Landscapers

The ancient art of gardening professionally, as a service for others, has become a popular business in and around major cities. Landscapers have been excited about compost over the last several years for good reason. Landscapers today are similar to gardeners from centuries past because they use organic matter as a key ingredient to a successful overall formula. The five most common uses are outlined below and in more detail in the rest of the chapter. These common uses have evolved rapidly over the last ten years and make Landscapers one of the leading market sectors for using compost. In many markets, they are the first and only market targeted through marketing programs.

The environmental movement has boosted awareness of compost products because of the environmentally acceptable option composting (the process) provides as a resource management alternative. Furthermore, landscapers find that the increase in available organic matter from compost additions has improved plant growth anywhere from 20 % to 100 %, while maintaining higher than average survival rates. Field results have supported this claim and have been replicated and validated in research (Smith, 1991, 1992, Maynard, 1993).

Many landscapers use compost and organic matter, at a reasonable cost, in place of peat or other organic sources. These other sources usually cost anywhere from $5.00 to $35.00 per cubic yard but typically are higher than locally produced compost and more difficult to work with. For instance, locally available peats are often black, mucky and dry slowly even after excavation from the bog, making handling difficult. Compost offers excellent micro- and macronutrients, disease suppression and workability, most of which are lacking in peat moss. Compost is also a replenishable, recycled, annually renewable organic resource.

Using soil is the foundation for development of all successful landscapes. Using poor soil usually results in many headaches and problems in the landscape while using high quality soil in the proper job produces excellent results. Professional landscape managers often cite "poor soil" as the most common problem in landscapes today (Darrah, 94).

Accurately measuring compost needed for any application is a significant key to success. So it should be no surprise that landscapers are currently using large quantities of composts produced from a range of municipal and agricultural organic materials. For many of these uses, large quantities of compost are required and have led to adaptation of composts having various quality and physical characteristics. The type of compost utilized by each landscaper depends on product availability, the specific application itself and customer preference.

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Turfgrass Establishment

The largest and most common use for compost in the landscape market has historically been turf establishment. Compost used as a general soil amendment for turf establishment can improve poor urban soil situations found in common landscape projects. Almost all soils should contain at least 5% organic matter.

The driving force behind having a well manicured turf is the general public, due to their increasing demand for green aesthetics. In a Gallup survey, residents cited beautification, relaxation, increased value and other positive reasons for maintaining attractive lawns (Chadbourne, 1994). Another poll showed 9 of 10 U.S. households recognize the value of a well maintained lawn and landscape (Code, 1994). This is a significant change compared to 40 or 50 years ago when a more rural, less manicured lawn was acceptable.

Turf establishment for seed or sod using organic matteris an accepted practice across a wide range of markets. For instance, the same basic steps to establish turf using organic matter apply to landscapers, golf courses, grounds maintenance personal, and the average homeowner. Thumb rule guidelines for most soils is a one inch application of compost (evenly applied) and tilled to a depth of five inches, achieving an approximate 20% by volume inclusion rate. A two inch application rate, tilled to a depth of 8", has also been widely accepted, especially in sandy or clay soils. However, many rototillers only reach about 5" into the soil, limiting the amount of organic matter needed. A light dusting of compost as a final cover over seeded lawns helps increase germination and reduces the need for similar applications of straw.

...deeper is more expensive

When soil is found to be low in organic matter content and nutrition, highly compacted or lacking water holding capacity, compost is excellent to use as an amendment. The addition of compost improves the soil both physically and chemically allowing for healthy growth of turf and Ornamentals Alexander and Tyler, 1992). Research has shown that the application of sludge compost at a rate of 260 metric tons per hectare (approximately 235 cubic yards/acre) enhances the establishment of turfgrass from seed (Alexander and Tyler, 1992,). The application of 180 metric tons per hectare (approximately 160 cubic yards/acre) of compost was adequate for the establishment of turfgrass sod. In both experiments, compost significantly improved the rate of establishment and general appearance of the turfgrass (Alexander and Tyler, 1992, after Angle 1981).

The amount of compost or organic matter that has to be added to soil to increase the final organic matter content is deceiving. Since compost is usually lighter than soil, the contribution of organic matter (by weight) may not be as significant as adding another soil that is higher in organic matter content. The table below shows an example.

(Source: Darrah, 1994)

Note the increase in the amount of compost required as the bulk density of each soil increases. Sand is heavier than clay and requires more total organic matter to create the same increase in organic matter of the final mix.

Compost used as a soil amendment for turf establishment should be rich in organic matter (over 50%), free of weed seeds, and possess a texture and moisture content which allows for easy spreading (Alexander and Tyler, 1992). Compost with moisture less then 20% may make applications dusty while moisture contents of over 50% may be difficult to screen or apply with appropriate equipment. The pH and soluble salt content of the compost is dependent upon the characteristics of the soil being amended and the plant materials to be established. Generally, a ph of 6-8 and soluble salts of 5 mmhos/cm is considered safe enough for turf (Alexander and Tyler, 1992).

Soluble salt characteristics will not be as critical for turf establishment as it would be for a garden of annuals or perennial plants because turf is generally not as salt sensitive. In garden applications, the soluble salt content of the compost is significant in that excessive levels in the soil mixture may be damaging to certain plants (i.e., geraniums...see "s" in PHOIMS in chapter 8).

