In the west where lot sizes are often smaller, the growing season longer and materials easily accessible, it's the contractor who most often handles the task. In the end, fertilization is just a small piece of the overall landscape management puzzle, but it is important in terms of managing both plant health and company profitability.

Landscape fertilization consists of several different components. Turf fertilization is probably the most important in terms of impact and expense. Ground cover, trees, shrubs and annual color follow. Another important function fertilization can offers is weed control.

The first step in determining how to handle landscape fertilization is to examine the nutritional needs of turf and ornamentals, and then to develop an annual plan including a cost analysis. Planning is critical for a successful program. Although, some landscapers have had successful careers using the "eyeball" approach, today's increasingly competitive market demands a basic understanding of turf nutrition and a fertilization plan beyond the "what's on sale" mentality. This plan should not only improve the health of turf but also the health a company's bottom line.

There are 17 essential elements, or nutrients, required for optimum plant health. Water and air supply carbon, hydrogen and oxygen to the soil for plant uptake. This process underlines the importance of having healthy soil and the need for aeration in situations where there is compaction due to heavy traffic or clay soil. Of the remaining 14 nutrients, nitrogen, phosphorus and potash are required in sufficient quantity to be called primary nutrients. Calcium, magnesium and sulfur are classified as secondary nutrients. The remaining eight elements are used in such small quantity that they are referred to as micronutrients. Iron, zinc and manganese are, as a rule, are considered the most important of these.

Soil generally supplies most if not all of the micro and secondary nutrients as well as some of the primary nutrients. It is the role of fertilizer to provide the remainder. Most turf species use nitrogen (N) phosphorous (P) and potassium (K) in a ratio of 3-1-2 to 4-1-2. This means for every three to four pounds of N, turf uses about one pound of P and two pounds of K.

Turf type, location and use are all factors in determining exact needs for acceptable color and manageable growth of each individual situation. The best way to identify nutritional needs is routine soil test. This will provide an exact fertility recommendation. It is, however, not always practical, affordable or necessary. A general recommendation is be four to eight pounds of nitrogen per 1000 square feet per year.

Cooler climates with shorter growing seasons will require lower amounts while warmer longer seasons need more. Cool season turf species like bluegrass, rye and fescue use less while warm season varieties such as bermuda and zoysia will use more. For most situations five to six pounds of N with one pound of P and about two pounds of K will produce healthy turf with acceptable color. Since soil and rain supply some of the necessary N-P-K, a good plan will provides an additional four to six pounds of nitrogen, one half to one pound of phosphorous and at least one to two pounds of potash.

Understanding the growth cycles of turf is also a necessary step to successfully planning fertilizer applications. Cool season turf, like its name suggests, has two annual growth peaks in the cool parts of the growing season. The major spurt is in spring with a lesser one in the fall. Warm season varieties have one major growth period in the heat of summer. Both cool and warm season species benefit greatly from a properly timed fall application. This is when nutrients are used most effectively to build root systems, and produce and store carbohydrates. This will, in turn, create healthier turf the following spring.

Creating a Plan

A fertilization plan does not need to be rocket science. A good plan should project approximate timing based on expected longevity of the materials applied and include totals of the N-P-K used throughout the year.

The table below is a good example of a fertilization plan. It illustrates a 10-month growing season and provides target application dates and usage information. A reasonable idea of the acreage to be covered allows the opportunity to purchase materials in quantity and in a timely manner, which usually translates to lower costs.

The mid-March application is a quick release product, which, during the cooler days of spring, should last about six weeks. This application supplies high levels of P and K, used during this critical growth spurt. The May, July and September applications use a product with a significant percentage of "slowly available" nitrogen. Most manufactures should be able to provide reasonable estimates of their products' release profile. The turf response from this application should extend for eight to 10 weeks. This product also supplies some P and K for improved heat tolerance and disease resistance during the summer.

The final product recommended for November contains a portion of its nitrogen in the nitrate form. This type of nitrogen is immediately available in cooler weather. Along with potash and iron it will provide excellent color going into the winter. This late season application will also assist the turf plant in producing and storing those valuable carbohydrates.

Applying Fertilizer

The factors to consider with any method of fertilizer application are performance and cost. How often do applications need to made? What does it cost? How manageable are the results? Whether injecting, spreading or having someone spray, it is critical to have a plan. It will help budget, purchase and increase control over fertilizer cost and valuable labor hours.

In an ideal world, it would be the norm to apply just the right amount of fertilizer daily for optimal color and manageable growth. However, in most cases this is impractical if not impossible. There are three types of application used commonly -- injecting, spreading or spraying.

