Abstract

Water quality and water supply are essential for organic greenhouse grown crops to prevent soil contaminationby undesirable chemicals and microorganisms, while providing a sufficient amount of water for plant growth.The absence of natural precipitation combined with higher evapotranspiration due to higher temperatureand longer cropping period requires an adequate supply of water. Water quality is commonly defined by itschemical, physical, and biological attributes. It is closely linked to the soil/rock native components, surroundingenvironment and land use. The runoff from urban, industrial, farming, mining, and forestry activities alsosignificantly affects the quality of water available for greenhouse horticulture. High water quality is particularlyimportant in organic greenhouse production in order to prevent soil salinization and ensure optimal soil biologicalactivity. Indeed, unbalanced organic fertilizer inputs may contribute to soil salinity, while soil microbial activitiesresponsible for nutrient mineralization, soil suppressiveness and plant health, are affected by soil pH, ions, andcontaminants. Poor water quality can also result in drip and micro irrigation clogging, plant toxicity, and productcontamination by human pathogen or illicit compounds.To achieve sustainable water management, good knowledge of crops' water requirements is essential as isknowledge of the soil water characteristics that determine the irrigation scheduling. Moreover, the adequacyof the irrigation distribution system determines the accuracy of the water supplied. Crop water needs areoften determined on the basis of daily evapotranspiration and solar radiation levels. Different irrigation controltools such as soil moisture sensors, plant sensors, lysimeters and models contribute to the optimization of theirrigation management of organic greenhouse crops. In addition to determining crop productivity, water qualityand water management also impact on product quality.In this booklet we first illustrate the water flows through different organic greenhouse growing systems. Westate the importance of water quality for organic greenhouse horticulture and give some guidelines regardingthe required water quality attributes in terms of inorganic, organic and microbial loads as well as hazardousmicroorganisms and compounds. We also define advantages and disadvantages of different water resourcesand describe the important drivers for crop and soil water demand. We then report the effects of salinity on soilmineralisation and crop development in organic greenhouse production systems. The main irrigation technologyused for organic greenhouse horticulture is described along with the most important management aspects forirrigation. Because quality attributes of greenhouse products drive consumer demand for organic products, wedefine the impact of water quality and irrigation management on product quality. Organic farming should usecultural practices that maintain land resources and ecological balance, in addition to promoting biodiversity,biological cycles, and soil biological activity. We therefore state the importance of water resources and their usefor organic greenhouse system sustainability. We then conclude by summarizing main aspects of water qualityand irrigation management, and by identifying knowledge gaps.Better prediction of the temporal dynamics of plant and soil microbial water needs in relation to sustainableproductivity and high water use efficiency is needed for greenhouse horticultural crops. It is also importantin terms of reduced attractiveness to pests and susceptibility to diseases. A reduction in spatial and temporalcrop heterogeneity should result from improved growing systems and better water and crop management.Nevertheless, advances in irrigation management for conventional greenhouse crops and development of newcontrol tools can be adapted for use in organic greenhouse horticulture. Similarly, some water treatmentsof drained or collected waters such as thermal, UV, ozone and biological treatments can be used by growersaccording to their organic regulation. Consequently, research is needed in different areas of organic greenhousehorticulture: (i) water quality in terms of relevant thresholds for contaminants and potential risks related toplant and human pathogens; (ii) efficient measures to prevent clogging of the irrigation systems; (iii) alternativewater treatments and system cleaning products; (iv) better knowledge and guidelines for non-leaching systems;(v) affordable and highly efficient control tools to assist growers; and (vi) knowledge about the environmentalimpact of different water management and water sources used for organic greenhouse horticulture to helpgrowers fulfilling the organic principles and improve their sustainability.

Keywords

irrigation management, irrigation technology, salinity, sustainability, water conservation, water demand, water flows, water quality, water resources, water treatment,

Published in

Publisher: BioGreenhouse COST

SLU Authors

• Alsanius, Beatrix

  • Department of Biosystems and Technology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Horticulture


Publication identifier

DOI: https://doi.org/10.18174/373585

ISBN: 978-94-6257-538-7

Permanent link to this page (URI)

https://res.slu.se/id/publ/79292