“ Substances listed in their own niche of the Periodic Table of the Elements may represent the best way to track and pinpoint sources of–soil erosion that causes billions of dollars in damage each year.

In rare-earth elements, ARS scientists John Zhang, a hydrologist, and Mark A. Nearing, an agricultural engineer, see a last, accurate, and sale tool for documenting this erosion. It was Nearing who introduced the technology here, after preliminary studies in China.

Despite their name, rare-earth elements are actually abundant in Earth’s crust. They’re usually found in an oxidized form. Zhang and Nearing mix them with soil and distribute them with a device similar to a fertilizer spreader. Later, they collect samples of eroded soil, or sediment. In the lab, they can detect the rare-earth elements in the sediment samples either through instrumental neutron activation analysis or with a new technique they developed.

“All soil contains some rare-earth elements, so you have to be able to detect the tracer you are using,” says Zhang. “The trick is to ensure that there will be an adequate amount of tracer in the sediment–about three times the element’s concentration in the soil.”

There are 30 rare-earth elements. The scientists are working with seven lanthanide oxides: lanthanum, which is used in carbon lighting applications and optical glass manufacturing; cerium, used as a catalyst in sell-cleaning ovens; praseodymium, commonly used in an alloy found in lighter flints and carbon electrodes for are lighting; neodymium, used for coloring glass and ceramics and for filtering infrared radiation; samarium, used in magnets, in alloys with cobalt, and in nuclear reactors: and gadolinium, which is also used in magnets.

“Effective soil-erosion control requires a thorough understanding of how soil is detached, transported, and deposited along a hill slope or within a watershed,” says Zhang. “We examined how well these oxides reflect the actual movement of soil that they are placed on.”

The researchers say the fine-powder rare-earth elements are a more effective tool for tracking movement of eroding sediment than what’s currently the best tracer: minuscule amounts of the radioactive element cesium ([.sup.137.Cs]) that originated from nuclear-bomb testing and spread across the landscape through the atmosphere. [sup.137.Cs], which has a half-life of 30 years, is traced with radiation-measuring equipment.

Soil erosion can also be tracked with naturally occurring radioactive nuclides, natural and fluorescent dye-coated particles, and small beads.

“Rare-earth elements have advantages over all these,” says Zhang. “They bind strongly to soil, are readily incorporated into soil aggregates, have high analytical sensitivity, are easy and inexpensive to measure, don’t interfere with sediment transport, and have low plant uptake.”

“And the main advantage,” says Nearing, “is that rare-earth elements provide multiple tracers. With cesium, pinpointing the erosion’s source is difficult because there’s no differentiation among sites of origin. With rare-earth elements, we can use five or six tracers on the same field and tell precisely where certain soil eroded from.”

Nearing emphasizes that none of the tracers currently used presents any risk to the environment or to the user.

A New Extraction Method, Too

Zhang and Nearing have developed and tested a quick, acid-leaching method for extracting for analysis these oxides from soil and sediment samples.

The technique employs inductively coupled plasma-mass spectrometry, a widely used technique for routine determination of trace elements in liquids. “It may help scientists better understand soil transport, and it could aid conservationists as they develop and evaluate new erosion-control measures,” says Nearing.

The researchers started working with rare-earth elements when they were with ARS’s National Soil Erosion Research Laboratory in West Lafayette, Indiana. Zhang now works with ARS’s Grazing lands Research Laboratory in El Reno, Oklahoma, and Nearing is now with ARS’s Southwest Watershed Research Center in Tucson, Arizona.

Zhang first explored rare-earth elements’ effectiveness with small-scale plot studies. Nearing conducted large-scale studies with the elements on ARS’s North Appalachian Experimental Watershed in Coshocton, Ohio.

“These tracers were first used in China,” says Zhang. “But those studies were limited. We’ve confirmed their ability to bind to soil–the most important aspect of this technology.” Zhang found that the most severe soil erosion occurred in the upper-middle part of a slope. “The rare-earth elements traced sediment movement and redistribution with fairly good accuracy,” he says.

Nearing–with help from Zhang and Akitsu Kimoto, who is doing postdoctoral work funded by Japan–is studying the oxides’ performance in watersheds in the semiarid American Southwest’s alluvial soil near Tombstone, Arizona.

Overcoming Preferential Binding

Nearing says the powdered tracers bind well to the gravelly, sandy-loam soils typical of the Southwest’s rugged rangelands. And although this work revealed that the tracers have a quirky trait, the researchers have found two effective ways to deal with it.

“We noticed that rare-earth elements bind better to fine-sized particles than to sand-sized ones,” he says. “This preferential binding would skew your results if you simply measured detectable tracers in an intact sample.”

The team found that this can be avoided by either premixing the tracers with separate size classes of soil particles, then allowing them to bind before spreading them on the ground, or–later on, when field samples are collected–separating the samples by particle size before measuring the tracers.

“When we applied tracers to soil samples, poured water over them, and then separated the samples into four different particle-size classes, we found that we could detect the tracers to within 4-percent accuracy, which is very acceptable,” Nearing says.

Nearing wants to use tracer data to increase the accuracy of math-based models that predict erosion from rugged rangelands. “That could aid managers of flood-control structures who need to anticipate how much sediment can move downstream after rainstorms,” he says. “And it might help cattle ranchers fine-tune grazing plans and thus safeguard sensitive parts of the landscape.”

