Improving the Productivity, Quality, and Storability of ‘Katja’ Apple by Better Orchard Management Procedures

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  • 1 Faculty of Landscape Planning, Horticulture and Agricultural Sciences, The Swedish University of Agricultural Sciences, P.O. Box 44, SE-230 53 Alnarp, Sweden

This 4-year study at the Kivik research station, southeastern Sweden (≈55°N), investigated optimal orchard management procedures to improve tree growth, yield, fruit quality, and storability in the important early season apple cultivar ‘Katja’. Two procedures (one standard, one novel) were applied within pruning, weed control, fertigation, and thinning, yielding a total of 16 different combinations (treatments). Tree vegetative growth, yield, fruit size, fruit color, firmness, soluble solids concentration, malic acid, nitrogen and calcium content, and percentage fruit with storage rot (Pezicula malicorticis) were evaluated for all 16 treatments. Changing to the novel alternative in only one or two of the areas did not produce significant improvements in all investigated parameters. The optimal treatment consisted of radical winter pruning + summer pruning (novel), bark mulching (novel), fertigation with 0.13 g N (standard), and hand thinning after full bloom (novel).

Abstract

This 4-year study at the Kivik research station, southeastern Sweden (≈55°N), investigated optimal orchard management procedures to improve tree growth, yield, fruit quality, and storability in the important early season apple cultivar ‘Katja’. Two procedures (one standard, one novel) were applied within pruning, weed control, fertigation, and thinning, yielding a total of 16 different combinations (treatments). Tree vegetative growth, yield, fruit size, fruit color, firmness, soluble solids concentration, malic acid, nitrogen and calcium content, and percentage fruit with storage rot (Pezicula malicorticis) were evaluated for all 16 treatments. Changing to the novel alternative in only one or two of the areas did not produce significant improvements in all investigated parameters. The optimal treatment consisted of radical winter pruning + summer pruning (novel), bark mulching (novel), fertigation with 0.13 g N (standard), and hand thinning after full bloom (novel).

‘Katja’ is a commercially important early season apple cultivar in Sweden. Difficulties such as very weak growth, rapid quality deterioration, and low fruit storage potential limit growers' ability to meet quality standards set by markets (http://www.algonet.se). These problems could be alleviated through better understanding of the close relationships between cultural practices and fruit storability (Tromp, 2005).

Pruning intensity, time, and method have varying effects on apple quality at harvest and during storage (Tomala, 1997; Wertheim, 2005). Winter pruning improves tree growth, fruit coloration, acidity, sugar content, and storability and increases fruit weight (Marini and Barden, 2004; Tahir et al., 2007). Summer pruning further improves fruit coloration and size but decreases yield and causes poor fruit storability (Fathi and Mukhtar, 1998; Goldschmidt, 1997; Tromp, 2005). Covering the soil surface in orchards instead of using herbicides can prevent weeds, change soil environmental conditions, improve availability of nutrients to trees, enhance vegetative growth, increase yield, and improve fruit storability (Rubauskis et al., 2002; Tahir et al., 2005). However, in some cases, soil covering can decrease fruit yield and sugar content (Fausett and Rom, 2001). Fertigation systems need careful adjustment, because higher nitrogen levels or excess water supply can cause poor fruit storability (Meheriuk et al., 1996; Rubauskis et al., 2002). Fertilization and irrigation normally increase trunk cross-sectional area and yield (Ghosh et al., 2004; Jadczuk et al., 2001). The international trend for organic cultivation practices rather than chemical has renewed interest in hand thinning (Pretorious et al., 2004). In most cases, thinning increases fruit size (Marini, 2004; Tomala, 1997), firmness, and sweetness (Basak, 1999; Bergh, 1990) and improves superficial color (Link, 2000). Although some studies report no visible effects of thinning on fruit storability (Krzewinska et al., 2002), others report a tendency for decreased storage potential related to thinning (Wójcik et al., 2001) and decreased yield (Basak, 1999).

Most studies relating apple fruit quality to orchard management procedures involve individual testing of each practice. This study sought to improve ‘Katja’ apple quality and storability by combining different management practices, namely application of bark mulch, pruning, hand thinning, and nitrogen fertigation, regulated at two different levels, resulting in 16 treatments.

