Feb. 27, 2012 — Catawba River District Voices

As I’ve mentioned in other blogs, we’ve lived in North Carolina for about 21 years – making us almost native. I love this area and consider myself a “Carolina girl”. The weather is wonderful, the people so friendly … but the one thing that has almost brought me to my knees is the RED CLAY SOIL! Stick your shovel in that, and it’s like picking up a sticky brick. And for those of you reading this blog who have not had the pleasure of laundering your children’s clothes after they’ve played outside in that red clay … it ain’t no picnic. Gardening with such soil can cause some heartache, too. The clay is so dense that it often seems like the only thing it will grow is weeds.
Well here comes my secret weapon … my husband! He’s a soils engineer who specializes in clay liners for landfills and racetracks. Chris also is an unofficial scientist and hands-on farmer. How convenient! I’m going to interview him about conditioning your soil for this week’s blog. It is that time of the year to get your garden ready so hopefully this will inspire you to get out your shovel.

So Chris…why is this Carolina Clay so hard to garden in? 

The clay soils in the Carolinas can have good nutrients, but the high clay content makes it hard to till, plant and condition with organic materials. Clay is a fine-particle material where water particles are bound to the soils, making it hard and blocky. Another problem is that clay soils tend to trap and preserve weed seeds for many years. When older clay soils are tilled, these weed seeds obtain moisture and sprout fresh weed seedlings.

What can a gardener do to get the soil in better shape? 

Three main things: first, adjust the pH higher by adding lime; second, till in more organic matter to provide flow pathways for nutrients and root growth; and third, develop a system to regularly condition the soils with green and/or composted brown manure to increase natural nutrients that feed the plant roots.

What should the pH of my soil be? And how do I achieve that? Most plants thrive in a soil pH from 6.5 to 7.5. The best way to achieve that pH is to break up the clay and add a combination of pelletized lime and gypsum (CaSO4). Then to maintain a healthy pH, add lots of natural organic matter and nutrients with compost or composted manure.

You have mentioned compost, green manure or composted brown or farm-animal manure. What do you mean by these terms?

Green manures are cover crops like clover and greens that are grown with the intention of turning them back into the soil. Green manures tend to suppress weeds and prevent erosion and nutrient runoff in areas that would otherwise be unplanted. Green plants can assist with creating good soil structure and food for the microbes, once they are tilled in and begin to decompose.

Compost is a mixture of decaying organic matter, as from leaves and manure, that is used to improve soil structure and provide nutrients. One of the most important things to remember is that compost created with animal manure typically needs to be turned on a regular basis to increase microbial activity and bring the temperature to 120 to 160 degrees and kill pathogens. Meats and non-vegetable proteins should not be added to compost because of the danger of unhealthy pathogens and microorganisms. Finished compost is crumbly, evenly textured, earthy-smelling and a dark brown or brown/black material that is similar to a commercial potting soil.

Brown or farm animal manure (from cows, chickens, goats, etc.) can be used in compost, but as explained above the compost should be turned on a regular basis to aerate and increase temperatures to allow the decomposition process to be completed before using in a vegetable garden.

Should I get rid of all my Carolina clay?Finished compost that contains brown or animal manure will have that healthy crumbly and earthy smell that is common of processed potting soil. It typically takes one to three months for animal manure to compost adequately in the summer months, and four to six months in the winter months. If you have any doubts about your compost developed from farm animal or plant manure, it is best to consult a soil scientist or composting specialist to make sure it is safe in vegetable gardens.

In my opinion NO! Carolina clay soils also retain water during drought conditions and grow wonderful tasting vegetables – especially tomatoes and squash. If the blocky structure of the clay soils can be broken up and managed with the addition of lime and/or gypsum, organic matter or compost, then even red Carolina clay soils can be excellent for vegetable gardens and small-scale farming. The most important thing, like a sustainable-farming lifestyle, is balance. Of course, a balanced soil conditioning and pH adjustment program takes time and…. That’s Farming.