Studies at Penn State showed soluble salt concentrations of up to 8.1 mmhos/cm (using extract method) did not inhibit seedling growth on turf when compost was added at 1" and 2" depths to native soils (Landschoot and McNitt, 1994).

Higher quality and more refined composts, up to this point, have proven to be more popular in soil incorporation projects in garden areas and on homeowner lawns (Alexander and Tyler, 1992). Landscapers, often driven more by economics than quality selection of materials, have lesser demands for quality products. Less refined products, such as composts coarser in nature and somewhat odorous, have seemed to be more acceptable in commercial and/or industrial applications. Perhaps this is the reason for general acceptance of biosolids (sludge) compost by most contractors and the lack of acceptance by the general public (Alexander and Tyler, 1992).

Example specifications for using compost in turf establishment are becoming more generally accepted. These specifications result in an increased market demand for compost to be used for turf establishment through a number of different markets. Many states are adopting similar specifications and passing procurement policies to favor purchases of compost products. At least 17 states have procurement policies and California requires that 40% of funds spent on topsoil and organic products must be spent on compost by 1995 (Snow, 1994).

Fertility in composts, mostly nitrogen and phosphorous, is a significant contributing factor to turf establishment (Landschoot and McNitt, 1994). However, varying feedstocks and applications rates can have equally varying results upon turf establishment or maintenance. Most composts used for turf establishment increased rate of establishment when compared to controls (Landschoot and McNitt, 1994). Although starter fertilizer is often used in turf establishment, a high quality, nutrient dense compost that is used mainly for organic matter value may also deliver plenty of fertilizer value for establishment (Landschoot and McNitt, 1994).

Soil tests, compost tests and advice from expert turf managers should be used by contractors who want to reduce or eliminate fertilizer applications. However, in the study at Penn State, most of the products used provided a portion of nutrients for at least two growing seasons, indicating a change in normal maintenance fertilizer applications could be in order (Landschoot and McNitt, 1994). The use of compost in soil preparation for turf will often reduce fertilizer and lime requirements (Alexander and Tyler, 1992).

On landscape sites where coarser texture soils exist (sandy soils), a coarser compost should be used. This is because the coarser compost will resist rapid oxidation which may occur in highly aerated soils. Finer soils require a finer textured organic matter source, to increase aeration and reduce the soil bulk density. Climate, including temperature and rainfall, also play a big role in selecting particle of products.

The benefits of moisture holding capacity of composts are generally accepted, but when used on sandy soils, composts really help hold water. A 3" layer of leaf compost, rototilled to a 6" depth, increased water holding capacity 2.5 times that of a native sandy soil and provided almost a 7 day supply of plant available water (Maynard, 1994, after Hill, 1978).

Compost spread evenly over one acre at a depth of one inch equals about 135 cubic yards. This is a common benchmark from which the green industry often derives further calculations based on applications of compost per 1000 square feet. To accurately calculate compost volumes, the square footage multiplied by the depth in feet, divided by 27 cubic feet yields total cubic yards (which landscapers must know to order compost).

(Source: Tyler, 1993) Formula: (Square feet x depth (in ft.))/27 = cubic yards required.

Calculations can become challenging if the area for compost applications is not a common geometric figure like a square or circle. Landscape designs that create these hard to measure areas are limited only to the imagination of each designer. However, since most designs begin on graph paper and are done according to scale, most areas have an automatic square footage associated with them (the architect could actually count squares). Additionally, some of the computer aided designs of more progressive landscape firms allow a computer-aided graphic representation that automatically calculates square footage (for each geometric area). This should not be used as an excuse for the lack of understanding of basic square footage calculations in the field. For larger areas of compost applications, often occurring commercially, the chart below may be more helpful in determining total compost needed (Tyler, 1993).

Table 3: Cubic yards of compost required per acre.
INCHES OF COMPOST TO BE APPLIED
Acres	1/4	1/2	1	1 1/2	2
1	34	67	134	201	268
2	67	134	268	402	536
3	101	201	402	606	804
4	134	268	536	804	1072
5	168	335	670	1005	1340
6	201	402	804	1206	1608
7	235	468	938	1407	1876
8	268	536	1072	1668	2144
9	302	603	1206	1809	2412
10	335	670	1340	2010	2680

(Source: Tyler, 1993).

A simple, step by step formula to successfully to install a new seed lawn is outlined in the steps below.

1). Remove old sod, weeds or current vegetation. For new sites, clear away rocks, brush or other debris that will keep seed to soil contact from occurring. Level the area by using a machine like a rototiller, rake or a tractor. A level lawn helps prevent future scalping by the mower.

2). Prepare the seedbed. Germination of grass is best when seed to soil contact in maximized. Spread about 1-2" of compost on the surface and work into the soil using a rototiller, rake, shovel or other mechanical device. It is best to loosen the soil once before applying the compost to make sure adequate mixing occurs when the rototiller passes through both materials. It may be necessary to make two or more passes in each area if soils are extremely poor and high in clay content. The incorporation should reach at least to a five inch depth.

3). Sow the seed of your choice. Select a seed variety that suites your planting area. For instance, shade areas are more suited to shady varieties of turfgrass. Consult your local garden center or extension agent to discuss what may be best for your area and climate. Try to avoid seeding on windy days due to challenges associated with even applications. Cover the soil and seed with a light dusting of compost.

