Urban agriculture covers a whole range of production systems, methods, techniques and socio-economic aspects. The diversity of the products can be divided into:
• Vegetable horticulture,
• Animal husbandry,
• Fuel and food forestry, including agroforestry,
• Integrated waste-water aquaculture, including fish production.
• Other specializations include the cultivation of herbs, ornamental plants, fruits and the production of silk.
The urban context offers opportunities for production, use of raw materials and marketing, which people living in rural areas do not have. But, this may also have its limitations. There are very many successful, locally-adapted variants of small-scale urban agriculture, worldwide. However, techniques are not always transferable from city to city or from country to country.
You may be growing vegetables on a small scale around your home primarily for your own food supply. You could then sell a surplus production at the market. In other words: you may give food security priority over economic efficiency.
You may, on the other hand, be involved in large-scale farming for the market at a location at a reasonable distance from this market. Household income from sales is then your main target, and therefore you should take into account cost-effectiveness. Economy involves not
only finances: expenditure, investment and market sales. It also embraces the level of inputs, time investment and labour input.
Before you spend time and money or invest in urban agriculture there is something important that you must take into account. Research shows that investing one’s own savings in urban agriculture can be interesting. However, an investment may be slow in showing any return, especially if you first need to experiment with risks and time investment, or if you use your produce for your own consumption needs.
The techniques have to do with urban horticulture. They are especially about growing vegetables in combination with the preparation of good quality compost and garden soil.
Potential locations of urban horticulture include: houses and courtyards, parks, open spaces for public access, flat roofs, balconies, and walls, containers of all sorts, greenhouses, wetlands (floodplains of rivers), terraces and slopes.
These are systems that focus on the culture of fish and other water organisms, or on the cultivation of water plants such as seaweed. There are many types of naturally-occurring surface water suitable for one or other culture or scale of production. Cultivation in ponds is also a possibility.
Hydroculture or hydroponics
These are small-scale vegetable growing on a medium that does not contain any soil; usually it is only water with minerals. These mainly are highly specialised and vulnerable cultivation techniques involving rather high investments.
These involves the raising of animals and poultry birds (chickens,turkey, duck etc.) for the purpose of egg and meat productions.
Arboriculture or tree breeding is useful for the production of wood for fuel or for building, producing fruits or nuts and for providing compost.
Furthermore, trees give shade, purify the air and keep the soil healthy – provided that the soil around the tree is not misused for other purposes.
Non-food and minimal processing products
This has to do with ornamental plants, flowers, (ingredients for) medicines, herbs, spices, ingredients for drinks, (ingredients for) insecticides and fibre crops. Animal production involves sericulture (silkworm breeding), worms and honey bees. It is about the production of plant parts or animal products that mostly need a little processing to give them added value. Relatively good earnings make selling these products often more interesting than using or consuming them oneself.
For instance, if they have good keeping qualities, can be transported over longer distances, or are attractive for consumers with spending power.
• Grow crops that are less susceptible to contamination: fruit that needs peeling will transmit fewer pathogens than a leaf crop;
• Crops that are used for livestock are a step away from human consumption and therefore usually present fewer health risks;
• If you find suitable sales opportunities, and if you need not necessarily grow food crops: try and grow crops for fuel, construction and ornamental purposes, as these are completely safe for health.
Choice of growing location
• Try to avoid growing food crops in the immediate vicinity along roads, by refuse heaps and rubbish dumps, on places where factories, companies or households discharge their wastewater, and on former factory sites;
• If you need to grow leafy vegetables near public roads, then take into account a minimum distance of 10 metres;
• Plant trees or quick-growing shrubs close to and along the road as a protective hedge, and grow susceptible, e.g. leafy crops immediately behind it.
Growing on beds
Crop growing on beds looks very similar to soil-based horticulture. A shallow bed consists of a thin layer of soil that is regularly watered. It is simple to construct provided there is enough (open) space, preferably with direct sunlight, a good growing medium and water close by.
A shallow bed can also be constructed on a robust roof, roof terrace or big balcony, but this needs adjustments: raised edges and an impermeable (plastic) base, and the balcony will naturally need to have an adequate supporting capacity.
Choice of crop
The choice of crop will largely be determined by the rooting depth of the bed. Some deep-rooting plants can adjust their root system in a shallow bed, which you will have to discover by trial and error. Plants grown for their tap root like taro or cocoyam, however, will be difficult or impossible to grow because they will have too little space to yield harvestable roots. Plants with thin and large, hairless leave and with no natural wax layer lose too much water through evaporation during growing and that can be problematic.
You can increase the yield of crops grown as individual plants, for example cabbage, by more intensive use of the limited surface area of the bed. Plant in rows but zigzag the planting.
Maintenance and care
Regular watering is the most important aspect of daily maintenance, as the soil dries out quickly especially if it is a shallow bed. It is advisable to cover the bed when the seedlings are emerging, or the nursery plants are taking root. At the start of the growing season it is important that the organic matter is decayed, so that the nutrients can be released for the benefit of the plants. You can add artificial fertilizer during the growing season, but ensure that you spread it evenly and that it dissolves well to prevent scorching. Adhere closely to the dosage and use no more than half of the quantity prescribed for natural soil in open ground.
Weeds compete with the plants for water and nutrients, but they also have advantages: they root rapidly improving the structure of the soil in a newly-laid bed, and their roots help to keep an established growing bed airy.
At the end of the growing season you need to check whether the bed is still high enough for the next crop. Soil with much organic matter in the form of compost subsides during the decaying process. It might sometimes become too dense for optimum root growth and will not drain well. Therefore, after the harvest remove up to 5 cm of the used, composted bed and mix it loosely in the top layer on a newly-laid bed.
If after one crop a growing bed is still deep and loose enough, leave it after the harvest and do not turn it. Sometimes working organic matter into the soil together with artificial fertiliser
Pay attention to soil-linked diseases: preferably, avoid planting the same or related crops in succession in the same soil.