Annual report 2002 LBI organic fruit growing research

Overview of projects, project results, funding bodies and partners in 2002 and plans for 2003 Including: SOIL MANAGEMENT * Evaluation of leaf analysis in organic fruit growing as a tool for measuring the uptake of nutrients: Consultants and researchers exchanged practical experiences and the LBI hopes to work with target values. * Impact of sulphur stress: The fruit quality seemed to be better in the reduced sulphur treatment (27 kg /ha instead of 60 kg /ha after flowering). * Fertilisation: In a late summer fertilisation trial with Elstar, trees fertilised late summer/autumn have a higher nitrogen content in the bud the following spring. And fertilising just before winter leads to increased growth of weeds in the next season. * Ground cover: The key to white clover undergrowth is to ‘do it properly or not at all’. It is difficult for an organic grower to restore undergrowth which has been invaded by grasses to bare earth. Undergrowth is definitely not the answer for fruit growers who have any difficulty with mechanical weeding. The management of ground cover requires at least as much mechanisation as the bare tree strip. REGULATING GROWTH AND CROP * Steps to counter biennialism in Elstar: A trial was set up at three orchards combining various measures: thinning or not thinning with two or three applications of lime sulphur, adapted pruning, 3 levels of fruit bearing (30, 40, 50 tonne/ha) and early or late manual thinning. This trial should demonstrate the relative significance of the various measures. Flowering will be evaluated in the spring of 2003. * Fruiting spur pruning in Elstar: To obtain better insight into the effect of different pruning methods three pruning treatments were used: standard pruning, removal of an extra large amount of fruiting spurs, and removal of extra fruiting spurs but sparing smooth one-year-old shoots. The production of the trees has been estimated and the blossom will be evaluated in the spring of 2003. * Effect of thinning times, fertilisation and bearing on regularity of production and fruit quality in Elstar: Ripening was delayed by the high nitrogen dose and associated higher acid content. Despite the late ripening the firmness was still lower, the calcium content lower and the nitrogen content higher. All three factors pro- duce a clear deterioration in quality. On the other hand, the sugar and acidity were higher in this case, but both these values fall within the target band. The trial will continue in 2003 CANKER * Administering calcium hydroxide against Cancer through the sprinkler irrigation system: Despite its effectiveness, sprinkling with calcium hydroxide cannot as yet be generally recommended for practical application. All the difficulties stem from the fact that the agent does not really dissolve, and the suspension formed very rapidly settles out. FRUIT QUALITY * Optimum picking time for Santana: Santana is a relatively new variety, and further investigation is required into optimising cultivation and storage. The apples only developed their full flavour when picked some time after the point of physiological ripeness. * Sprinkling to combat sunscald: By sprinkling under specific conditions an average of 1.38 fruits per tree was protected from sunscald. Per hectare sprinkling on these three days yielded around € 621 per ha. (Assuming: 3000 trees/ha, 6 fruits/kg, price € 1.10 or € 0.20 for industrial use). * Rot resistance test: The Louis Bolk Instituut is attempting to develop a test for the evaluation of the natural resistance of the fruit. This demonstrates, for example that apples with a high nitrogen content have more and larger areas of rot than apples with a lower nitrogen content. * Prospects offered by calcium chloride (CaCl2 ) before or after harvest: A pilot experiment was carried out on a farm to look into the prospects of spraying with CaCl2 before the harvest or rinsing with CaCl2 after harvest to reduce fruit rot. Neither treatment led to a reduction in fruit rot, but rather to an increase. * International association for ‘Organic Food, Quality and Health’ (FQH): The purpose of the group of researchers and traders brought together under the FQH banner is to develop a new concept of quality based on life processes and to select and further develop relevant methods of measurement

