Horticultural production in greenhouses: efficient use of water

The central thesis of this paper is that greenhouse production of vegetables is the most water-efficient food production system and thus can contribute to meeting the challenge of feeding a better diet to an increasing world population, without increasing the need for irrigation water. The various physiological and managerial components of agricultural water use efficiency are unravelled and the potential improvements achieved by using a greenhouse are analysed. In the first place it is shown that greenhouse growers usually have better tools for water management; then it is discussed how and why a greenhouse environment leads naturally to higher productivity and transpiration efficiency than growing in the field; finally the high economic productivity of water in greenhouses is quantified. It is discussed that this would warrant the investments in infrastructure and tools that are needed to increase water use efficiency. It is also shown that, contrary to accepted wisdom, greenhouse production makes it possible to decrease the environmental impact of vegetable pro-duction.