Does Organic Matter (OM) Matter?

By Royce Hall

Clay soil with little organic matter - by armchairbuilder.com
Clay soil with little organic matter – by armchairbuilder.com

I recently traveled up north with my family, and as we were passing field after bare field in of Illinois farmland, we were surprised by the dark rich color of their soil. It’s striking in contrast with the orangey clay we are used to in Kentucky. This dark material is known as organic matter, and it is something you should encourage in your lawn and landscape soils.

Loosens Soil

One main reason you should be interested in adding organic matter to your soil is because it helps loosen the heavy clay soils we have in Kentucky. OM particles are much larger than clay particles, making it is easier for air, water, and nutrients to penetrate the soil and become accessible to your plants.

More Nutrition

OM also holds nutrients very well. On a soil test you can see a soil’s ability to hold on to nutrients expressed as the Cation Exchange Capacity (CEC); the higher the number, the better the soil’s ability to hold on to nutrients. For example, predominantly sandy soils may have a CEC as low as 3, whereas clayey soils may be between 10 and 25. Soils rich in organic matter, however, may have a CEC between 50 and 100. The result is that nutrients are less likely to leach out of the soil and become pollution, and the nutrients stay available to the plants for longer. Carbon filters are engineered based on this same concept. Carbon particles have a lot of surface area, letting them cling on to a great amount of pollutants.

Not only does OM hold nutrients, but as it decomposes the nutrients naturally occurring in the OM become available to your plants.

Holds Water

OM can hold up to 90% of its weight in water. This means that a soil rich in organic matter has less storm water runoff since the rain penetrates deeper into the soil and be absorbed more readily. This also results in less erosion. After watering events, the additional store of water becomes available to plants, keeping them hydrated longer than they would be more in more sandy or clayey soils.

Sources of OM

Topdressing
Limbwalker adding compost to a lawn

There are many organic products on the market these days, but one of the best sources of organic matter continues to be quality aged compost. There are several local sources of compost, or you can create your own compost bin and compost your yard waste (you should not compost any material that has been treated chemically if you intend to use the compost on food products).

For lawn applications we recommend spreading the compost equally across your lawn at a depth of 1/4-1/2 inch. Any more compost and you may smother your turf.  Limbwalker provides this service using cutting edge technology and equipment after core aeration to incorporate the OM into the soil. We recommend this application for soils with less than 6% OM content. For garden applications, you can easily incorporate a few inches of compost with a tiller.

There are also many fertilizes you can buy that contain OM. Many people in the organic community use feed meals, such as corn gluten meal, for this purpose. There are also fertilizers that combine more traditional nutrient sources with organic materials. The result is a higher nutrient value fertilizer that also builds the soil (often at a lower price than purely organic fertilizers).

If you have any questions about Organic Matter or Limbwalker’s compost topdressing services, please call us at 502-634-0400, or contact Royce at rhall@limbwalkertree.com.