The management of the fertilization of soil grown crops in greenhouses can be distinguished in the addition of fertilizers before cultivation, the base dressing and those added during the cultivations period of the crops, the top dressing. The growing period of the crops in greenhouse production varies strongly. Some vegetable crops like radish and lettuce have a growing period between 4 and 15 weeks mainly dependent on the growing season, whereby different crops can be grown successively in one year. Other vegetable crops like tomato, sweet pepper and cucumber can be grown year round in moderate climatic conditions, while in relatively hot climates, like the Mediterranean area, such crops can be grown for about 8 months, because of the high temperatures in the greenhouses in summer. The length of the growing period of most flower crops shows at least the same variation as those for vegetable in view of the great diversity of these crops grown in greenhouses. For some flower crops the growing period can cover several years, like roses. It will be clear that drastic changes in the soil, like the application of soil improvers, adjustment of the pH, base dressings, flooding and soil tillage only can be carried out between cropping periods in the greenhouse. Some handlings need to be carried out simultaneously, like the addition of less soluble fertilizers as base dressing and the soil tillage. Such fertilizers must be intensively mixed throughout the soil.