Top Dressing -- Amending Existing Landscapes

Topdressing the Soil in an Existing Landscape

To amend existing beds, topdressing with organic and inorganic matter is recommended. To increase the fertility of your existing perennial beds or borders, pull back any mulch covering you already have. Add a three-inch layer of good quality compost and gently work it into the top few inches of bare areas between the plants. Earthworms will do the rest. As the years go by, your earthworm population should increase and pull the compost into the soil.

If you don't want to disturb the mulch, poke holes with a garden fork or hand aerator in the beds and pour a fine compost blend down the holes. Repeat this process spring and fall, or more often depending on your soil conditions until good soil tilth is attained. This is a long-term process.

A similar technique may also be used in lawns and over large areas. After aeration, spread the compost on the area with a rake. Repeat this process each spring and fall. This is an effective technique for supplementing nutrients for trees as well.

Foliar feeding is an even higher maintenance activity. Higher maintenance because is needs to be repeated often. Liquid compost, worm tea, liquid seaweed. trace minerals, liquid molasses, liquid humate and other organic liquid products can all be used. Follow directions on the container. Foliar feeding is an excellent way to give the landscape a boost in the heat of the summer or after a hail storm. But to improve the soil texture and soil organic content, organic solids need to be incorporated into the soil. There are thousands of different types of microbes that perform many different functions for the plants and soil requiring organic matter (carbon) in different forms.

Compost Tea

You may decide to improve the soil by spraying with compost tea to add nutrients, stimulate microbial growth or inoculate microbes to the bed and/or landscape. Improvements have been made to the way compost tea is brewed.

Compost tea that has been properly aerated contains increased biotic life, and is called Aerobically Activated Compost Teas, or AACT. To make Aerobically Activated Compost Tea, start with good aerobic composted manure, vermicompost or compost you make yourself that has a good earthy smell. You can purchase a tea brewing system, or make your own. To purchase a brewing system, go the Internet and type in compost tea in the address bar. Several AACT companies should come up.

You will need an air infused system, such as an aquarium air pump and air stones and a paint strainer bag. Add 1 – 2 pounds of compost to a paint strainer bag for a five-gallon container of water, 1 – 2 ounces of horticultural molasses and fill with chlorinated-free water. Don't over feed the microbes; it's better to underfeed than overfeed them. You can de-chlorinate (degas) your water in a couple of hours in the open air. Check with your Water Department to determine if they use chloramines, which will not degas. Catching rainwater and using it is a good option. Hook up your aerator. Float the bag with compost above the air stones.

Let it steep for 12 – 24 hours, in the shade to keep the mixture cooler in the summer. If it smells bad, it went anaerobic. Throw it out. It should smell like good rich, earthy compost. Pour off the solids from the bag into your compost pile or use as mulch in other areas of your garden. Pour the liquid on plants or spray your xeric beds or borders and landscape in general with the compost tea. Use within 24 – 36 hours, the microbes begins to decline after that. A five-gallon container will inoculate and foliar feed an acre; it takes only 44 fluid ounces, ½ gallon, for each 1000 sq. feet. Excellent for container plants as well.

Repeated applications of AACT provide needed microbial and organic content to compacted, starved or abused soil. It's an effective way to rejuvenate tired and worn-out soil and hard-to-amend turf areas.

Herbicide Carryover – Killer or Contaminated Compost

Unfortunately, one of the most beneficial and natural products, compost, is becoming contaminated. Farmers and home gardeners across the United States have reported damage to vegetable, flower and fruit crops after applying composted manure (whether from cows or horses) or composted hay, straw or grass clippings to the soil. Shortly after these applications as soil amendments or mulch, they noticed stunted growth, poor germination, death of plants, deformed plants and fruit. In most cases, the damage was caused by a group of synthetic chemicals known as pyridine carboxylic acids, sometimes referred to as pyralids, namely, aminopyralid, clopyralid, fluroxypyr, picloram, triclopyr and/or aminicyclopyrachlor. Products containing these chemicals include Curtail, Forefront, Grazon Next, Grazon P+D, Milestone, Redeem R&P, Surmount, Confront, Lontrel, Millennium Ultra Plus and Plus2, Clopyr AG, Stinger and Imprelis. In September, 2009, Mother Earth News reported that a previously considered organic product, Grab 'n Grow, contained one of the above chemicals and caused damage to a vegetable garden of Grab 'n Grows manager, Don Liepold.

Subsequently “I have been testing  and detecting herbicide residues and thus rejecting cow manure, horse manure, turkey mulch, rice hulls, mushroom compost and yard trimmings,” says Grab n’ Grow manager Don Liepold. “I spent $20,000 in lab fees in 2008, and am on the same track for 2009,” he says.”

