Organic cropping systems for vegetable production
The objective of this project is to contribute to our understanding of the effects of organic cropping systems on vegetable quality and on the environment. Producing food of a better quality and in a more environmentally friendly way are some of the main goals of organic farming. Sales and public support for organic farming are based on the expectation that these things are achieved. In order to increase the support for organic farming, there is a clear need to show that the goals are actually achieved.
This is difficult to document, as the results of many years of research have shown. This is difficult for two main reasons: 1) effects on quality and on the environment are highly complex and thus difficult to study, and 2) organic farming is not just one well defined cropping system; within the rules for organic farming, many very different systems can be made. Organic farming is developing and changing, and this can make consumers and politicians question whether it is moving away from its original ideas.
To answer some of these questions, we will compare four different cropping systems for vegetable production, one conventional and three organic systems. All of the organic systems will comply with the regulations of organic farming, but in very different ways. One system will be much like the conventional, though using organic fertilizers and no pesticides. In the second organic system, green manure or catch crops will be grown in the autumn as often as possible. In the last system, stripes of the green manure will be left at soil tillage, to grow as intercrops between the rows of the vegetable crops, in order to improve the conditions for organisms involved in natural regulation.
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Together, these systems represent large variations in growth conditions for the crops. There are systems with or without use of chemical inputs, but also large variations in the biological surroundings, which the crops will meet in terms of insect pests, fungi, beneficial organisms and other plants. There will also be large differences in nutrient balances and the availability of plant nutrients, creating effects on the environment and on crop quality.
Vegetable quality will be studied in a number of ways, to cover a range of this highly complex question. We will measure contents of secondary metabolites in cabbage, lettuce and carrot, focussing on metabolites, which are known to affect human health. We will measure quality parameters important for product marketing, but also taste and volatile aroma compounds. Aspects of product storability will be measured. Carrots from the different cropping systems will be stored, and the interactions between their physiology, metabolic activity, contents of secondary metabolites and the development of fungal diseases will be studied. With the disease liquorice rot, detailed studies of the interactions during the storage time will be made.
To get an even broader picture of the effect of cropping systems on the crop, we will examine them with the methods of proteomic analysis. These methods show that proteins are expressed in the plants, and for which proteins the level of expression is affected by the cropping methods. Subsequently, the function of the responding proteins can be elucidated. The results of the proteomic analysis will supplement the more specific measures of quality obtained by the other methods.
Natural regulation mechanisms in the field will be studied with a focus on insect pathogenic fungi in the soil, and prevalence and diversity of insects. We will examine how the insect pathogenic fungi interact with pest insects. By studying this in the four systems, we can see how the use of pesticides and inorganic fertilizers, growing of autumn green manures or intercropping affects natural regulation.
In addition the effects of the cropping systems on nutrient balances, root growth and effect on nitrogen leaching losses will be studied. The conventional and two of the organic systems are already "well developed" systems, but the system with intercropping is not. This system holds many promising possibilities, but also problems. Therefore, we will work on developing this system further. We will study the yield and cost of the different systems, and compare this to their effects on quality, biodiversity, natural regulation and the environment. In this way we will illustrate the cost of the systems, and the tradeoffs between quality, environment and production economy, which are likely to be found. While many of the quality measures are specific, we get many different measures. We will use this to study whether more general effects on crop composition and quality can be found.
Project title
Organic cropping Systems for Vegetable production - product Quality, natural Regulation and Environmental effects (VegQure)
Project leader
Kristian Thorup-Kristensen, Head of research unit, Faculty of Agricultural Sciences, University of Aarhus, Dept. of Horticulture, Kirstinebjergvej 10, DK-5792 Aarslev. Phone: +45 8999 3228. Fax: +45 8999 3494. E-mail: ktk@agrsci.dk
Project participants
Lars Porskjær Christensen, Hanne Lakkenborg Kristensen, Dorte Bodin Dresbøll and Ulla Kidmose (Faculty of Agriculture, University of Aarhus), Peter Mose Larsen and Stephen J. Fey (University of Southern Denmark), Dan Funck Jensen, Jørgen Eilenberg, Birgit Jensen, Inge Knudsen, Nicolai Vitt Meyling, Holger Philipsen and Christina Wolsted (Faculty of Life, University of Copenhagen)
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