This research is part of Water Quality and Management, an ARS National Program.

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It may not be the most glamorous garden tool, but many millions of Americans will buy a lawn mower this year. If you are buying your first or replacing an old one, you confront a potentially daunting number of choices: reduced emissions, polymer decks, zero radius, overhead valves, 24 volts, and deadman switches, not to mention prices ranging between $200 and several thousands of dollars. Clearly, lawn mowers are significant investments, not disposable toys. Making an informed choice is not easy.

How can you control the process? Call manufacturers for brochures and warranty information and interview all local dealers. Ask about accessories and availability of replacement parts. Read on to gain a working knowledge of the tremendous range of mowers available today.

Six Types of Lawn Mowers

Most lawn mowers are either reel or rotary types. Walk-behind rotary mowers are most popular. These cut the grass with a blade spinning one to four inches above the soil. They may be self-propelled or manual, with side or rear bagging and with or without the latest trend on mowers – the “mulching” option. But the whole idea of clipping grass started in England some 160 years ago when an inventor adapted some carpet making machinery to the out-of-doors.

Reel Mowers

Invented in 1830 by Englishman Edwin Budding, the reel mower has a series of twisted metal blades arranged as a reel between the wheel assembly. Reel mowers cut like scissors. They are more effective on grasses 1 1/2 inches tall or less. When no motor or engine is used, the mower is economical, easy to use and maintain, and very safe. These “push-type” reel mowers produce no emissions or noise, so they are easy on the environment and neighborhood. Using one also provides healthful exercise, burning as many calories per hour as tennis or low-impact aerobics.

Lightweight alloys and plastics have reduced the former 40- to 60-pound weight range of the units to the current 16- to 32-pound range. If your lawn is 1,000 square feet or less, a reel mower is an excellent choice. All reel mowers follow the surface contours of your lawn more than a rotary. They reveal humps and hollows that a rotary mower disguises. Reel mowers tend to flatten tall grasses and weeds without cutting them, however. Prices are generally under $100.

Self-propelled reel mowers with gasoline engines (and, rarely, electric motors) are also available. There are two basic types. Turf professionals use the kind that discharges clippings to the front. Although these produce the finest cut, you probably don’t need one unless you’re mowing a golf-course green, or a lawn that looks like one. Short-growing, dense grasses such as bentgrass, hybrid Bermuda, St. Augustine, and zoysia look best if cut with a power reel mower. Reel mowers that throw clippings to the rear are more general purpose. The cost of powered reel mowers begins at about $400 for front-throw types and $250 for rear-throw types.

Rotary Power Mowers

Leonard B. Goodall from Warrensburg, Missouri, invented the push-type rotary mower in 1939. The most popular type of mower available today, it employs a gasoline engine or electric motor that spins a metal blade (or occasionally a heavy filament line) at constant speed. The engine is mounted on a deck supported by four adjustable wheels, all connected to a long handle that has controls for operation.

Push-type machines cost about $100 less than self-propelled mowers you walk behind, and at least $500 less than mowers you ride. Push models come in two basic designs: those with the grass catching (or bag) mounted at the rear, and those with it mounted on the side. Rear-bagging mowers hold more clippings than side-bagging mowers and allow close trimming in whatever direction you are mowing. Side-bagging mowers are usually lighter and less expensive than rear-bagging mowers. They allow close trimming only on the side opposite the bag. Regardless, a good side- or rear-bagger will literally vacuum the grass clippings and leave little, if any, on the ground. When shopping for a bagger, be sure to remove the bag from the mower and replace it to evaluate the ease of the operation. Also check the size of the bag opening. A small opening clogs more easily and inhibits quick and easy dumping of the clippings.

Manufacturers use steel, aluminum polycarbonate, or Xenoy resin for the deck material. Steel costs less but rusts, shortening the life of the mower. Aluminum is a little heavier, but does not rust. Decks of modern plastics are virtually indestructible.

Finally, plastic catcher bags are generally more durable than cloth bags. Appropriate for lawns up to half-acre size, the standard mower ranges in price from about $150 to $400 for the side-bagging models, and about $200 to $800 for the rear-bagging mowers.

Self-propelled rotary mowers use a power-drive mechanism. These machines require the operator to squeeze a bar or a lever to engage the mower. If the lever is released, the drive system and blade both stop. Some models abruptly start, while others move forward gradually. The latter is much easier to control. The self-propelling feature adds at least $100 to the cost of the mower. These require more horsepower – 4 1/2 is ideal.

I prefer rear-wheel drive over front-wheel drive. The rear-wheel-drive machines move in a straight pattern. Front-wheel-drive units seem to pull the machine forward, creating a somewhat erratic movement that requires guidance.

Mulching Mowers

Mulching mowers are the basic mower for most home lawns today. They burst on the scene about a decade ago, once American communities began to exhaust landfill space. Their capacity to mulch clippings so you can leave them in place is useful if you don’t want to collect them.

Some manufacturers create mulching mowers by simply blocking all clipping exit channels. Mowers designed to be mulchers have a doughnut-shaped deck housing with various baffles and a specially shaped blade, all to ensure clippings are cut several times. Compared with mowers that bag clippings, these save time because you don’t have to stop and empty the bag every few rows, and they can shred leaves into near-invisible pieces along with the grass. Also, they are safer because there is no avenue for discharge of a rock from the side or rear of the machine.