Materials and Methods

Experimental design and treatments

The influence of management procedures on fruit yield and quality was investigated in a ‘Katja’ apple orchard at Kivik research station, southeastern Sweden (≈55°N), during four growing seasons (2000 to 2003) to eliminate confounding climate effects. Trees were grafted onto M26 rootstock and planted in 1997 (4 m interrow × 2 m intertree spacing). Fruit first appeared only 1 year later, resulting in very weak vegetative growth and poor fruit quality. A completely randomized block design with six single tree blocks was used in the study. All trees were trained as Geneva Y-trellis ≈1 m in height, the Y angle was 60°, and the Y junction was 0.6 m above the ground. The investigated orchard management procedures were:

  1. Pruning (P). Two types of pruning were tested: a) standard pruning (Ps): all upper shoots growing close to the arms removed and all side shoots shortened to ≈30 cm long in early April. Both arms shortened with a head cut into the basal fifth leaf; and b) radical pruning (Pr): two-thirds of each tree arm pruned and all upper and lateral shoots totally removed or shortened to 5 to 10 cm in early April of each year. Starting in Year 2, all shoots shortened (weaker removed) again in July to the nearest bearing shoot. All nonproductive limbs causing too much shading thinned and all new shoots arising in the main stem or Y arms removed. Some drooping shoots head cut to restore horizontal shape.

  2. Weed control (W). Soil surface kept free from weeds by: a) herbicides (Ws): mixture of glyphosate (360 g·L−1) Roundup (N-phosphomethylglycine; Monsanto, Brussels, Belgium) and MCPA [Duplosan super, (4-chloro-2-methylphenoxy), BASF, Gothenburg, Sweden] sprayed onto the soil twice a year (May, July). Herbicide dose 3 L·ha−1 on sprayed areas, liquid rate 320 L·ha−1, and travel speed 3.5 km·h−1; b) bark mulching (Wm): soil covered during the vegetative period with a layer (20 cm thick) of 1-year-old chopped pine bark. More bark added every year.

  3. Fertilization (F). All trees drip-irrigated (0.8 L/tree) May to August every season and fertigated as: a) standard fertigation (Fs) of 0.13 g Red Superba and Gartnersalpeter, 1:200 (7N–4P–21K with Mg, S, and micronutrients; HYDROAGRI, Årsta, Sweden); b) excess nitrogen fertigation (Fx) with trees given additional nitrogen [2 × 25 g (15.5% N and 19.0% Ca); HYDROAGRI], applied 1 May and 1 June.

  4. Thinning (T): a) unthinned trees (Ts); b) hand thinning (Tn), all flowers within each cluster except the king flower removed 1 to 2 weeks after full bloom.

These procedures were arranged in 16 different treatments: Tr1: control, standard procedures (Ps.Ws.Fs.Ts); Tr2 to Tr5: treatments with one procedure changed compared with control (Tr2: Pr.Ws.Fs.Ts; Tr3: Ps.Wm.Fs.Ts; Tr4: Ps.Ws.Fx.Ts; Tr5: Ps.Ws.Fs.Tn). Tr6 to Tr11: treatments with two procedures changed compared with control (Tr6: Pr.Wm.Fs.Ts; Tr7: Pr.Ws.Fx.Ts; Tr8: Pr.Ws.Fs.Tn; Tr9: Ps.Wm.Fx.Ts, Tr10: Ps.Wm.Fs.Tn; Tr11: Ps.Ws.Fx.Tn). Tr12 to Tr15: treatments with three procedures changed compared with control (Tr12: Pr.Wm.Fx.Ts; Tr13: Pr.Wm.Fs.Tn; Tr14: Pr.Ws.Fx.Tn; Tr15: Ps.Wm.Fx.Tn). Tr16: Treatment with all procedures changed compared with control, Pr.Wm.Fx.Tn.

Evaluation

Tree growth and light distribution.

Trunk diameter was measured 30 cm above the scion–rootstock union. The average of two readings (taken across and along the row) was converted to trunk cross-sectional area (TCSA; 3.14 stem radius2). Total shoot length was measured in May (before summer pruning) of each year. Light distribution within the crown was measured by light meter (L1-188; L1-COR, Frederickson, Copenhagen, Denmark). Data were recorded at the center of the trunk from the four directions of the crown at 70 cm above the ground. Light (μEm2·sec−1) was estimated on cloudless days on three occasions during 2001 at two positions per procedure. Full sunlight was measured (same time and height) in a free area (between rows). Data are presented as mean percentage transmission.

Fruit quality.

Optimum harvesting date was determined by estimating starch score three times a week during the maturation period. Fruit firmness was estimated with a penetrometer (model FT 327; Effigy, Milan, Italy; plunger diameter 11.1 mm) on opposite sides of each fruit. Subsamples were homogenized in a Waring blender (1 min) with ultrapure water (1:1; w/v). After centrifugation (10,000 × g) for 10 min, percentage soluble solids concentration (SSC) was determined with a refractrometer (RMF 80; Bellingham and Standley Ltd., UK). From the supernatant, 5 mL were diluted with 20 mL ultrapure water and titrated as malic acid with NaOH (0.05 M) to pH 8.1 with a Radiometer (PHM64; Denmark). Fruit surface color was assessed with a Chroma Meter model CR 200 with an 8-mm diameter window (Minolta Camera Co., Ltd., Osaka, Japan), at three spots per fruit and expressed as H°, i.e., hue angle (H° = tan−1 b*/a *), where b* is the yellow/blue and a* the red/green color coordinates. H° = 0, totally red, H° = 90° totally yellow and H° = 180° totally green peel color (McGuire, 1992). Two additional fruits from each tree were analyzed at harvesting to estimate the mineral content (N, K, Ca, and Mg), using NMKL6 and HNO3 – ICP-AES methods.

