The Importance of Organic Matter in Lawns
Fred Newcombe

Organic Matter is necessary to fuel resilient turf, especially during Spring’s moisture and fluctuating temperatures. The importance of Organic Matter (OM) is evident. OM is a critical component in soil structure and a food source for the microbes. According to the USDA NRCS, “One percent of organic matter in the top six inches of soil would hold approximately 27,000 gallons of water per acre”. 

graphic of soil layers showing the importance of organic matter on the top layer
Image Source: Turf Dietitian
Benefits of Organic Matter
  1. increase microbial diversity and activity
  2. help soil’s water holding capacity
  3. improve soil’s nutrient retention 
Box Comparison 

from The Art of Balancing Soil Nutrients by William McKibben… 

For example, imagine two boxes of completely air-dried soil, each weighing 100 pounds. The first box contains a soil that is 2% organic matter and the second box contains a soil that is 4.5% organic matter. How much water could we pour in each of the boxes before the water would run out?

Approximately 45 pounds of water could be added to the 2% organic matter soil box. On the other hand, almost 150 pounds of water could be added to the 4.5% organic matter soil box. A small increase in organic matter can have a huge increase in water-holding  and nutrient-holding capacity. Therefore, the relationship of the water-holding-capacity to organic matter content is not linear but logarithmic.

Contributing to OM levels

Notably, OM is continually being depleted through the normal decomposition process. Therefore, OM needs to be continually added or it will start decreasing. 

Levels of organic matter can be raised through:

Mowing Practices to Improve Organic Matter

Grass clippings add OM to the soil and serve as a natural fertilizer equal to one application per season. Healthy soil biology breaks down the grass clippings. In addition, mowing high aids in the production of organic matter. Because, mowing high encourages deeper rooting of the grass plant. Then, as the roots mature, their ability to absorb water and nutrients diminishes. Eventually, the root dies and sloughs off, adding organic matter to the soil.

In conclusion, remember the importance of Organic Matter. Healthy soil is a long-term, sustainable need for our earth. Therefore, if you’re a landscaper, school, or municipality interested in organic turf care…reach out! PJC Organic offers product and cultural practice recommendations that improve OM and overall turf health (without the use of harmful chemicals).