Mulching mowers save resources. Lawns cut with mulchers need less fertilizer. Also, you consume less landfill space by not disposing of clippings. On the downside, mulching mowers work less well on wet or overly tall grass compared with nonmulching rotaries, and the cutting blade must be sharp. Mulching mowers also require somewhat more powerful engines – at least four horsepower.

Some mulching mowers only mulch; others allow the option of bagging clippings. Cost ranges between $250 and $550. Electric mulchers are available ($400), as are riding mowers that mulch clippings ($1,000 to $2,000).

Electric Rotary Mowers

The greatest virtue of electric mowers is the noise they make … or rather the lack of it. If you live where noise is an issue or if you’ve simply had enough of it yourself, I recommend you consider a mower powered by an electric mower. Keep in mind, however, that electric mowers rarely have the power of a gasoline engine mower.

The least-expensive electric mowers are powered by a standard electric motor connected by an extension cord to an outlet. These are for small lawns accessible with no more than a 100-foot power cord. (Electrical resistance in cords longer than 100 feet could damage the motor.) The cost of these mowers is in the $100 to $200 range.

Another type of electric mower features rechargeable batteries. For instance, the Ryobi Mulchinator promises to cut half an acre of lawn, or to deliver about one hour of mowing time per 16-hour charge on its nickel-cadmium batteries. It is convenient and easy to use, and the 24-volt recharger is built in. The Black & Decker CM500 is similar. It uses 12-volt lead-acid batteries and also allows about an hour of mowing after a 24-hour recharge. These cost $400 to $500.

Solar-Powered

These may be the mowers of the future. Poulan/Weed Eater introduced the first solar-powered robotic mower. It wanders around the yard by itself – you don’t have to touch it. Small razor blade-type cutters clip the grass a little at a time. A wire, placed around the perimeter of the yard or flower beds, keeps the robotic mower within the bounds of the lawn. The unit clips grass all day long. If it hits an obstruction, such as a fence post or sprinkler, it stops, backs up, then goes forward again in another direction. Still, it requires level areas that include a minimum of obstructions. At $2,000, this mower is perhaps more a political statement than a practical way to keep your lawn trimmed.

Solar Power International offers a walk-behind solar-electric mower. The manufacturer claims that eight hours of direct sunlight charges the 12-volt lead-acid battery enough to cut grass for nearly two hours with the power of a four-horsepower gasoline mower. An optional charger you can plug in is also available. Cutting width is 21 inches, and cost is about $900.

Lawn Tractor

This category includes the widest range of sizes and prices. The general advice is to use some sort of riding mower for lawns larger than half an acre. But if your three-fourths-acre lawn is dotted with trees, flowerbeds, edged walkways, and other obstructions, a walk-behind might be still be a better choice. Typical horsepower ratings are provided here, but more isn’t always better. In some cases, the less refined machine has more horsepower to compensate for its reduced efficiency.

The simplest kinds are riding mowers that are smaller than lawn tractors. They are usually easier to maneuver, but less capable on slopes. In most cases, you sit in a sort of chair with the mowing deck out in front and the engine in the rear. The turning radius is much tighter than on a lawn or garden tractor. Some claim a zero” radius, and 12 to 24 inches is typical. You steer by controlling the drive on the rear wheels; the front wheels are like those on shopping carts. This creates limitations, such as the inability to maneuver across a slope. The mowing deck is 30 to 42 inches wide, and the engines deliver 8 to 13 horsepower. At least one, the Turfstar 2000 Electra by Ardisam, is powered by six six-volt batteries that provide a two-hour run time. Some are mulchers, or easily converted into one. Accessories such as tow carts for leaves and clippings are also available. The typical cost for a riding mower is between $700 to $1,000.

Lawn tractors are larger and look more like a car. You sit and look out over a hood covering the engine, and the mowing deck is underneath you. Commonly 10 to 15 horsepower, lawn tractors cut with a 38- to 42-inch deck. Mulcher conversions and tow carts are usually available. Cost is $700 to $4,000.

Garden tractors are scaled-down versions of farm tractors, with 12- to 20-horsepower engines and 38- to 60-inch mowing decks. Compare frames, axles, transmissions, efficiency from power takeoff to attachments, and interchangeability of attachments. Typical attachments include chipper, rototiller, and snowblower. Tow carts and reel mower gangs are also available. Price start around $1,000 and reach upwards of $6,000.

Comfort is a major concern when purchasing these larger machines. Your body should fit the, machine so that the steering wheel, seat, pedals, controls, key starter, and movement controls are easily accessible. Ride the unit. I’ve tested some that are noisy, full of unwanted vibration, and simply uncomfortable. You test-drive a new car; why not a riding mower?

Tooling Up For Spring and Summer

“Ergonomic” design has become a catch phrase in lawn and garden circles. In lay language, it means “designed to work better, or to be operated more efficiently or easily.” Manufacturers naturally strive to make ergonomic improvements in their products, and it’s fun to survey the field at the beginning of a new gardening season for those innovative steps in engineering that have produced great leaps for gardening kind. The following are just a few time-, energy-, and frustration-saving devices that we find worthy of note. You may want to put them on your wish list as you head into another season 6f lawn and garden care.

