# Promoting Urban Farming for Creating Sustainable Cities in Nepal
## 3 Materials and Methods
### Urban Agriculture in the USA  
The Metro Phoenix region in Arizona, USA, is an urbanized region of almost 5 million people (2022). In most of the municipalities of the metro area, urban agriculture is promoted by the municipal governments for several reasons, including food security, reduction in transportation needs, mitigation of the heat island effect, and self-reliance of households on food. For example, the City of Phoenix (2022) 2025 Food Action Plan states the following: \"Achievement of local food system goals results in reduced rates of hunger, obesity, and diet-related diseases through the elimination of food deserts, increasing urban agriculture and adopting zoning, land use guidelines, and other policies to improve the food system\". Similarly, the City of Tempe (2014) in Arizona, in its General Plan 2040, includes a strategy to \"Expand opportunity for urban agriculture\"-home gardens, community gardens, urban farms, farmers markets, as well as food availability and accessibility promotes urban agriculture\" [23]. Many other cities in Metro Phoenix and elsewhere in Arizona have plans and programs to promote and encourage urban agriculture. Figures 5 and 6 show examples of urban agriculture in Metro Phoenix.  
Figure 5: Citrus trees planted in the retention areas in housing areas in Gilbert, Arizona, USA. Photo by [PERSON].  
Agrotopia, a mixed-use community in the burgeoning Town of Gilbert, is an example of how urban agriculture could be woven into the urban fabric and make it more appealing. Agrotopia provides the tour of its urban agriculture to promote the practice and utilizes urban agriculture not only for local food production but also to make the community more attractive for the urban residents. The juxtaposition of urban agriculture and restaurants which use the food produced there is an example of the symbiotic relationship between the urban environment and urban agriculture.  
On an experimental basis, the University of Central Missouri (UCM) is growing tomatoes on a hydroponic system inside the greenhouse year-round, without the need for supplemental heating and cooling systems (Figure 7a,b). In a hydroponics system, nutrient water is circulated through the water container and plant. No soil is used, but the plants are supported by various substrates. The substrates provide some holes for air circulation. Under normal temperatures, tomato seeds start germination between 5 and 14 days. Before transplanting plants into the hydroponic system, it is necessary to put blocks into hydroponic baskets, as tomatoes grow quickly.  
Figure 6: Urban farming in “Agrotopia”, a mixed-use urban development in Gilbert, Arizona, USA. Photo by [PERSON].  
Figure 7: _Cont._  
The nutrient-rich water contains all the necessary macro- and micronutrients required by the plants for optimum growth. The water flows from the nutrient tank through the plant system and back into the nutrient tank. The nutrient water is pumped into a trough. The water then slowly returns to the nutrient tank through a valve in the trough. Nutrient-rich water is pumped through a series of thin plastic spaghetti pipes into the buckets. The water supply should be uninterrupted.  
Tomatoes perform better when the ambient temperature is between 21 \({}^{\circ}\)C and 26 \({}^{\circ}\)C and the electrical conductivity is between 2 and 4 milli siemens. (One milli siemens is the electrical conductance equal to 1/1000 of a siemens, which is equal to one ampere per volt.) The optimum water pH ranges from 6 to 6.5 for tomato plants. Calcium is required at the time of fruiting, and lower amounts of potassium nitrate and calcium nitrate are great hydroponic fertilizers. If the pH ranges are not ideal, this condition prevents nitrogen and calcium uptake by the root system even if they are present in the nutrient solution.