Fruit Ca Concentration Research Articles

Effect of adjuvants on apple fruit and leaf calcium and nitrogen concentrations at three fruit growth stages

In a field trial, 0.006% v/v Agral-90® and four alternative adjuvants were evaluated to determine their effects on calcium (Ca) and nitrogen (N) uptake by leaves and fruit of ‘Golden Delicious’ apple from 0.45% m/v calcium nitrate sprays. No bitter pit was observed at harvest or after storage, all trees having received 12 sprays. The industry standard, 0.006% Agral-90®, did not affect fruit or leaf Ca or N levels, or Ca/N ratios, relative to the adjuvant-free control, after 6, 9 or 12 (harvest) sprays. Break-Thru® (0.025%), and 0.05% AG6210, significantly (P = 0.05) increased fruit Ca concentrations after nine (but not six or 12) sprays. Fruit Ca/N ratios at harvest, did not differ from the adjuvant free control in any treatment. Increased leaf Ca concentrations were observed after 9 sprays where Break-Thru® (0.025%), SEW (0.05%), AL2575 (0.05% and 0.10%) and AG6210 (0.10%) were added. SEW (0.05%) increased leaf Ca levels after six sprays. At harvest, after 12 sprays, leaf Ca concentrations in the various adjuvant treatments were similar to those in the adjuvant-free control. Leaf Ca/N ratios were greater than the control in the 0.05% SEW treatment after six sprays, in the Break-Thru® (0.025%), SEW (0.05% and 0.10%) and AL2575 (0.05%) treatments after nine sprays, and in the AG6210 (0.05%) treatment at harvest.

Relationships Between Leaf and Fruit Nutrients and Fruit Quality Attributes in Golden Smoothee Apples Using Multivariate Regression Techniques

The relationships between leaf and fruit nutrients in “Golden Smoothee” apples (Malus domestica Borkh. L) were analyzed using partial least squares regressions (PLS). The aim of the study is to identify the most relevant concentration nutrients for fruit quality in leaves (l) and fruits (f), and to work out the correlation among them and also in relation with some apple fruit quality attributes. The majority of leaf mineral concentrations [nitrogen (N), calcium (Ca), magnesium (Mg), and boron (B)] display a negative correlation with fruit N at harvest. There are positive correlations between fruit minerals [phosphorus (P), potassium (K), Mg, and boron (B)] and fruit N concentration, except for fruit Ca, which correlates negatively with fruit N. The results obtained suggest that leaf K concentration appears to be highly correlated positively with fruit K and P concentrations at harvest. Fruit B content displays a highly negative regression coefficient with leaf B concentration. Leaf Ca seems to exhibit no clear relationship with fruit Ca at harvest and this manifests as a negative correlation with many macronutrients in fruit, such as N, P, and K. These results suggest that leaf K, Ca, and Mg concentrations are good indicators for predicting the fruit K at harvest, with the leaf K influencing this positively, while leaf Ca and Mg exercise a highly negative influence. Fruit quality attributes, such as fruit acidity, are positively influenced by K and P nutrients, both in the leaf and fruit. Fruit firmness shows a positive correlation with the fruit Ca content and bitter pit incidence correlates negatively with this nutrient concentration.

Blossom-end Rot Incidence of Tomato as Affected by Irrigation Quantity, Calcium Source, and Reduced Potassium