An Easy-Starting String Trimmer

String trimmers traditionally come in two types – gas and electric. The electrics have cords that get tangled in bushes and flower beds and must be reeled up when the job is finished. Gas trimmers have irksome pull starters that can wrench your arm while raising your blood pressure.

Now, however, there’s a new option that solves both problems – a two-cycle, gas-powered trimmer that starts as easily as an electric. The Electric-Start Trimmer is activated by a rechargeable nickel-cadmium battery, providing 40 easy starts before needing a recharge. To recharge, simply pull out the battery pack and plug it into a home electrical outlet. The trimmer also features a redesigned fuel tank that reduces spillage, and a quieter muffler, which should eliminate possible complaints from the neighbors.

The World’s Quietest Chain Saw

“Quiet” and “chain saw” are two terms that ordinarily don’t go together. In fact, chain saws can be among the most annoying of outdoor tools for those in close proximity – unless, that is, you are using the new STIHL 023L chain saw, which has been termed “the quietest gas-powered chainsaw anywhere.”

How quiet is it? Manufacturers claim this saw produces a noise level of only 92 decibels at the operator’s ear. Although that’s a little louder than the average power lawn mower, it handily beats the average chain saw that emits 100 decibels.

In decibel mathematics, 100 is 10 times louder than 90, so the 023L is about seven times quieter than the average chain saw. Because noise levels abate over a given distance, listeners ten yards away will hear a sound equivalent to an electric typewriter when the 023L is running. From STIHL, price: $349.95.

Easy-Operating Mower

Ever dream of mowing the lawn without leaving your easy chair? This mid-sized, zero-turn radius mower may be the next best thing. It can be operated with mere fingertip pressure on a patented combination forward speed control (a kind of cruise control) and steering levers. You can sit with your feet up because braking is done by hand, too – no steering wheels, gear shifts, or foot pedals. Grass collection and vacuuming capabilities are built right into the mower. There are no bulky grass-catcher attachments. So how are you going to get any exercise using this lawn mower? Simple. With the time you save on this easy rider, you’ll have a lot more extra time for the activities you enjoy – be it tennis, golf, swimming, or jogging. From Walker Manufacturing Company, prices start at $5,000.

Versatile Mowing System

“Time is money.” Anyone who has used a power riding mower knows how much time it can take to remove a mowing deck for cleaning, maintenance, or to put on a different attachment – not to mention how frustrating the process can be.

Here’s a mower that can save you the hassle. Equipped with a Quick-D-Tach[R] mounting system, the Grasshopper mower allows the operator to remove or reattach decks quickly and easily.

It also comes with a new Quick-D-Tach Combo Mulching Deck[R] that can be switched easily from collection to discharge to mulching, without changing decks at all.

Attachment buffs will find a treasure trove of options, including angle dozer blade, V-Snow plow, rotary broom, snow thrower, dethatcher, bed shaper, sun shade, and cab enclosure, to name a few. From The Grasshopper Company, prices start at $4,390.

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How to choose and use organic materials to improve your soil

Deciding which natural soil additions to use can seem like a mystery, especially when you’re facing the stacks of bagged materials sold at nurseries and garden centers. Various composts and manures, peat moss, and other compounds all promise to do something good for your garden soil, but you’re not sure exactly what.

Relax. You don’t have to be a detective to choose organic additions and use them successfully. Most natural additions improve the soil’s texture and ability to retain moisture. Many of them make good mulches. And some have good nutritional value, although they may contain widely varying amounts of the three essential nutrients: nitrogen (N), phosphorus (P), and potassium (K).

By “natural” or “organic” soil additions, we mean ones derived from living or once-living organisms, be they cows or worms, trees or other plants.

Commercially packaged soil additions come from a number of sources, including the agricultural industry. Cattle and chicken ranchers sell manure to packagers. Farmers sell mushroom compost, rice hulls, and byproducts from other crops. Some cities collect and compost yard waste, then package it for retail sale or let residents pick it up free in bulk.

When and how to use additions

Fall through late winter is a good time to dig or till organic additions into your planting beds. Work additions into the soil to a depth of at least 1 foot. In sandy soil, they can help bind the loose particles together and increase water retention. They can break up the heavy texture of clay soil and allow better root penetration.

You can also spread a top-dressing of 1 to 2 inches of addition over established beds and just let it sit. When spring arrives, plants will push their way up through the mulch.

Read the labels

When you’re shopping, read the labels on the bags. Some manufacturers list the materials’ nutritive values; others do not. If the label describes the material as “ground,” “screened,” or “aged,” you know you’re getting something that wasn’t just scraped off the floor of the barn and put in a bag. Grinding gives it a uniform texture. Screening sifts out all the rocks and big chunks. Aging allows the organic material to break down so that it doesn’t rob the soil of nitrogen as it decomposes and the animal urines have time to leach out.

One way to avoid using a manure that’s too strong, or “hot,” is to sniff the stuff. If the material has a strong smell of ammonia, let it sit in a pile for six weeks, turning it periodically, before you spread it on beds.