Some sites have been designed to include fertilizer injection systems. This technique is known as fertigation and is able to put small amounts of fertilizer through an irrigation system. Fertigation has proven successful on large-scale projects. On smaller more intricate landscapes this method requires an irrigation system with accuracy that is difficult to achieve. Fertigation systems require soluble or liquid fertilizer and can be convenient. However, they require some maintenance and monitoring to ensure the fertilizer is properly metered out.

Another means of accomplishing "daily feeding" is to spread granular fertilizers that are available slowly over time. The other option is to contract with one of the companies who specialize in landscape fertilization. These companies use a variety of methods and products including some granular materials. The majority spray liquid fertilizers.

Understanding Absorption

Developing an understanding of how nutrients are absorbed by plants and how each type of nutrient responds to soil and climatic conditions is helpful for selecting the proper fertilizer and improving the performance of the nutrients applied.

The three primary nutrients: nitrogen (N), phosphorus (P), and potassium (K) are the nutrients generally required by the plants in the largest amounts and most likely to be deficient or below the levels required to maintain a healthy landscape. Of the three primary nutrients, nitrogen is normally required in the highest amounts for turfgrass maintenance.

Plants absorb nitrogen primarily as nitrate (NO3 -) or ammonium (NH4+). The nitrate nitrogen molecule has a negative electrical charge as do most soil particles, two negative charges repel each other allowing the nitrate to float freely in the soil solution (the water that flows between the soil particles). Ammonium nitrogen, however, has a positive charge while the soil particles have a negative charge. A positive and a negative attract each other causing the ammonium molecule to be held to the soil until bacteria convert it to nitrate or a root absorbs the molecule. When soil temperatures are warm (55 degrees F and above) soil bacteria are active converting ammonium to nitrate.

This conversion process is called nitrification and is an essential part of our ecosystem and life itself. Nitrate can be easily leached from the plant root zone through irrigation or rainfall and care should be taken to avoid excessive vegetative growth and plant stress during warm climatic conditions. While use of some nitrate-based fertilizers during the coldest winter months may be beneficial to cool season turfgrass in California, application of nitrate should be limited to the cooler climatic zones after March 1.

Dry Fertilizer Technology

In today's market, professional turfgrass managers, golf course superintendents and landscape managers have basically three types of dry fertilizers from which to choose:

(1) Homogeneous fertilizer pellets which have excellent uniformity;

(2) Blends of two or three homogeneous pellets that contain different plant food nutrients that are nearly as uniform as the 100 percent homogeneous pellets;

(3) Granular bulk blended fertilizers that are a non-uniform mixture of several different materials and are subject to segregation and uneven application.

Agricultural grade blends are commonly promoted into the turfgrass market as a way to save a few dollars per ton in manufacturing costs. This practice, however, can lead to decreased performance and damage in some situations. It is often very difficult to achieve uniform distribution of granular blends due to fertilizer segregation. Granular blends are a mixture of several different materials with particles of different shapes, sizes, and density. If you pour a mixture of these kinds of materials into a pile, as is commonly done in bulk storage or when loading a spreader, the heavier more dense particles will tend to go to the bottom and edges of the pile while the lighter less dense particles will accumulate in the center. This segregation process is referred to as "coning segregation." As the granular blend is transported over the road or rides in the spreader, the bumps, jolts and vibration of travel will shift and separate the different materials. This process is called "sifting segregation."

Perhaps the most noticeable and troublesome process of segregation is "ballistic segregation." As the granular blend is applied to turfgrass or a landscape area, the spinning or "cyclone" type applicator throws the dense, heavier particles a greater distance than the less dense, lighter particles. Unfortunately this variation in particles is most often between the nitrogen, phosphorus, and potash sources giving you an uneven distribution of NPK.

Additionally, when micronutrients such as iron are added, a small amount of highly concentrated pellets are often blended into the fertilizer formulation. With as little as 30 to 40 pounds of iron in a ton of product, for example, there is little chance of getting a uniform application of that iron over the landscape. Even worse, when the concentrated iron pellets come in contact with concrete, it may leave an unsightly orange/red stain from a reaction between the iron and the calcium in the cement. Blended fertilizers primarily use high analysis pellets such as 46-0-0 and 11-52-0 in their formulation that are far more likely to cause a burn in their concentrated form than a homogenous pellet with an analysis of only 15-15-15 or 16-6-8.

Slow-Release Fertilizers

Slowly available nitrogen sources currently used on turf and ornamentals can be classified into three categories: natural organic, synthetic organic and coated materials. General characteristics of slowly available N sources include low water solubility, low salt index and slow initial turfgrass response.

1) Natural Organic

Natural organic N sources were the first slow-release products available to landscape managers. Most of these products are waste or by-products that include bone and blood meal, cottonseed meal or activated sewage sludge. These products typically contain a low percentage of nitrogen and, therefore, a higher cost per unit of material. Activated sewage sludge accounts for the highest use from these sources. Complex organic compounds contain the N in these products, so they usually have microbial break down to release N to the plant. Microbial activity is dependent on factors such as soil moisture, pH, temperature and particle size.

