by Mary Sage Napolitan
Every garden tells a story, and each one of those stories begins and ends with soil. After all, it is the home of our fruits and our vegetables, our flowers and our weeds. It’s the delicately balanced fuel of plants and animals alike—the currency that determines the richness of our crops, the triumph of our food and bodies. It’s the living system out of which all things grow, and to which they all eventually return.
And here’s the thing: Almost every vegetative ailment can be traced back to a problem with the soil, an imbalance in its make-up. Thus, in cultivating healthy soils, we cultivate healthy plants. The quality of these tiny flecks of earth determines everything: moisture, water movement, aeration, nutrient uptake, and biotic activity— all things necessary to produce the healthy, productive plants that every gardener, amateur and professional, seeks. Rich soil doesn’t just allow for high yields: it helps to protect plants from pests and disease, acting as an immune system much like our own.
It is the gardener’s responsibility to feed and replenish her soil, so that her soil will continue to feed her in return. Healthy soils require a number of ingredients: components that form an active, living system of microorganisms, mineral particles, organic matter, inorganic nutrients, water, and air. Together, these components create the soil system; this system provides a home for plants. Soil science is a complex study, but there are basic characteristics that can be understood and addressed in order to build the healthiest possible soil for your garden.
Soil structure and texture is defined by the size of its mineral particles. Soil can be sand (.02-2mm in diameter), silt (.002- .02mm), or clay (
<.002mm), or some combination of the three. This texture directly affects other crucial components of soil, including water, air, and soil organisms. Loam is the ideal soil structure, made up of equal parts sand, silt and clay—that’s what you should be aiming for when cultivating your soil. If soil is too clayey, it becomes susceptible to compaction and doesn’t allow for water movement, aeration, and biotic activity, and restricts root penetration. If too sandy, it doesn’t hold enough water, and nutrients will be washed out before the plants are able to uptake them. Loamy soil allows for soil moisture without becoming over-saturated, and enough space and air for soil microorganisms and organic matter breakdown.
Soil pH, the measure of soil acidity or alkalinity, affects the levels of crucial inorganic nutrients in the soil (nitrogen, phosphorous, and potassium, to name a few) and the ability of plants to access them. If soil is too acidic or alkaline, certain nu- trients can rise to levels that become toxic to plants. Even if all the necessary nutrients are present at accept- able levels, if the soil pH is off-balance, the nutrients will not be soluble and will thus be unable to be accessed by the plants.
Most vegetables grow best in slightly acidic soils, with a pH of 6.0- 6.8. (Often, whole regions of soils can be characterized by their pH.) There are certain indicators for pH imbalance, such as what weeds tend to invade the soil. While these indicators are a good way to get a baseline idea of what kind of soil you’re dealing with, the best way to find out is to get a comprehensive soil test.
ORGANIC MATTER ￼
Organic matter is, hands-down, the number one most important aspect of healthy soil. Most soil deficiencies can be corrected with the addition of rich organic matter. Simply, organic matter is carbon-based matter, i.e. any matter present from once-living things, including compost, mulch, manure, leaf litter, and other plant material added to soil. Organic matter improves soil structure, moisture and fertility, and provides plants and other organisms with all of their essential nutrients. Because it is consumed and digested by soil organisms, it must be regularly added to soil to maintain fertility.
Soil organisms are various types of micro- and macro-fauna, from single-cell protozoa to the well-known earthworm. Other soil organisms include algae, bacteria, arthropods, nematodes, and mollusks. These organisms play a crucial role in the formation of soil and soil fertility, and so a diverse population of soil biota must be maintained to keep healthy soil and plants.
The main function of soil organisms is to digest soil organic matter and convert their nutrients into forms accessible to plants. Without these organisms, our plants would not be able to access the nutrients that are in the soil and soil organic matter. When we feed the soil, what we are really doing is feeding the soil organisms in order to cycle nutrients and feed our plants. They also hold nutrients in the “rootzone” of soil so that plants are able to access them, build soil structure, prevent erosion, and often compete with (and deter) other harmful soils bacteria, fungi and insects that could cause disease and pest infestation.
The first step in building your own rich soil is to determine what you’re already working with. The easiest way to determine basic soil structure is a matter of touch. Take the ribbon test: grab a handful of moist soil and roll it between your palms until it forms a ribbon. If the consistency is gritty and crumbles apart, your soil is sandy. If its smooth and stays together shortly before crumbling, it is silt. If it feels sticky and stays together in a ribbon, it is clay. That’s it!
But the quickest, most thorough way to work with the particularities of your soil is to submit a sample to the UMass Extension Soil and Plant Testing Lab, in Amherst, Massachusetts, for analysis. This test will give you information about soil pH, nutrient content, and organic matter levels, and how to address your soil’s particular deficiencies. The pricing varies by complexity of test, but a basic soil analysis is just $15—a steal, if you consider it’ll unlock the door to your rich, new garden.
Both of these tests are great tools for identifying problems with your soil, and knowing where to begin addressing their particular deficiencies. And from there? You’re well on your way to ensuring a bountiful garden all year-round.