No matter where in the country you live, the soil conditions are rarely perfect. Soil quality is something we have to work for. Enter: soil amendments.
Technically, soil amendments are materials you add to the soil to improve its physical or chemical properties. Some amendments are designed to improve water uptake and or retention; others improve fertility by altering soil pH. Some address issues with texture which, when improved, can encourage root growth.
Depending on which state you are in, there are labeling restrictions regarding what materials can specifically be marked as soil amendments. (Compost may not be labeled as such, though it is widely used to amend soils.)
What’s important to know is there are options out there for amending soil, from certified compost to biosolids to mycorrhizae fungi.
“This is a growth area in lawn and landscape management, and whether you are using these materials as the focus of your business or to supplement a traditional lawn program, soil amendments used properly are a great way to improve soils,” says Mike Goatley, professor and extension turfgrass specialist at Virginia Tech.
Soil amendments are good for plants and turf, and good for your clients. “If your plants go in and thrive and look great – if (customers) see the lawn and it comes in and looks great and you maintain it with little extra inputs – that will shine back on you for your expertise,” says John Raffiani, owner of Fair Lawn, New Jersey-based Raffiani’s Automatic Sprinkler Service.
He recently delivered a webinar focused on soil amendments for the New Jersey Landscape Contractors Association’s “Branching Out – the Webinar Series.” Soil amendments are also an add-on service opportunity, Raffiani says.
That is, when appropriate materials are properly applied. “Everyone would do it if it were easier to apply,” Goatley says, speaking specifically of compost.
Soil amendments are not about instant gratification. However, over time, results from using organic materials can surpass synthetic outcomes. That’s what Virginia Tech researchers are finding in a soil trial currently in progress. One plot is receiving traditional fertilizer while another is getting applications of composted biosolids.
“In year one, the clear winner in terms of color and turf growth was the synthetic product,” Goatley says. “But now in years two and three, it’s the hare vs. the tortoise and the soil amendments are now winning the battle quite considerably because the composted biosolids are absorbing.”
So, what do you need to know about your soil to select the right amendments? And what results can you expect?
Some soil science is necessary to understand how amendment products work so you can make the best choices. If you could see a deep cross-section of soil, you’d notice the strata, Raffiani says in his webinar. “This is rock or soil layers that are easily distinguished from other layers.”
The horizon is a shallow version of strata. “If you take a shovel full of soil, from a side view, you’ll see the various horizons,” Raffiani says.
Soil pH is critical to know before selecting any soil amendment. “Soil pH affects everything in growing, including micronutrients, root development and whether or not a particular plant is happy with the soil,” Raffiani says.
Soil is composed of three parts: air, water and minerals. Within those minerals is organic matter, and that’s the smallest component of any soil. Within that is humus – well decomposed, stable organic matter – assorted organisms and roots.
Soils are prone to be heavy in clay, sand or silt depending on where you live. The ideal soil is a loam texture. “Loam is where it’s at in terms of growing,” Raffiani says. Any other extreme (clay, sand, silt) will give roots a tough time.
Before you can choose a soil amendment, you must find out what type of soil exists on a property. Raffiani recommends collecting 10 soil samples from a 100 to 150 square foot area, mixing them, and sending the sample to a university extension for analysis.
As for pH, an inexpensive pH meter can be inserted into the soil and will indicate soil pH in any given area. The pH of the water you use on plants and turf also affects overall soil pH, Raffiani says.
For example, in New Jersey, irrigation systems that use rainfall water collected in a reservoir provide acidic water. “Your plants will love it,” he says, adding that the sweet spot for growing is 5.9 to 6.9 pH. (The pH scale is 0 to 14, with 7 being neutral and 14 being highly alkaline.)
Spring water and surface water sources tend to be more alkaline. So, if you’re watering plants and turf from these sources, you’re adding alkalinity to the soil. While adjusting soil pH is not technically amending, it’s necessary to improve soil quality, Raffiani says.
Limestone or dolomite will slowly increase the pH of soil where turf grows. Sulfates like ammonium and aluminum sulfate will rapidly decrease pH. Sulfur and iron sulfate will slowly decrease soil pH. Once you understand your soil pH and texture, you can begin addressing weaknesses in clients’ soil.
Soil amendment roundup.
There are several basic types of organic materials used as soil amendments for the lawn and landscape. Those are:
- Humus: Stabilized organic matter. “Use too much and it will cause problems for root and water uptake,” Raffiani says.
- Humates: Prehistoric, naturally occurring humified organic plant matter that is rich in humic and fulvic acids. “This is the single most productive input for sustainable plant health and growth,” Raffiani says, noting that humates promote beneficial fungi growth and buffer the effects of sodium. They also aid in moisture and nutrient retention, improving soil structure.
- Compost: Compost made from plant material. You can buy organic pelletized dry compost derived from leaf and yard trimmings. “It is free of manure and food wastes, and easy to apply with a rotary spreader.” (Raffiani is speaking of a brand called Easy Flo that dissolves quickly into the soil.) Many use traditional certified compost as a topdressing. Remember, topdressing takes time to seep down into the soil layers. Initially, it creates an additional, healthy “horizon.”
- Composted manure: Stabilized manures are easy to spread, do not smell and are nothing like what comes from the farm.
- Biosolids: Human waste digested by microbes and kiln dried.
- Moisture managers: If amending with water conservation in mind, there are products available that aggregate free water in the soil and make it more readily available for plants. “Only half of the water in soil is actually available to plants,” Raffiani says. “The other half adheres to soil particles.” Water absorbent polymersare best used in landscape beds, Goatley says.
- Biostimulants: This refers to any substance or microorganism that enhances nutrient efficiency and reduces plant stress. “These allow plants to reach their full potential by absorbing more soil nutrients,” Raffiani says. Biostimulants can limit the need for traditional fertilizers and reduce nutrient run-off. These are best applied before plant stress.
- Mycorrhizae fungus: Raffiani calls this “the good fungus,” noting that most land-based plant species use mycorrhizae. The fungi gather nutrients and deliver them to the plant. Mycorrhizae attach to roots and allow nutrients to feed directly into them.
- Sand: Sand has no nutritional value for soil, and most research shows your soil content has to be 60 to 75 percent volume before achieving marked drainage improvement, Goatley says. A common mistake is to use sand as topdressing, or to incorporate only small amounts into the soil.
“Think about the formula to make bricks: a lot of clay and a little bit of sand,” he says.
“If you go out and start adding sand to soils without adding a proper amount, you will see filtration rates that decline rather than improve.”
Add soil amendments.
There is no single cure-all soil amendment that works for every soil type. That is why the steps of taking soil samples and testing pH are critical for selecting the best product. But generally speaking, certified compost is a helpful addition as topdressing for most lawns.
A quarter-inch of certified compost applied twice annually during the growing season will improve soil health and plant vitality, Goatley says, pointing to the Virginia Tech research. More is not better with application. “And, if you can coordinate compost application with core aeration, it works even better,” he says.
Use materials that are fully composted, Goatley says. Look for compost certified by the U.S. Composting Council.
In general, if you are considering starting a soil management program or even including soil amendments as part of a specialized lawn care program, you’ll want to come up with some systems for marketing and selling the service. Raffiani suggests creating a form to use so you can chart areas of a property you’ll improve.
“Show your clients the benefits in definitive terms,” he says. Explain the advantages of soil amending, such as:
- Improving turf/plant health
- Correcting drainage issues
- Saving water
- Reducing fertilizer use
Goatley says he expects to see more use of soil amendments in lawn care programs as clients are increasingly interested in organic solutions. “Used properly, they’re a great way to improve soils,” he says.