2) Synthetic Organic

Synthetic organics include several products that have been widely used in the industry and include products such as Hydroform, Nitroform, Nutralene, Triaform and isobutylidene diurea (IBDU).

Urea formaldehyde (UF) was first commercially synthesized in 1955 under the trade names Uramite (DuPont) and Nitroform (Nitroform Corp.). Urea formaldehyde starts with the reaction of urea and formaldehyde. The end products from the reactions are methylene urea polymer chains of various lengths and unreacted urea. Mineralization and nitrification (chemical break down and release of N) of UF fertilizers is dependent on the molecular size of the methylene urea polymer chains. The rate of mineralization and nitrification is decreased with the increased length of the methylene urea chain. Formulations with a higher portion of short and medium length methylene urea chains (e.g., Nutralene, Hydrolene, and Triaform) react faster in the soil, with longevity up to 16 weeks, than formulations with a higher portion of longer length methylene urea chains (e.g., Nitroform, Hydroform) offering longevity up to 40 weeks.

Converting UF to available nitrogen for plant uptake involves several steps, including dissolution and decomposition. UF is converted to plant available nitrogen through either microbial decomposition or hydrolysis. Microbial decomposition is the primary mechanism of conversion. Other factors that affect microbial activity in the soil include soil temperature, moisture, pH and aeration or oxygen availability.

Isobutylidene diurea (IBDU) is manufactured by the condensation reaction of urea and isobutyraldehyde. Nitrogen release is by dissolution and hydrolysis and is not significantly affected by microbial activity. Pure IBDU contains 32 percent nitrogen and has solubility in water of only 0.01 to 0.10 percent, depending on pH and temperature. The principal factor known to increase the rate of dissolution and hydrolysis is the decrease in particle size and pH. The smaller the size of the granular, the faster nitrogen will be released.

3) Coated Materials

The third classification of slowly available nitrogen is coated fertilizers. They can be classified into two categories: polymer-coated and sulfur-coated fertilizers. Sulfur-coated fertilizers also usually having a thin outside coating of polymer or a sealant to help reduce damage to the brittle sulfur coating. Coated fertilizers are characterized by having water-soluble fertilizer core covered with a water insoluble coating. The coating limits or controls the amount of water penetrating to the soluble core. Once the water penetrates through the core, the coating can control the release of solubilized fertilizers (polymer-coated fertilizers) or the coating can degrade rapidly resulting in a rapid release of nutrients (sulfur-coated urea).

The Tennessee Valley Authority (TVA) developed sulfur-coated technology in the 1960s and 1970s. The TVA process of producing sulfur-coated urea (SCU) includes spraying molten sulfur on urea prills or granules that have been heated, then adding sealing layer of soft wax, followed by the addition of a flow conditioner.

The mechanism of release from SCU is coating failure by allowing water to penetrate through micropores and imperfections in the sulfur coating. The goal of a quality SCU is to space this coating failure over

a period of a few weeks with a low percentage of granules failing at application. In recent years newer versions of this technology called polymer-coated SCU have replaced the layer of soft wax and conditioners with advanced polymers. This has improved SCU by making the coating more durable without changing the method of release.

Polymer-Coated Fertilizers represent the most technically advanced method in controlling granular nutrient release. Fertilizers are coated with several types of polymers (plastic) through unique and patented processes. Because these specific polymers allow diffusion through the polymer coating at a predictable rate, based on coating thickness and temperature, the rate of nutrient release is predictable. This allows nutrient application based on plant requirements and local climatic conditions. Pursell Technologies Polyon and O.M. Scott's Osmocote are two of the most popular and successful technologies on the market today.

Combination Products

Generally speaking, it is good to accomplish two tasks with one effort. This is definitely true in the world of fertilization and weed control. Healthy, vigorously growing turf is the best defense against persistent weed pressures and trouble areas. In many cases, however, additional tools are required to effect and obtain satisfactory control of the situation. For example, there are many good pre-emergent and post-emergent herbicides available on the market today. While the most effective method of application for the majority of them is spraying, some actually have an improved efficacy when applied in conjunction with a granular fertilizer.

When considering a combination herbicide/fertilizer product, however, it is important to take in to account the value of the fertilizer, the value of the herbicide and the cost of one application versus two applications.

While both newer and older pre-emergent herbicides have their pros and cons, they have one thing in common -- they are all compatible with fertilizer. Since most fertilization plans include a spring application, a combination product can easily substitute for this application. Try to select a product that provides a full fertilization along with the herbicide. Timing is probably the most important as pre-emergent herbicides need to be applied, as there name suggests, before targeted weed species germinate. Homogeneous fertilizers and "mini"-sized pellets are valuable as application rates are often lower for combination products than routine rates. Even coverage is also critical for effectiveness.

