by: Megan Belongia, Conservation Education Program Coordinator, City Sprouts
We were delighted to see many of you in March for the “Healthy Soils: Foundation of Regenerative Agriculture” talk with Dr. Carolina Córdova! Dr. Córdova is a Statewide Soil Health Specialist with the Nebraska Extension and Assistant Professor in the Department of Agronomy and Horticulture at UNL, and we were fortunate to have her join us to share this presentation with our urban growing community. During her talk, Dr. Córdova shared useful insights for urban growers interested in understanding and improving their soil health.
Dr. Córdova opened her talk by exploring the benefits of healthy soils. She underscored four main functions of soil health: soil fertility, environmental and climate regulation, social benefits, and economic benefits. She called particular attention to the social benefits of soil health, which include ensuring food security, increasing the nutritional value of food, and supporting community physical and mental health. These benefits often go unrecognized, but they are particularly consequential for urban farmers and gardeners.
For urban growers, Dr. Córdova emphasized the importance of getting to know the history and health status of your soil before you start growing. If you are new to your home or growing area, she recommends talking to your neighbors, searching property records, or visiting the library for additional resources to learn about the history of your growing space. It is important to know what previous activities and structures were present at and around your growing site, which may hint to possible contamination or soil health concerns.
Homeowners located in Eastern Omaha should be particularly alert to the potential for soil lead contamination. Historic lead refining and smelting activities as well as the use of lead paint and leaded gasoline all contributed to this region of the city’s eventual designation as the largest residential superfund site in the US. While remediation efforts have been underway since the 1990s, contamination remains unaddressed on thousands of outstanding properties. Property owners can check whether their parcel(s) have qualified for and received past remediation treatment by visiting the Omaha Lead Registry.
It is important to note, however, that lead is not the only contaminant of concern. Other heavy metals (e.g arsenic), solvents, toxic debris (e.g. asbestos), pesticides, and other pollutants may be present in urban soils. Some soil contaminants (e.g. copper) do not present a health risk to humans at the concentrations typically found in polluted soils but can be toxic to plants. If you are familiar with the history of your growing space, you may suspect which contaminants are present. However, a soil test is needed to confirm whether your soil is indeed impacted. During her talk, Dr. Córdova encouraged new growers to test their soil if they suspect contamination.
She also encouraged new growers to test their soil fertility and health before they start growing. This data can help growers identify soil performance concerns (e.g., low soil organic matter, nutrient depletion) and inform management decisions off the bat. The practice also helps growers establish a baseline against which to compare future results to observe soil health and quality changes over time. A simple soil fertility test is typically the cheapest option, but more complex analysis packages are available that assess soil health with additional indicators (e.g., CO2 respiration, water-extractable carbon, water-extractable nitrogen). There are several local options available if you are interested in submitting a sample for analysis, including Midwest Labs (Omaha), AgSource Laboratories (Lincoln), and Ward Laboratories (Kearney).
The fact is, many urban soils suffer poor soil health. These soils, known as technosols for the considerable alterations made by human activity, are often a product of their land use history. Urban growers commonly encounter demolition debris, soil compaction from previous structures or traffic, mixed/inverted soil (e.g. subsoil placed over topsoil following construction), and other challenges. Subsurface debris alone presents several concerns. The abundance of solid material in the soil impedes root growth and reduces the pore space available for water and air. Additionally, the presence of carbonate-rich building debris (e.g. concrete) increases alkalinity (high pH) in urban soils, which can inhibit the growth of many plants. For those seeking to grow within the footprint of a former building, compaction will almost certainly be a concern. Given the unique challenges of growing in an urban environment, it is important to take advantage of conservation practices to help improve soil health.
You can continue your soil health journey and learn more about conservation practices by attending upcoming UNL soil health events or registering for a workshop at City Sprouts!