Long-term effects of managed grass competition and two pruning methods on growth and yield of peach trees

Ground cover competition and tree training strongly affect development of newly planted peach trees and eventual productivity of peach orchards. This experiment characterized the long-term interactive effects of three levels of competition and two pruning criteria on yield, fruit size, and marketable yield efficiency. Trees of two cultivars (’Jersey Dawn’, JD, and ‘Redskin’, RS, on Lovell) of peach (Prunuspersica (L.) Batsch) were planted in an orchard in 1993 and grown for 14 years in a vegetation free area (VFA) width of 0.6 or 2.4 m. A separate group of trees that were in the 2.4 m VFA had grass seeded beneath them in 1998 to obtain 0 m VFA. All trees were pruned to maintain canopy size with wide-angled scaffold limbs and intense pruning (IP) or upright branch form with reduced pruning (RP). In general, RS had greater yield than JD and yield was greatest in the 2.4 m VFA with RP and least in the 0.6 m VFA with IP. Cumulative marketable (≥6.35 cm) and average annual total yield of both cultivars was similar for RP trees in 0 m VFA and IP trees in 2.4 m VFA's although more of the fruit were in the largest size class (>6.98 cm) in the IP trees. Reduced pruning increased crop load. Fruit weight decreased with increased crop load more in RS than JD and this response was similar for all VFA's within each cultivar. Grass competition tended to reduce both the number and weight of fruit per tree but the average weight of individual marketable fruit was reduced only in the 0.6 m VFA of RS. Tree size was reduced by grass competition and pruning times measured from 1995 to 2000 were less in RP than IP. Consequently, marketable yield efficiency of marketable fruit (grams fruit ≥6.35 cm/cm² trunk cross-sectional area, TCSA) measured from 2004 to 2007 was generally greater in trees with RP than IP and in the 0.6 than the 0 and 2.4 m VFA. The results indicate that persistent competition will reduce total annual yield per tree but with reduced pruning the concomitant increased crop load can help maintain marketable yield.     

Two new planting systems for early ripening peaches (Prunus persica L. Batsch): Yield and fruit quality in four low-chill cultivars

Summary

Trees of peach cvs Flordastar, Flordaprince, Flordacrest and Maravilha, low in chill requirement (Flordaprince 150; Flordacrest 350 C.U.), with a short fruit development period (Flordaprince 90; Flordacrest 110 d) and a very early ripening time (Flordastar mid May; Flordacrest first week of June), were planted in Sicily (37° 30′ Lat. N) both in a medium (667 trees per ha) and a high density (2000 trees per ha) plantation system. In the medium density planting system, the trees were trained to a Fusetto, and in the high density to a Y-shape. Both in the Fusetto and Y, the size of the trees was controlled by severe pruning soon after harvest, consisting in the shortening of most of the one year old wood. From mid June to October, the trees of all four cultivars were able to recover a “fruiting canopy”; flower bud density, flower fertility, fruit set, fruit quality and crop efficiency were not affected by the severe summer pruning. Due to the planting density and the pruning, the tree growth was restricted: no platforms or ladders were required to perform the cultivation techniques at the top of the Fusetto nor was the wire-trellis necessary to sustain the Y-shaped trees. To distinguish these training systems from the original ones, Fusetto and Tatura trellis, we called them “dwarfed Fusetto” (dF) and “free standing Tatura” (fsT), respectively. Although production per tree was higher in the dF, due to planting density fsT yielded more per hectare.     

Effect of hail nets on the microclimate,irrigation requirements,tree growth,and fruit yield of peach orchards in Catalonia (Spain)

Summary

Hail nets protect orchards from storm damage, but also offer potential water savings for fruit trees grown in arid areas. We investigated the effects of black nets on water use, growth, yield, and fruit quality in peach trees growing in Catalonia, Spain, over 2 years (2006 and 2007). Water savings were quantified by irrigating the netted trees to a similar midday stem water potential (Ψ_stem) as the control trees. This method was only partially successful in 2006, with the netted trees being over-watered early in the season (i.e., higher Ψ_stem than the controls), and under-watered (i.e., lower Ψ_stem than the controls) later in the season. A combination of water stress and a hail net resulted in lower yields because of a smaller fruit size. Skin colour was more enhanced in control fruit. In 2007, Ψ_stem values were similar between treatments. Any difference in tree performance was therefore due to the hail net per se. Fruit size was similar between treatments, and the lower yields of netted trees were due to decreased fruit number. There were no treatment differences in fruit skin colour or flesh firmness. Soluble solids concentrations were higher in nonnetted fruit. In both years, water savings amounted to approx. 25%, if irrigation replaced the potential evapotranspiration that was measured. Hail nets are therefore recommended for their effects on water saving in arid areas, despite lower fruit yields.     