To calculate an accurate total cost, it is important to look at the number of applications necessary for the length of control desired. Though combination products are often slightly more expensive than individual applications, the convenience of a combination product will usually make it well worthwhile.

Post-emergent combination products often have a reduced efficacy versus their sprayable counterparts. They can, however, do an excellent job if weed pressure is light to moderate. Again, key factors to be aware of are particle size and proper application rate.

Post-emergent products function by sticking fertilizer granules to the leaf surfaces of broad leaf weeds and then translocating the chemical into the plant. Having a small amount of moisture present during application and withholding irrigation for at least 24 hours usually produces the best results. It is critical to read and understand the directions on all products, but especially fertilizer/herbicide combinations. Depending on the plan, it is usually easy to substitute a combination product for one of the scheduled applications. Combination herbicide/fertilizer products can be a real convenience not to mention a great value.

Application

The ultimate goal of fertilization is to supplement or replace the 17 essential nutrients necessary for plant growth. As a result, understanding application strategies is crucial to the success of any successful fertilization program. What is a pound of actual nutrient? How much will each bag cover? How is a spreader properly calibrated?

For years, the rule for turfgrass fertilization has been to apply no more than one pound of actual nitrogen per 1,000 square feet at any one time. The exception to this rule is slow release fertilizers, which can be applied up one and a half pounds of nitrogen per 1,000 square feet, depending on the longevity of the slow release product.

So what is a pound of actual nitrogen and how does it affect application rates? Since, fertilizer analysis are expressed as a percentage of 100, a bag of fertilizer containing 16 percent nitrogen equals .16 pounds of nitrogen per pound of material. In order to get one pound of actual nitrogen, one must be divided by the nitrogen content. The result is the amount of fertilizer you must apply to equal one pound of actual nitrogen.

For example if you have a 16 percent nitrogen product, divide one by .16, which equals 6.2 pounds of material. This is the amount of material necessary to equal one pound of actual nitrogen per 1,000 square feet. To get pounds of actual nitrogen per acre, multiply 6.2 by 43.56 to arrive at 276 pounds per acre.

A bag of 16-6-8 fertilizer contains 16 percent nitrogen, six percent phosphorus and eight percent potassium. To find out how many pounds of actual nutrients it contains simply multiply the weight the percent of each nutrient on the label. So, if there is a 100-pound bag of 16-6-8 fertilizer there are 16 pounds of nitrogen, six pounds of Phosphorus and eight pounds of potassium.

For fifty-pound bags, you cut the analysis in half so that a bag of 16-6-8 contains eight pounds of nitrogen, three pounds of phosphorus and four pounds of potassium. If you wanted one pound of nitrogen per 1,000 square feet, a bag of 16-6-8 would cover 8,000 square feet. The same equation applies to any product analysis.

This is a great tool to make sure that the right amount of nutrients is being put down in the field. For example, if 32,000 square feet are to be fertilized with 16-6-8, four 50-pound bags will be needed. Anything less would be under the recommended amount. This is one of the first areas to check if the response from application was inadequate.

Spreader calibration is, perhaps, the single most important factor for putting on the right amount of fertilizer. Whether the spreader is a handheld or rotary push, calibration based on the walking speed of the operator is important to ensure that the desired nutrients are applied evenly and accurately. Inadequate fertilizer can lead to inadequate growth, less disease resistance and less stress tolerance. And too much fertilizer can create excessive growth, which can bring on disease, stress and a lot more clippings. The correct amount plays a vital role in the outcome of the application process.

Getting the right amount requires spreader calibration each time fertilizer analysis is changed. A 50-pound bag of 46-0-0 will cover 23,000 square feet, while a 50-pound bag of 21-0-0 will only cover 10,500 square feet. Switching from a 21-0-0 to a 46-0-0 product without calibrating would result over two pounds of actual nitrogen per 1,000 square feet.

Putting It All Together

Clearly, successful landscape fertilization should not be left to chance. Proper planning, application and product selection are all important pieces to a successful landscape fertilization puzzle. There is one last area that maybe just as important. Communication.

Everyone involved in the fertilization process know what the goal is and the plan to obtain it. Solid communication can be the difference between success and failure. The more the team understands a plan, the better the plane will work. Equally important in the communication loop is the customer. Every client expects results, but results are often relative. If a customer's expectations require wasteful or ineffective fertilization methods, it is the duty of an industry professional to help create realistic expectations. This is especially true in the west where lush vigorously growing turf has been the rule. By educating customers about healthier turf and better environmental practices, everyone will benefit. LCM

Steve Franzen, Dave Goodrich, and Allen Van Peter are with Simplot Turf and Horticulture/BEST Professional Products in Lathrop, CA (800) 992-6066 (www.bestfertilizer.com).