The Mother Earth News article continues “It is extremely difficult to keep contaminated materials out of commercial compost. “One load of contaminated grass clippings can ruin a batch of compost,” says Eric Philip of Anatek Labs in Moscow, Idaho. Philip has seen so many positive tests for clopyralid residues in compost that he would not use untested compost in his own garden.

“When folks have plants die in their home gardens, their first assumption is that they did something wrong,” Philip says. But with pyralid-laced commercial compost becoming more common, contaminated soil amendments are often to blame.

The effects of contaminated compost and composted manure might be transferred to foliar sprays as well, although I have not read any reports mentioning them specifically.

The source of pyralid pollution can be impossible to trace. For example, a horse stable may use hay brought in from a neighboring state, without knowing that it is laced with pyralid herbicides. If the horse’s manure or stable litter ends up in a garden, disaster is ready to strike. It’s better to be safe than sorry. Liepold stopped making one of Grab n’ Grow’s most popular products, Mango Mulch, for more than a year because he could not find an uncontaminated manure supply. Now he’s getting it from two local organic dairies.”

Mother Earth News first sounded the alarm on “killer compost” in 2008, and has continued to report as new information comes to light. In 2011, Dupont's Imprelis, an herbicide praised for being a “green alternative” because of its long residual, made headlines as it killed trees and shrubs in numerous states from New England across the Midwest into the northern Plains States. Currently, the EPA Stop Sale Order on Imprelis, but not on the other products by Dow AgroScience and Dupont.

Dupont did notice that Imprelis could create killer compost. From Page 7 of the 9 page label on Dupont's Imprelis: “Do not use grass clippings from treated areas for mulching or compost, or allow for collection to composting facilities. Grass clippings must either be left on the treated area or, if allowed by local yard waste regulations, disposed of in the trash. Applicators must give verbal or written notice to property owner/property managers/residents to not use grass clippings from treated turf for mulch or compost.”

It is well known that the “label is the law”. How many people do you imagine read the entire label when purchasing herbicides? Although Imprelis was sold only to licensed applicators, how many of them read the label or warned home or corporate owner/managers when they applied Imprelis of the long term effects regarding compost? In areas where community composting is practiced, it is easy to see how contamination of these resources can occur.

North Carolina University Cooperative Extension issued an excellent bulletin entitled “Herbicide Carryover in Hay, Manure, Compost and Grass clippings warning “farmers and home gardeners of reported damage to vegetable and flower crops after applying horse or livestock manure, compost, hay or grass clippings to the soil,” ( Although the above mentioned products were licensed for use in agriculture by licensed applicators, Imprelis was licensed for use on residential lawns by licensed applicators.

Just because many of these products were for agricultural use, doesn't mean home gardeners are safe from the herbicides long term effects. The warning for vegetable growers and home gardeners is to be aware of your source for hay, straw, manure or compost from hay, straw or manure. These herbicides can be active up to four years or more. The person you purchase or receive these products from may not even know this class of herbicides have been sprayed on them, or be aware of the longterm effects.

Here is an example of why it is difficult to find out. A friend of yours offers you horse manure that has been composted. You might ask him/her if herbicides were used, with the farmer replying the manure/compost is "safe" because the animal has not been effected. The horse or cattle were fed hay that was sprayed with one of these herbicides (it's reported not to be harmful to animals). The horse eats the hay, and the resulting horse manure contains active residues of the herbicide, even after it composts. You spread the manure in your vegetable garden and your vegetables are stunted and fail to thrive, or die outright.

You might think this couldn't happen to you, but a case very similar to what I described happened to a family member of mine. After he did some research, he went back to the neighbor where he got the manure and found out the man did indeed spray his hay with one of these chemicals.

Unless you are absolutely sure hay or straw does not have a history with these herbicides, I would not use them in compost or on your garden soil or ornamental beds.

The affected composted manure would be safe to spread on your turfgrass. To be safe, I would not compost the grass clippings or use the grass clippings in beds or borders. It would be safe to cut your turf with a mulching mow, returning the clippings to the soil if you had already used contaminated compost there. I'm unsure of the effects of these chemicals on trees (except for Imprelis). The North Carolina bulletin goes on to describe how to do tests to determine whether the compost or hay/straw contains residues of one of these herbicides.

The latest warning has come from Mother Earth News, published in the February/March 2013 issue. They noted that livestock feeds now contain the contaminated chemicals and are passed through the animal into the manure in this manner. Because of the growing contamination problem, Mother Earth News advises gardeners that “the time has come for the public to stop buying compost or manure products unless they come from suppliers that are able to afford testing and can screen feedstocks for herbicide residues.”

Once again, the buyer needs to be very aware.

Read More: a FAQ sheet from the US Composting Council on contaminated compost:

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