Enhancing Environmental Quality in Agricultural Systems

Abstract

Greenhouses have been extremely successful in providing abundant, cheap and high-quality produce, by using resources (water, minerals, pesticides) with a very high economic efficiency. Marginal agricultural land is being rapidly converted into protected cultivation in many (semi-arid) regions of the world, hoping to prosper both from primary and secondary activities. Water use efficiency of greenhouse production is about five times as high as field production of vegetables. However, in spite of using resources more efficiently, greenhouse areas have an enormous visual and environmental impact: diversion of limited good water resources; contamination due to pollutants released with over-abundant irrigation; production of plastic and mineral waste and biological by-products; contamination due to plant protection chemicals and emission of "greenhouse" gases (CO 2 ) by heating with fossil fuels in Northern countries. In addition, greenhouse production has an "image" problem: there is a general perception among European consumers that such an "industrial" production of food is non-natural and unhealthy, although in the Americas, for instance, the "cleanliness" of the production process is considered an advantage. Since, the "polluter pays" very seldom, environment-friendly production is more expensive. Therefore a large market in "eco-labels" has developed in response to consumers' misgivings and in the hope of recovering (part of) the costs through higher prices. However, there is little clarity about agricultural practices associated to each label and there are doubts about enforcement. This paper analyses advantages and draw-backs of greenhouse production, and attempts to review the items where improvement is necessary in order to ensure that greenhouse production is sustainable, yet profitable also in the future. INTRODUCTIONConsumers in developed countries are so used to get appealing, clean looking and cheap vegetables the whole year round, that very few of them are aware that such a luxury was unthinkable just 20 years ago. This abundance is most commonly generated under shelters (protected cultivation) that, for a large fraction of the year, ensure growing conditions much better suited for crop production than open field. This is not new: the advantages of ambient modification in this respect were certainly known in ancient Rome, as Plinius (77A.D.) maintained that the emperor Tiberius could eat year-round cucumbers from plants that were withdrawn under semi-transparent shelters whenever conditions were unfavourable. Similarly, orangeries (buildings devoted to create growing conditions of citrus where citrus would not grow) have been built in the gardens of rich people for many centuries. What is new of the last 20 years is that year-round abundance is so cheap as to be taken for granted. This has been caused by the large-scale application of horticulture under plastic that has transformed formerly marginal agricultural land into a highly efficient and profitable crop production. The most striking exa...

Does growing vegetables in plastic greenhouses enhance regional ecosystem services beyond the food supply?

“…The technology is easily adopted and relatively inexpensive and, in many regions, PGVC can supply more abundant off‐season and high‐quality vegetables than conventional vegetable cultivation (CVC; Costa and Heuvelink 2004; Ali 2008). Furthermore, PGVC uses fewer resources (eg water, fertilizers, pesticides) per unit of vegetable production than CVC (Stanghellini et al . 2003).…”

Deficit Irrigation as a Strategy to Save Water: Physiology and Potential Application to Horticulture

“…drip irrigation, use of irrigation calendars based on the depth of water table and soil salinity, reuse of wastewater) (Chaves et al 2003; Pereira et al 2006). Drip irrigation, mulching and protected cultivation have contributed to improve WUE in agriculture by significantly reducing runoff and evapotranspiration losses (Stanghellini et al 2003; Jones 2004; Kirnak and Demirtas 2006). Mediterranean countries like Israel or Spain led developments in drip irrigation and cultivation under plastic in the past decades, but China has been strongly investing in these techniques.…”

Closed Water Loop in Greenhouses: Effect of Water Quality and Value of Produce

“…Closed systems in greenhouses are the vegetable production system with the highest economic water use efficiency by far (Stanghellini et al, 2003) and thus can afford a relatively expensive irrigation water (Table 3). Expansion of such systems should, therefore, be welcomed, particularly in semi-arid regions.…”