Volumes of Water Used A typical floriculture greenhouse crop uses about 4000 cubic metres of water per hectare per year. A typical greenhouse vegetable crop uses approximately double that, or between 7000 and 8000 cubic metres of water per hectare per year. The requirement for leaching is strongly related to the tolerance of the crops grown to accumulations of salts in growing media. In a tomato greenhouse, for example, water leaching annually amounts to about 0.23 m3 per m2 of greenhouse or per 50 kg of production.
Practical options are available to reduce water consumption in greenhouses.
A regulated irrigation schedule sensitive to crop requirements is a most effective approach, but may be difficult to implement without an accurate, well designed, watering system. For example, a computerized irrigation scheduler using a drip system can reduce overwatering and excessive leaching commonly associated with an overhead system. The substantial costs of these technological systems are often justified in terms of savings in labour, better timing, and water use efficiency. The choice of growing media in greenhouse operations has a significant effect on overall water consumption. Watering efficiency can be increasedthrough the choice of substrates with higher water holding capacity and requiring less frequent watering.