Root growth following defruiting improves peach tree water status

Summary

Tree growth and water status throughout the growing season and after fruit removal were studied in container-grown peach trees. Trees with fruit (F) and defruited (DF) trees were sampled destructively at bud break (8 March), 1 month after fruit removal (3 June), at harvest (6 August), and before leaf fall (15 October) to determine the mass of leaves, current season shoots, branches, trunk, and the entire root system. Tree water status was determined from the mid-day stem water potential (SWP) the day before each sampling date. Root growth in DF trees was greater than that observed in F trees, while the above-ground biomass was similar in DF and F trees. DF trees therefore had lower leaf:root biomass ratios than F trees throughout the fruit growing season. Environmental factors did not fully explain the seasonal variations in SWP, but there was a significant correlation between leaf:root biomass ratios and SWP. Reductions in leaf:root biomass ratios were accompanied by increases in SWP and, ultimately, DF trees had higher SWP values than F trees in mid-Summer. Improvements in tree water status following fruit removal can be explained, in part, by additional root growth.     

Verfrühung von Süßkirschen unter geschlossener Folie

The sweet cherry cvs. ‘Burlat’, ‘Earlise’, ‘Samba’, ‘Souvenir’, and clone M, all with early ripening, large, dark, red-black fruit, were cultivated at a spacing of 3.80x1.75 m under complete rain cover in a whole orchard at the Klein-Altendorf Research Station near Bonn, Germany during April and May 2004. Under such cover, these sweet cherry trees flowered 6–13 days earlier and their fruit ripened 12–19 days earlier than those from uncovered control trees, indicating shorter or enhanced fruit development and maturation in up to 1 week. The cover proved insufficient for frost protection at night, despite increased daytime air and soil temperatures (by as much as 15°C and 5°C, respectively). Trickle irrigation was used to overcome loss of soil moisture due to the rain cover. Burlat leaves grown under this cover were thinner and softer and contained less chlorophyll a, chlorophyll b, and total chlorophyll than the leaves of uncovered control trees, without limiting photosynthesis. In contrast, the chlorophyll content of clone M leaves grown under cover equalled that of uncovered controls. Three of the five cvs. employed developed fruit mass of 9–15 g (25–33 mm fruit diameter). Three-year-old sweet cherry trees on dwarfing GiSelA 5 rootstocks were more vigorous than those without cover and produced 3–4.5 kg fruit per tree. The cover had no adverse effect on fruit colouration. The cherries grown under cover were slightly smaller, softer, with attractive colouration, and tasted better due to increases in both sugar and acidity, with sugar:acid ratios of 25–30:1.     

Influence of rootstock on orchard productivity and fruit quality in peach cv. ‘Redhaven’

Summary

We have evaluated the influence of four different peach rootstocks (Prunus pumila,‘GF 655/2’ ,‘Missour’ and ‘GF 677’ as a standard) planted in medium-heavy to heavy soil on phenological events (flowering and harvest date), growth, yield, fruit quality and mortality of peach (P. persica L.) scions of cv. ‘Redhaven’. At the end of flowering, there were no significant differences between the different rootstocks in the years 1999, 2000, 2003 and 2004. In 2001, trees grafted on P. pumila reached the end of flowering 2 d before trees grafted on the other rootstocks. ‘Redhaven’ fruits ripened on the same day on trees grafted on the different rootstocks. The differences were only between years. The results showed that significantly less vigorous trees, according to their trunk cross-sectional area (TCSA) and canopy volume, with the lowest yield, were observed on P. pumila rootstock. The rootstock P. pumila had a significant negative influence on fruit dimensions and mortality was 50%. Trees grafted on ‘GF 655/2’ rootstock produced significantly lower yields than those grafted on ‘GF 677’ or ‘Missour’ rootstocks. Only the ‘GF 655/2’ rootstock had root suckers. Trees grafted on ‘GF 677’ rootstock were significantly more vigorous than on the other rootstocks, and produced the highest yield with good fruit quality. The final canopy volumes of peach trees grafted on the different rootstocks were very different. The most vigorous trees were those grafted on ‘GF 677’ rootstock, where the final tree volume was 12.8 m³. Trees grafted on P. pumila and ‘GF 655/2’ had significantly lower TCSA values than on the other rootstocks.     