4). Water the entire area thoroughly, soaking the soil to a depth of six inches. After the initial soaking, water lightly for about 10 minutes about two or three times a day, depending on weather conditions. When grass begins to grow, gradually decrease the frequency and increase the duration of each watering until mother nature takes it's course. Fertilizer should not be needed for the entire first growing season if at least one inch of compost is used, especially if the compost has about a 1-1-1 N-P-K analysis.

5). Maintain the lawn regularly including aerifying and topdressing with finely screened compost at least once per year. An occasional fertilizer application may be needed, depending upon your objectives and how much you want your grass to grow. A program of aerifying and topdressing twice yearly, (once in the spring and fall) should supply adequate nutrients for survival of the grass.

(Adapted from Sanchez and Sears, 1994).

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Planting Bed Preparation

Different species of plant materials will respond differently to the application of compost, however research has demonstrated that various annuals and herbaceous perennials respond favorably to the application of compost at a rate of 10-30 percent of a garden mixture (Smith 1992). A one (1) inch application rate of compost tilled to a depth of five (5) inches is about a 20 percent inclusion rate. It is also important that compost used in this application is stable (well cured), so that nitrogen immobilization does not occur.

Composts have been used as a component to various landscape soil mixes such as roof top, raised planter, and Backfill mixes. These mixes usually include compost at a rate of 25-33% as well as other ingredients like topsoil, peat moss, sand, styrofoam, vermiculite and perlite (Alexander and Tyler, 1992). Compost in these mixes may help improve drainage, water holding capacity, encourage deep rooting and supply a rich source of organic matter and nutrition. The organic matter supplied by compost will also increase the cation exchange capacity of the mix and supply valuable humic acid, which converts nutrients into plant available forms of food. The compost used in these applications must have a pH and soluble salt content which, when mixed with the other planting components, are acceptable to the plant species grown. Compost used for planting beds must be weed free, have a workable texture and must be mature to avoid nitrogen immobilization (Alexander and Tyler, 1992).

Annual and perennial flowers are a colorful part of most landscapes today. In the past 10 years, both categories have increased in popularity with service oriented landscapers and especially with do-it-yourself weekend gardeners. In many nurseries, perennials now account for 25 percent of all plants grown, compared to less than about 5 % 10 years ago (Tyler, 1993).

Progressive landscapers are currently offering annual or perennial programs whereby they package the installation of annuals or perennials with some type of regular maintenance program, often including some type of compost product for planting bed preparation.

The results in both field and lab are exciting. At the recommended 1-inch compost application rate, research conducted by Dr. Elton Smith at The Ohio State University resulted in an average dry weight increase of 29% for perennials and more than 40% for annuals. This study showed equally promising increased growth for annuals and perennials when a 2 inch layer compost was applied as a mulch (Tyler, 1993).

(Source: Roche, 1992, after Professional Plant Growers Assn.).

Compost used as a mulch in annual beds may be rototilled or otherwise worked into the soil in the fall and ultimately helps build up the soil, naturally setting the stage for the following season. This automatic amending program is becoming more popular because as the years roll by, the soil becomes more friable and it is not necessary to rely as heavily on a rototiller to incorporate organic residuals into the soil. Be cautious that the mulch used is not too fine. Compost screened at about 3/4" to 1.5" seem acceptable as a mulch, offering effective weed control from many of the coarser particles.

At many Cooperative Extension education outreach programs, the importance of proper bed preparation and maintenance is a leading topic (Tyler, 1993). Extension agents normally promote soil testing of scheduled bed areas and emphasize proper bed preparation using organic materials. For compost marketers, it is a wise investment of time and energy to keep the extension agents up to date about product testing programs relating to local compost products.

The annual or perennial programs offered by landscapers can help create additional "menu items" for their clients to choose from. These relatively new options of additional service and revenue offer attractive diversification alternatives to even the smallest of landscape companies. Due to the low overhead associated with the materials needed to incorporate these programs, they will continue to increase in the future as long as quality products are locally available.

Soil compaction in all parts of the landscape is a prime problem for many contractors. This problem is enhanced in planting beds because the soil texture is destroyed when rototilled, predisposing the bed area to compaction. Both construction and foot traffic during wet weather are especially problematic, but even vibrations caused by heavy traffic on adjacent roads help create a more compact soil (Kurtz and McCoy, 1989). Fill dirt, often used to raise planting beds to appropriate levels, is usually low quality, compactable and often contaminated with man made materials, like brick, block, asphalt or other materials. Organic matter additions in the form of compost help revive dead soils by reducing potential compaction and letting them breath. Compost acts like a sponge when added to compactable soils, giving the final mixture more spring back potential.

If amending soils for planting beds on site is not feasible, importing topsoil is the next best option (see section on topsoil blenders). Although the word topsoil may mean different things to different people, a "good" topsoil is one having a sandy loam or loamy characteristic with a relatively high (4-8% by weight) organic content (Kurtz and McCoy, 1989, McCoy, 1995). Topsoil purchases from blending companies can require a higher initial investment but compared to the long term, may actually reduce costs associated with plant losses, irrigation or fertilization (Kurtz and McCoy, 1989).

