Soils: Nourishing Gardens from the Ground Up

August 31, 2017

Soils are the backbone of the landscape, nurturing gardens from the ground up. As we transition from warm late summer months into the harvest of fall, now is the time to evaluate your garden’s soil conditions and plan for next year. The health of your gardens is determined by the health of your soils. Understanding soil dynamics and the soil type in your backyard will ensure the highest yield for your vegetable gardens and a flourishing, flowering landscape come springtime.

Soils are the hub of life on our planet, the depot through which nature transports and transforms nutrients, air, water and carbon through to their destinations. The nutrient cycle is the movement of organic and inorganic matter into the production of living matter. Decomposition, another essential life cycle, transforms the living material above soils back into the raw inorganic materials that become the nutrients for the next generation of plants.

These systems are another example of ecosystem services: the valuable processes conducted by nature that benefit people and wildlife. These benefits can be direct or indirect, small or large. When we construct our built environment to include green infrastructure, we support systems that make our communities more inhabitable.

The rate of decomposition and nutrient cycles are determined by other conditions like soil type, weather, soil structure and soil pH. Soil types vary by the concentration of sand, silt, and clay present in the soil substrate. The major mineral particles are responsible for rate at which nutrient cycles and other cycles, such as gas exchange and water movement, can occur. Sandy soils have larger particles and therefore greater spaces between them. Water flows easily through these soils; however, nutrients are not held as easily as when silt and clay are present to hold water and nutrients. Loamy soils are ideal for many plants as they offer good aeration, balanced water retention to draining and nutrient retention.

Balancing the pH of your garden soil is an essential part of ensuring the vitality of your garden. Soil pH influences the availability of nutrients for plants to absorb in the root systems. Depending on the acidity or alkalinity of the soil, some nutrients may be more easily dissolved in the soil solution than others; therefore, selecting the proper plants for your soil’s pH will influence the garden yield.

Another way soil pH plays a major role in nutrition and well being of plants is on the growth and productivity of microorganisms. Just like in the human biome, bacteria are necessary to help break down organic matter and increase nutrient availability. On the extreme ends of the pH spectrum, within either highly acidic or highly alkaline soils, bacterial growth can be hindered, resulting in either too much or too little nutrients available for plant uptake. For these reasons, it’s important to test your soil pH to learn what types of soil amendments are needed in your garden ecosystem to maintain optimal nutrient availability and bacterial growth.

Soils on the Southern Highlands Reserve are typical of high elevation mountaintops in Western North Carolina — a low pH or highly acidic. In order to correct this issue, our gardeners add pelletized lime which dissolves quickly, neutralizing soil immediately. Regular testing is required to ensure pH levels are maintained. Due to the geology beneath the soil substrate, different rock formations cause the acidity to rise in the soil throughout the year, requiring neutralizing pelletized lime to be added on a yearly basis. Contact your local county Cooperative Extension Office for soil ph testing kits and guidance on the best ways to test.

Late summer and early fall are the ideal times to ensure garden soils are prepared and ready for the spring. Add soil amendments in the fall and incorporate them back into the soil to ensure proper aeration and nutrient cycling. Be sure to cover tilled earth with mulch and compost so as to not leave it exposed to weather conditions; harsh conditions can compact soil, reducing aeration and slowing the nutrient cycle. You may also plant a cover crop where applicable to add nutrients to the next year’s cycle and keep weeds out. Plants in the brassica family can be left in the ground over winter to help deter soil pests. With careful planning and preparation, your garden will be ready to wake up healthy in the springtime and nourish a bountiful growing season.