Comparative movement of labelled nitrogen and zinc in 1-year-old peach [Prunus persica (L.) Batsch] trees following late-season foliar application

Summary

Late in the season, a double-labelled solution containing ¹⁵N-enriched urea and ⁶⁸Zn sulphate was painted on the entire leaf area of 15, 1-year-old ‘O’Henry/Nemaguard’ peach trees to quantify N and Zn movement out of leaves following foliar application, and redistribution of these nutrients to new growth in the following Spring. About 47% of the labelled N and only 7% of the labelled Zn painted on the leaf surfaces was recovered in the permanent structure of the trees after leaf fall. Thus, it is concluded that foliar applications of Zn in the Autumn are not very efficient at supplying Zn to peach trees, especially when compared to supplying N as urea sprays in the Autumn. These data raise the possibility that foliar applications of Zn may actually be considered as soil applications, because 90% or more of the foliar-applied Zn may be carried to the orchard floor at the time of leaf fall. Therefore, future research needs to focus on assessing the efficacy of foliar applications for Zn nutrition of fruit trees, and identification of potentially detrimental effects from possible excessive soil accumulation of Zn. Once within the tree, however, labelled Zn was quite mobile and was stored throughout the plant, including in the roots. Of the labelled N and Zn exported from treated leaves prior to leaf fall, a substantial redistribution from storage was evident by 2 weeks after bloom and, by 4 weeks after bloom, 38% and 56% of the labelled N and Zn, respectively, had been redistributed from storage in roots, trunk and 1-year-old shoots to new growth. The biomass of new, above-ground growth tripled between 2 – 4 weeks after bloom and was coincident with a conspicuous influx of both N and Zn from the soil.     

果树根域限制栽培研究进展

根域限制这一新技术的原理是将根系置于一个可控的范围内,通过控制根系生长来调节地上部和地下部、营养生长和生殖生长的关系。已在葡萄、桃和柑橘等近10种果树上开展了试验研究,几乎所有的实验都肯定了抑制幼树营养生长、促进早期花芽形成和提高果实品质的效果。葡萄根域限制技术基本成熟,适宜的根域容积是每平方米树冠投影面积50L,并确立了适宜的土壤水分管理和营养液供给技术,但其他果树植物根域限制的应用技术还不完备。综合有关文献就根域限制的概念、形式、迄今为止的研究进展和存在的问题作简要探讨。     

A carbon sequestration strategy involving temperate fruit crops in the trans-Himalayan region

Summary

A current major concern is increasing levels of atmospheric CO₂ which may be responsible for global warming or climate change. Fruit tree orchards have received attention in recent years by virtue of their potential to act as carbon pools. The trans-Himalayan valley (i.e., the Nubra Valley) at an altitude of 3,048 m, is covered by > 60,000 temperate fruit trees. The focus of this paper is on the potential of these fruit-yielding trees as a means of carbon sequestration in the Nubra Valley. The valley produces approx. 4,650 metric tonnes (MT) of apricot, apple, walnut, mulberry, grape, and plum fruit. It was observed that the total biomass of the temperate fruit trees (i.e., apricot, apple, and walnut) in the area surveyed was 40,000 MT dry weight (DW). Thus, 22,300 MT of carbon has been sequestered by these fruit species. This study revealed that the cultivation of temperate fruit crops species such as apricot, apple, and walnut could be exploited more efficiently for carbon sequestration which subsequently helps in mitigating global CO₂ levels and restoring degraded land in these cold, arid areas by improving soil organic carbon (SOC) contents. These results concluded, in part, that growing biomass to sequester carbon is a beneficial grow-and-store process for sustainable development.     

BTH对南山甜桃采后生理和炭疽病的影响

以深圳南山甜桃为试材,研究了采前对树体进行BTH喷雾处理对采后果实炭疽病及成熟衰老的影响。结果表明,采前喷施BTH 50 mg.L-1可以有效防治采后果实炭疽病,减少腐烂;降低了采后甜桃果实呼吸速率和乙烯释放率,延缓了果实硬度的下降和果实的成熟衰老。     

Effects of different organic apple production systems on seasonal nutrient variations of soil and leaf

An organic apple (Malus × domestica Borkh.) orchard was established to study the interaction effects of ground cover management systems (GMS) and nutrient sources (NS) on soil and tree nutrients in the Southern U.S.A. GMS mulches as follows: green compost (GC), wood chips (WC), shredded paper (SP), and mow-and-blow (MB). Across GMS, one of three NS treatments was applied: commercial organic fertilizer (CF), poultry litter (PL), and no fertilizer (NF). GC-treated plots had greater soil solution nitrate concentrations in year 3. GC plots also maintained greater seasonal soil organic matter and macronutrient concentrations during 3 years compared with the other GMS. Seasonal foliar nutrient concentrations grown under GMS in year 3 tended to follow nutrient concentration patterns similar to those observed in conventional apple orchards. GC and WC trees had overall greater leaf area, dry weight, and total foliar nutrient contents in year 3 than the SP and MB trees.     