Annual report 2003 LBI organic fruit growing research: including plans for 2004

Our objectives in soil management research combine a number of issues: soil fertility, production, fruit quality, growth regulation, prevention of night frost damage, leaf decomposition (scab) and practical feasibility. This will result in different regimes of weed control, fertilisation, foliar feeding and watering for each plot. The evaluation criteria remain particularly difficult to assess. The proposed revised edition of the soil book (LF39) is combined with the final publication of the regulation project which appeared in de winter of 2003 as a hand-book “Biologische Appels en Peren – teeltmaatregelen voor kwaliteitsfruit-” (Organic apples and pears – cultivation measures for quality fruit) (LF75, ed. Joke Bloksma). Time after time our research shows that good crop regulation is the basis for a quality crop. This applies to all varieties, but Elstar requires special attention because of its susceptibility to biennialism. This last year lime sulphur was available for controlling scab. This enabled us to benefit from the side effects of blossom thinning. Trials are still being run internationally on new thinning agents for organic growing. To date however there is no prospect of a more efficacious agent than lime sulphur without the undesirable side effects. This begs the question of how much more energy should be spent on this research. We take the view that there are other areas to be developed which are essential to good crop regulation. There is scope for further development of an adapted pruning method which very specifically anticipates the prospects for the coming year. Pruning also seems to be important for the new variety Topaz, while we still need to ensure that we get sufficient fruit on the tree. Many trials in which we monitor flowering and bearing rates show time and again that Elstar trees with slightly excessive growth levels have much poorer flowering rates in the following year, even where there is no excessive vigour. Thus much attention still needs to be paid to growth regulation. LaMi is running a project in Utrecht province in which demonstration trials are being carried out to encourage the use of calcium hydroxide in conventional fruit growing. As advisor the LBI contributed its experience from the projects in previous years. Infection of a fruit by fungi or disease depends among other things on the resistance of the fruit. The resistance of a product to fungi, pests and diseases is a parameter for the quality of the product. The Louis Bolk Institute is attempting to develop a test for the evaluation of the natural resistance of the fruit, in which the apple can demonstrate how well or poorly a fruit rot fungus (Botrytis c.) can spread in the flesh of the fruit. The LBI has previous experience with self-disintegration tests. The problems here were the replicability and the unknown sources of infection. Fruit quality is an increasingly important aspect of fruit production. The supermarkets in particular continually raise the standards required for (external) product quality. Using organic growing methods it may not always be possible to meet the high standards for external quality. This means that the internal quality will become increasingly important. LBI is currently running 2 projects on apple quality: “Classy Apples in the Chain” (2001-2004) which involves monitoring and working with partners in the chain to reduce the quality gap between supply and demand and also reduce the distance between the start and end of the chain. The second project, “Parameters for Fruit Quality” (2001-2003) addresses more fundamental issues about suitable quality parameters for organic production. (See also 2002 report)

Differences in leaf litter, ascospore production and infection of pear scab (Venturia pirina) in Dutch organic orchards

The last two years we measured the amounts of leaf litter and ascospore production per unit of leaf litter area in 7 organic pear orchards throughout the Netherlands. In one of the orchards, adapted managements strategies were implemented two years ago, being grass/clover that is grown as ground cover on the tree-strip, and organic cattle-manure that replaces chicken manure pellets, in order to stimulate the earthworm population and change the palatability of the leaf litter. First results indicate large differences between orchards in percentage of ground covered by dead leaves at the time of major ascospore infections, but also in number of ascospores per cm 2 leaf litter and in resulting potential ascospore dose. We used these data, together with weather data (temperature, rainfall), in a simple multivariate analysis to gain insight in the dynamics of the system. In 2010, 85 % of the variation in pear scab was explained with a model with rainfall during summer and the amount of asco sores per unit of leaf area. In 2011, 81 % of the variation was explained by a model with the amounts of ascospores per unit leaf area and the potential ascospore dose. In the adapted management experiment we measured no changes in leaf litter in the treatments yet. We discuss that our first results show that, to a limited degree, leaf litter was indeed important for the scab epidemic in 2011, whereas in 2010 the high amount of rainfall in the second part of the growing season must have led to a high conidial infection pressure. Surprisingly, in both years ascospore number per unit leaf area was of more importance than leaf litter area or potential ascospore dose. This raises questions on for example the correlation with branch-lesions that we did not measure, and whether the number of ascospores per unit of leaf litter is a direct or an indirect factor that steers the scab incidence in the orchards