Fruit storability.

Samples of 30 fruits from each block/treatment were stored at 2.5 °C and 90% relative humidity for 10 weeks. Fruit quality was estimated after storage as explained previously. The percentage incidence of storage decay was visually determined according to the storage decay index described in Rein (1996).

Statistical analyses.

For light transmission, yield, and fruit weight of ‘Katja’ apples, means and sds were calculated using the MS Excel program (Microsoft, Redmond, WA). Following recommendations in Fernandez (2007), analysis of variance (ANOVA procedure) was carried out using SAS (SAS Inst. Inc., Cary, NC). Four comparisons of various managements and their interactions on tree vegetative growth, trunk growth, yield, and fruit quality parameters were analyzed. After ANOVA analyses, the Turkey's studentized range at P < 0.05 was calculated for each of the parameters in the 16 treatments.

Results

Vegetative growth and light transmission.

Over the 4 years, standard orchard management (Ps.Ws.Fs.Ts) of ‘Katja’ apples caused slow growth (27% relative increase in TCSA) and weak trees (total annual new growth of shoots was 18 cm) (Tables 1 and 2; P < 0.05). Radical pruning (Pr.Ws.Fs.Ts) increased TCSA (by 38%) and produced three times longer new shoots than the control trees (Ps.Ws.Fs.Ts). Bark mulching (Ps.Wm.Fs.Ts), application of excess N fertigation (Ps.Ws.Fx.Ts) or hand thinning (Ps.Ws.Fs.Tn) had no significant effect on trunk growth and annual shoot growth in comparison with control trees (Table 2).

Table 1.

Mean squares from analyses of variance of shoot length, yield, fruit weight and fruit quality, and storability as related to orchard management.z

Table 1.
Table 2.

Vegetative growth, tree productivity and fruit quality of Katja apple resulting from application of different management procedures (2000 to 2003 average).z

Table 2.

Although changing two procedures of four (Tr. 6 to 11) slightly improved vegetative growth compared with standard or individual procedures (Tr. 1 to 5), the effects were lower than for radical pruning alone (Tables 1 and 2). Of the treatments with three novel procedures (Tr. 12 to 15), Pr.Wm.Fs.Tn caused the highest relative increase in TCSA (165% in comparison with standard managed and 92% in comparison with radically pruned trees) (Tables 1 and 2). Total annual new growth of shoots in trees that were managed by these procedures was six times longer than that in control trees and two times longer than in radically pruned trees (Tables 1 and 2). Even larger trunk and higher increase in shoots growth were achieved with Tr.16 (Pr.Wm.Fx.Tn), where trunks were 170% thicker than trunks of control trees and 95% thicker than trunks of radically pruned trees, and the total annual new growth of shoots was nine, three, and two times longer than total annual new growth of shoots in standard (Tr.1), two-procedure (Tr. 6 to 11), and three-procedure (Tr. 12 to 15) treatments, respectively. Radical pruning and bark mulching were the essential factors in the fourfold treatment (Tr.16), because removal of any one of these procedures had the largest influence on shoot growth (Tables 1 and 2). The interactions between season and treatments were significant in most cases (Table 1).

Excess N fertigation (Ps.Ws.Fx.Ts) decreased the incoming light measured at 70 cm by 20% in comparison with control trees (Fig. 1; P < 0.05). Ps.Wm.Fx.Ts or Ps.Ws.Fx.Tn caused the same negative effect. A three-procedure treatment, Ps.Wm.Fx.Tn, also showed 15% less light transmission (Fig. 1), whereas Pr.Ws.Fs.Ts or Pr.Wm.Fs.Tn improved light transmission by 39% to 45% in comparison with standard treatment. It also decreased the negative effect of other practices on the light penetration within the crown when these practices were applied in a four-factor treatment (Pr.Wm.Fx.Tn) (Fig. 1).

Fig. 1.
Fig. 1.

Light transmission as percent of diffuse light within tree crown of ‘Katja’ apple trees in July to Aug. 2001. Bars represent sd ± (n = 96). Data were obtained by dividing the within canopy photosynthetic photon flux (PPF) by the simultaneously recorded open sky PPF. Procedures: Pruning (P)—standard (Ps) or radical (Pr); weed control (W)—herbicides (Ws) or bark mulching (Wm); fertilization (F)—standard fertigation (Fs) or excess nitrogen (Fx); and thinning (T)—no thinning (Ts) or hand thinning (Tn).

Citation: HortScience horts 43, 3; 10.21273/HORTSCI.43.3.725

Tree productivity.