Consistently brilliant flower color does not happen by chance but is a result of careful planning and prompt management of landscapes involving regular additions of organic matter. Successful recipes for annual and perennial beds include 20 to 40% compost added by volume (or about 1" deep) incorporated with native soils or purchased as a topsoil blend reflecting this ratio (Tyler, 1993?).

Since planting beds are all shapes and sizes, square footage calculation to determine volumes of compost needed are handled the same as described in the turf section above. (see chart xx) Most planting beds, especially if away from buildings, have a slight crown in the middle of the bed, allowing for drainage and giving the bed a unique, uneven depth. Rounding upwards the nearest cubic yard seems to be popular among successful landscapers.

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Fertilizer Value of Compost in the Landscape

Manure has been used as an organic source of nutrients for centuries. Compost and organic fertilizers may be the organic source of nutrients for the next century. Yearly applications of biosolids compost have shown increases in soil fertility and organic matter (Tester, 1990). How realistic is it for landscape contractors to use compost on a yearly basis in various applications? Perhaps an integrated approach is the wave of the future.

Many organic residual management options have created products available to the green industry. Many more will become available in the future as more of the organic residuals are converted to marketable products. Bio-fermentation and anaerobic digestion offer pelleted products that are substituted for commercial fertilizers. Compost, on the other hand, does not seem to be readily recognized as a source of fertilizer, yet it is a pleasant surprise to calculate the total available nutrients in average compost applications. The single chemical fertilizer application is being rapidly replaced with multiple applications and combinations of fertilizer and organic products that satisfy nutritional needs. The future needs to be greeted with open minds to understand how these organic materials impact the green industry and each owner's bottom line.

Urban soils (those soils native to the urban environment) are most often disturbed and destroyed by the time they become utilized by anyone in the green industry. Even soils on the urban fringes often undergo this change when housing developments are constructed and leave the topsoil buried under the subsoil excavated from the foundations of the homes. Expecting success from such a poor beginning is optimistic at best. Adding organic matter helps improve the physical structure of soil by reducing compaction, increasing drainage, aeration and moisture retention and recharging soil with microbial life.

Understanding fertility associated with compost applications may allow contractors to save money on fertilizer costs. Compost is usually overlooked by most contractors as a significant component of soil fertility. When compost is used at 1-2" rates or at maximum limits, most nutrients plants need will be supplied through the first growing season (Rynk, 1992).

(Source: Tyler, 1994, after Dick and McCoy, 1992).

The equation is really quite simple...Experts have already performed thousands of research projects to determine the amount of nutrients needed for optimum plant growth for almost all landscape plants. Look in any plant book to find a reference about ideal fertility conditions and what each plant requires. Therefore we know what we need. From soil tests, we can find out what we have. The difference, logically, is what we need to apply. The summary presented in table XX shows example fertilizer recommendations from The Ohio State University for various landscape plants.

(Source: Tyler, 1994).

(What we need) - (What we have) = (What we need to apply)

Even the "experts" get confused when fertilizer options include organic and commercial fertilizers releasing at varying rates. Table XX identifies approximate fertility available from compost additions. The chart is based on fertility calculations of composts and is adapted from research performed with composts and manures.

(Adapted from Tester, 1990 and Fricke, 1993).

Example calculation for % available nitrogen: (Assuming 1 yard = 800 lb at 70% dry weight)
((yards of compost applied/acre) x (weight of compost/yard) x ( % N) x ( % dry weight) x (25% available))/43.56 = lb of N available per 1000 square feet. For 1/2" topdressing, with a 1% N product, the calculation would be: 67.5 yards x 800 lbs/yard x 1% N x 70 % dry matter x 25% available = 94.5 lb N per acre or 2.2 lb of N per 1000 square feet. (94.5 lb per acre/43.56). Note the available %N may vary, depending on type of compost used.

Several challenges exist in calculating fertilizer value properly. Vast differences among N availability in products, confusing yards (volume) and tons (weight), lack of label laws listing fertilizer analysis, and forgetting to calculate values on a dry basis all have stumped even the brightest horticulturists at one time or another. The calculation below takes these factors into account and can be followed in form by substituting appropriate numbers from any compost or organic fertilizer. (Remember some organic fertilizers are 90% dry matter).

Another example of a one inch application of compost would yield:
(135 yards x 800 lb/yard x 1 lb N/100 lb compost x 70% dry matter x 25% availability in year one)/ 43.56 = 4.33 lb N per 1000 square feet (or 189 lb of N/acre). No wonder organic gardeners keep telling us how valuable organic matter is!

Understanding these fertilizer calculations from organic matter only lead to the next logical question: "How much fertilizer do I need if I already applied compost? Since not all composts and organic fertilizers react the same, the answer is not as easy. However, for the above example, few plants would require more than 4.33 lb of nitrogen per 1000 square feet for the first season (see table XX). From year to year, decreasing amounts of nutrients will be released from the organic matter.

How much nutrients are additive from year to year? The additive effect of yearly compost applications for total nitrogen is shown in Table 8. Available N (% available) figures are listed in the boxes, but be careful not to confuse availability with effectiveness. Remember that 100% of urea fertilizer is theoretically available. However, on a hot August day, just how much of that fertilizer actually gets used by the plant? Organic fertilizers, on the other hand, are not prone to volatization like the quickly available forms of commercial fertilizer. The bottom line result is that organic N is longer lasting than many commercial fertilizers and depends on moisture, microbes and favorable soil conditions for significant release. Once the fertility is "used up", humus remains to further benefit the soil for many years.

