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Article

Mechanical Crop Load Management (CLM) Improves Fruit Quality and Reduces Fruit Drop and Alternate Bearing in European Plum (Prunus domestica L.)

1
INRES-Horticultural Science, University of Bonn, D-53121 Bonn, Germany
2
Agricultural Engineering Department, University of Bonn, D-53121 Bonn, Germany
*
Author to whom correspondence should be addressed.
Horticulturae 2020, 6(3), 52; https://doi.org/10.3390/horticulturae6030052
Received: 17 July 2020 / Revised: 24 August 2020 / Accepted: 26 August 2020 / Published: 2 September 2020
(This article belongs to the Special Issue Feature Papers in Horticulturae)
(1) Background: With ca. 10 million tons of annual production worldwide, the plum (Prunus ssp.) ranks as a major fruit crop and can suffer from small fruit size, premature fruit drop and alternate bearing, which are addressed in this paper using a range of crop load management (CLM) tools. (2) Methods: Sixty 10-year-old European plum cv. “Ortenauer” trees on dwarfing St. Julien INRA GF 655/2 rootstock (slender spindle; 4.25 × 2.80 m) in a commercial orchard near Bonn (50°N), Germany, were thinned in 2 years and flower intensity assessed in the following year. Thinning was performed either mechanically (type Bonn/Baum) or chemically, with ATS (ammonium thiosulfate) or ethephon (Flordimex), or by a combination of mechanical and chemical methods, to improve fruit quality and the proportion of Class 1 fruit. Adjacent un-thinned trees served as controls. (3) Results: Natural fruit drop in June was reduced from 290 fruits per tree in the un-thinned controls to 265 fruits after ATS blossom treatment, and to 148 fruits after mechanical thinning at 380 rpm at a 5 km/h tractor speed at full bloom. The un-thinned control trees developed a large number of small, undersized fruits. The yield of Class 1 fruits increased per tree from 47% in the un-thinned controls, up to 69% after crop load management. Sugar content and fruit firmness were unaffected. (4) Conclusions: The study has shown that fruit quality (i.e., fruit size) and financial returns could be improved by either mechanical (380 rpm at 5 km/h) or chemical thinning, or a combination of both. View Full-Text
Keywords: European plum (Prunus domestica L.); alternate bearing; crop load management (CLM); fruit drop; fruit quality; mechanical thinning; reducing chemical input; sustainability European plum (Prunus domestica L.); alternate bearing; crop load management (CLM); fruit drop; fruit quality; mechanical thinning; reducing chemical input; sustainability
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MDPI and ACS Style

Lammerich, S.; Kunz, A.; Damerow, L.; Blanke, M. Mechanical Crop Load Management (CLM) Improves Fruit Quality and Reduces Fruit Drop and Alternate Bearing in European Plum (Prunus domestica L.). Horticulturae 2020, 6, 52. https://doi.org/10.3390/horticulturae6030052

AMA Style

Lammerich S, Kunz A, Damerow L, Blanke M. Mechanical Crop Load Management (CLM) Improves Fruit Quality and Reduces Fruit Drop and Alternate Bearing in European Plum (Prunus domestica L.). Horticulturae. 2020; 6(3):52. https://doi.org/10.3390/horticulturae6030052

Chicago/Turabian Style

Lammerich, Sebastian, Achim Kunz, Lutz Damerow, and Michael Blanke. 2020. "Mechanical Crop Load Management (CLM) Improves Fruit Quality and Reduces Fruit Drop and Alternate Bearing in European Plum (Prunus domestica L.)" Horticulturae 6, no. 3: 52. https://doi.org/10.3390/horticulturae6030052

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