Compost & The Contractor

Compost is the only annually renewable, recycled, 100 percent natural organic product that gives so much value to the soil. And peat moss, barks, manures and other organic sources work in combination with compost in mixtures that help contractors adjust soil pH and fertility.

But how can the landscape contractor spot quality compost? For starters, look at the projects where it was used successfully last year. Quality compost is most easily separated from average compost in the performance of plants where it is used. However, without the time and ability to remember all of the places compost is used, the following few points may make it easier for comparing products.

OPTIONS ABOUND. Unfortunately, there isn’t enough research about all of the types of soils, composts, climates, application rates and plants to be able to guide contractors as to what kind of compost to buy.

Fortunately, though, the answer is quite simple. All composts help almost any plant grow better if they are used correctly. As a general guide, composts with higher fertility work well when used with plants which are heavy feeders. Likewise, plants that are sensitive to over-fertilization or high soluble salt levels are a better fit for composts of a lower fertility level. As a general rule, most perennials, especially grasses, respond well to compost. Although trees and shrubs do not double in size like many annuals and perennials do when planted in compost amended soils, these plants often stay alive longer and perform better when compost is used. If you are still unsure of where to turn for answers, contact your local extension office or testing laboratory and they should be able to answer your questions.

THE SHOPPING LIST. At the same time, there are some critical items to consider when going shopping for compost. Be sure that the source of the material to be used is consistent. Nothing is worse than getting halfway through a project and finding out that you cannot get any more of a particular product. When you arrange to get your compost, make sure to ask some questions of the provider:

1. Does the vendor provide directions for proper use of the product in the application you have chosen?

2. Is a steady, consistent supply available at all times?

3. Is the source of the compost the same...ie., if you buy from a garden center, does it buy from only one compost facility or many?

4. Has the product been tested? If so, are the test results available?

5. Has the compost been used in any local projects such as demonstration plots, university research programs or award winning landscapes?

6. Does the vendor have the ability to custom mix the product to your needs?

7. Does the product have favorable price and packaging?

Notice that these issues are arguably in descending order of importance, with price being the last consideration. Without quality, what good is a low price? Quality is an important part of making, selling and using compost. Using a compost product that is not yet ready may not fulfill your growing goals.

IT’S TIME TO CHOOSE. The growing popularity of compost use among landscape contractors means a lot of professionals may be working with these products for the first time. Selecting quality compost material to work with is obviously a key to the project’s success, and some tips to selecting the best material follow:

1. Pick up the product and run it through your hands. Does it smell earthy like soil or sour like vinegar? If it smells earthy, it is probably stable and ready for use. If it smells like vinegar, it needs to compost more.

2. Look at the material’s color. Most composts that are ready to be used are very dark brown to black in color. There are some exceptions. Chicken manure compost, for example, is normally a little lighter in color. But most products are consistently dark without great variation of color through the compost pile.

3. Fertilizer analysis should be “around” a 1-1-1 N-P-K value, but this does not mean that a compost having a 1-.5-.5, N-P-K value is useless. Remember, the main value of using compost is for the organic matter added to the soil. Biosolid-based composts, chicken manures and some other manure composts, often have N-P-K ranges from 1-1-1 to 3-3-3 or slightly higher. Most composts never get above a 5 percent N level, so depending on the application rate, additional fertilizer may be needed. However, if 1 inch of 1-1-1 N-P-K compost is used in annual or perennial flower beds, tree planting, turf or ornamental beds, it will normally supply enough nutrients for the first growing season.

Many landscape contractors choose to fertilize in addition to using compost to ensure that the plants are getting plenty of nutrients. An analysis of the compost’s value as a fertilizer can save these fertilizer dollars.

4. Check to see if tests for soluble salts have been conducted. This is an important test for contractors to be aware of as it relates to the type of plants that are grown in the compost amended soil. For instance, several tender annuals are very salt sensitive and struggle during transplanting. This is sometimes referred to as “transplanting shock,” but can often be a slight burn from the salts.

Make sure the soluble salts in the compost are below the safe level for the plants used in the project and proper irrigation is provided after transplanting. Salt tolerance levels of various plants are often available at many labs that do the testing. If they do not have what you are looking for, contact your local extension office, but a good rule of thumb is that most plants do well if salts levels are below 5mmhos/cm.

5. The original ingredients of the compost should be unrecognizable. If the compost is made from leaves, you should not be able to see any leaf parts in the finished compost. Likewise, if the compost is made from twigs and branches, none should be visible in a product for sale.

Keep in mind there are uses for “mulchy” composts. Some contractors actually use a one-half or three-quarters composted mix in mulches that they feel help offer a wider spectrum of food for the soil over time. If you use compost like this as a mulch, still limit applications to the normal 2 inches per year to be effective.