Very interesting question.  I have observed a lot of urban agriculture in California, and the only true consistency I would say is that they are located in urban areas.  Some are dirt farmers, some are raised beds on rooftops, some are hydroponics.  Some are private, some are public, some are community run and some are organizationally run. Some grow vegetables, some grow fish, some grown products for value added. Some are focused on production, some on engagement, some on education. Some sell their products some give them away.  I have seen virtually every form of agriculture conceivable be classified as urban agriculture, with the ONLY clear, consistent commonality being that they are located in urban areas.  There are some common themes certainly as others have noted, but none of them are exclusive to, or purely inclusive of, urban agriculture.

One thing I am not sure of that might be worth looking into is that, I think, none of these operations were on lands zoned for agriculture.  That would be an interesting definition of urban agriculture...agriculture practiced on lands zoned residential, commercial, or public rather than zoned for agriculture.

dear Kbrom,

there is not a defenite distinction but the first and most obvious feature is that UA be within an urban area. Then size of the plot and  the variety of grown plants and final destination of the yield are distinctive. Often UA is run by non-professional farmers.

I would also add that in many cases UA disregards any environmental quality consideration relevant to soil+water.

In the DRC, particularly in the city of Kinshasa, urban agriculture is mainly dominated by the production of vegetables. Cultures in UA have usually a short production cycle. The fresh unprocessed products often are sold directly in the city. This agriculture is much more intensive than rural agriculture. Areas occupied by urban agriculture are small compared to the rural agriculture.

Dear Kbrom,

In Brazil there are some forms that I understand like examples of urban agriculture:

a) In the public areas, such as plazas, central site between roads, roof gardens, etc. They have different objectives: recreative, food diversity, educational and even as income activity for some families. Besides the rain, usually the irrigation water is the same treated for human consumption. This proximity makes the use of chemicals to control pests and diseases isn't possible due risks to human heath, so they use other ways, like mechanical, biological and organic control. It´s a good solution to cities and citizens, but unhappy we have few success cases to a so big country.

b) neighbor areas, these have farm characteristics, but are urban areas too. Are usually cultivated vegetables for the market. Generally are conventional, more technical, use all chemical resources, are little areas. In this case we have a concern, the use of water from rivers that receive the influence of the city, ie, with the possibility to carry chemical and biological contaminants to the crops.

Very interesting question.  I have observed a lot of urban agriculture in California, and the only true consistency I would say is that they are located in urban areas.  Some are dirt farmers, some are raised beds on rooftops, some are hydroponics.  Some are private, some are public, some are community run and some are organizationally run. Some grow vegetables, some grow fish, some grown products for value added. Some are focused on production, some on engagement, some on education. Some sell their products some give them away.  I have seen virtually every form of agriculture conceivable be classified as urban agriculture, with the ONLY clear, consistent commonality being that they are located in urban areas.  There are some common themes certainly as others have noted, but none of them are exclusive to, or purely inclusive of, urban agriculture.

One thing I am not sure of that might be worth looking into is that, I think, none of these operations were on lands zoned for agriculture.  That would be an interesting definition of urban agriculture...agriculture practiced on lands zoned residential, commercial, or public rather than zoned for agriculture.

urban agriculture means cultivation of agriculture crops in urban areas like municipality and corporation areas in India. 

Dear Kbrom,

Conventional agriculture refers to the practices that are followed traditionally. The farmers who are into conventional agriculture are late or very late adopters of improved technologies. Whereas, urban agriculture is a modern practice usually followed in urban (non-rural) areas.

I advise you to read about "Peri-Urban Agriculture". It explains the different features of urban agriculture. FAO's publications are good sources. If it helps you, you can download a piece of information about Urban Agriculture in Ethiopia on my homepage.

Is urban agriculture practiced simply for the heck of it? 

