A Method for Quantifying Whole-tree Pruning Severity in Mature Tall Spindle Apple Plantings

in HortScience

Pruning is the cutting away of vegetation from plants for horticultural purposes. Pruning is known to reduce apple tree size, increase fruit size and quality, and decrease yield. Methods for studying the effects of varying degrees of severity of pruning on a whole-tree basis have used qualitative descriptions of treatments rather than repeatable whole-tree quantitative metrics. In this study, we introduce a pruning severity index calculated from the sum of the cross-sectional area of all branches on a tree at 2.5 cm from their union to the central leader divided by the cross-sectional area of its central leader at 30 cm from the graft union. This limb to trunk ratio (LTR) was then modified by successively removing the largest branches of ‘Buckeye Gala’ to achieve six severity levels ranging from LTR 0.5 to LTR 1.75, with lower values representing more extreme pruning with less whole-tree limb area relative to trunk area. Pruning treatments were applied for three consecutive years and tree growth and cropping responses were observed for the first 2 years. With increasing pruning severity the following characteristics increased after seasonal growth: number of renewal limbs, number of shoots, shoot length, number of shoot leaves, shoot leaf area, final fruit set, fruit size, yield of large fruit, crop value from large fruit, soluble solids, and titratable acidity. The following characteristics decreased: limb age, number of secondary limbs, number of spurs, number of spur leaves, spur leaf area, the ratio of spur leaf area to shoot leaf area, fruit count per tree, yield, yield efficiency, crop value from small fruit, overall crop value, and sugar:acid ratio. The LTR provides a measurable way to define and create different levels of pruning severity and achieve consistent outcomes. This allows a greater degree of accuracy and precision to dormant pruning of tall spindle apple trees. The use of the LTR to establish the level of pruning severity allows the orchard manager to set crop load potential through regulation of the canopy bearing surface. This metric is also a necessary step in the development of autonomous pruning systems.

Contributor Notes

The authors gratefully acknowledge funding support from the USDA NIFA Specialty Crop Research Initiative (Grant no. 2012-51181-19878) and the State Horticultural Association of Pennsylvania, along with industry partners who provided project matching funds.

Corresponding author. E-mail: jrs42@psu.edu.

Article Sections

Article Figures

  • View in gallery

    The number of limbs removed per tree to obtain the six prescribed levels of pruning severity on ‘Buckeye Gala’ in the 3 years of the study. Limb to trunk ratio (LTR) is defined as the ratio between the summation of the limb cross sectional area for all limbs on the tree divided by the cross sectional area of the trunk at 30 cm above the graft union. Its values are the inverse of pruning severity with higher LTR values indicating less severe pruning.

  • View in gallery

    Renewal limbs per tree, counted at the end of the seasonal growth period as influenced by pruning severity [limb to trunk ratio (LTR)]. Renewal limbs are defined here as number of new limbs growing from the central leader in the growing season after pruning treatment. LTR is defined as the ratio between the summation of the limb cross sectional area for all limbs on the tree divided by the cross sectional area of the trunk at 30 cm above the graft union. Its values are the inverse of pruning severity with higher LTR values indicating less severe pruning.

  • View in gallery

    Average photosynthetically active radiation levels relative to ambient light measured 1.8 m from the ground for six levels of pruning severity in the first 2 years of the study. Limb to trunk ratio (LTR) is defined as the ratio between the summation of the limb cross sectional area for all limbs on the tree divided by the cross sectional area of the trunk at 30 cm above the graft union. Its values are the inverse of pruning severity with higher LTR values indicating less severe pruning.

  • View in gallery

    The influence of pruning severity [limb to trunk ratio (LTR)] on number of fruit harvested per tree and average fruit weight for the 2 years. LTR is defined as the ratio between the summation of the limb cross sectional area for all limbs on the tree divided by the cross sectional area of the trunk at 30 cm above the graft union. Its values are the inverse of pruning severity with higher LTR values indicating less severe pruning.

  • View in gallery

    The influence of pruning severity [limb to trunk ratio (LTR)] on crop value ($ per tree) for the 2 years of the study, and the percentage of crop value from large (>70 mm in diameter) fruit. LTR is defined as the ratio between the summation of the limb cross-sectional area for all limbs on the tree divided by the cross-sectional area of the trunk at 30 cm above the graft union. Its values are the inverse of pruning severity with higher LTR values indicating less severe pruning.