(Source: Tyler, 1994).

Similar results can be calculated for phosphorus and potassium, using 30% and 85% availability per yearly application respectively. Of course, these values may vary depending on the compost. Overwhelmingly, nitrogen fertilization seems to be the driving force behind many fertilizer purchases. Since the plants being fertilized cannot possibly use all the fertilizer at once, the delayed availability from organic sources is almost a blessing in disguise.

Consider another example of calculating the fertility of a soil after five seasons of compost applications. At a 1/4" application rate for five years, about 55% of the nitrogen for the whole five years is available in year five. For a 1% nitrogen compost, that would calculate to 11.9 lb of available N per 1000 square feet. (1.25" x 135 yds per acre x 800 lbs/yard x 70% dry matter x 1% N x 55% availability /43.56). Flowers growing in this soil will not need additional fertilizer and will be easier to keep alive due to the increased moisture holding capacity of the soil. The only reason they would not be burned from the high nitrogen is because the N is slowly available over the entire growing season. These calculations are estimates and field data to validate accuracy are scarce.

An equal level of fertilizer in the form of urea would surely be too much for the plants to handle. The natural slow release of organic N is the key to making compost a safe fertilizer option. Most composts contain the majority of their nitrogen in the organic form (Fricke, 1993) Nitrate and ammonia are often in concentration and so mobile in the soil that many contractors depend only on organic fertilizer values for long term calculations of available N.

the organic matter content of soils can affect nutrient availability. Organic matter can accumulate over time in temperate climates and increase water holding capacity of a given soil accordingly. Five yearly applications of compost increased soil water almost five fold over control soils which received common commercial fertilizer, while single applications doubled available soil water even after five years (Tester, 1990). As more and more concerns for water conservation become apparent, the ability of compost to retain moisture increases in value. In slightly arid climates where water is scarce or watering bans are in effect, compost could be used more as a long term water management tool than a soil conditioner. Additional compost would be needed in hot climates due to the faster decomposition of organic matter, especially as a mulch. Organic matter generally decomposes slower if incorporated into soil (McCoy, 1992).

Although water is "held" in the soil, at field capacity, it is not held so tightly that plant roots cannot absorb the moisture. Implications are obvious that survivability is increased in drought situations by the use of compost. Longer periods between watering are possible and overall plant vigor is improved. Plant roots in upper soil surfaces have greater moisture availability due to higher organic matter concentrations. However, soil below actual contact with organic matter is positively affected by increased moisture retention and nutrient exchange (McCoy, 1992).

Substantial increases in CEC from compost applications help hold applied nutrients longer, thereby increasing the effectiveness of the fertilizer. Most soils do not have high nutrient exchange capacities and fertilizer applied is often leached from the root zones soon after application. Compost releases carbon dioxide and "soil glues" as it decomposes, offering plants gases they need while the soil glues help form new aggregates.

In most horticultural books, under soil fertility, favorable soil conditions for optimum growth of plants are listed. In over 70% of these books, the most common denominator for growing healthy plants is a "well drained garden soil that is rich in organic matter and minerals". Obviously, compost is not sold exclusively for the hidden fertilizer value depicted above. In fact, compost is registered under soil conditioners (dept. of agriculture) rather than fertilizers (EPA) in most states. Using compost helps achieve the ideal physical soil described above while adding natural fertility in proportionate amounts.

All fertilizer recommendations should begin with a soil test. However, due to the seasonal nature of the industry, this rarely occurs. For temperate soils with organic matters below 5%, it is safe to assume that three consecutive yearly 1" applications of compost could be made without developing complications if the compost is properly incorporated into the soil. Soil tests should be consulted prior to the fourth yearly application. Once a soil reaches organic content of about 8% (by weight), compost applications may be spaced every two or three years. For warmer climates, it may be necessary to begin year one with a heavier application (2") to "jump start" the soil. Professionals should be able to offer certain clients testing services and include these costs in their total service package.

Familiar complications with overfertilized turf are easy to spot, including increased disease and increased thatch which predisposes turf to a host of insects and other pests. Since organic fertilizers do not have the characteristic quick release that predisposes the turf to the above, they may be generally healthier over the long term. Additionally, since most of the nutrients are made available by microbial action, moisture and favorable temperatures, very little of the fertilizer value is "wasted" during the non-growing portion of the season. In other words, compost applied in the fall is not wasted or washed away from winters forces as much as commercial fertilizers.

Organic fertilizers and composts are here to stay. Buying fertilizer strictly on a cost basis alone may prove detrimental to many green industry professionals over time as urban soils become more and more challenging to manage. History has a way of repeating itself for those who do not wish to stay up to speed. If green industry professionals want to sell results, there is certainly plenty of evidence that composts work and the audience who purchases these products and services are well aware of the environmental issues. The time to market these organic products within the contractors services could not be better.

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Backfill Mixes for Tree Planting

A landscaper's reputation, in part, lies in the good design of a project, implementation, the survival rate of plants and the type of picture painted by the finished landscape. Planting trees has historically been a large part of many landscapes, especially in large commercial or highway projects where hundreds may be planted at one time.

