1.1. INTRODUCTION Plastic covering, either framed or floating, is now used worldwide to protect crops from unfavorable growing conditions, such as severe weather and insects and birds. Protected cultivation in the broad sense, including mulching, has been widely spread by the innovation of plastic films. Paper, straw, and glass were the main materials used before the era of plastics. Utilization of plastics in agriculture started in the developed countries and is now spreading to the developing countries. Early utilization of plastic was in cold regions, and plastic was mainly used for protection from the cold. Now plastic is used also for protection from wind, insects and diseases. The use of covering techniques started with a simple system such as mulching, then row covers and small tunnels were developed, and finally plastic houses. Floating mulch was an exception to this sequence: it was introduced rather recently, although it is a simple structure. New development of functional and inexpensive films triggered widespread use of floating mulch. Table 1.1. The use a/plastic mulch in the world (after Jouet, 2001).

From mulching to greenhouses, the air space between the cover and the soil surface is the key to the classification of climates under cover. The same mechanism governs environments produced by the various covers. This book describes and analyses all the different environments from mulching to greenhouses. The relationship between plants and environment is another important topic in the book. Stress is placed on the link between quantitative phenomena and qualitative analyses. Most phenomena involved are nonlinear and non-steady-state. An approach called System Dynamics is used, and simulation models developed in the simulation language CSMP are fully used. The subjects covered are of relevance to graduate students, to scientists and researchers in agriculture and biological sciences and, of course, to agricultural organizations in both the developing and developed countries.

1.1. INTRODUCTION Plastic covering, either framed or floating, is now used worldwide to protect crops from unfavorable growing conditions, such as severe weather and insects and birds. Protected cultivation in the broad sense, including mulching, has been widely spread by the innovation of plastic films. Paper, straw, and glass were the main materials used before the era of plastics. Utilization of plastics in agriculture started in the developed countries and is now spreading to the developing countries. Early utilization of plastic was in cold regions, and plastic was mainly used for protection from the cold. Now plastic is used also for protection from wind, insects and diseases. The use of covering techniques started with a simple system such as mulching, then row covers and small tunnels were developed, and finally plastic houses. Floating mulch was an exception to this sequence: it was introduced rather recently, although it is a simple structure. New development of functional and inexpensive films triggered widespread use of floating mulch. Table 1.1. The use a/plastic mulch in the world (after Jouet, 2001).

From mulching to greenhouses, the air space between the cover and the soil surface is the key to the classification of climates under cover. The same mechanism governs environments produced by the various covers. This book describes and analyses all the different environments from mulching to greenhouses. The relationship between plants and environment is another important topic in the book. Stress is placed on the link between quantitative phenomena and qualitative analyses. Most phenomena involved are nonlinear and non-steady-state. An approach called System Dynamics is used, and simulation models developed in the simulation language CSMP are fully used. The subjects covered are of relevance to graduate students, to scientists and researchers in agriculture and biological sciences and, of course, to agricultural organizations in both the developing and developed countries.