`Equinox' tomatoes (Lycopersicon esculentum Mill.) were grown during the springs of 2001 and 2002 with black polyethylene-mulch and drip irrigation on an Arredondo fine sand in Gainesville, Fla., to study the influence of water quantity, Ca source, and reduced K on incidence of blossom-end rot (BER), marketable fruit yield, and fruit and leaf Ca concentration. Tensiometers were used to schedule irrigation in main plots when the soil matric potential reached 10 or 25 kPa. Subplot nutritional treatments were no added Ca, Ca(NO3)2, Ca thiosulfate, CaCl2, CaSO4, and K rate reduced by 50%. Interactions between year and treatment were significant. During 2001, total marketable yields were higher with Ca(NO3)2 or CaCl2 compared to plants that received Ca thiosulfate and were higher from plants irrigated at 10 kPa than irrigated at 25 kPa. Number and weight of BER fruit were lower with Ca(NO3)2 and reduced K than with no added Ca and CaSO4. Leaf and fruit Ca concentrations were generally higher with Ca(NO3)2 compared to all other nutritional treatments. Leaf and fruit Ca concentrations were generally higher from plants irrigated at 10 kPa than at 25 kPa. The reduction of NH4+-N, by the supply of N as NO3-, and the addition of supplemental Ca reduced the incidence of BER, and increased the leaf and fruit Ca concentrations. During 2002, marketable yields were higher with CaSO4 than with CaCl2 and reduced K. Weight and number of BER fruit were lower with irrigation at 10 kPa than at 25 kPa. Leaf and fruit Ca concentrations were higher or similar from plants that received Ca(NO3)2 than with all other nutritional treatments. During the 2002 season, rainfall was less and temperatures and daily evapotranspiration (ET) were higher than in the 2001 season. In the 2002 season, 3.28 × 106 L·ha-1 of irrigation was applied as compared to 1.58 × 106 L·ha-1 in 2001. With an average Ca concentration of 76 mg·L-1 in the irrigation water, much more Ca was applied during the higher ET 2002 season. With the higher transpiration and temperature, water uptake and hence, Ca uptake were increased. During both seasons, the lowest Ca concentration was observed at the blossom end of the fruit and the highest Ca at the stem end of the fruit. Fruit Ca concentrations were lower and BER was 5 times higher in the lower ET, higher rainfall (lower irrigation) 2001 season compared to the higher ET, lower rainfall (higher irrigation) 2002 season. These data support that BER was a symptom of Ca deficiency and this deficiency was aggravated by high rainfall, low ET, and the resulting reduced irrigation applied and reduced Ca uptake.

Effect of Soluble Calcium and IBA Treatments on Fruit Characteristics and Browning of Blossom End Part in `Fuyu' Sweet Persimmon

Sweet persimmon, `Fuyu', is the major cultivar for MA storage, but browning of blossom end part (BBEP) and darkening are occurring during storage and decrease fruit qualities in fresh fruit markets in Korea. The symptom of BBEP of fruit started to occur on the blossom end part and spread to the middle and stem end part. These fruits lose their marketable values. Calcium has very important role in cell membrane in physical and physiological. This study was conducted to investigate the effect of soluble Ca treatments of fertigation (FG) and foliar application (FA) on soil properties, tree growth and fruit quality and on the occurrence of BBEP. Ca content was high in Ca FA and Ca + IBA FG compared to other treatments. This increase might affect the soil pH, and so pH followed the same pattern of Ca content in soil. In leaves and fruits, Ca content was much higher in Ca Ca FA and Ca + IBA, Ca FG, respectively. Ca content in fruit parts showed stem end part “middle part” blossom end part. In fruit quality, fruit firmness, soluble solid content and fruit weight did not show any tendency in treatments. The occurrence rate of BBEP was very low 14% in Ca FA and 20% in Ca FG than 50% in control. These results showed that Ca content in soil, leaves and fruits was increased by soil FG and FA and the increased Ca content in blossom end part have a negative relationship with BBEP in sweet persimmon.

