The irrigating system developed within the FLOW-AID project integrates innovative sensor technologies into a decision support system, taking into consideration boundary conditions and constraints for a number of practical growing systems in the Mediterranean.
This water cycle management system has been evaluated at five sites located in Italy, Turkey, Lebanon, Jordan and the Netherlands. The sites differ in the type of local constraints, irrigation structures, crop types, local water supplies, availability of water and water sources in amount and quality, the local goals, and their complexity. The same equipment was used all the experiments, but as the local conditions differ widely in the different areas the technical equipment needed some altering to suit the local circumstances.
These water cycle monitoring experiments were performed in several trials during three growing seasons in 2007-2009. Testing and calibrating the modules in view of relevant factors included the following studies:
Container-grown landscaping ornamentals in a Mediterranean climate (Italy)
Over-irrigation problems are common in outdoor nurseries in the Pistoia area in Italy when using conventional drop or sprinkler irrigation. Cultivation of many different species on the same plot makes irrigation scheduling difficult and water quality is constantly worsening in the area. A prototype on-line sensing, root-zone based irrigation control was developed to suit these local conditions, and was evaluated through studies on four container-grown landscaping ornamentals in outdoor nurseries. Also, the application of closed-loop (recycling water from draining) growing systems was tested, preventing environmental pollution caused by the leaching of fertilisers, weed-control agents and pesticides.
Drip-irrigated cucumber grown in greenhouses under a mild winter-climate (Turkey)
This field test took place in the surroundings of the third largest city in Turkey, the city of Izmir, where the Tahtali dam provides drinking water for the city. Within the preservation area of the dam, greenhouse production is an important agricultural activity. Pollution risks within the catchment area of the dam have brought forward regulations for leaching from the authorities. Over-irrigation is common among farmers, and to prevent leaching while ensuring crop yields, the tested irrigation decision support system was programmed to minimise the amount or chemical content of drain water.
Drip-irrigated tomato in arid climate (Jordan)
In Jordan, water demand is increasing and the average yearly rainfall adds very little available water due to high evaporation. Therefore, the main sources of irrigation water are ground water with different qualities and reclaimed wastewater. Scarcity and quality of irrigation water are major constraints to agricultural development in the region. The main purpose of this test was to evaluate the performance of the irrigation system when access to fresh water is limited, and the rest of the water needs are fulfilled by poor quality water.
Drip-irrigated eggplant in semi-arid climate (Lebanon)
The Bekaa Valley is a semi-arid area accounting for about half of the agricultural production in Lebanon. A quarter of the area is used for irrigated agriculture and about half of the water amount used for irrigation comes from deep-well groundwater sources. Water distributing costs have gone up drastically due to energy demand and water quality has shown a gradual deterioration, so farmers with an improper farm-level water management need to adopt new water saving techniques. A field trial was conducted to evaluate how the technological level of the irrigation method affects the performance of the irrigation system, in particular the ability of the system to manage deficit irrigation under water constraints.
Drip-irrigated lettuce under rain-fed conditions (the Netherlands):
In Limburg, in the south of the Netherlands, crops suffer rapidly from drought and nutrients leach into the ground water during heavy rain-fall due to the sandy soils in the area. To reduce nitrate emission while keeping a high crop quality and yield, growers must apply water and fertilizers more precisely. An experiment was conducted on iceberg lettuce grown on covered loamy-sandy soil beds (preventing infiltration of rain) with the aim to prevent leaching by maintaining a constant water level in the root zone at two depths.
These case studies succeeded in identifying several aspects that are important to the project results. For instance, deficit irrigation scheduling activated by sensing devices may largely enhance water use efficiency, compared to common grower practices. Leaching can be reduced, or even be prevented. A good marketable crop quality can be obtained when applying moderate deficit regimes. Acceptable marketable yields can be obtained at higher depletion values or while using poor-quality irrigation. However, the applied deficit depth must be chosen very carefully, and an optimized fertigation strategy is a prerequisite to maintain sustainability.
FLOW-AID project final report (The Netherlands, 2010)