Nature Safe lists the Carbon to Nitrogen Ratio (C: N ratio) for each Nature Safe product in the Product Brochure. What is the importance of this ratio to a turfgrass manager? For Nature Safe, it correlates to one of the best benefits we provide turf – thatch reduction. To understand the role of the C: N ratio, we first must understand what thatch is, how it forms and how, in a perfect world, thatch is controlled.
Thatch is defined as the layer of living and dead plant material that has accumulated between the green vegetation and the soil surface. Excess thatch can accumulate when the rate of dead organic matter from an actively growing turf exceeds the rate of decomposition. When this accumulation occurs, water, nutrients, fungicides, insecticides and oxygen have problems getting to the soil. This can result in localized dry spot, soil compaction, increased disease pressures from dollar spot, brown patch, and leaf spots, a decrease in root density and a turfgrass plant more prone to environmental stresses due to structural changes. The turfgrass plant’s crown, rhizomes and stolons will grow above the soil to accommodate the increasing thatch region leaving the plant vulnerable to environmental stresses. Thatch control is achieved through decomposition. Ultimately, a turf manager relies on soil microbes to accomplish this process.
In an ideal turf environment, beneficial microbes are abundant within the soil surrounding the roots of turfgrass. According to E.C. Roberts, populations can run over 900 billion organisms for 1 lb. of soil! What is missing though? Thatch! The large populations of microbes keep thatch under control. Decaying plant tissue has varying amounts of cellulose, lignin, and hemicellulose, all high sources of Carbon. Carbon is the primary food for microbes, providing energy for their life processes. As dying plant material is introduced to the soil surface, microbes begin the degradation process using available Nitrogen to break down the Carbon for food and releasing CO2 and NH4 as by-products. Plant materials also contain Phosphorus, Calcium, Potassium, other minerals, sugars, etc. The microbes ingest these nutrients and additional Carbon and Nitrogen through immobilization. This process changes elemental forms of the nutrients to a chelated form. Immobilization makes nutrients unavailable to other organisms until the microbe dies. As the microbes die, they “mineralize” releasing nutrients in this readily available form for future plant use.
In the real “turf manager” world, there are many other factors that influence thatch build up. Temperature, moisture, pH, soil compaction, mowing heights and chemical usage can all influence thatch build up and microbial populations. As a rule, any factor that improves microbial activity will increase the breakdown of thatch. Likewise, any factor that impedes microbial activity will decrease the breakdown of thatch. The C: N ratio of the products becomes significant at this point. This ratio compares the amount of Carbon to the amount of Nitrogen within a material. Carbon is higher in organic products than the Nitrogen. Since microbes need Nitrogen to accomplish this decomposition, Nitrogen within the product becomes a limiting factor. Here is a chart with some typical C: N Ratios and results:
The lower the ratio, the more Nitrogen is available and the quicker decomposition and mineralization. A ratio of 15:1 or higher may not have enough Nitrogen available. This forces the microbes to pull in inorganic Nitrogen from the soil, slowing mineralization down. Any ratio over 30:1 is considered extremely high and can result in some soil Nitrogen deficiencies. The microbes, which tend to be more competitive than the plant, will completely exhaust the Nitrogen resources in the soil. Depending on the C: N ratio, this could go on for a considerable length of time. With no added Nitrogen, grass growth will completely halt. Nitrogen needs to be applied at higher rates just to get the turfgrass to respond.
Nature Safe has a very low C: N ratio. The microbes can easily break down the Nature Safe, releasing some NH4 and CO2 in the process, and mineralizing Carbon, Nitrogen and other nutrients for later plant use. Mineralization is why Nature Safe will not leach nutrients into the surrounding soil or water table. Nature Safe significantly increases microbial populations to keep thatch under control. Check out our research by Dr. Janicke, EKU, on leaching and Dr. Lazarovits, Agriculture/Agri-Food Canada, on our ability to increase microbial populations. For programs for your particular area tailored to thatch problems talk to your Nature Safe Regional Manager.