Radical pruning (Pr.Ws.Fs.Ts) decreased tree yield by 14% and hand thinning (Ps.Ws.Fs.Tn) by 19%, whereas bark mulching (Ps.Wm.Fs.Ts) and excess nitrogen fertigation (Ps.Ws.Fs.Tn) increased it by 7% and 11%, respectively, in comparison with control trees (Table 1; Fig. 2; P < 0.05). The negative effect of radical pruning or hand thinning on tree yield disappeared when either was applied in a two-factor treatment with bark mulching (Pr.Wm.Fs.Ts; Ps.Wm.Fs.Tn) or excess nitrogen fertigation (Pr.Ws.Fx.Ts; Ps.Ws.Fx.Tn) (Fig. 2). Tr. 12 to 16 generally increased yield compared with Tr. 2 to 11. Pr.Wm.Fx.Ts increased yield by 28% in comparison with standard treatment (Tr. 1), 16% in comparison with Pr.Wm.Fs.Ts (Tr. 6), and 24% in comparison with Pr.Ws.Fx.Ts (Tr. 7) (Fig. 2). The highest yield was found for Pr.Wm.Fx.Tn (Tr.16). Removal of hand thinning from this treatment did not significantly affect the yield (Fig. 2). The interaction between season and treatment effect on yield was seldom significant (Table 1).

Fig. 2.
Fig. 2.

Tree production of ‘Katja’ apples (2001 to 2003 average) Bars represent sd ±. Values are means of 4 years, 16 models of six single blocks (n = 384). Interaction between season and models was not significant at (P < 0.05). Procedures: Pruning (P)—standard (Ps) or radical (Pr); weed control (W)—herbicides (Ws) or bark mulching (Wm); fertilization (F)—standard fertigation (Fs) or excess nitrogen (Fx); and thinning (T)—no thinning (Ts) or hand thinning (Tn).

Citation: HortScience horts 43, 3; 10.21273/HORTSCI.43.3.725

Fruit quality and storability.

Fruits from radically pruned (Pr.Ws.Fs.Ts) or hand-thinned (Ps.Ws.Fs.Tn) trees were 16% and 13% larger, respectively, than fruits from trees treated by standard management (Table 1; Fig. 3; P < 0.05). The combination of these procedures (Pr.Ws.Fs.Tn; Tr. 8) increased fruit weight by 20% in comparison with fruits from only radically pruned trees and by 23% in comparison with fruits from only hand-thinned trees (Fig. 3). Fruits from bark-mulched trees were 13% larger than fruits from the control trees. Pr.Wm.Fs.Ts increased fruit weight by 13% in comparison with radically pruning alone and by 42% in comparison with bark mulching alone (Fig. 3). Fruits from the three- (Tr. 12 to 15) or four-factor treatment (Tr. 16) were 50% to 70% heavier than fruits from control trees. Pr.Wm.Fs.Tn caused the largest fruits (Fig. 3).

Fig. 3.
Fig. 3.

Mean weight of ‘Katja’ apples (2001 to 2003 average). Bars represent sd ±. Values are means of 4 years, 16 models of six single blocks (n = 384). Interaction between season and models was not significant at P < 0.05. Procedures: Pruning (P)—standard (Ps) or radical (Pr); weed control (W)—herbicides (Ws) or bark mulching (Wm); fertilization (F)—standard fertigation (Fs) or excess nitrogen (Fx); and thinning (T)—no thinning (Ts) or hand thinning (Tn).

Citation: HortScience horts 43, 3; 10.21273/HORTSCI.43.3.725

The peel color of ‘Katja’ apple was significantly affected by season (Table 1). Radical pruning (Pr.Ws.Fs.Ts during two seasons) increased red color (25% lower H° value) in comparison with fruits from control trees (Table 2; P < 0.05). Pr.Ws.Fs.Tn or Pr.Wm.Fs.Ts did not improve fruit coloration in comparison with radical pruning alone (Table 2). Excess N fertigation always had a negative effect on fruit coloration. It also neutralized the positive effect of radical pruning when a combination (Pr.Ws.Fx.Ts) of these two treatments was applied (Table 2). The best fruit coloration during three seasons (40% lower H° value) was achieved by Pr.Wm.Fs.Tn (Table 2).

Trees that were treated by Pr.Ws.Fs.Tn had 15% firmer fruits than control trees. Applying bark mulching to this two-factor treatment (Pr.Wm.Fs.Tn) improved fruit firmness by 20% (Table 2; P < 0.05). Treatments did not show any significant effect on fruit sweetness. Pr.Wm.Fs.Ts or Ps.Wm.Fs.Tn caused higher fruit acidity in comparison with other treatments (Table 2). Trees treated with a three-factor combination of these procedures (Pr.Wm.Fs.Tn) showed better fruit flavor quality (sugar–acid ratio) (Table 2).

