PROBLEMS OF GREENHOUSE WINTER PRODUCTION IN MOROCCO
There are a number of special problems that affect the greenhouse industry. These include water quality, particularly salinity, special root disease, particularly nematodes, and a number of foliage diseases such as mildew caused by high humidity. Irrigation management has been a problem but the new trickle irrigation system is very successful where well managed. Nutrition problems have not been severe except for magnesium deficiency in cucurbits during the coolest months, but most growers tend to over use chemical fertilizers despite their high cost. There is a need for crop diversification because the present reliance on tomato causes extreme variations in returns from year to year as a result of severe price fluctuation. In the last 6 years, planting of banana in special controlled plastic greenhouses has increased from 5 to 1,300 ha and all imports are excluded. Nematodes are presently the most severe problem.