Manures

Cattle manure (from steers and dairy cows) may contain as much as 1 or 2 percent nitrogen, 0.3 to 0.5 percent phosphorus, and 0.5 to 1 percent potassium. Dairy cow manure tends to have fewer salts than steer manure does. Well-aged manure is a good amendment for vegetables, annuals, and perennials.

Chicken manure is a rich, fertile amendment with nutrient values that can run up to 3 percent nitrogen, 4 percent phosphorus, and 3 percent potassium. It can be strong smelling. It can also burn plants, so don’t use it on sensitive or shallow-rooted plants. If used properly, it gets annuals and vegetables off to a fast start. To avoid burning plants, spread it no more than 1 inch thick, and till it as deep as you can.

Guano and exotic droppings include bat guano, which typically has an N-P-K rating of 10-3-1, the highest nitrogen content of the additions we list. Because of its potency, guano is the most likely to burn plants. Use it sparingly as a top-dressing. Whitney Farms of Independence, Oregon, imports bat droppings from caves in Mexico and other countries, then processes and packages the guano.

Some zoos collect and package manure from various animals. Elephant manure is most commonly sold; the huge vegetarians produce a gentle substance that is on par with cow manure.

Conditioners

Municipal compost is often made from grass clippings, leaves, and tree prunings gathered and composted by municipal agencies, then given free to residents or sold in packages or bulk quantities. Compost improves soil texture and water retention as it slowly releases nutrients. Nutritional values vary: Seattle-based Cedar Grove Composting, for example, rates its compost at 1.3 to 1.5 percent nitrogen, 0.15 to 0.22 percent phosphorus, and 0.44 to 0.60 percent potassium.

Mushroom compost, a byproduct of commercial mushroom farming, is low in nitrogen and phosphorus but quite high in potassium. It makes an excellent top-dressing for roses. This alkaline amendment works best in areas where it helps balance acid soils.

Peat and sphagnum moss are great for holding moisture in the soil and loosening up dense soils. Peat moss increases soil acidity, so it’s the amendment of choice for azaleas, rhododendrons, and other plants that thrive in acid soil. The moss is difficult to get wet initially. Suppliers suggest that you lay the plastic bag it comes in on its side, make a small slit in the plastic, insert a hose, and let it drip into the bag for a day or so before you dig the peat moss into the soil. Most peat moss comes from Canada, and there is some controversy concerning the depletion of this natural resource.

Redwood soil conditioner, made from the bark and sawdust of redwood trees and treated with nitrogen and iron, is a mainstay in California for loosening up hardpan soil. It decomposes slowly.

Worm castings are available packaged – or buy a vermicomposter and feed the worms vegetable scraps from the kitchen, then harvest the castings. Their nutritive value is low, but castings aerate the soil and improve its ability to retain and release nutrients.

Rice hulls and other agricultural byproducts are usually available in areas where crops are grown. All are worthy additions, provided they are well aged and don’t have heavy concentrations of animal urines.

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“You can’t tell anything without a soil sample.” This cliché has been repeated so often — sometimes as the punch line of a joke — people often overlook the truth in the statement. Of course, you can tell some things about soil without an analysis, but the chemical properties that make a soil good or bad are mostly difficult or impossible to discern by sight. So you must submit a soil sample to a reputable lab for proper chemical analysis if you wish to get a handle on what shape your soil’s in.

Most laboratory soil analyses are fairly routine. If an error occurs in the process, it’s not likely to have occurred in the lab. Rather, the sample itself is likely to be where the problem lies. And that’s where you come in. The lab can only test what you give them, so you need to give them a sample that will tell you something meaningful. That means taking samples in the right places, at the right depths and with the right tools; all while keeping a meticulous record of where and how you sampled.

The right tools

If you are in the turf or horticulture trade, you ought to have a soil tube. They are fairly inexpensive, durable and allow you to sample soil quickly at controlled depths. Because soil tubes are also useful just for “poking around” in landscapes, it’s a good idea to have one on hand. However, an alternative is to use a spade or shovel (as discussed in “Taking the sample,” below). Augers, trowels and powered samplers all may be suitable as well.

Location, location

Soils vary from spot to spot, sometimes over just a short distance. A representative sample, therefore, should include soil from different points at the site. Further, the cores that you combine to form the sample you submit should be roughly the same size so that no single sample will skew the results.

Most labs request that your sample includes soil from at least a dozen individual points in the sampling area. You may end up using quite a few more than this, depending on the size of the area, however. It often is helpful to sample in a systematic fashion to ensure that you thoroughly cover the site.

The key to determining sampling units is to define a more or less homogeneous area. For example, don’t mix turf samples with those from a shrub bed. On a golf course, sample tees, fairways and greens separately. At a residential site, keep front and back lawn samples separate. Use your judgment when defining the sampling area. It may be acceptable to submit one sample for a relatively large area (a fairway or athletic field, for instance) if the entire area is more or less uniform and maintained similarly.

If you’re sampling an area because you’re trying to diagnose a specific problem, be sure to sample only from the affected area. (However, the lab may ask you to sample from a healthy area for comparison.)

Sampling correctly – Be consistent

Soil samples should always be taken in a consistent manner. In particular, make sure each sample is the same size, and that each core or slice is uniform from the soil surface down to the sampling depth. A soil tube makes consistent sampling easier, but you still can also take good samples with a spade or trowel, though it will require a bit more care during sampling.