Ps.Wm.Fx.Ts, Ps.Ws.Fx.Tn, or Ps.Wm.Fx.Tn increased N content by 25% (Table 3; P < 0.05). K/Ca ratio in the fruits increased as a result of hand thinning (Ps.Ws.Fs.Tn). Procedures that included bark mulching (Ps.Wm.Fs.Tn and Pr.Wm.Fx.Tn) decreased K/Ca ratio and their fruits had higher Ca content (Table 3; P < 0.05).

Table 3.

Fruit mineral content at harvest and fruit quality of Katja apple after storage at 2.5 °C and 90% relative humidity for 10 weeks (2000 to 2003 average).z

Table 3.

Fruit storability was affected by orchard management. Bull's eye rot caused by Pezicula malicorticis and internal breakdown were the most important reasons for storage loss. Radical pruning (Pr.Ws.Fs.Ts) and excess N fertigation (Ps.Ws.Fx.Ts) increased storage decay by 20% and 11%, respectively (Tables 1 and 3). Pr.Wm.Fs.Ts or Pr.Wm.Fs.Tn improved fruit resistance to pathogen rot (54% and 70% lower decay, respectively, in comparison with fruits from control trees) (Table 3). Fruits from standard treatment lost 30%, 10%, and 50% of their firmness, SSC, and malic acid content, respectively, during storage (Table 3). Ps.Wm.Fs.Tn or Pr.Wm.Fs.Tn resulted in a lower decline in fruit firmness (≈20%) and malic acid content (≈10%) in comparison with fruits from control or radically pruned trees (Table 3). Ps.Ws.Fx.Ts or Pr.Ws.Fx.Ts caused faster decrease in fruit firmness and flavor quality (40%) in comparison with treatments without excess nitrogen (Table 3).

Discussion

The potential to change the growth habit of ‘Katja’ trees (improvement of vegetative growth, regulation of bearing, and production of high fruit quality and storability) by the use of different cultural practices depends on the ability of these practices to adjust the competition for carbohydrate consumption between vegetative and generative organs so that more carbohydrates are translocated to the fruits and not to new vegetative growth (Bepete and Lakso, 1998; Goffinet et al., 1995; Tromp, 2005). Contradictory to earlier results in other apple cultivars (Fathi and Mukhtar, 1998; Ghosh et al., 2004), the present investigation showed that one-factor orchard management treatments (Tr. 2 to 5) were not sufficient to improve the productivity, quality, and storability of ‘Katja’ apples. Although radical pruning increased TCSA, encouraged shoot growth, and improved fruit coloration, it simultaneously decreased yield and fruit storability, attributable perhaps to high competition for carbohydrates between fruits and rapid-grown shoots during the first 40 d after full bloom (Grappadelli et al., 1994). Thinning has been reported to positively influence regulated bearing, light transmission, and fruit quality (Fathi and Mukhtar, 1998; Ystaas, 1992), but such a relationship was not found for ‘Katja’ apples in the present investigation, where hand thinning decreased yield without any color improvement. Similarly to previous results (Tahir et al., 2005), bark mulching increased yield and fruit firmness, but in the present investigation, it did not improve vegetative growth as has been reported by several authors (Choi-Seong and Choi, 2000; Pfammatter and Dossimoz, 1997). High nitrogen rates caused better growth and yield, but also decreased light transmission, promoted greenness, and decreased red color, as has been reported previously (Meheriuk et al., 1996). High nitrogen negatively affected fruit storage potential as a result of increasing shading and decreasing fruit Ca content.

Interactions between the management procedures were investigated in 10 different treatments (Tr. 6 to 16). A combination of radical pruning, which improved red color as a result of better light distribution in the canopy (Marini and Barden, 2004), and excess nitrogen fertigation, which increased yield, was not a useful solution because this combination also led to high storage decay and insufficient fruit color. Radical pruning in combination with bark mulching and hand thinning decreased the negative effect of each practice alone. Except for the first year, this combination caused the highest relative change in TCSA, larger fruits, high regular yield, and better fruit quality (color and flavor) and storability. This indicates that applying these procedures together could activate or neutralize some of the positive or negative effects originating from each of them alone. Early decapitation of the current-year shoots might provide sufficient carbohydrates for the formation of high-quality buds, resulting in large and healthy fruits. An optimum early season hand thinning (1 to 2 weeks after full bloom) not only led to improved fruit size, regulated bearing, and decreased storage decay, but also improved the pruning effect on light penetration within the crown. Bark mulching consolidates fruit quality and storability probably by saving soil moisture, increasing nutrition availability, and adjusting K/Ca ratio (Tahir et al., 2005). Bark mulching in Pr.Wm.Fs.Tn cancelled the negative effect of thinning and radical pruning on Ca content, resulting in better storage potential. Because of the nonsignificant difference between this treatment and the four-factor treatment (i.e., with excess fertigation also included), growers can apply this threefold treatment to limit excess application of nitrogen and thereby decrease their costs and protect the environment.