Effect of split applications of oil cake on leaf nutrient contents,tree growth,and fruit quality in non-astringent persimmon trees

Oil cake, widely used as an organic source of nutrients in horticultural production in South Korea, is a by-product when oil is extracted from various oilseeds. Split applications of oil cake were supplied to evaluate their effects on tree growth and fruit production in organic, non-astringent persimmon (Diospyros × kaki Thunb.) trees in 2009 and in 2010. Treatments included a single annual application of oil cake at 150 kg N ha^?1 in April (single application), two applications in April and July (105 and 45 kg N ha^?1, respectively; two-split application), or three applications in April, June, and August (60, 45, and 45 kg N ha^?1, respectively; three-split application), as well as zero application of oil cake (control). All applications of oil cake significantly increased the amount of ground-cover vegetation compared to the control. The single and two-split applications increased soil organic matter (OM), K₂O, CaO, and MgO concentrations, and cation exchange capacity to a soil depth of 0–30 cm in 2010. Oil cake applications increased soil porosity in 2010, as well as overall chlorophyll (SPAD values) and macronutrient concentrations in leaves in 2009 and 2010. Single and two-split applications stimulated water-sprout development, reduced the light intensity inside the tree canopy, and increased fruit drop. Fruit yield was higher in the two-split [24.7 metric tonnes (MT) ha^?1] and three-split application trees (25.0 MT ha^?1) compared to zero application control trees (19.8 MT ha^?1) and single application trees (21.0 MT ha^?1) in 2010. A single application resulted in soft fruit and slow skin colouration during maturation. Total soluble solids contents were higher in the control and three-split application trees in both years. The three-split application in 2010 increased the estimated production income by approx. 21% compared to the zero application, and by approx. 33% compared to a single application of oil cake.     

The influence of fungicides and gibberellin (A4+7) applications on russet control of ‘Golden Delicious’ apple fruit

Summary

Various fungicides, gibberellins (A₄₁₇) and their mixtures were tested for the control of russet of ‘Golden Delicious’ apple fruit in the major apple-growing area in Israel. Four foliar applications of captan, metiram, the strobilurins kresoxim-methyl, trifloxystrobin, azoxystrobin, or the polyoxin B compound Polar from the green tip stage to the end of the petal fall stage gave similar reductions in russeting, compared with the controls, but none eliminated it. Tank mixtures of the gibberellins (A₄₁₇) Regulex and Perlan with captan, each at full rate, did not improve russet control, compared with each component alone at the same rate. Similarly, both captan and trifioxystrobin, and the gibberellin (A₄₁₇) Cytolin or their mixtures at full rates provided similar significant level of control of russet on fruit. Fruit in the upper part of the tree had significantly more russet than fruit in the lower part of the tree, regardless of treatment applied. In addition, russet was more severe on fruits of trees grown in the west side of the row, than those of trees grown on the east side. Data suggest that factors other than fungicides, which may act by reducing russet-inducing microorganisms, may be involved in russet development.     

Effects of Vegetation-Free Strip Width and Irrigation on Newly Planted Peach

Field experiments were conducted at two locations (Clayton and Jackson Springs, NC) to determine the influence of vegetation-free strip width (VFSW) and irrigation on newly planted peach growth and yield in a low-density orchard with a volunteer weedy ground cover. The experiments included VFSW of 0, 0.6, 1.2, 2.4, 3, or 3.6 m under irrigated or nonirrigated conditions. Seasonal variation in the orchard floor vegetation was observed as different weed species reported in summer and winter. However, this difference was not apparent with respect to VFSF and irrigation. At Jackson Springs, NC, the predicted irrigated VFSW which would produce the same trunk cross-sectional area (TCSA) as the grower standard (3-m nonirrigated) was 1.5, 1.3, and 0.8 m for one-, two-, and three-year-old trees, respectively. The predicted irrigated VFSW which would produce the same yield as the grower standard was 1.16 m. At Clayton, TCSA and fruit yield were not different by irrigation, but did increase linearly with VFSW. At both locations, leaf nitrogen (N) concentration was lower in irrigated trees than nonirrigated trees. Leaf N, leaf area, and SPAD were positively related to VFSW at Jackson Springs. In contrast, leaf N concentration was not different by VFSW at Clayton. However, leaf area and SPAD were positively related to VFSW at Clayton. These results suggest that a 1.5 m VFSW combined with proper irrigation and fertilization will produce tree growth and yield in newly planted orchard with volunteer weedy vegetation similar to the current grower standard in the southeastern USA.     

