Agronomists study management of soil which I call dirt. There are many kinds of soil, and an eight-year old future agronomist might observe sand on a beach is not the same as dirt, yet some soil is sandy.
Gene Logdsdon, author of several books on farming and related issues, recalled in The Gardener’s Guide to Better Soil how one morning his plowing at one end of a field was very difficult compared to the other end because he was developing an area in which erosion had removed the topsoil leaving hardpacked subsoil on the surface. Rain would pool up or run off, and not much would grow there.
He said loam, a well-balanced mixture of sand and clay plus humus, is the dirt gardeners are looking for. Soil scientist George Scarseth opined that if humans took care of the top seven inches of the earth’s crust, everything else would take care of it itself. So, how to make good dirt. Sounds important.
Somebody counted and the arithmetic says an ounce of dirt contains billions of organisms belonging to thousands of species. Many of these living beings have not been identified or studied, and as recently as 2015 researchers discovered in soil bacteria a new antibiotic.
A typical soil sample is about half minerals with some organic matter, but the other half is air and water. During rainy spells, the sample would have less air and more water, but the solids remain about the same.
Poor soil management or long-term neglect might result in topsoil being washed away into nearby streams thereby disrupting the ecosystems of both the fields and streams. Left behind would be the barren soil Logsdon tried to plow.
On a trip from New Jersey to Chicago, Logsdon identified more than a dozen distinct types of soil along the way from barren pine soil and red soil to loam to clay and muck. Sand, clay and silt in whatever proportions make up the texture of a soil.
I once created a garden in adobe soil which was so clayey it stuck to the shovel, whatever tool I used to remove the adobe from the shovel plus my boots, hands, pants and attitude. Nevertheless, it was full of nutrients, so I moderated the texture with organic matter such as compost and sand to grow vegetables. It still stuck to my boots.
Gardeners can improve all kinds of dirt by mixing in organic matter, by which I mean compost, leaf mulch, straw, grass clippings, rice hulls and more, plus aged manure from cows, horses, chickens and rabbits. It is a gardener’s delight to stick a trowel into a bed treated two months previously with horse manure.
Chemistry also matters. The soil in my garden area is naturally acidic. Without even testing, I know this because huckleberries flourish here. Microorganisms prefer a more neutral soil, and so do beets, onions and lettuce, so I moderate the pH by adding wood ashes to beds twice a year. I also add other organic amendments such as dolomite and greensand for calcium and potassium.
Also, adding leaves, grass clippings or straw on top of a garden bed initiates a healthy soil economy whereby bugs, worms and bacteria move in and proliferate, and their daily activities release minerals from the soil components. The dirt comes to life.
In spring, when henbit and chickweed sprout, I wait until the perfect time to harvest them and neatly pile the young upstarts in a corner of the bed they sprang from. Soon enough, underneath them communities develop, and henbit, chickweed and I will have done our duty for the dirt… for the moment.
However, soil maintenance never ends. Take care of the soil and the soil will take care of the plants.