The larger the number, the easier it is to understand the importance of the survival rate to a customer procuring landscaping services. It is equally important to a landscaper if he has to pay to replace dead trees. Many landscape contracts are required to include guarantees for plant growth or survival for a minimum of one year. Using compost as a portion of the backfill mixture has been a popular way to increase organic matter and survivability in tree plantings (Tyler, 1993).

Areas prepared to plant trees are usually circular on the surface but cylindrical in depth. Again, the challenge to calculate the correct volume for compost additions arises. The guidelines for compost used as backfill media ingredient are typically 20% to 40% by volume of the total backfill mix. This can be more compost than you think, due to some recent changes in planting specifications.

Old specifications for planting trees often left the organic matter out and suggested rototilling 2X the area of the root ball. As the planting and designs of landscapes have become more elaborate in the last few years, increases in the soil preparation mode have resulted. Current specs often call for preparation of 5 times the diameter of the rootball instead of the previously accepted 2x diameter preparation guidelines. Results seem to be related to preparation and proper amendment uses, because this specification criteria continues to expand.

Due to the on site mixing effort required in backfill preparation, many landscapers have opted to utilize premixed backfill media and to haul excavation "waste soil" away. The utilization of these preblended materials often completes the interactive loop that exists in the green industries, including topsoil blenders. Although backfill medias can be successful in absorbing water beneficial for plant growth, Corely points out a danger that also exists:

"The amended backfill will hold more water than the unamended backfill, but as the soil dries, water can be drawn from the amended backfill into the surrounding soil, thus drying the amended backfill at a greater rate and to a greater degree than the surrounding soil itself (Craul, 1992, after Corely, 1984).

This "wicking" action has to be tempered with adequate irrigation if success is the plantsman's goal.

An example may help. Suppose a landscape project requires planing 20 pine trees that have root balls of one foot in diameter. The landscaper would measure about five feet for each tree pit, rototil the area, mix in about 30% compost by volume, and plant the tree accordingly. Remember that the soil amended is going to be anywhere from 4" to 12" deep (or more for large trees) and that the volume of compost needed can be calculated by using one inch of compost for each 3" of soil depth. In the case of the pine trees, this would require about 4" of compost (12" diameter root ball x 1" compost/3" soil = 4" compost required). A total of 4" of compost distributed over five feet of amended area is easy to calculate from the previous square footage guidelines.

For trees and other large ball and burlap landscape plants, (or large containerized plants) the backfill media needs to encourage water movement into the "old soil" as well as the "new soil". Many nurseries use bare root stock which enables the entire soil horizon, including rooting area, to be equally exposed to even water movement which results in good growth. Therefore, the interface of two distinctly different soils may be eliminated with the use of bare root stocks (Craul, 1992).

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Topdressing In the Landscape

Topdressing is a proven turf maintenance practice in the golf course industry (see earlier sections) and has grown in popularity in commercial and home lawn applications. The practice entails applying a thin layer of topdressing material over an established and usually declining turf area. The practice is usually done in conjunction with aerification, where small plugs of soil are removed from the soil surface. Reseeding of the area often follows. This process improves soil drainage, increases the water holding capacity of the soil and reduces soil compaction (Alexander and Tyler, 1992).

Compost used as a topdressing must not only be consistent in its chemical characteristics, but also in its physical characteristics. Batches of chemically "uneven" compost could produce patches of varying colored turf while physically resulting in localized dry spots or drainage problems. The compost used in this application must be finely screened and have a texture which makes it easy to handle. It must also be free of foreign matter and objectionable odors, since much of the material will be left on the soil surface. This market is expected to grow with the popularity of low input landscaping and/or maintenance practices which utilize organic materials. The chemical and biological characteristics of compost help improve the degradation of thatch which may be a nuisance in some established turf areas (Alexander and Tyler, 1992).

A common feature of topdressing programs is to have a drag unit behind the applicator to help the compost work into the existing turf. The unit usually consists of a chain link fence, 2 x 4, or other items efficient in dispersing soil plugs and compost. This practice also stands the turf up, alleviating potential damage or smothering by damp compost. Topdressing with pure compost or sand/compost mixes has become an accepted practice in many areas. Compost is often considered the "poor man's topdressing" due to local availability and low cost.

For extremely thatchy turf, it is not recommended to topdress without aeration because the lightweight compost does not penetrate the thatch effectively (McCoy, 1992). The same is true for peat moss. By mixing sand with the compost, increasing the bulk density, penetration of the thatch is improved. For large areas, such as corporate lawns that have extensive maintenance programs serviced by landscape firms, topdressing, aeration, and dragging the resulting mixture into the vacant holes offers an acceptable alternative to a sand/compost mix (McCoy, 1992). This practice has been validated by golf courses performing similar activities in fairways or roughs for many years.

An extra fertility bonus exists for lawn care companies that topdress as part of their total service package. Compost consisting of a 1-1-1 N-P-K analysis and 25% availability yields about 1.2 pounds of available nitrogen per 1,000 square feet at 1/4 inch application rates (Logan, 1993, Tyler, 1994). Since this is highly adequate to replace a single application of fertilizer, which normally ranges from .25 to 1 lb on N per 1,000 square feet, the money normally spent on that portion of the fertilizer program can be applied to compost topdressing program costs (Alexander and Tyler, 1992).

