By JOE LAMP’L
True gardeners rarely refer to soil as simply dirt. They understand the difference between the stuff you dig up in your backyard versus the “black gold” that consist of compost, manure, decomposed organic matter and millions of beneficial microbes that are actively at work underground.
Fortunately, converting dirt to soil is an easy process. Within this context, understanding three commonly used gardening terms - texture, structure, and tilth - should help clear up one of the dirtier mysteries of gardening.
Let’s start with soil texture. Texture refers to the relative percentage of sand, silt and clay within the dirt. Ideally, you want to have an equal amount of each. When these three are proportionate, the soil is said to be loamy. Soil with great texture allows plant roots to spread, moisture to be retained (but not to excess) and essential air pockets to exist between the tiny spaces of the soil particles.
Next is soil structure. Simply put, structure is how sand, silt and clay fit together. Good structure is evident when the soil holds together if squeezed, but breaks apart or crumbles easily when disturbed. As I work to achieve ideal soil structure, I am constantly working to blend the right amounts sand, silt and clay to get the results I described above.
In my North Carolina garden, (which was mostly clay) I usually find adding plenty of compost and aged manure do the trick. The compost is home made. However, the cow manure is another story. Since I live in a suburban neighborhood, a pasture of cows or stable of horses is not an option. Fortunately, composted manure is available by the bag at many garden centers and home improvement stores.
But all bagged manure is not the same! Many contain fillers and are inferior in quality. I’ve had great results with Black Kow composted cow manure because it’s pure composted manure. It cost a bit more per bag but, as with most things in life, you get what you pay for. Unfortunately, it is not available outside the southeast.
When soil has good tilth, it drains well. It is loose enough to allow for adequate drainage, yet dense enough to retain moisture long enough for plant roots to utilize it. This is why garden soil should neither contain too much sand or too much clay.
The key is to know from which extreme you are starting. If soil is too dense, then your action is to loosen it up by adding gritty organic material like composted bark. For soils that are too loose, you want to increase the water holding capacity. Sphagnum peat moss is an option for this. However, in either case, organic material continues to break down over time. Monitor your soil constantly, and amend when needed.
Understanding what makes perfect soil will get you well on your way to having the best garden ever. Regardless of your current soil texture, structure or tilth, you can change what you already have. Call it a soil makeover. By adding organic material like compost, humus, composted cow manure, leaf mulch, peat moss, etc. – and a bit of persistence – you can greatly improve your soil.