The positive interacting effects of radical pruning, bark mulching, and hand thinning were very clearly demonstrated in this study and thus provide a method to solve production problems for ‘Katja’ apple orchards.

Literature Cited

  • Basak, A. 1999 The storage quality of apples after fruitlets thinning Acta Hort. 485 47 54

  • Bepete, M. & Lakso, A.N. 1998 Differential effects of shade on early season fruit and shoot growth rates in ‘Empire’ apple branches HortScience 33 823 825

    • Search Google Scholar
    • Export Citation
  • Bergh, O. 1990 Effect of time of hand thinning on apple fruit size S. Afr. J. Plant Soil 7 1 10

  • Choi-Seong, Y. & Choi, S. 2000 The effect of mulching material on the shoot and root growth and fruit quality of ‘Fugi’/M.26 apple J. Korean Soc. HortScience 41 512 516

    • Search Google Scholar
    • Export Citation
  • Fathi, M.A. & Mukhtar, H. 1998 Influence of summer pruning on growth, fruit set and fruit quality of Anna apple trees Egypt. J. Agr. Res. 76 721 732

    • Search Google Scholar
    • Export Citation
  • Fausett, J.B. & Rom, C.R. 2001 The effects of transitioning a mature high-density orchard from standard herbicide ground cover management system to organic ground-cover management systems Arkansas Agr. Expt. Sta. 483 33 36

    • Search Google Scholar
    • Export Citation
  • Fernandez, G.C.J. 2007 Design and analysis of commonly used comparative horticultural experiments HortScience 42 1052 1069

  • Ghosh, S.N., Manna, S. & Mathew, B. 2004 Effect of nitrogen and potassium fertilization on custard apple grown under rain fed late rite soils Environ. Ecol. 22 144 147

    • Search Google Scholar
    • Export Citation
  • Goffinet, M.C., Robinson, T.L. & Lakso, A.N. 1995 A comparison of ‘Empire’ apple fruit in unthinned and hand-thinned trees J. Hort. Sci. 70 375 387

    • Search Google Scholar
    • Export Citation
  • Goldschmidt, R.E. 1997 Regulating trees of apple and pear by pruning and bending Swedish J. Agr. Res. 27 45 52

  • Grappadelli, L.C., Lakso, A.N. & Flore, J.A. 1994 Early season pattern of carbohydrate portioning in exposed and shaded apple branches J. Amer. Soc. Hort. Sci. 119 596 603

    • Search Google Scholar
    • Export Citation
  • Jadczuk, E., Pietranek, A. & Dziuban, R. 2001 Irrigation and K fertilization effects on the cropping and fruit quality of ‘Katja’ apple trees on four different rootstocks Folia. Hort. 13 47 60 (abstr.)

    • Search Google Scholar
    • Export Citation
  • Krzewinska, D., Basak, A., Mika, A. & Michalska, B. 2002 The effect of time and intensity of hand thinning on the distribution of apples in size and colour classes Zeszyty Naukowe Instytutu Sadownictwa i Kwiaciarstwa W Skierniewicach 10 89 99 (abstr.).

    • Search Google Scholar
    • Export Citation
  • Link, H. 2000 Significance of flower and fruit thinning on fruit quality Plant Growth Regulat. 31 17 26

  • Marini, R.P. 2004 Combinations of ethophon and Accel for thinning ‘Delicious’ apple trees J. Amer. Soc. Hort. Sci. 129 175 181

  • Marini, R.P. & Barden, J.A. 2004 Yield, fruit size, red colour, and a hand economic analysis for ‘Delicious’ and ‘Empire’ in the NC-140 1994 System Trail in Virginia J. Amer. Pomol. Soc. 58 4 11

    • Search Google Scholar
    • Export Citation
  • McGuire, R.G. 1992 Reporting of objective colour measurements HortScience 27 1254 1255

  • Meheriuk, M., Mckenzie, D.L., Neilsen, G.H. & Hall, J.W. 1996 Fruit pigmentation of four green apple cultivars responds to urea sprays but not to nitrogen fertilization HortScience 31 992 993

    • Search Google Scholar
    • Export Citation
  • Pfammatter, W. & Dossimoz, A. 1997 Influence of irrigation and ground cover on development and yields of young apple trees Revue. Suisse. De. Viticulture. D'Arboriculture et d'Horticulture 29 301 304

    • Search Google Scholar
    • Export Citation
  • Pretorious, J.J.B., Wand, S.J.E. & Theron, K.L. 2004 Fruit and shoot growth following combined girdling and thinning of ‘Royal Gala’ apple trees Acta Hort. 636 401 407

    • Search Google Scholar
    • Export Citation
  • Rein, A. 1996 Apple storage disorders (original title in Swedish: Skador på äpplen vid inlagring) Swedish Board of Agr. Agro. Info. 3810 Gvarv

