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Towards Grower-friendly Apple Crop Thinning by Tree Shading

Widmer, A.; Kockerols, K.; Schwan, S.; Stadler, W. and Bertschinger, L. (2008) Towards Grower-friendly Apple Crop Thinning by Tree Shading. In: Boos, Markus (Ed.) Ecofruit - 13th International Conference on Cultivation Technique and Phytopathological Problems in Organic Fruit-Growing: Proceedings to the Conference from 18thFebruary to 20th February 2008 at Weinsberg/Germany, pp. 314-318.

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Summary

Light management with shading nets, which reduce sunlight by 74%, might be an
alternative to chemicals commonly used for thinning on apple trees. To study the effect of
shading on crop load and fruit quality, trials were conducted in field experiments with the
cultivars Golden Delicious and Elstar in 2006. Trees were either covered 25 days after full
bloom (DAFB) with a net during three days, or until the peak of fruit fall, observed after
seven days shading. Ideal time length for optimal crop yield was seven days shading for
Elstar and three days shading for Golden Delicious. Alternate bearing could be decreased
as flower initiation counts the following year showed. In both experiments, inner quality of
fruit such as sugar and firmness showed good values at optimal shading duration
compared with chemical + hand thinning. In 2007, a second field trial was conducted with
cultivars Golden Delicious and Topaz to study the time period for shading in further detail.
Shading was done for three days at 19, 26 and 33 DAFB using two net types (three- and
two-meter-net width, covering the trees entirely or only down to 50 cm above ground). For
Golden Delicious, shading after 19 and 26 days reduced fruits per 100 flower cluster to the
same extent as with chemical + hand thinning. There was no difference between the two
net types. For Topaz, shading after 19 days showed the best results. Regarding inner
quality of both cultivars, only sugar content for Golden Delicious could be significantly
improved after 19 and 26 days shading. Further analyses are still under way (e.g. for
acidity).
This study is part of an effort for increasing European consumption with fruit from
sustainable production systems, the ISAFRUIT-EU-project.


EPrint Type:Conference paper, poster, etc.
Type of presentation:Paper
Keywords:Thinning, Shading net, Flower initiation, Crop load, Fruit quality
Subjects: Crop husbandry > Crop health, quality, protection
Crop husbandry > Production systems > Fruit and berries
Research affiliation: International Conferences > 2008: Ecofruit
Related Links:http://www.ecofruit.net
Deposited By: Tagung, Ecofruit
ID Code:13738
Deposited On:24 Jul 2008
Last Modified:12 Apr 2010 07:37
Document Language:English
Status:Published
Refereed:Peer-reviewed and accepted

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