Management of nutrition and irrigation in soil-grown and soilless cultivations in mild-winter climates: problems, constraints and trends in the Mediterranean region.

摘要

Balanced fertilization and irrigation schedules play a key role in the production of uniform, good quality vegetables in greenhouses. In soil-grown crops, the use of modern tensiometers to monitor soil moisture status, in combination with the application of liquid fertilization via the irrigation system according to the results of chemical soil analysis, may considerably enhance yield and produce quality. The determination of the water extractable nutrient levels in the greenhouse soil seems to be a rapid and reliable method to assess its nutritional status. Alternatively, the total levels of plant available nutrients may be measured in saturation extracts, which renders a more reliable estimation of the soil nutrient status, but this procedure is time-consuming due to the need to dry and grind the soil samples. In the Mediterranean region, greenhouse production takes place under simple constructions which take advantage of the favourable natural conditions, such as mild winters and high solar irradiation. In contrast to northern Europe, where the greenhouses sector relies mainly on soilless culture, most greenhouse crops in the Mediterranean basin are grown in the soil. However, the phase-out of methyl bromide for soil fumigation in compliance with the Montreal Protocol increasingly forces Mediterranean greenhouse growers to switch to soilless culture. In this paper, some aspects related to the impact of nutrition on the quality of fresh vegetables, nitrogen nutrition and its impact on pH and nutrient availability in the root zone, as well as salt accumulation and irrigation scheduling in closed-cycle soilless cultivation systems are presented and discussed.