The Effect of Calcium Sprays and Crop Load on Bitter Pit Incidence in `Honeycrisp' Apple

`Honeycrisp', a relatively new apple cultivar, is susceptible to bitter pit, a physiological disorder that develops mainly during storage. Although the cause of bitter pit is unknown, calcium (Ca) content of the fruit is known to be involved. A field experiment was conducted in Chanhassen, Minn. to refine recommendations for use of Ca sprays for reduction of bitter pit in `Honeycrisp' apple. Specific objectives were to determine: 1) Ca concentration and content throughout the fruit growing season; and 2) the association of bitter pit incidence with Ca concentration, crop load, vegetative growth and fruit size. Six treatments tested included: control; Ca(NO3)2 sprays all season; Ca(NO3)2 sprays early in the season; Ca(NO3)2 sprays late in the season; hand-thinning combined with Ca(NO3)2 sprays all season and hand-thinning. Ca concentration in fruits was measured bi-weekly using three different sampling methods: segments, cores and plugs. A randomized block design with four trees as experimental unit and five replications was used. Results suggest lower crop loads increase bitter pit incidence. While fruit from the thinned treatments was larger in size by the end of the experiment, no bitter pit was present at harvest. After 4 months of storage, the hand thinning treatment had 7.4% bitter pit, while thinning plus Ca reduced bitter pit to 2.4%. The other treatments had less than 1% bitter pit. Fruit analyses at the end of the growing season indicate that early and full season sprays resulted in the highest Ca concentration in fruit segments and cores. The lowest values were found for the thinning treatment. No association was found between vegetative growth and bitter pit incidence.

EFFECTS OF NITROGEN AND CALCIUM SUPPLY ON THE INCIDENCE OF INTERNAL FRUIT BREAKDOWN IN ¿TOMMY ATKINS¿ MANGOES (MANGIFERA INDICA L.) GROWN IN A SOILLESS SYSTEM

Tommy Atkins mangoes grafted on 13-1 were grown in a soilless system, with basaltic lapilli as substrate, to study the effect of nitrogen and calcium supply on internal fruit breakdown (IFB). Treatments consisted in a complete factorial of 2 nitrogen (0.72 and 5.36 mmol/L) and 2 calcium levels (0.62 and 2.5 mmol/L). Water consumption and nutrient uptake were calculated by difference between quantities supplied and drained. Fruits were harvested at full maturity and the degree of IFB and yield were assessed for each treatment, determining mesocarp mineral content. Nutrient uptake increased as fruit developed, in a greater proportion for Ca than for N, decreasing from the onset of physiological maturity. A significant interaction between the effects of N and Ca was observed for all the studied variables. For low Ca treatments total yield and Ca content of fruits were remarkably reduced in the presence of high nitrogen. The degree of IFB and total-N content of fruits were remarkably greater in the high N treatments, although to a lesser extent for the higher Ca level. The incidence of IFB showed a high positive correlation with the fruit N content and a negative relation with the Ca content.

EFFECTS OF SUBSTRATES ON YIELD, QUALITY AND MINERAL COMPOSITION OF SOILLESS-GROWN CUCUMBERS

Cucumber plants (Cucumis sativus L.) were grown in soilless culture under greenhouse conditions at the Experimental farm of University of Tuscia, Central Italy to evaluate the effects of four substrates (rockwool, pumice, perlite, and coir) on growth, yield, fruit quality, and plant mineral composition. Plants grown in coir, perlite and pumice yielded more than those grown in rockwool. Similar results were obtained for dry weight of leaves, stems, and fruits. Fruit quality in term of dry matter, soluble solid content, titratable acidity, and pH was not significant affected by treatments. Concentrations of K and Na were highest in nutrient solution, and fruits of coir treatment while perlite and pumice treatments had highest Ca concentration in nutrient solution, leaves and fruits. Phosphorus and Mg were highest in nutrient solution and plant organs of coir treatment, respectively. The above findings may be explain by the different chemical and physical properties of substrates and their interaction with nutrient solution composition and plant nutrient uptake.

