-5) 1⁄7 the amount of 34-0-0 fertilizer to provide = 23 lb 5-5-5 the same amount of N as 100 lb of 5-5-5, or 5 lb N 2 about 15 lb. = 1.15 lb N per 1,000 ft and For homeowners, nutrient recommenda- Based on this calculation, we need 1.15 (1.15 lb N) x (100 lb 34-0-0) = 3.4 lb 34-0-0 tions in soil tests are often expressed in lb lb of N for every 1,000 ft2 of area to be 34 lb N of nutrient/1,000 ft2 of lawn or garden area, fertilized, but the 1.15 refers to lb of actual but may be reported in lb of nutrients/acre. N, not lb of fertilizer. To determine the Recommendations in lb/acre can be con- amount of needed fertilizer, the fertilizer

3 products such as straw, grass clippings, In summary, many home-site soils For more information on home gar- or shredded paper or a synthetic product are not ideally suited for gardens, lawns, dening and lawn care consult Univer- such as plastic. Plant-based mulches are or other plants and need improvement, sity of Kentucky Cooperative Extension usually preferred over synthetic products which usually takes time and diligence. publications Improving Yard and Garden due to cost, nutrient value, and ease of You reap what you sow with the home Care (IP-62) at http://www.ca.uky.edu/ disposal (they can be incorporated as garden or lawn. Yields or productivity agc/pubs/ip/ip62/ip62.pdf and Home additional organic matter before plant- might be lower initially but will increase and Vegetable Gardening in Kentucky ing a cover crop). They also are more over time, especially if improvements are (ID-128) at http://www.ca.uky.edu/agc/ environmentally friendly. Either type of made with care and best management pubs/id/id128/id128.pdf. product will work, however. practices are followed.

Educational programs of Kentucky Cooperative Extension serve all people regardless of race, color, age, sex, religion, disability, or national origin. Issued in furtherance of Coop- erative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, M. Scott Smith, Director of Cooperative Extension Programs, Uni- versity of Kentucky College of Agriculture, Lexington, and Kentucky State University, Frankfort. Copyright © 2011 for materials developed by University of Kentucky Cooperative Extension. This publication may be reproduced in portions or its entirety for educational or nonprofit purposes only. Permitted users shall give credit to the author(s) and include this copyright notice. Publications are also available on the World Wide Web at www.ca.uky.edu. Issued 8-2011