ISHS Acta Horticulturae 1346: XII International Symposium on Integrating Canopy, Rootstock and Environmental Physiology in Orchard Systems
Effects of planting density on light interception and distribution, physiological and agronomic performance of ‘Gala’ apple orchards |
| Authors: | M. Leão de Sousa, M. Gonçalves |
| Keywords: | tree density, canopy radiation, physiology, photosynthesis, reflectance, yield |
| DOI: | 10.17660/ActaHortic.2022.1346.42 |
| Abstract:
Portuguese apple orchards located in the central west region, registered as ‘Maçã de Alcobaça’ protected geographical indication (EC 1107/96), have grown under managing practices according to the principles of precision and integrated production (DGADR, 2011). However, without a stabilized model regarding planting densities. Four orchards of Malus × domestica Borkh ‘Gala Schniga’, grafted onto ‘M.9’ rootstock, with 1,481 (4.5×1.5 m – orchard O1), 3,704 (3.0×0.9 m – O2), 3,861 (3.7×0.7 m – O3) and 4,762 (3.5×0.6 m – O4) trees ha‑1, planted in 2004 (O1), 2015 (O3 and O4) and 2016 (O2), were studied to compare light interception and distribution, photosynthesis, stomatal conductance, intrinsic and instantaneous water use efficiency (WUE), specific leaf area (SLA), reflectance parameters, yield, fruit distribution per position and harvest. Orchards O4 and O2 intercepted more light at solar noon, with maximum intercepted fractions near 0.50 and 0.45, respectively. The lowest canopy volume (8,781 m3 ha‑1) of O3 was reflected on a maximum intercepted fraction similar to O1 at solar noon (below 0.35). Leaves from O1 and O3 showed the highest photosynthetic rates and stomatal conductance in outside leaves at 1,500 and 150 µmol m‑2 s‑1. Leaves from O4 showed the best intrinsic and instantaneous WUE, SLA at the beginning of the season, normalized difference vegetation index (NDVI), maximum quantum yield of the PSII photochemistry, and performance index (PIabs). Orchard O4 had the highest productivity (113 t ha‑1). Average fruit weight and amount of fruits from the first harvest were also higher in O4 and O2 due to more light exposed surface area. On the contrary, O1 had a higher fruit number per tree and smaller fruit weight, although high productivity. This work pretends to clarify the most appropriate range of tree densities to use in modern orchards, benefits, and special care in high density orchards management. | |
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