Light distribution in apple orchard systems in relation to production and fruit quality

Summary

The effect of tree density (2000, 2667, and 4000 trees per ha) and the ratio of between to within-row distance (1:1, 2:1, and 3:1) on light interception, fruit production, colour and individual fruit weight was evaluated in a ten-year comparative field study with apple at two sites in The Netherlands (51° 30′ and 52°0′ N) and one site in Denmark (55°30′). For each combination of tree density and rectangularity, trees were pruned at three heights (1.50, 1.88, or 2.25 m). Fruit production over nine years and seasonal incoming radiation between bloom and harvest were 20 and 15% greater in The Netherlands. Climate-based estimates of potential production as provided by a crop-growth model, predicted 18% higher fruit production in The Netherlands. Production was proportional to light interception and increased with tree density, but the amount of well-coloured fruit per ha in later years did not increase with planting density. With more than 70% light interception in later years, a large proportion of shade within the canopy was found. Fruits were smaller and less coloured at the Danish site. Fruits were more coloured in the taller and more open trees, even at the highest tree densities. Plantings with 1:1 and 2:1 between-to within-row distances intercepted more light and had a more uniform light distribution than 3:1 designs. This led to higher fruit production and better fruit colour. Fruit weight was not influenced by tree density, rectangularity, or tree height.     

Evaluating weed control and response of newly planted peach trees to herbicides

ABSTRACT

Field experiments were conducted in North Carolina to determine peach response to herbicides. Mesotrione, rimsulfuron, and sulfentrazone did not injure newly planted peach trees. However, halosulfuron at the higher rate caused injury to peach trees, but did not reduce tree cross-sectional area or winter pruning weight. Another field experiment was conducted to determine the effect of herbicide-based programs on weed control. Sulfentrazone alone controlled common lamb’s-quarters and henbit but provided poor control of large crabgrass and yellow foxtail. However, a tank mix of norflurazon or oryzalin with sulfentrazone improved control of these weeds over sulfentrazone alone. Terbacil alone or in tank mix rimsulfuron, and flumioxazin alone gave excellent control of large crabgrass and yellow foxtail.     

Performance of ‘Coscia’ pear (Pyrus communis) on seven rootstocks in a warm climate

Summary

The vegetative and reproductive performance of ‘Coscia’ pear (Pyrus communis L.) growing on seven rootstocks [OHF 69, OHF 97, OHF 513 and BP 1 (P. communis), clonal seedling (Davis AxB) of P. betulifolia, and quince BA 29 and EMA (Cydonia oblonga)] were compared over an 8-year period. The trial was conducted at the Experimental Orchard Farm Station in northern Israel, on a well-drained soil with pH 7.5. Trees were planted in December 1998 at a distance of 4.0 m 2.0 m, and trained with a central axis. The most vigorous trees were on P. betulifolia seedling, followed by BP 1 and the three OHF rootstocks (69, 97, 513). All the above rootstocks demonstrated greater vigour than quince BA 29 or EMA. The reason for this effect, at least in part, appeared to be the excellent water status (high midday stem water potential values) of trees on P. betulifolia in comparison with the other rootstocks. The highest cumulative yields per tree were harvested from trees on P. betulifolia and BP 1, followed by the three OHF rootstocks (69, 97, 513). However, the highest cumulative yield of large fruit (> 60 mm) was obtained from trees on P. betulifolia, followed by the OHF series and BP 1. The two quince rootstocks had the lowest cumulative yield, and the lowest yield of large fruit. A positive correlation was found between the vigour of the tree, as affected by the rootstock, and both total yield and fruit size. We conclude that, in a warm climate, yield efficiency is not the only parameter that should be taken into account, and building a strong tree for the weak scion cultivar is the first requirement for establishing an orchard. Fruit quality at harvest and during cold storage were examined for fruit from three rootstocks only. The highest soluble solids content values at harvest were obtained in fruit grown on quince EMA, compared to values for BP 1 and P. betulifolia fruit.     

