Feature

By Ron Alexander | R. Alexander Associates, Inc. | www.alexassoc.net | Apex, NC | Ron@alexassoc.net

The climate is changing, and with it our weather patterns. This could be a particular problem for North Carolina. While the end of 2021 found many coastal counties in severe drought conditions, we also saw mud slides in the NC mountains caused by heavy and lengthy rainstorms. While some still debate the reality of climate change, others are working to adjust the way they do business to better mitigate its affects, or at least, better adapt to its affects. Even though land management practices — including landscaping and turf management — are slowly changing, they really need to do so at a much more rapid pace in order to meet the requirements of both clients and the environment (and related regulations). Improving the soil before establishing turf could be part of the solution.

In North Carolina, most of our soils are at the extreme. In the eastern part of the state, we have sandy, droughty soils that are low in organic matter, nutrients and nutrient holding capacity. These soils are prone to wind erosion. In most of the rest of the state, we have fine textured soils high in clay (and silt) content. While these soils can hold water and plant nutrients, they are also easy to compact and poor in water acceptance and percolation (which is why they are also prone to water erosion). Further, when they are dry, they can become extremely hard. Remember, most plants do not thrive in these clay soils, especially when they are compacted, as air and water movement – key to root growth – is restricted. Further, plants expel more energy to move their roots downward through a clay soil profile, as opposed to loamy or sandy soils (which contain larger pore spaces).

Both sandy and fine textured soils can be dramatically improved by amending them with stabilized organic matter, and the most economical and available form of such is commercially manufactured compost. There are various commercial-scale compost manufacturing facilities in North Carolina, operated by both private companies and public entities. Several of these compost manufacturers participate in the US Composting Council’s Seal of Testing Assurance Program (STA Program), which is the national compost testing and certification program for compost, and some are Organic Materials Review Institute (OMRI) Listed, which means that there are allowable for use in certified organic production. A few of the facilities manufacture products that are both STA Program certified and OMRI Listed (such as City of Raleigh (919-625-3175) and Mecklenburg County (704-621-7372)).

In sandy, porous soils, compost helps to fill large (macro) pore spaces. As water infiltrates through the soil profile, it is slowed down and the compost swells, absorbing significant amounts of water. This increases the water holding capacity of the soil, allowing for more extensive turf rooting to occur, enhancing the stability of the soil surface and reducing irrigation requirements. Compost and the humic substances that it possesses also enhance the soil’s ability to hold nutrients (by increasing the cation exchange capacity). And although, intuitively, many would try to add sand to clay-based soils to improve them, smaller amounts of organic matter (especially those in a more fibrous form, like compost) can work much more economically to do so.

Remember, the goal is to improve the structure of clay soils, improving the orientation of soil particles, to create larger pore spacing for improved air and water movement. Plant roots move more easily through soils possessing larger pore spacing. Through the addition of compost, the aggregation of smaller soil particles occurs, creating larger grouped particles. These ‘water stable’ particles can act more like sand particles in the soil, as larger pore spaces are formed around them. Note that while improved pore spacing can occur by physically placing compost particles in between clay particles, the biological activity that comes along with it stabilizes those particles into larger groups. Soil aggregation associated with microbial activity is driven by bacteria, which generate protein-based soil glues as they breakdown younger organic matter, and fungi, whose hyphae bind soil particles together, as they breakdown older organic matter. Clay soil particles tend to pack tightly together, rather than form aggregates. As an example, notice how all 7 composts in research completed by Penn State University’s (PSU) Department of Agronomy illustrates that by increasing the organic matter content using compost, you can reduce the bulk density and increase the water infiltration rate of finer soils (clay-loam). These soil characteristics demonstrate improved pore spacing in the soil, while turf cover was also enhanced over the control, topsoil and peat enhanced plots. Although water holding capacity (WHC) was not monitored as part of the PSU research, other research has illustrated that when amending these denser soils with compost, WHC is also improved along with infiltration rates. It’s all about the creation of larger pore spaces. We can improve NC clay soils to better hold water, when the droughts are upon us, and accept and infiltrate water, when the storms come.

Smart and more thorough land management practices can be utilized which will not only allow us to establish and grow better turfgrass in North Carolina, in extremer conditions, but also allow soils to better function in a climate with more extreme weather events.

Turf managers and landscapers can help their clients establish and maintain higher quality turf, while better managing conditions of drought and heavy storms. The turf established on these enhanced soils should require less irrigation and fertilizer applications and should better resist erosion and nutrient migration. However, these improvements cannot be achieved with half measures. The practice of establishing turf in soil treated with some lime, fertilizer and a few bags of ‘soil amender’ (pine fines) needs to be replaced with a more comprehensive and long-term approach.

Research and field experience over the past 4–5 decades has shown that the application of 1 to 2 inches of compost, incorporated into 4 to 8 inches (20 to 30% inclusion rate) of North Carolina soil can transform the soil structure, allowing for longterm turf success. These same soils will assist the industry in growing better turf stands, which can remove more carbon-dioxide from the atmosphere.

Site managers can better preserve the organic matter in their enhanced soils by properly fertilizing and watering them, preserving a dense turf cover, and by core aerating and topdressing with compost from time to time. If the industry can move toward bringing the organic matter content of its soils to 4 or 5 %, before establishing turf (and a landscape), site management will be improved for decades to come. Let’s help the soil work for us and our clients.

Mr. Alexander is a horticulturalist who has been involved in compost specification end use for over 35 years. As a consultant, he has authored various end use tools (such as “The Field Guide to Compost Use" and "Landscape Architecture Specifications for the Utilization of Compost”) and has developed compost specifications for a variety of applications, including turf. Mr. Alexander also managed the national compost testing program, the US Composting Council’s Seal of Testing Assurance Program, for 10 years.