table 1.1 shows the use of plastic mulch in the world.wide use in asia and oceania in apparent. it is not clearly shown in the table,but in recent years it has been reported that chaina has the largest area of plastic mulch use,now more than one million ha since yearly expansion is so rapid especially in asis,these data cannot convey the details.table 1.2 lists the areas of low tunnels and roe covers in the countries where the area of their use more than 5000 ha .since construction and dismantling of these facilities are frequent, statistical data are less reliable than those for more stable structures, glasshouses for example.CIPA(Comite International des Plastiques en Agriculture)in France is one of the organizations that publish this kind of worldwide statistical data, but it is not a governmental body and has some difficulty in collecting and updating these data.in any case ,according to this table, the area of low tunnels and row covers in japan is the largest,and again expansion in Asia is rapid.the total area of greenhouses in the main horticultural countries is shown in table 1.3,in order from largest to smallest.again all data were taken in different years, and there are no data for spain,where the area would certainly be greater than 10000 ha. in most countries,greenhouses are made of plastic the majority are plastic ,although,as is well known,almost all greenhouses are glass in the netherlands.Glasshouses and rigid-plastic houses are long-life structures , and therefore are mostly located in cold regions where these structures can be used throughout the year.in Japan,year-round use of greenhouses is becoming predominant,but in moderate and warm climate regions they are still only used i winter.Double cropping systems, of rice cultivation in open fields and strawberry cultivation in plastic houses on the same fields, is common in some regions in Japan.