Lingaraju - I would say that urban agriculture is practiced for many reasons. Here are some of them off the top of my head:

1) many urban areas do not have good access to fresh vegetables. many urban agriculture developments are community based, focused on allowing people to have access to the food that is grown

2) culturally and educationally many people worry that the disconnect from natural processes that people experience in cities is unhealthy, psychologically and from a values based perspective. urban agriculture allows for engagement and education of people and especially children who might not even understand the concept that our food is grown out of the eart

3) urban agriculture maximizes urban utility, often using wasted space such as rooftops to turn them into productive areas. it reduces the transportation costs of food into the city and, if done correctly, can also provide other services (for example, can mitigate rainwater runoff that can overflow sewer systems).

4) they provide greenspace and aesthetic value to the city

5) gardening is a popular hobby for many people, and urban farming allows a non-destructive, cheap, positive thing for urban dwellers to do

6) allows for the "know your farmer" concept even in cities

Iʻm sure there are a lot of other good reasons, but this is what comes to mind immediately.

Urban agriculture can help in relieving the pressure on conventional agriculture - particularly for the fruits and vegetable crops but not fully. Urban agriculture could still be conventional  although limitations on land and input availability may make it difficult to follow full set of package of practices. further. urban agriculture may need to depend on the treated waste water rather than fresh water. This has implications for food safety. 

The urban agriculture is linked with the growing of crops or ornamental s in the urban or sub urban areas. In general the crops require intensive care and cash value   

Urban and peri-urban agriculture can be defined as growing plants and raising animals within and around cities. The UPA provides food products of different types of crops (grains, roots, vegetables, mushrooms, fruits), animals (birds, rabbits, goats, sheep, cattle, pigs, guinea pigs, fish, etc.) as well as products non-food (aromatic and medicinal plants, ornamental plants, tree products). In a broad sense would seek this type of farming more agroecological and therefore not dependent on the use of agrochemicals as conventional agriculture.

Interesting facts about this activity:

• Urban agriculture is practiced by 800 million people worldwide. Helps low-income urban residents save money on food shopping.
• Gardens can be 15 times more productive than rural farms. An area of just one square meter can provide 20 kg of food per year. Urban gardeners spend less on transport, packaging and storage, and can sell directly to food stalls on the street and in the market. So get more income rather than being released into the middleman.
• Urban agriculture provides employment and income for poor women and other disadvantaged groups.
• Horticulture can generate one job for every 100 square meters of garden with the production, input supply, marketing and added value from producer to consumer.
• However, in many countries, this activity does not get recognition in agricultural policy and urban planning. Producers often operate without permits.

You can follow this link and may find some answers:

https://www.researchgate.net/publication/28641815_Urban_agriculture_in_Tanzania__issues_of_sustainability

Book Urban agriculture in Tanzania : issues of sustainability

In my point of view urban agriclture depend on nature cultivation. I mean they cultivate all of what the nature tought them and mainly based on what they need from foods or natural traditional medicin. This kind of agriclure Iis positive for human, animal and for environment as well. These peoples follow their senses and they are not looking for money or commercilization.on the other hand convential agriclture may depends on what they others needs and how much they will pay for the products resulted from this agricuture. Also, the farmers will used everything evdn the prohibirted chemicals to get high yield or make it ready for harvesting early, which affect the human, animal halth and left adrow back effect on the environment.  I hope one day the nature back to us as Allah created it for us in the begining of earth creation. 

Urban agriculture can be view as the crops especially vegetables that has ready markets and high demand and it is usually cultivated in the proximity of transport to the marketing centers where as conventional agriculture will involve mixed farming usually grown for a diverse purposes either for markets (raw material, export, processing) or subsistence. 

There is no concept like like urban agriculture. Conventional agriculture refers to traditional practices or age old practices that still prevails. It is away  from mainly mechanization /computation etc advanced tools. Urban agriculture is characterized by high input intensive agriculture mainly growing vegetables etc short duration  crops. It is influence of peri-urban/ city/urban output on agriculture practices.