Use of physiological principles to guide precision orchard management and facilitate increased yields of premium quality fruit

K.C. Breen, D.S. Tustin, B.M. van Hooijdonk, C.J. Stanley, C. Scofield, J.M. Wilson, M.J. Oliver, G.A. Dayatilake
Deciduous fruit producers sell products into competitive markets where consumers make choices on visual appeal, pricing and experience. Although orchard income is linked with yield, it may be considerably improved by ensuring that every fruit grown is of premium quality. Environmental conditions and management decisions at both the seasonal and orchard-life time-scales play a large role in fruit quality. The ability of trees to capture photosynthetically active radiation is the basic function regulating productivity. On an orchard basis, yield is closely correlated with orchard light interception. However, if light penetration into the canopy falls below a critical minimum, productivity and fruit quality are compromised. This not only reduces overall yield, but greatly increases fruit quality variability and ultimately compromises consumer experiences. Light interception and penetration are functions of orchard and canopy design. Within-canopy light relations in deciduous trees and vines have been a discussion topic for at least 400 years, and orchard design and pruning for over 2.5 centuries. However, in today's commercial sector, orchard design and tree pruning remain highly subjective topics and there are few metrics to assist growers and designers of automated pruning technology, to seek and achieve planned, measurable outcomes. Consequently, pruning by hand is regarded an art, and non-quantitative automated pruning risks contributing to the problem not the solution. Our research illustrates that applying physiologically-based quantifiable metrics to both current and new tree canopy designs (branches per vertical metre, buds per branch cross-sectional area, planar cordons), can increase apple and stonefruit yields to ~80-100% more than current commercial expectations. These metrics also enable GROTERDAN80% of fruit produced at such elevated yields to achieve the highest internal and external quality grades. Removing subjectivity in orchard systems and tree canopy management will greatly improve consistency of hand pruning and greatly facilitate the development of “intelligent” automated pruning.
Breen, K.C., Tustin, D.S., van Hooijdonk, B.M., Stanley, C.J., Scofield, C., Wilson, J.M., Oliver, M.J. and Dayatilake, G.A. (2021). Use of physiological principles to guide precision orchard management and facilitate increased yields of premium quality fruit. Acta Hortic. 1314, 241-252
DOI: 10.17660/ActaHortic.2021.1314.31
apple, apricot, cherry, stonefruit, training system, canopy management, pruning, light interception, irradiance, artificial spur extinction

Acta Horticulturae