    • Search Google Scholar
    • Export Citation
  • Rubauskis, E., Skrivele, M., Dimza, I. & Berlands, V. 2002 The response of apple trees to fertigation and mulch Sodininkyste ir Darzininkyste. 21 126 133

    • Search Google Scholar
    • Export Citation
  • Tahir, I., Johansson, E. & Olsson, M.E. 2005 Groundcover materials improve quality and storability of ‘Aroma’ apples HortScience 40 1416 1420

  • Tahir, I., Johansson, E. & Olsson, M.E. 2007 Improvement of quality and storability of apple cv. Aroma by adjustment of some pre-harvest conditions Scientia Hort. 12 164 171

    • Search Google Scholar
    • Export Citation
  • Tomala, K. 1997 Orchard factors affecting nutrient content and fruit quality Acta Hort. 448 257 264

  • Tromp, J. 2005 Mineral nutrition 55 63 Tromp J., Webster A.D. & Wertheim S.J. Fundamentals of temperate zone tree fruit production Backhuys Publishers Leiden, The Netherlands

    • Search Google Scholar
    • Export Citation
  • Wertheim, S.J. 2005 Pruning 176 185 Tromp J., Webster A.D. & Wertheim S.J. Fundamentals of temperate zone tree fruit production. Backhuys Publishers Leiden, The Netherlands

    • Search Google Scholar
    • Export Citation
  • Wójcik, P., Rutkoeski, K. & Treder, W. 2001 Quality and storability of ‘Gala’ apples as affected by crop load Folia Hort. 13 89 96 (abstr.)

  • Ystaas, J. 1992 Effects of summer pruning on yield, fruit size, and fruit quality of the apple cultivar ’Summerred’ Acta Hort. 322 277 282

Contributor Notes

To whom reprint requests should be addressed; e-mail ibrahim.tahir@ltj.slu.se

  • View in gallery

    Light transmission as percent of diffuse light within tree crown of ‘Katja’ apple trees in July to Aug. 2001. Bars represent sd ± (n = 96). Data were obtained by dividing the within canopy photosynthetic photon flux (PPF) by the simultaneously recorded open sky PPF. Procedures: Pruning (P)—standard (Ps) or radical (Pr); weed control (W)—herbicides (Ws) or bark mulching (Wm); fertilization (F)—standard fertigation (Fs) or excess nitrogen (Fx); and thinning (T)—no thinning (Ts) or hand thinning (Tn).

  • View in gallery

    Tree production of ‘Katja’ apples (2001 to 2003 average) Bars represent sd ±. Values are means of 4 years, 16 models of six single blocks (n = 384). Interaction between season and models was not significant at (P < 0.05). Procedures: Pruning (P)—standard (Ps) or radical (Pr); weed control (W)—herbicides (Ws) or bark mulching (Wm); fertilization (F)—standard fertigation (Fs) or excess nitrogen (Fx); and thinning (T)—no thinning (Ts) or hand thinning (Tn).

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    Mean weight of ‘Katja’ apples (2001 to 2003 average). Bars represent sd ±. Values are means of 4 years, 16 models of six single blocks (n = 384). Interaction between season and models was not significant at P < 0.05. Procedures: Pruning (P)—standard (Ps) or radical (Pr); weed control (W)—herbicides (Ws) or bark mulching (Wm); fertilization (F)—standard fertigation (Fs) or excess nitrogen (Fx); and thinning (T)—no thinning (Ts) or hand thinning (Tn).

  • Basak, A. 1999 The storage quality of apples after fruitlets thinning Acta Hort. 485 47 54

  • Bepete, M. & Lakso, A.N. 1998 Differential effects of shade on early season fruit and shoot growth rates in ‘Empire’ apple branches HortScience 33 823 825

    • Search Google Scholar
    • Export Citation
  • Bergh, O. 1990 Effect of time of hand thinning on apple fruit size S. Afr. J. Plant Soil 7 1 10

  • Choi-Seong, Y. & Choi, S. 2000 The effect of mulching material on the shoot and root growth and fruit quality of ‘Fugi’/M.26 apple J. Korean Soc. HortScience 41 512 516

    • Search Google Scholar
    • Export Citation
  • Fathi, M.A. & Mukhtar, H. 1998 Influence of summer pruning on growth, fruit set and fruit quality of Anna apple trees Egypt. J. Agr. Res. 76 721 732

    • Search Google Scholar
    • Export Citation
  • Fausett, J.B. & Rom, C.R. 2001 The effects of transitioning a mature high-density orchard from standard herbicide ground cover management system to organic ground-cover management systems Arkansas Agr. Expt. Sta. 483 33 36

    • Search Google Scholar
    • Export Citation
  • Fernandez, G.C.J. 2007 Design and analysis of commonly used comparative horticultural experiments HortScience 42 1052 1069

  • Ghosh, S.N., Manna, S. & Mathew, B. 2004 Effect of nitrogen and potassium fertilization on custard apple grown under rain fed late rite soils Environ. Ecol. 22 144 147