Also, in larger areas, sample systematically so that your sampling pattern resembles a grid or some other pattern that ensures more or less even spacing between sampling points.

Use appropriate depth

Six inches is adequate in most cases, including tree, shrub and bedding areas, or open ground you’re preparing for planting. Three to 4 inches is usually adequate for established turf, since most turf roots don’t reach deeper than this.

Remove debris

Be sure you remove surface debris (sticks, leaves, etc.) and rocks from the sample. Also remove turf mat and thatch.

Collect and mix samples

Carry a pail or similar container with you as a receptacle for the samples. After you have completed sampling the area, thoroughly mix all the soil together. Labs usually only need about a pint, so put that amount into the sampling bag (often provided by the lab) and then discard the rest. For small areas, make sure you pull enough samples to provide an adequate sample.

Record information

Be sure you record all the information requested by the lab, and label each sample bag clearly.

Follow laboratory instructions

The preceding steps are general instructions. Labs may request that you follow specific steps that could differ. Be sure to read and follow any instructions the lab provides to you, including how to deliver the sample to the lab.

Timing

Timing is not critical, with a few obvious exceptions, such as wet or frozen soils that would make sampling difficult. Another situation where timing might be important is with salt damage (such as from deicers). Salt leaches through soil, so if you are testing to confirm salt damage, do so quickly before concentrations drop due to leaching. Further, be sure not to sample within a month after applying fertilizer or soil additions, because these materials will skew the lab results.

Remember that if you are getting ready to install new turf, test the soil first so that you can make any additions that the lab results might suggest before installing the turf.

Good record-keeping

Be sure to keep copies of all records relating to soil testing. Obviously, you need to match the results to the right locations, but it’s also useful to compare current test results to those from past years to see if and how your soil might be changing.

“Garbage in, garbage out” is a saying applied to computers. The principle is the same with soil analyses — the analysis is only as meaningful as the sample. Ensure that you get your money’s worth by delivering a proper sample to your laboratory.

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The idea of fertilizing trees to meet specific objectives is taking root.

Tree fertilization is a controversial subject. Even the use of the word “feed” is something that many grounds managers understandably take issue with. After all, by fertilizing, we are only adding essential elements. Trees produce their own food (sugars) through photosynthesis.

Regardless of our terminology, the why, what, when, how and how much of fertilizing trees is surrounded by controversy. To the extent that it focuses attention on the matter, this controversy is good. For too long, arborists and other grounds managers have concentrated, sometime exclusively, on the above ground portions of the tree. In fact, recent surveys by the National Arborist Association and other organizations show that the majority of tree-care companies’ sales volume comes from pruning and brush removal. In other words, the chain saw remains our most common tree-management tool. Fertilizing and other soil treatments represent only a small fraction of arborists’ activity. Yet, we run a great risk if we ignore the management of the below-ground tree.

Roots To manage the below-ground parts of trees, it helps to know their functions and where they are located. Roots have been inaccurately described in many books and articles. We have all seen drawings of the “carrot-root” tree, in which the spread and depth of the root system is almost a mirror image of the trunk and canopy. Actually, such tree species are rare. A better description of a tree – the entire tree – is a goblet standing on a platter. Woody roots, the long-lived roots that provide stability, transport materials and absorb water and nutrients, often extend out a distance equal or greater than the tree’s height. With some exceptions, roots rarely go deep. Ten or 15 feet is the usual maximum, with the majority of roots located in the upper 2 feet of soil (the record for the deepest live roots is about 200 feet, on a juniper tree).

Woody roots serve as a platform to support the growth of non-woody roots. These fine roots grow from the woody roots, “foraging” in rich topsoil and litter for water and nutrients. These roots are mycorrhizal, meaning they have formed a beneficial partnership with certain fungi. This symbiotic relationship provides food and sugars to the fungus from the roots, while the fungus increases the absorptive area of the root system.

Non-woody roots are not permanent structures but are periodically “shed.” Think of them as below-ground leaves – temporary gatherers that are shed after functioning for several months or years. The similarity of leaves and non-woody roots goes a little further. The amount of organic matter incorporated into the soil is greater from the shedding of non-woody roots than from leaves. This autumn, if you walk through a pile of leaves under a mature deciduous tree, imagine a greater amount of non-woody roots shed in the soil beneath your feet.

The relationship between the aboveground and below-ground tree is finely balanced. When growth is limited by a nutrient deficiency, root growth tends to be favored over shoot growth. When growth is limited by a light deficiency, then shoot growth is favored over root growth. The part that is resource-limited is allocated more growth so that it can obtain more of the limited resource it’s designed to gather. This has important implications for fertilizing. For example, the addition of fertilizer may increase the mortality of fine roots while increasing shoot growth, not necessarily a desirable outcome.

Knowing a little about where roots occur and how they function, it’s easier to understand the reasons and methods of fertilizing. So now let’s examine the why, what, when, how and how much of fertilizing trees.

Why are you fertilizing? The answer to “Why fertilize?” is found in the new American National Standards Institute (ANSI) A300 Fertilizing Standards for Trees and Shrubs. The objective of fertilizing is to supply nutrients that are deficient to achieve a clearly defined objective. This fits the industry movement toward “prescription fertilizing” (“prescription” meaning a treatment specific to the soil conditions and species rather than a blanket 10-10-10 or similarly balanced fertilizer). Blanket fertilization once dominated the industry and still is a common homeowner practice for fertilizing trees.