Ground cover increases spatial aggregation and association of insect herbivores and their predators in an agricultural landscape

Context

Enhancing ground cover vegetation is an important agricultural practice that regulates herbivore and predator insects in agricultural landscapes. However, the effects of ground cover on the spatial distributions of these organisms have scarcely been explored.

Objectives

Our goal was to measure the effects of ground cover on the spatial aggregation and association of insect herbivores and predators, which might contribute to the control of herbivorous pests.

Methods

We conducted our experiments in peach orchards at two sites in eastern China. The two sites have experimental units with ground cover treatments that created a heterogeneous landscape. We conducted a 2-year experiment to investigate the abundance and distribution of herbivores (leafhoppers) and predators (ladybirds), using geostatistics to analyze their spatial aggregation and association.

Results

The abundance of predators increased and that of herbivores decreased in ground cover orchards compared to control orchards without ground cover. The proportion of spatial structure was greater than 0.75 for both herbivores and predators in the control orchards, indicating a lack of spatial aggregation, and less than 0.75 in peach orchards with ground cover, indicating spatial aggregation. The correlation of spatial aggregation between herbivores and predators was significantly positive in the ground cover treatment, indicating association of the two insect guilds. In control orchards, on the other hand, this was not significant.

Conclusions

The presence of ground cover increased predator abundance, spatial aggregation of herbivores and predators as well as their spatial association, suggesting a mechanism for more efficient control of herbivorous pests in peach orchards.

     

Genetic diversity in fruiting-mei,apricot, plum and peach revealed by AFLP analysis

Summary

High-throughput amplified fragment length polymorphism (AFLP) analysis, employing a two-dye automated DNA sequencer, was used to genotype accessions of four important Prunus spp. fruit crops in China, fruiting-mei (P. mume), apricot (P. armeniaca), plum (P. salicina, and P. ussuriensis) and peach (P. persica). Nine primer pairs generated a total of 2,089 AFLP bands, of which 94.4% were polymorphic. Levels of polymorphism and the genetic relationships among the crops were studied.The fixation index (F_st) of the four different fruit trees ranged from 0.53 – 0.82, and the average genetic diversity (AGD) in these species ranged from 3.2% to 12.8%. These four stone fruit species could be clustered into four clear groups on a phylogenetic tree based on bootstrap analysis. Phylogenetically, fruiting-mei was shown to be closest to apricot and most distant from peach.     

Flower thinning method affects mineral composition of `Braeburn' and `Fiesta' apple fruit

Summary

Fruit mineral concentrations measured at harvest can have major effects on apple fruit quality on the tree or during storage. Orchard practices must therefore seek to optimize fruit mineral composition. The purpose of this study was to describe and elucidate the effects of hand thinning on whole trees and individual spurs on apple fruit mineral composition. Two methods of flower and fruitlet thinning were compared with no thinning on `Braeburn' and `Fiesta' apple trees. Alternate whole flower/fruitlet clusters or all but one flower/fruitlet within every cluster were removed at full bloom or 14±21 d after full bloom. Alternate-cluster thinning reduced final fruit numbers per tree and fruit Ca concentrations by up to 22%, while increasing final fruit size by up to 21%, compared with no thinning. These effects on fruit Ca concentrations were also measured across a range of fruit size classes. Within-cluster thinning at full bloom or up to 21 d after full bloom also reduced fruit numbers per tree but increased fruit size substantially, by up to 65% compared with no thinning, this effect being less for later thinning. However, fruit mineral concentrations were not influenced by this treatment. Some fruiting spurs were singled to one fruit 14 d after full bloom on alternately flower cluster thinned trees and on trees that had not been thinned at bloom, and compared with unthinned spurs on the same trees. Fruit Ca concentrations, primary spur leaf areas and primary spur leaf areas per fruit were greater for spurs bearing a single fruit (achieved by thinning manually or through natural abscission) than for multi-fruited spurs on the same trees. Spurs bearing one fruit on unthinned trees had greater fruit Ca concentrations, primary spur leaf areas and primary spur leaf areas per fruit, but lower fruit weight than the same spurs on alternate-cluster thinned trees. However, spurs on unthinned and alternate-cluster thinned trees with the same primary leaf areas per fruit had similar final Ca concentrations. Fruit size and crop loads were found not to be important in explaining fruit Ca concentration differences between thinning methods. However our results suggest that thinning method may affect Ca accumulation in apple fruit by altering the relationship between fruit numbers and leaf areas on individual spurs.