Established turf can utilize considerable amounts of compost. Even more importantly, the amounts of nutrients supplied and the general visual quality can be significantly increased with compost applications (Van Derwerf, 1993).

General recommendations for topdressing differ according to turf types, climate, mowing height, and soil conditions, but generally a 1/8 to 1/2 inch layer of compost product is applied at least once per season, following aeration. Calculations for total amounts needed are available in the previous cubic yardage calculation tables.

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Mulch Applications

Some composts have been utilized as a decorative mulch in planting/garden beds with great success and they are usually applied to the soil surface to a depth of 2-3 inches. Mulches are used in order to conserve moisture, lower soil temperature, reduce erosion, provide nutrients, and discourage the establishment of weeds (LaGasse, 1993).

Because mulches are also used for decorative purposes, the materials used must have an acceptable aesthetic "look". The compost should have a uniform appearance, possess a dark color and should readily absorb moisture. The compost should also be free of weed seeds and have a pH and soluble salt content which will not negatively affect the growth of the plant materials being mulched. Composts produced from both sludge and leaf/yard waste are currently being used successfully as decorative mulches while composts produced from municipal solid waste have not been as popular in this application because they often contain foreign matter, giving it a nonuniform appearance.

Rob McCartney at Sea World of Ohio has used compost extensively in all types of landscape settings. McCartney says "the dark color of compost gives the theme park's floral displays more sparkle," (Hall, 1994). The results, according to visitor surveys, show the landscape display is at the top of the list of attractions they like most, ahead of the animal exhibits (Hall, 1994).

Mulches have grown in popularity due to many factors, including utilization of organic residuals such as bark, water conservation efforts, and an increase to satisfy customer aesthetic appeal. Mulch, according to Craul, is:

"Any suitable protective layer, organic or inorganic material applied, left on or near the soil surface as a temporary aid in stabilizing the surface and improving soil microclimatic conditions for establishing (or maintaining) vegetation". (Craul, 1992, after Slick and Curtis, 1985).

(Source: Adapted from Craul, 1993).

The concern with overmulching is often limited to specific plant families as identified below. Since many of these plants may be included in a comprehensive landscape planting, care should be taken to avoid overmulching of these varieties.

(Adapted from Craul, 1993).

Mulching is often thought of as strictly an organic application of material around plants. However, as the table below indicates, there are many more common mulches, many of which are inorganic but still effective in achieving many of the benefits of traditional organic mulches. They are listed in decreasing order of preference, according to Rodale Press, Inc.

Top Ten Mulch List (from Rodale Press, Inc.)

10). Wood chips. The best choice for mulching Ornamentals and creating garden paths. A thick layer (4 to 6 inches) will discourage even the most pernicious perennial weed along paths. Age fresh chips a year before using.

9). Black plastic. The mulch of last resort for stubborn perennial weed problems like field bindweed: cover it with something attractive, like wood chips.

8). Sawdust. A good choice for garden paths. It can deplete soil nitrogen as it decomposes, so age it for at least a year before using it as a mulch around veggies.

7. Pine needles. Slow to break down, acidic and moisture retentive. Good for controlling weeds around acid-loving small fruits and Ornamentals.

6). Locally abundant available materials. Cocoa bean hulls, rice hulls, wool, seaweed, etc.

5). Paper. A fluffy layer of black and white newspaper sheets or shredded white office paper will control most annual weeds. Make a thick blanket of paper to smother tough annual weeds.

4). Straw. Good for general light weed control...spread it on thick because it packs down quickly. Hay can be weedy.

3). Shredded leaves. Use where you need a really thick, dense layer of mulch, especially good at controlling grassy weeds.

2). Grass clippings. This nitrogen rich, downright smothering mulch was the clear winner in weed suppression studies at the Rodale Institute Research Center. Works especially well on annual weeds and is aesthetically pleasing. Let clippings dry a day or two before applying.

1). Compost. Spread a thick layer on top of the soil to smother weeds, protect against diseases and boost the garden's fertility. An especially thick layer will control most weeds.

(Source: Jesiolowski, 1994)

As a general rule, the old cliche "the finer the grind, the quicker the reaction" can be used as a mulching guide with respect to predicting potential nitrogen draw. There is considerable argument in the green industry between lab and field personnel over what is dangerous or safe for a compost or other organic material to be used as a mulch. The example offered here is general but helps add perspective to products used in the field.

Consider two examples of adding a carbonaceous material on top of the soil: on one hand, sawdust would have a large soil surface contact. On the other hand, wood chips measuring 2"x 2" would have a lot less contact due to the decreased surface area. Accordingly, even if the two materials were made out of the same material, potential for N immobilization would be greater in the sawdust product, due to greater surface area contact and ability to hold moisture.

For many green industry professionals, combining fertilizer applications with mulch applications has been convenient "insurance" to reduce potential N immobilization. The general rule of thumb has been 1 lb of N per 1000 square feet (Smith, 1994, Maynard, 1994) to negate potential N immobilization effects of "immature" composts or mulches. Even when no Nitrogen is added, the robbing effect usually disappears within a year (Golueke, 1973). However, the particle size should be considered because materials with small particle size will decompose more rapidly than larger chips which results in greater nutritional needs (Craul, 1992).