Determining nutrient needs is not an easy task. A “cookbook” showing precisely what each tree species requires does not exist. Also note the phrase “clearly defined objective.” Are you fertilizing to increase growth? This is a reasonable objective for young trees, but should you force growth on a mature tree? Are you fertilizing to increase vigor for better pest tolerance? Fertilizing may increase, rather than reduce, pest problems. Some insects are attracted to the higher nutrient content of foliage on fertilized trees. Fertilizing may also result in more growth but less production of defensive chemicals, thus increasing the likelihood of a successful pest attack. The same is true of the practice of fertilizing declining trees. Unless the decline is due to a nutrient deficiency, the application may hasten the decline by allocating the tree’s limited energy reserves to fuel unnecessary shoot growth.

It’s impossible for me to cover here all the possible factors that could affect your decision to fertilize. But your “clearly defined objective” should be well-considered and take into account all possible potential negative consequences.

What should you fertilize with? All the possible variables make determining the “what” a more difficult task. No longer can the generic, one-size-fits-all approach be used for fertilizing trees. Instead, foliage and soil nutrient analysis is used to determine specific nutrient deficiencies. Foliage analysis can provide an accurate picture of the tree’s nutrient status, but it cannot tell you why a nutrient may be deficient. In addition, few laboratories are equipped to conduct foliage analysis of ornamental trees or interpret the results. That’s why you’ll need a soil analysis, and this is still the most common means of determining need. Soil analysis provides more information than just nutrient levels. Soil pH and soil organic-matter content are other valuable pieces of information that you can glean from a soil analysis.

Soil pH is closely tied to iron availability. Alkaline soils – those with a pH above 7.0 – may have adequate iron but the tree will be unable to use it. Thus, merely adding iron may not improve the tree unless you correct the pH – not always a simple task. Sometimes the best recommendation may be to remove the tree and plant one better adapted to the alkaline soils.

Soil organic matter should be between 3 and 5 percent. It is rarely higher in urban soils, but it is often lower, sometimes less than 1 percent. Adequate organic matter is an important part of a healthy soil. It’s difficult to maintain a healthy tree without a healthy soil regardless of the amount of fertilizer you add. Soils with a higher organic-matter content have the bacteria and other organisms important for fixing nitrogen, producing plant growth regulators and deterring root diseases. If soils are deficient in organic matter, you should correct this by surface mulching, vertical mulching or other means.

Nitrogen is the most universal nutrient added through fertilizing. Often, even though other nutrients may be present in adequate quantities, nitrogen may be lacking. Nitrogen deficiencies are considered to be the most limiting factor in tree growth (after air and water). Nitrogen is easily lost through volatilization and leaching. Unlike the natural forest where nutrients are supplied by a turnover of organic matter, our lawns are swept clean of leaves, grass clippings and other sources of organic matter. In addition, trees may have a difficult time acquiring nitrogen in a turf environment. Turfgrass roots may be several times denser than tree roots inhabiting the same soil, and turfgrasses absorb nitrogen after an application faster than trees.

Nitrogen fertilizers should be slow-release, at least half the nitrogen in a water-insoluble form, with a salt index of less than 50.

When should you fertilize? The “when” is not clearly defined in the A300 standards, nor should it be. They say to “apply so nutrients are available to growing roots.” Tremendous differences in trees, soils and climate exist across the United States. The “when” for a live oak in Louisiana can be different from a red maple in Minnesota. Early spring, before shoot expansion, is often identified as the ideal time for fertilizing. However, autumn – after the completion of the growing season – also offers possibilities and may be the preferred time if you’re making only a single annual application. Some research shows that timing is not particularly critical. Forestry studies indicate that the spring growth flush in trees uses nitrogen already stored in the plant, not from external late winter or spring applications.

A frequent concern regarding autumn applications, particularly in northern states, is that they will delay hardening off and consequently increase the risk of winter injury. However, most research on the topic has not found this to be the case. In fact, autumn nitrogen fertilizing seems to have no effect on winter hardiness, or it may increase it slightly. I should note, however, that some conifers may open their buds earlier in the spring if fertilized in autumn, so there is a slightly higher risk of spring frost damage.

How should you apply fertilizer? The A300 standards discuss more than one application technique. Several methods, surface and subsurface, granular and liquid, are acceptable for applying nutrients. Foliar applications, injections and implants have their place too, but should be limited to situations where it is impractical or impossible to fertilize via the roots.

The application coverage area should extend at least to the drip line for trees with spreading canopies. For columnar or trees, the radius of the application area, in feet, should equal the trunk diameter, in inches. (For example, a 20-inch-diameter trunk would warrant an application area radiating 20 feet out from the trunk.) Tree roots usually extend farther than this – whichever method you use – but expanding fertilizer coverage farther may not show much additional benefit.

