Horticultural Production Physiology

Organic greenhouse production is challenging, as volumes of growing media are often limited, or in the case of soil-bound production, the possibilities for crop rotation are restricted. The major challenge regarding fertilization is the fact that the mineralization of nutrients from organic nutrient sources is low and hard to predict, thus causing mismatch between uptake and availability. In current projects, financed by Expansion in Horticulture and C.F. Lundströms foundation, we study the availability for nutrients by using mixtures of different nutrient sources, and different climatic conditions.

Phosphorus is a limited resource and may cause problems with eutrofication and algal blooms both in freshwater and in the Baltic sea. We are studying how the utilization of soil and fertilizer phosphorus can be improved for plants grown in the greenhouse or in the field.

Most agricultural and horticultural plants can create symbiosis with mycorrhiza mushrooms. The mushroom can contribute to the uptake of nutrients of the host plant, and can also provide protection from different types of stress and diseases. Sometimes, however, high levels of plant nutrients in arable land or cultivation substrates may inhibit the formation of mycorrhiza on cultivated plants.

Cultivation substrates with a poor ability to bind nutrients are often used in greenhouses and nursery-gardens. We investigate whether mycorrhiza can be established on plants in different types of cultivation substrates in organic and conventional cultivation systems through inoculation with mycorrhiza mushrooms in combination with reduced levels of nutrients. If it is possible to grow vegetables with mycorrhiza at lower fertilizer levels, both the fertilizer costs and the risk of nutrient loss is reduced. We also study presence and impact of mycorrhiza for plants grown in the open.

The sustainable society must be resource-efficient and organic wastes recycled as far as possible. During decomposition processes organic matter is degraded into simpler components that can be reused. The degradation process is different depending on the chemical composition of the material and the environment in which it takes place.

Biofertiliser produced in the biogas process is an example of an organic waste which is recycled when it is returned to the field. In our research, we investigate the possibility of using biofertilizer in other cropping systems such as hydroponics and algaculture. Organic waste is not limited to this but there is a wide choice of residues originating from e.g. food industry and forestry. The organisms which we use in our research are plants, algae and fungi.

In addition to recycling in order to achieve resource-efficiency, also health- and safety issues are important aspects. Consideration must be given to harmful substances, e.g. heavy metals and persistent substances such as certain pesticides, which can be present in the organic matter and thus accumulates to harmful levels. In the research we do on organic waste products, and how they can be recycled, the aspect of safety and risk of accumulation is always included.

We have studied the uptake of heavy metals, like cadmium, in several plant species like potato, carrots and lettuce. As the solubility of cadmium in the soil solution increases at low pH, the choice of N-fertilizers in particular may affect the uptake of cadmium. We have investigated the influence of nitrogen form on cadmium uptake in both nutrient solution and field experiments. 

Calcium deficiency in potato tubers may result in impaired quality such as internal brown spot, hollow heart and an increased sensitivity for blue spot. Soils usually contain high amounts of calcium, but in forms unavailable to the tubers. To be able to find the calcium strategy that gives the highest calcium concentration in tubers, we grow potatoes both in field and pot trials. We also study the interaction between calcium and boron since the uptake of these essential substances is affected by each other.

The LED-technology is developing rapidly and has in recent years become more attractive for use in greenhouse crop production. The freedom of choice regarding the spectral distribution of the light and the design of the fittings opens up new possibilities for the use of light within protected horticulture. In the current projects the LED-technology is adapted for use in greenhouse horticulture. We are developing light strategies for reduced consumption of energy and chemical growth retardants.