Costs of purchasing and applying mulches vary greatly on a regional or state-wide basis. Application services are available from a variety of green industry firms, mainly landscapers. Example prices for traditional mulch products are listed below.

2/ D = local delivery (generally less than 10 miles);
P = picked up at site.
3/ Price stated is for one cubic foot.
4/ Price stated is for three cubic feet.

(Source: USEPA/530-SW-90-073A, 1993).

Mulches of a coarse, loose nature tend to offer the best cooling effect in hot climates. Finer mulches tend to pack easier and transmit moisture by capillary action to the surface where it evaporates (Mastalerz, 1993). Finer mulches, when packed, also transmit more heat, elevating soil temperatures (Mastalerz, 1993).

Mulch has a cushioning effect in playground situations where falls of several feet, from swingsets or other structures, is common. The U.S. Consumer Products Safety Commission estimates that 100,000 injuries resulting from falls from playground equipment to the ground are treated each year in the U.S. hospital emergency rooms (Nursery Manager Magazine, 1992). The use of mulches to help reduce injuries on playgrounds has increased due to their cushioning nature. The chart below shows the comparison of different types of mulches in critical height tests. Mulches used to cushion the fall are generically referred to as playground mulches. Obviously, materials used in this application must be extremely high quality, with especially low inert contaminants. The shock absorbing nature of mulches varies with moisture, long-term use, and degree of maintenance (Nursery Manager, 1992).

(Source: Nursery Manager, 1992).

Then use of mulches will continue to grow because consumers have demanded the aesthetic appeal of mulch in ghe landscape. Compost will be a leading mulch used among the more serious gardeners.

Chapter Summary

Four interesting examples follow that portray real life examples for green industry professionals. The figures expressed are approximations from experience and observation of test results over a number of years.

Q: Should green industry professionals buy topsoil amended with 20% compost in instead of a cheaper, non-amended soil for a 5000 square foot project requiring 4" of topsoil?

A: Let the figures below be your guide. Assume compost has 1% N-P-K and compost weighs 800 lb per yard compared to soil at 2500 lb per yard. For this project, 62 yards of soil would be needed. Instead of comparing strictly price, consider the convenience of the fertility in the amended soil. A soil amended with 20% compost with an analysis of 1% total N and 25% available, will be sufficient to support most annual, perennial, tree and shrub growth for the first year without any additional fertilizer. Overfertilization may result in stunting of root systems caused by high total soluble salts. Additionally, these blended soils offer micronutrients contributed by the compost which are usually left out in standard fertilizer programs. When customers ask why the contractor is not using any fertilizer, they can respond..."It's in there!"

Q: How much fertilizer is needed when one inch of compost is used as a soil amendment for annual or perennial bed construction?

A: Generally, none for at least the first year. See figures below.

1" compost = (135yds/acre x 800 lbs/yard x 1% n x 70% dry weight x 25% availability)/43.56 =

4.33 lb available N per 1000 square feet. Most recommendations for annuals and perennials are from two to four lbs. N per 1000 square feet. Because N from compost is not as available in cool weather, contractors may want to consider applying small amounts of quick release fertilizer during spring planting. This will ensure adequate fertility until warm weather releases latent nutrients in the compost. If fertilizer combinations like this are used, it is wise to have at minimum, 30% of N from each source (McCoy, 1992).

Q: How much fertilizer should I add to my turf if I topdress after aerification with 1/8" of compost in the spring and the fall?

A: General recommendations for turf maintenance range from 2-6 lbs of nitrogen per 1000 square feet depending of turf cultivars and maintenance practices. Consult one of the available guides on turfgrass cultivars and corresponding fertilizer needs or contact your local county extension agent. Calculations below should help identify additional fertilizer needs.

1/8" compost = (16.9 yards/acre x 800 lb/yard x 1% N x 70% dry weight x 25% available)/43.56 = .54 lb N per 1000 square feet. Since two applications are indicated, total N applied for the year is 2 x .54 = 1.08 lb N. Assuming that 4 lb of N would be adequate for average maintenance, an additional 2.91 lbs of N should be applied in at least two additional applications. (4 lb N needed - 1.08 lb N avail = 2.91 lb needed).

Q: Last year I used 1" of compost to install an annual flower bed. I would like to use a mulch this year to add a dark contrast to the bright flower color. What is my best option?

A: Two options...1) Use organic fertilizer and some type of composted hardwood mulch . An additional application of 1 lb N per 1000 square feet should negate any nitrogen robbing potential caused by the hardwood bark. 2) Use compost or a compost-mulch blend as a mulch which will feed soil and be able to be incorporated at the end of the year, creating a higher organic soil for next year's crop.

For the sake of simplicity, 1% N composts were used in these examples. Actual values need to be calculated in each specific instance in the field. This is especially important due to the variety of products available on the market today and their varying nitrogen availability. Research in the field of using composts for their fertility value is scarce. More work must be done in the future as more products and combinations become available.

Rod Tyler is owner of Green Horizons in Medina, Ohio, and is a Certified Professional Agronomist. Part of the information contained in this article has been taken from his new book, "Winning the Organics Game-The Compost Marketers Handbook", (ASHS 1996).

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