Remediating Urban Soils for Food Production

Urban agriculture faces challenges with soil health, including relatively high heavy metal and soil toxicity concentrations. One contaminant, lead, can enter the soil from multiple sources and will remain long after the sources, such as leaded gasoline and paint, have stopped being used (McClintock, 2012). Addressing these issues often involves digging up contaminated soils, “capping” the ground with a layer of impermeable clay, and trucking in clean soil from outside the area. These are expensive and burdensome techniques that aren’t viable options for every community.

In support of human health, Greenleaf Communities convenes teams of experts to address soil health issues and conducts research that identifies ways to improve soil and plant health in urban agriculture. We develop tools that can reclaim contaminated soils and put them to productive use, supporting the health and nutrition of urban communities. Our work with gypsum soil amendments has already demonstrated water management and pollution control benefits. Greenleaf’s new research will demonstrate cost-effective techniques to improve nutritional value and reduce contamination of fruits and vegetables grown in urban soils.

Background:

Proper nutrition is an integral component of human health. Food deserts, contaminated soils, and malnourishment are all issues that impact quality nutrition. These issues can negatively affect human health and create problems such as cancer, obesity, and cardiovascular disease among many others.

In the United States, 23.5 million people live in low-income areas that are over 1 mile from a large grocery store and considered to be food deserts. The USDA identifies food deserts as areas with low incomes and low food access. Food deserts also tend to suffer from lack of other infrastructure such as banks and have limited health service access, which could lead to worsened health (ERS, USDA, 2013). Lower income areas are more likely to have a greater number of fast food restaurants and residents of these areas are less likely to eat healthier foods due to lack of access to grocery stores (Lydon et al, 2011). Food deserts were found to have a lower median income and higher unemployment than other non-food desert areas (McClintock, 2012).

In part due to lack of proper nutrition, the number of children that are obese or overweight has been increasing over the past 30 years and the trend is likely to continue. One study that compared food consumption habits to USDA recommendations found that only 36% of children met daily vegetable requirements and that fat intake was 35% of the total calories consumed daily (Munoz et al, 1997). Children in poverty were less likely to meet the daily requirements than children not in poverty and 17% of children in low-income areas are obese (Kranz et al, 2009). Obesity and its symptoms increase healthcare costs. To help mitigate the effects of obesity, we need to improve healthy eating. Knowledge itself is not sufficient; food options in schools and communities need to improve. Environmental, behavioral and psychological factors all contribute to the obesity epidemic.

Vacant lands are a burden to communities. They can increase crime and encourage the dumping of litter, tires, appliances, chemicals and other pollutants (Garvin et al, 2013). In certain areas, contamination can spread through runoff and groundwater infiltration (Swickard, 2008). Vacant lands can also reduce the property values, result in uncollected taxes and create maintenance costs for the city (Yang et al, 2007). Community gardens are popular solutions for reclaiming vacant lots and strengthening social ties, both of which have been linked with health benefits. The USDA has a grant program designed to decrease the impact of food deserts by helping residents start community gardens, increase food self-reliance and meet the nutritional needs of the community. The program addresses many issues, including food assistance enrollment, sustainable agriculture, healthy diet education and increased healthy food availability. However, there are still challenges with acquiring land and assuring that the lots are suitable for food production (Ploeg et al, 2009).

Soil also plays an important role in plant nutrition. Healthy soil correlates with healthy food. Proper soil structure helps ensure sufficient water infiltration, which reduces erosion and loss of important nutrients from runoff (Chen and Dick, 2011). There are a number of soil management groups and stakeholders that aim to develop and share best management practices to produce healthy crops and reduce adverse environmental problems associated with poor soil management. Some of these practices include no or low tillage, crop rotation, cover crops, soil amendments, such as gypsum, and no or little use of pesticides and fertilizers.

While there has been much soil management research for rural farms, less has been conducted in support of urban community gardens. Urban centers often have higher heavy metal and toxicity concentrations due to contaminated industrial sites and vehicle exhaust. It is important that urban gardens provide fresh, healthy foods to combat food deserts and imbalanced diets, while also ensuring that crops are not grown in contaminated soils. Thus, more research into urban soil health is necessary. Gypsum has been used as a fertilizer to improve soil health and leads to larger crop yields and greater uptake of nutrients (Chen et al, 2008). Further research of the effects of FGD gypsum as a soil amendment on plant nutrition and the mitigation of heavy metal uptake is needed.

Greenleaf Communities strives to create a healthy and sustainable world, with particular emphasis on improved human nutrition through sustainable agricultural practices. Greenleaf has experience with applied soil management research and partners with leading soil scientists and top health and nutrition experts to tackle environmental health problems.

Greenleaf engages in outreach to inform stakeholders of its research and development of best management practices.