Article References

Commission Internationale de l-Eclairage1978Recommendations on uniform color spaces color difference equations and metric color terms. Suppl. No. 2 to Pub. No. 15. Commission Internationale de l-Eclairage Paris France

ElfvingD.C.ForsheyC.G.1976Growth and fruiting responses of vigorous apple branches to pruning and branch orientation treatmentsJ. Amer. Soc. Hort. Sci.101290293

FerreeD.C.SchuppJ.R.2003Pruning and training physiology p. 319–344. In: D.C. Ferree and I.J. Warrington (eds.). Apples: Botany production and uses. CABI Publishing Wallingford UK

ForsheyC.G.ElfvingD.C.1979Branch samples for yield and fruit size comparisons in appleHortScience14143144

ForsheyC.G.ElfvingD.C.StebbinsR.L.1992Training and pruning apple and pear trees. Amer. Soc. Hort. Sci. Alexandria VA

FumeyD.LauriP.É.GuédonY.GodinC.CostesE.2011How young trees cope with removal of whole or parts of shoots: An analysis of local and distant responses to pruning in 1-year-old apple (Malus ×domestica; rosaceae) treesAmer. J. Bot.9817371751

GardnerV.R.BradfordF.C.HookerH.D.1922The fundamentals of fruit production. McGraw Hill New York NY

HoweG.H.1923Growth and yield of apple trees pruned in various ways p. 4–10. Ch. 1. Little versus much pruning. N.Y. Agr. Expt. Sta. Bul. 500. NYAES New York NY

JonkersH.1982Testing Koopmann’s rules of apple tree pruningSci. Hort.16209215

KonT.M.SchuppJ.R.2013Thinning tall spindle apple based on estimations made with a hand-thinning gaugeHortTechnology23830835

LaksoA.N.1984Leaf area development patterns in young pruned and unpruned apple treesJ. Amer. Soc. Hort. Sci.109861865

LauriP.-E.WillaumeM.LarriveG.LespinasseJ.-M.2004The concept of centrifugal training in apple aimed at optimizing the relationship between growth and fruitingActa Hort.6363542

LittellR.C.MillikenG.A.StroupW.W.WolfingerR.D.SchabenbergerO.2006SAS for mixed models. 2nd ed. SAS Inst. Cary NC

LittellR.C.StroupW.W.FreundR.J.2002SAS for linear models. 4th ed. SAS Inst. Cary NC

LombardP.B.CallanN.W.DennisF.G.LooneyN.E.MartinG.C.RenquistA.R.MielkeE.A.1988Towards a standardized nomenclature, procedures, values and units in determining fruit and nut tree yield performanceHortScience23813817

MariniR.P.2003Peach yield, fruit weight, and crop value are affected by number off fruiting shoots per treeHortScience38512514

MariniR.P.BardenJ.A.1982aGrowth and flowering of vigorous apple trees as affected by summer or dormant pruningJ. Amer. Soc. Hort. Sci.1073439

MariniR.P.BardenJ.A.1982bYield, fruit size, and quality of three apple cultivars as influenced by summer or dormant pruningJ. Amer. Soc. Hort. Sci.107474479

MikaA.1986Physiological responses of fruit trees to pruningHort. Rev8337378

MillikenG.A.JohnsonD.E.2002Analysis of messy data. Vol. III: Analysis of covariance. Chapman and Hall/CRC New York NY

MyersR.H.1990Classical and modern regression with applications. 2nd ed. PWS-Kent Boston MA

RobinsonT.L.2003Apple orchard training systems p. 345–408. In: D.C. Ferree and I.J. Warrington (eds.). Apples: Botany production and uses. CABI Publishing Wallingford UK

RobinsonT.L.HoyingS.A.ReginatoG.H.2006The tall spindle apple production systemNew York Fruit Qrtly.1422128

SeleznyovaA.N.DayatilakeG.A.WatsonA.E.TustinD.S.2013After initial invigoration by heading, young pear trees show reduction in axis vigor and increased propensity to flowerFunct. Plant Biol.403443

WertheimS.J.1968The training of the slender spindle. Proefstation voor de Fruiteelt Wilheminadorp Publ. No. 7. p. 7

WestwoodM.N.RobertsA.N.1970The relationship between trunk cross-sectional area and weight of apple treesJ. Amer. Soc. Hort. Sci.952830

Article Information

Google Scholar

Related Content

Article Metrics

All Time Past Year Past 30 Days
Abstract Views 118 118 66
Full Text Views 59 59 26
PDF Downloads 13 13 5