|MILLER, STEPHEN - Retired ARS Employee|
|Hott, Chris - Chris|
Submitted to: Journal of Applied Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2015
Publication Date: 10/26/2015
Citation: Miller, S., Tworkoski, T., Hott, C.F. 2015. Shade effects on growth, flowering, and fruit of apple. Journal of Applied Horticulture. 17(2):101-105.
Interpretive Summary: Light is a critically important resource for apple tree growth and fruit productio, but in orchards, self-shade within the canopy and from nearby trees can be detrimental to yield. In this experiment, mature apple trees were exposed to whole-tree shading for the whole-day or half-day during the morning or afternoon. Yield of trees grown in full shade, morning shade, and afternoon shade decreased, respectively, to 4, 36, and 55 percent of trees grown with no shade. Morning shade may have adversely affected photosynthesis at a time of day that was most conducive to higher rates of photosynthesis. Training systems that reduce shading, particularly in the morning, should help sustain yield.
Technical Abstract: Light is a critical resource needed by plants for growth and reproduction. A major portion of the apple (Malus xdomestica Borkh.) tree’s canopy is subjected to shade during most daylight hours each day and such shade may affect productivity. The current research determined effects of morning, afternoon, and all-day shading on processes that are significant to orchard productivity. In 1996, 'Ginger Gold'/M.9 apple trees were planted in the field near Kearneysville, WV and shade treatments were imposed from 2002 to 2005. Trunk and branch growth were reduced consistently by morning shade (MS) compared to no shade (NS) and full shade (FS), and afternoon shade (AS) had intermediate effects. Total branch growth from 2002 to 2005 was 164, 168, 145, and 157 cm for FS, NS, MS, and AS, respectively. Although shade affected yield inconsistently from year-to-year, total yield from 2002 to 2005 was 7.8, 201.6, 72.5, and 110.6 kg/tree for FS, NS, MS, and AS, respectively. Time of shading clearly affected yield with full shade causing the greatest reduction, followed by partial shade treatments, MS and AS. Concentrations of soluble carbohydrates, particularly sorbitol, were greater in leaves of AS compared to MS. It is postulated that MS may have adversely affected photosynthesis at a time of day that was most conducive to high net assimilation. Planting and training apple trees to minimize shade, especially morning shade, may benefit orchard productivity.