For example, increasing the use of short-cycle crops boosts productivity and decreases the use of potentially contaminated water. Because many safe practices are knowledge-based, they are also affordable and easily adopted by farmers. Producers can be taught to avoid the use of polluted organic or chemical fertilizers on specific crops or to draw water from wells instead of rivers. Urban farmers can have mutually beneficial contracts with municipal waste-disposal services, and nonfood urban agriculture can be used to rehabilitate contaminated water bodies and soils, generating income in the process. NGOs can help determine the scale of composting that would be both cost-effective and environmentally suitable.
Cities can treat and recirculate wastewater.
Challenges to urban agriculture remain to be addressed from the community up to the national level. Governments must apply the wealth of local experiences to creating institutional structures for implementing urban agriculture policies. Overall, experience shows that prohibition of urban agriculture has been ineffective. NGOs can help create and mediate among the various organizations. Experience also has shown that urban agriculture is most viable where it is mainstreamed into robust strategies for land use, poverty alleviation, economic development, and sound environmental management.