Spring is the time of year when the region’s Riverkeepers are particularly concerned about water quality and stream health. With the onset of strong seasonal rains comes the risk of sewer overflows from combined sewer systems throughout the Kansas City Metro area, and the result is increased pollution of our creeks, streams and rivers.
The growing popularity of urban agriculture presents an opportunity to reduce the amount of water and pollutants entering our combined sewer systems. Urban farmers and our community as a whole have much to gain from implementing a few simple techniques to reduce runoff and pollution of our urban watershed. Our productive urban landscapes (i.e., farms and gardens) have the potential to be more environmentally friendly than the many chemically treated lawns and unproductive green spaces we currently see throughout our city. Converting a lawn to an organically managed agricultural landscape can promote a healthy environment and capture ecosystem services (such as food production) which were previously underutilized. But to realize these benefits, it is important that we keep several key design principles in mind as we build our urban farms and gardens.
1. Soil Management
From the perspective of storm water management, an important benefit of creating productive urban landscapes is that farmers tend to reduce soil compaction in the process. Storm water runoff is aggravated by the many impervious and compacted pervious surfaces in our cities.
Urban farmers generally work hard to reverse soil compaction and create spongy, loose soils for their crops to thrive. High organic matter content is particularly beneficial to plant health and also increases the soil’s nutrient and water holding capacity. But once we have created healthy soils, we have to prevent them from being eroded or compacted again.
On small urban operations, farm-scale mulching is both feasible and very useful. Under the protective cover of mulch soil is less subject to erosion and compaction by heavy spring rains. However, mulch can slow down spring soil warming and farmers may decide to delay applying mulch until after the soil has warmed up sufficiently.
Special attention is often warranted when farming on slopes; building terraces, contour farming and alternating permanently planted green strips with growing beds are techniques that have been widely used to control erosion on large-scale farms and may be appropriate for small urban farms as well. Also, all farmers should consider ways to minimize tillage as it tends to degrade the soil and create a new layer of soil compaction a few inches down.
2. Nutrient Management
The loss of nutrients from farms and other sources is responsible for such ecological disasters as the Dead Zones in the Gulf of Mexico and elsewhere. Nitrates and other chemicals run off cropland and animal feeding operations and accumulate in our streams which carry them to the ocean. There they cause spikes of algae growth which lead to oxygen depletion and massive fish kill. Urban farmers should avoid contributing to this problem and apply fertilizers in modest amounts, especially synthetic fertilizers which are highly soluble and easily carried away with runoff. Instead, they may wish to consider organic fertilizers such as compost, well-rotted manures, alfalfa pellets, rock phosphate and similar products. These will stay in your soils longer and release their nutrients more slowly.
Regular soil nutrient testing may be a valuable tool to determine the amount of fertilizer needed and to monitor soil health over a period of years. Using soil test results as well as historical yield data and taking into account any nitrogen fixed by legumes, urban farmers can determine appropriate fertilization levels and avoid over-fertilizing their gardens and fields.
3. Pest and Weed Management
According to information published by Friends of the Kaw, the chemical atrazine is one of the most commonly used herbicides in the US. It is regularly applied to corn as well as lawns, parks and golf courses. The chemical has found its way into our drinking water supply causing some to be concerned about adverse health effects.
Urban agriculture provides an opportunity to take land stewardship seriously in our backyards, vacant lots and other urban green spaces by reducing or eliminating the use of synthetic pesticides and herbicides. Fortunately, it is our experience that the majority of urban farmers uses sustainable or organic practices. For those who feel they must apply synthetic chemicals to their urban fields we suggest following all application instructions on the product label and creating vegetative buffer zones to filter contaminated runoff and reduce chemical drift.
4. Irrigation Practices
Finally, we can serve our streams and rivers by adopting water conservation practices. These include harvesting water wherever possible from nearby roofs or trapping it in infiltration swales on sloped terrain. Both measures will reduce the amount of water that runs off the site — therefore lowering the burden on the combined sewer system and possibly reducing overflow events — and also lower the farm’s irrigation bill. However, in a few cases water running across an urban farm may have been contaminated by sources upstream. Such water may not be suited for irrigating food crops and may best be diverted from them.
The benefits of mulch have already been mentioned but bear repeating here. A layer of mulch will trap rainwater and reduce runoff in addition to reducing the need for irrigation during the hot months of the year. And finally, drip irrigation is a practice which gives the farmer more control over how water flows across an urban farm. The lines slowly deliver the water directly to the crops’ root zone, usually without puddles and unwanted runoff; and the lines can be placed under a layer of mulch where evaporation levels are low.
The above techniques are just a few of the steps urban farmers can take to protect the health and quality of our urban watershed and of the streams and rivers connected to it. As we become more productive and ambitious as urban farmers, it will be helpful to spend some time on reviewing our water management strategies and to control the movement of soil, nutrients, potentially harmful chemicals and, of course, precious water from our urban farms. In doing so we will become more connected to the land we farm and better stewards of the natural resources around us. That—in addition to our fresh vegetables—is definitely something worth sharing with our neighbors.
Daniel Dermitzel is the Associate Director and farmer with Kansas City Center for Urban Agriculture (KCCUA). He has years of experience in organic and city farming, and maintains a special interest in permaculture.
In 2010 the local nonprofit Friends of the Kaw included the Kansas City Center for Urban Agriculture in a grant to raise awareness of water quality issues relative to the Kansas River. In this article we hope to contribute to that effort. Our appreciation goes to Laura Calwell, Kansas Riverkeeper for Friends of the Kaw, for her support of KCCUA.
Thanks to the authors of "The River Friendly Farm — Profitability, Stewardship, Qualify of Life" (published by K-State Extension) whose paper was a valuable resource in compiling this article.