Classy Apple project' to reduce the quality gab between suppley and demand of organic apples

LBI has started a project (2001-2003) to explore and reduce the bottlenecks and obstacles to fruit quality in the various market sectors by working with fruit growers, traders, extension services and research institutes together

Parameters for apple quality - 2 - and the development of the ‘inner quality concept’ 2001-2003

We found clear correlations between management measures, tree characteristics and fruit characteristics. This means that growers can regulate apple quality during the growing season. On the basis of the two apple experiments, we can distinguish respective sets of growth and differentiation parameters and evaluate them in the light of conventional fruit cultivation science. Our results have little new value for fruit growing in practice, however. The value of our research lies in the approach developed to draw up a quality concept and the way in which we can apply this concept to crops about which little knowledge exists regarding the relationship between management measures, crop characteristics and product quality characteristics. Our research also offers a method to validate experimental parameters

Controlling broad-leaved dock (Rumex obtusifolius) in grass clover mixtures

This article describes three experiments on the control of broad-leaved dock. Experiment 1: Dock seeds were ensiled in grass silages of different dry matter percentages; 23, 34 and 60% respectively. All silages showed a decline of seed vitality in time. Grass clover with dock seeds should be ensiled at a low dry matter percentage or remain in the silage bin for a longer period than 8 weeks. Experiment 2: In a potassium fertilisation trial on grass clover the development of dock was followed. After two years of potassium fertilisation, the number of dock and the root mass was not significant different between the fertilised and the unfertilised plots. It is concluded that potassium fertilisation at a low potassium status does not positively influence the dock development. Experiment 3: In a resown grass clover, dock seedlings were cut at three frequencies; 2, 4 and 6 weeks. After 3 months the number of seedlings had decreased the same in all treatments. However the root biomass of the seedlings was significantly affected. It is concluded that frequent cutting has a negative effect on root biomass but should be practised for a longer period than 12 weeks to have an effect on seedling numbers

Leaf series as an image of shoot growth

The sequential leaves of the shoot show a 'biography' of the growing season. The shape of the leaves shows the conditions under which the leaves are formed. This method was developed to help answer the questions of fruit growers and researchers. Fruit cultivation researchers need to record vegetative development during the course of the growing season. The quality of the shoots with the leaves determines the 'production capacity' of the tree and the quality of the fruit and the buds for the next year

Informatie en literatuur voor de biologische fruitteelt : Information and literature for organic fruit growing

Informatie over organisaties voor de biologische fruitteelt in diverse landen. Verwijzingen naar onderzoek

Biologisch-dynamische Qualität im Obstbau. Erkennen, erzeugen und vermitteln

Das Projekt bietet ein schönes Beispiel, bei dem sich die Betriebsmerkmale so deutlich in den Baum- und Fruchtmerkmalen widerspiegeln. Die Bildschaffende Methoden waren eine gute Hilfe um die Zusammenhang zwischen Baum, Frucht und Kulturmaßnahmen zum Ausdruck zu bringen. Die Arbeit an den Versuchsfragen hat gezeigt, dass Bäume eine gewisse Vitalität brauchen, um eine gute Fruchtqualität zu erzielen. Dieses ist möglich durch die Anwendung allgemein bekannter Schnitt- und Ausdünnungsmaßnahmen , die auf einen vitalen Baum mit beherrschter Wuchskraft abzielen. Die unterschiedlichen Pflanzabstände mit den entsprechenden Unterschieden im Wachstumsverhalten lassen als noch keine eindeutiges Unterschied sehen. Darum ist es sinnvoll, die Beobachtungen der Varianten fortzusetzen, um diesen Zusammenhang weiter zu erforschen

Effects of beetroot-Vinasse on ascospore formation of Venturia pirina in a one-year field trial on an organic conference orchard (presentation)

In a one year experiment in an organic Conference orchard, a single treatment with 500 l/ha beetroot Vinasse was tested as a means to reduce the formation of ascospores by Venturia pirina on the leaf litter