Indianapolis ranks last in food access of major metropolitan areas in the US. This lack of food security could be partially addressed by small urban farms. In addition to providing fresh produce in urban areas with limited food access, these farms could also restore other ecosystem services (e.g. water filtration, C sequestration, recreation and cultural activities) on abandoned urban plots that have suffered substantial soil degradation. However, in order to facilitate these potential benefits, urban farms must have good soil health to support these other ecosystem services. Our main goal was to examine several small urban farms in Indianapolis and evaluate if soil management practices applied there altered several metrics of soil health, and if those alterations lead to soils that more closely resembled natural ecosystems.
We examined several farms in Indianapolis that shared similar land-use histories (degraded or abandoned lots prior to several years of agriculture). We sampled soils from 0-7.5 and 7.5-15cm under active cultivation and adjacent soils that remained degraded lots; we also sampled a restored prairie and mixed deciduous forest as natural habitats for comparison. Soils were analyzed for total Organic matter, total carbon and nitrogen, C:N, pH, bulk density, and standing nitrate pools.
Results/Conclusions
We found across all metrics, the farming practices in these small farms improved soil health to a point equal to, if not exceeding natural soils from surrounding areas. Total soil OM and C in growing areas of the farms was as high as the mixed forest and significantly higher than degraded background and prairie soils. Total nitrogen was also significantly higher in farm soils compared to background and prairie soils. Farm soil pH was near neutral (not different than forest), while the degraded background and prairie were significantly more acidic (more than 1 pH unit lower). Soil C:N was significantly higher in farm soils compared to all other soils. And there were minor differences in soil bulk density.
Our results suggest that urban farms can improve soil health, which bodes well for their long-term sustainability as food producers and potential sources of restored ecosystem services. Given that the farms we studied used predominately organic practices (though not officially certified organic), this suggests that these practices could be an effective strategy to both increase food production without losing other important ecosystem services. Continued monitoring of soil health could also lead to reduced cost for farmers increasing production in the future.