How much should you apply? The “how much” is changing as well. The nitrogen rate should be between 2 and 4 pounds of nitrogen per 1,000 square feet, the actual amount depending on the soil-nitrogen level and whether your objective is growth (primarily for young trees, which may need the higher end of the range) or maintenance (mature trees, which should receive the lower amounts). The old idea of 6 pounds per 1,000 square feet, regardless of the tree, may either be wasteful or result in undesirable shoot growth at the expense of root growth. Even 2 pounds may be too much for mature or over-mature trees growing in a mulch area.

Tree fertilizing is going through many changes and becoming more complicated as our understanding of nutritional needs improves. The attitude that the old methods (10-10-10 or 20-5-15 fertilizer drilled around every tree regardless of circumstances) work well enough will always exist. There will always be those who think that prescription fertilizing is overkill.

But consider the “why” again for a minute. The idea is not just to apply a product so it doesn’t hurt the tree, but so that it improves its vitality, appearance or meets some other objective. Prescription fertilizing is an important direction for the tree-care industry. Providing only what is needed to achieve a certain objective, at the best time and in the most appropriate manner, is the hallmark of a professional. Prescription fertilizing is where you are valued for what you know, not the amount of product you apply.

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For a better understanding of what kind of soil you’ve got, what it’s made of, what kind of texture it has and how well it drains, read on. You’ll also learn how to use old soil to rid your soil of weeds, pests and diseases.

Undercover Test

One of the best ways of gaining an understanding of your soil is to perform an undercover test. The test requires a fair amount of digging, so you might want to wait until you’re ready to plant a new tree or shrub. Dig a hole 18 to 24 inches deep and wide, piling the excavated soil nearby. Get down on the ground and look closely at the sides of the hole. What you’ll likely discover is a series of soil layers. The first layer is topsoil, and it should be at least 6 inches thick and fairly fluffy. The remaining layers, whose thickness and densities may vary considerably, are generally referred to as subsoil. Now look at the roots in the soil. In healthy soils, they grow straight down, but in poor soils, roots tend to grow horizontally due to a thin layer of topsoil or compaction in the subsoil, or both.

The different colors of the layers are probably the best indicators of soil health, and generally speaking, the darker the color, the better the soil. For instance, dark browns, reds and tans suggest soils with a high humus content. Soils with a blue or gray tint are indicators of poor drainage, usually a result of compaction.

Now look at the excavated soil for signs of life. It should contain a fair number of earthworms as well as other critters. If it doesn’t, the soil either lacks sufficient organic matter or has been maintained far too long on a diet of harsh, synthetic fertilizers. Actually, the undercover test isn’t so much a test as it is an observation. It can reveal all sorts of problems related to a lack of organic matter, compaction, poor drainage and the like.

If you use a rototiller a lot, the top 8 to 10 inches of your soil may be nice and fluffy, but below that, hard as a rock. That’s because excessive tilling can lead to the creation of something called hardpan, a layer of subsoil below the reach of the tiller’s tines. You can drive a pitchfork deep into the subsoil each time you till, to loosen the hardpan layer.

The Watering Test

Start by watering your lawn or garden thoroughly. Two days later, dig a 6-inch hole and check the moisture content of the soil. If the hole is dry at the bottom, your soil is draining too quickly for most plants to grow properly. If the hole is soggy, your soil isn’t draining fast enough. So how do you deal with soil problems? Whether your soil has too much sand or too much clay, drains too slowly or too quickly, or lacks sufficient nutrients and soil organisms, the solution is the same in every case: organic matter. Compost is the best source of organic matter. If you’ve got good soil, but each year you have problems with weeds, pests and diseases of one form or another, use a technique known as soil solarization, which is best done during the summer months.

Soil Solarization

First, rake the problem area smooth, getting rid of any clods along the way, and level it. Then water the area, soaking it more than usual. The next day, cover the area with 3- to 3-millimeter clear plastic, covering the edges with soil to hold it in place. Within four to six weeks, the greenhouse effect caused by the sun hitting the plastic will cause soil temperatures beneath the plastic to reach between 140 and 160 degrees Fahrenheit, which is hot enough to kill almost everything in the soil. At that point, you can remove the plastic and plant away.

Squeeze Test

To literally get a feel for the content and texture of your soil, perform a squeeze test, for which you need a handful of soil from your lawn or garden. First, roll the soil in your hand until it’s about the size of a golf ball. Then gently squeeze the soil between your thumb and index finger. Sand feels gritty, silt feels more like talcum powder and clay feels slippery. Now squeeze the ball in your hand. If it crumbles, it has a well-balanced texture. If it holds its shape, it has a fair amount of clay. And if you can roll it into a snake, it has more clay than you want.

Perc Test

Drainage problems account for an incredible number of problems in the lawn and garden. If the soil drains too quickly, plants may never have a chance to absorb enough water to adequately sustain their growth, no matter how often you water. And if the soil drains too slowly, plants may actually suffocate or rot. That’s why it’s a good idea to perform a perc test.

Dig a hole 6 inches wide and 1 foot deep using a shovel or post-hole digger. Then fill the hole with water and let it drain. When the water has drained completely, fill the hole again, and this time keep track of how long it takes for the water to drain completely from the hole. If the water drains completely within 3 hours or less, you have a drainage problem, probably due to sandy soil. If water is still standing in the hole after 8 hours, you have a drainage problem due to too much clay in the soil, and if the water drains within 4 to 6 hours, you don’t have a drainage problem.

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