    • Search Google Scholar
    • Export Citation
  • Goffinet, M.C., Robinson, T.L. & Lakso, A.N. 1995 A comparison of ‘Empire’ apple fruit in unthinned and hand-thinned trees J. Hort. Sci. 70 375 387

    • Search Google Scholar
    • Export Citation
  • Goldschmidt, R.E. 1997 Regulating trees of apple and pear by pruning and bending Swedish J. Agr. Res. 27 45 52

  • Grappadelli, L.C., Lakso, A.N. & Flore, J.A. 1994 Early season pattern of carbohydrate portioning in exposed and shaded apple branches J. Amer. Soc. Hort. Sci. 119 596 603

    • Search Google Scholar
    • Export Citation
  • Jadczuk, E., Pietranek, A. & Dziuban, R. 2001 Irrigation and K fertilization effects on the cropping and fruit quality of ‘Katja’ apple trees on four different rootstocks Folia. Hort. 13 47 60 (abstr.)

    • Search Google Scholar
    • Export Citation
  • Krzewinska, D., Basak, A., Mika, A. & Michalska, B. 2002 The effect of time and intensity of hand thinning on the distribution of apples in size and colour classes Zeszyty Naukowe Instytutu Sadownictwa i Kwiaciarstwa W Skierniewicach 10 89 99 (abstr.).

    • Search Google Scholar
    • Export Citation
  • Link, H. 2000 Significance of flower and fruit thinning on fruit quality Plant Growth Regulat. 31 17 26

  • Marini, R.P. 2004 Combinations of ethophon and Accel for thinning ‘Delicious’ apple trees J. Amer. Soc. Hort. Sci. 129 175 181

  • Marini, R.P. & Barden, J.A. 2004 Yield, fruit size, red colour, and a hand economic analysis for ‘Delicious’ and ‘Empire’ in the NC-140 1994 System Trail in Virginia J. Amer. Pomol. Soc. 58 4 11

    • Search Google Scholar
    • Export Citation
  • McGuire, R.G. 1992 Reporting of objective colour measurements HortScience 27 1254 1255

  • Meheriuk, M., Mckenzie, D.L., Neilsen, G.H. & Hall, J.W. 1996 Fruit pigmentation of four green apple cultivars responds to urea sprays but not to nitrogen fertilization HortScience 31 992 993

    • Search Google Scholar
    • Export Citation
  • Pfammatter, W. & Dossimoz, A. 1997 Influence of irrigation and ground cover on development and yields of young apple trees Revue. Suisse. De. Viticulture. D'Arboriculture et d'Horticulture 29 301 304

    • Search Google Scholar
    • Export Citation
  • Pretorious, J.J.B., Wand, S.J.E. & Theron, K.L. 2004 Fruit and shoot growth following combined girdling and thinning of ‘Royal Gala’ apple trees Acta Hort. 636 401 407

    • Search Google Scholar
    • Export Citation
  • Rein, A. 1996 Apple storage disorders (original title in Swedish: Skador på äpplen vid inlagring) Swedish Board of Agr. Agro. Info. 3810 Gvarv

    • Search Google Scholar
    • Export Citation
  • Rubauskis, E., Skrivele, M., Dimza, I. & Berlands, V. 2002 The response of apple trees to fertigation and mulch Sodininkyste ir Darzininkyste. 21 126 133

    • Search Google Scholar
    • Export Citation
  • Tahir, I., Johansson, E. & Olsson, M.E. 2005 Groundcover materials improve quality and storability of ‘Aroma’ apples HortScience 40 1416 1420

  • Tahir, I., Johansson, E. & Olsson, M.E. 2007 Improvement of quality and storability of apple cv. Aroma by adjustment of some pre-harvest conditions Scientia Hort. 12 164 171

    • Search Google Scholar
    • Export Citation
  • Tomala, K. 1997 Orchard factors affecting nutrient content and fruit quality Acta Hort. 448 257 264

  • Tromp, J. 2005 Mineral nutrition 55 63 Tromp J., Webster A.D. & Wertheim S.J. Fundamentals of temperate zone tree fruit production Backhuys Publishers Leiden, The Netherlands

    • Search Google Scholar
    • Export Citation
  • Wertheim, S.J. 2005 Pruning 176 185 Tromp J., Webster A.D. & Wertheim S.J. Fundamentals of temperate zone tree fruit production. Backhuys Publishers Leiden, The Netherlands

    • Search Google Scholar
    • Export Citation
  • Wójcik, P., Rutkoeski, K. & Treder, W. 2001 Quality and storability of ‘Gala’ apples as affected by crop load Folia Hort. 13 89 96 (abstr.)

  • Ystaas, J. 1992 Effects of summer pruning on yield, fruit size, and fruit quality of the apple cultivar ’Summerred’ Acta Hort. 322 277 282

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