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The project BIOSEEDLING “Robust planting material from seeds to young plants - an implementation oriented chain approach” aims to find improved production procedures for vegetable seedlings of lamb’s lettuce. First, the production of lamb’s lettuce seeds of a professional seed producer was analyzed and the effect of harvest time and seed size on the germination and disease rate in the seeds was studied. Then, using seeds naturally infected by Peronospora valerianellae and Acidovorax valerianellae, several seed disinfection methods were compared: aerated steam, hot water, sodium hypochlorite, ethanol, Calcium hydroxide, and compost pellet. After testing methods for the identification of the seed pathogens and the quantification of the infection, an assessment on how the different treatments reduce the pathogens and whether they alter the seeds germination capacity was made. In a third step, substrates suppressive of the soil borne pathogens Rhizoctonia solanii and Pythium ultimum were developed and several plant protection agents were tested against Peronospora valerianellae. Furthermore, the effect of night interruption on the sporulation of lamb’s lettuce downy mildew (Peronospora valerianellae) using periods of lighting in the red and blue regions was tested. The aim is to combine the best methods resulting from all the experiments cited above in a future experiment and compare them to the standard methods in an on-farm experiment.

Vigorous seedlings are an important base for vegetable production. Beside the availability of appropriate amounts of nutrients, the health of seedlings is decisive. Soil-borne diseases are a challenging problem in organic seedling production. Here, we present results on the development of disease-suppressive growing media. Three aspects were examined: (i) use of different components of growing media (peat, coconut fiber, wood fiber, compost), (ii) influence of selected organic nitrogen fertilizers and (iii) use of different microorganisms (including commercial biocontrol agents (BCA)). Three plant-pathogen systems were used in this study: cucumber-Pythium ultimum, cress-Pythium ultimum and basil-Rhizoctonia solani. Green waste compost showed a good capability to protect cress against P. ultimum. This effect was improved by using a chitin-containing N-fertilizer. However, an inappropriate storage of the compost diminished its efficacy. In contrast to coconut fibers, wood fibers showed a suppressive activity against P. ultimum when used as partial substitutes of peat. None of five tested commercial BCAs could improve the suppressiveness of the substrates against P. ultimum. However, one of newly tested strains of Trichoderma sp. was very suppressive against P. ultimum. The tested growing media showed only small differences in suppressiveness against R. solani on basil. In contrast, two of the new strains of Trichoderma sp., which were intermediately active against P. ultimum, could efficiently protect basil against R. solani. At the moment, we test combinations of different Trichoderma strains, compost, different types of peat and peat substitutes. The aim is to determine whether it is feasible to manufacture growing media which allow the production of healthy and robust seedlings also in the presence of high levels of pathogens.

The vast majority of southern European greenhouses are unheated. Nevertheless, during the coldest months growth is retarded, since average minimum temperatures in the warmest European areas are between 7 and 9°C. Therefore heating is highly desirable in the winter, but in spite of the positive response of crops to heating its economic profitability is open to debate. Heating is accepted by most organic regulations in different countries; provided it is done efficiently and if the energy source is predominantly renewable energy, heating fits well with the concept of organic production, since it is aligned with the idea of achieving maximum potential of available resources. Little data is available on the energy use for heating in greenhouse horticulture in southern Europe. This study tries to cover this gap of knowledge since it presents the energy consumption for heating in three locations particularly devoted to greenhouse production: Almeria (southern Spain), Faro (southern Portugal) and Acate, Ragusa province (southern Italy). Daily heat requirements based on the temperature difference between the night set-point temperature and the minimum open air temperature were calculated by a simple model. Cumulative heat requirements were estimated by the summation of daily requirements. Calculations show that heat requirements grow exponentially with the set point temperature. As expected, calculations for Faro and Ragusa presented higher values since the open air night time temperature was lower than in Almeria. Heat requirement can be reduced with the help of energy saving techniques such as double walls and thermal curtains. Our study presents the expected energy savings for the three locations under consideration in greenhouses with a polyethylene thermal screen. It also shows that the greenhouse can benefit from the use of passive means, that is, without the application of external energy.

In heated greenhouses, large amounts of energy are used to optimize climate conditions (temperature, humidity). In conventional tomatoes production, the estimated annual energy consumption is 320 kWh m-2 in France, with large differences across regions, 400 kWh m-2 in Brittany and 240 kWh m-2 in the South (ADEME, 2007). In Switzerland, it varies between 245 and 500 kWh m-2 according to the regions. With increasing energy prices and environmental concerns, growers have to find solutions to reduce their energy use and to improve the energy efficiency. Several axes could be used to achieve this goals, one of them is climate management. Within the working group "Energy saving and neutral production" of the Cost Action FA 1105 "BioGreenhouse", a review on the potential for energy saving in heated greenhouse thanks to climate management was done. Basically, there are two ways to reduce energy consumption: related to temperature control and to humidity control. The energy saving potential of lowered day and night temperature set points, temperature integration (TI) and screen management will be presented in relation to the effects on production. In Switzerland, three trials from 2006 to 2008 in tomato crops showed that an energy saving potential of 15 to 30% could be achieved with TI compared to the standard temperature treatment. An energy saving between 23 and 30% with screens management based on external temperature and light intensity compared to a management according to the sunrise was obtained. To reduce energy consumption related to humidity control, dehumidification with heat recovery was studied. A traditional dehumidification (ventilation and heating) was compared with dehumidification with a heat pump in tomatoes crop. In 2013, 15% energy saving was achieved with the dehumidifier and in 2014 reached 25%. No difference in plant growth, yield and fruit quality was measured.

The majority of greenhouses in northern latitudes are heated, in the winter mainly for temperature control and year round to control humidity. Heating is accepted by most organic regulations in different countries; if heating efficiently and the energy source is predominantly renewable energy, heating fits well into the concept of organic production, since it is aligned with the idea of achieving maximum potential with available resources. It is a fact that energy use for humidity control is more important than for heating. Indeed, the improved thermal performance (insulation) of high-tech greenhouses has decreased heating requirements while decreasing the discharge pathways of vapour at the same time. The need to control humidity is especially important in organic greenhouses, given the limited options to fight fungal diseases once they develop. Excess vapour can be discharged in three ways: through exchange with dry outside air (ventilation), through condensation on a cold surface and through hygroscopic adsorption. Ventilation can be uncontrolled (natural) or controlled (forced), and in the latter case can be controlled by a heat exchanger, recovering sensible heat in the ventilated air. Even then, however, the latent heat contained in the vapour (the energy used for evaporation) will be lost. In those cases where the greenhouse is dehumidified by withdrawing internal moisture, the loss of latent heat via ventilation is prevented and condensation on an internal surface recovers the latent heat. Obviously, it costs energy to cool the condensation surface and/or regenerate the hygroscopic salt. Experiments with these systems have been performed during the last years. Some growers have installed these types of systems and they have been monitored for their effect on moisture control and energy saving. The results of these experiments and model calculations to compare them are presented. In case dehumidification systems are well controlled they can save significant amounts of the energy and with an increase of technology level the saving can be improved. There is no generally best possible solution for dehumidification. The optimum system and its operation is dependent on desired temperature and humidity level in the greenhouse.