University of Maryland Extension

Water management

Author: 
Neith Little, Extension Agent, Urban Agriculture


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 Drip irrigation pairs well with mulch to direct water to crop roots while reducing weed pressure. Relatively inexpensive timers are available to automate irrigation through drip or overhead systems. Photos taken by Neith Little at Carroll County office of University of Maryland Extension.
Figure 20: Drip irrigation pairs well with mulch to direct water to crop roots while reducing weed pressure. Relatively inexpensive timers are available to automate irrigation through drip or overhead systems. Photos taken by Neith Little at Carroll County office of University of Maryland Extension.

Most urban growers rely on municipal water for irrigation, which can be expensive. This makes using water efficiently especially important. On some urban lots, getting access to municipal water can be a big challenge.

Some growers also collect rainwater, and most growers I’ve spoken with want to. This is one of those practices that makes a lot of sense financially and environmentally, but makes food safety scientists nervous because of potential risks of contamination if rooftops or other surfaces exposed to birds and rodents are used for rainwater collection. Researchers and Extension Agents are working on improving our recommendations for best practices for utilizing rainwater and other “non-traditional” water sources. For now, the best risk management practices recommended are to apply collected rainwater using drip irrigation or another precise method to the soil surface, so that it does not contact the edible portion of crops.

Urban farm irrigation systems are hand-watering with hoses and watering cans, overhead watering using sprinklers in high tunnels, drip irrigation using flexible tubing with small holes or emitters both outdoors and in high tunnels, and recirculating water in aquaponic and hydroponic systems. Hand-watering requires the lowest initial equipment investment, but over time costs a great deal of the growers’ time. Over-head sprinklers in high tunnels can be useful for cooling crops like lettuce and discouraging pests like spider mites, but overhead irrigation can also increase disease pressure, especially for tomatoes. Drip irrigation pairs well with mulching and is considered the most efficient method, but it does require an investment in tubing, as well as annual maintenance to repair leaks and to roll up tubing before tillage.

Irrigation water testing can provide important information about minerals, pH, and salinity. This is particularly important for growers using high tunnels, greenhouses and hydroponic/aquaponic systems (Will and Faust 2010).

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