Effects of fertilizer rates and dates of application on apricot (cv Bergeron) cropping and pitburn

Various nitrogen (N) and potassium (K) fertilizer rates and dates of application were assessed in an apricot orchard. High N fertilization enhanced vegetative growth, yield and average fruit weight and aggravated fruit pitburn incidence. Increasing K fertilization enhanced fruit soluble solids and colouring, but did not affect pitburn. Pre-harvest versus post-harvest applications of fertilizers did not influence vegetative growth, yield or average fruit weight, but tended to reduce fruit soluble solids and colouring. At all times of evaluation of pitburn, there was a positive correlation between fruit N content and pitburn incidence. Furthermore, for a given fruit N content, pitburn appeared to increase with the duration of conservation. A high fruit N content has to be considered as a main predisposing factor for pitburn in apricot. A negative correlation between pitburn incidence and fruit Ca content also was detected a week after harvest.

Number and concentration of calcium nitrate plus Kelpak® sprays for control of bitter pit in 'Braeburn5 apple fruit

In a spray trial to test the effects of calcium nitrate and a kelp extract (Kelpak®), fruit calcium (Ca) concentrations in ‘Braeburn’ apples peaked between 7.6 and 9.5 mg 100 g−1 fresh mass (FM) on 19 December 2000, then declined to between 2.3 and 3.2 mg 100 g−1 FM at harvest (22 March 2001). Fruit Ca concentrations on 19 December were highest where 12 sprays, each containing 117 g Ca per 100 I water were applied, without Kelpak®, at weekly intervals from 42 days after full bloom to 30 January. At harvest, fruit Ca in this treatment was no greater than where 12 sprays containing either 117 or 58.5 g Ca per 100 I water were applied with Kelpak®. Incidences of bitter pit in these treatments were, respectively, 1.0%, 1.3% and 3.4%. Where six half-strength sprays were applied, with Kelpak®, over the same time period, bitter pit increased to 9.3%. At harvest, fruit Ca concentrations were 0.25 mg Ca per 100 g−1 FM lower in pitted, than in bitter pit-free fruit. Total soluble solids and starch conversion were lower where 12 full-strength sprays were applied without Kelpak® than where 12 half-strength sprays were applied with Kelpak®. Starch conversion was greatest where six half-strength sprays were applied with Kelpak®. The effects on fruit colour of calcium nitrate, alone or with Kelpak®, were inconclusive

EFFECT OF FOLIAR ZN, FORM AND TIMING OF CA SPRAYS ON FRUIT CA CONCENTRATION IN NEW APPLE CULTIVARS

EFFECT OF FOLIAR ZN, FORM AND TIMING OF CA SPRAYS ON FRUIT CA CONCENTRATION IN NEW APPLE CULTIVARS

EFFECTS OF CALCIUM, BORON AND DWARFING INTER-STOCK ON FRUIT QUALITY OF CUSTARD APPLE (ANNONA SPP. HYBRID) CV. AFRICAN PRIDE

The quality of custard apple (Annona spp. hybrid) fruit is a major factor limiting expansion of this industry in Australia. Several internal disorders occur in custard apple; especially common is ‘woodiness’ which is characterised by the presence of woody seed pockets and gritty lumps in the flesh and `brown pulp’, which is a discolouration of the pulp. Surveys and experiments were conducted to evaluate the effects of soil-applied Ca and B on fruit quality of the custard apple cv. African Pride in subtropical Australia. Dwarfing inter-stocks and higher fruit Ca concentrations were associated with a 2- to 3-fold reduction in internal disorders. Fruit Ca concentrations may be improved through repeated soil applications of Ca but uptake and response may take several years to achieve. Fruit Ca concentrations need to be maintained at > 0.15% dry weight and leaf Ca > 1.6% dry weight. The current leaf nutrient standards of adequacy for Ca appear to be set too low. Our data indicate that in the early stages of development, fruit compete poorly against leaves and shoots for available Ca, especially when Ca concentrations in the xylem are low and transpiration high. Leaves that readily transpire accumulate more Ca. In the long term, dwarfing inter-stocks of sugar apple (Annona squamosa) or dwarfing rootstocks of cherimoya (Annona cherimola) may be the most efficient method of controlling ‘woodiness’ and improving fruit quality.

Relationship between Ca, K and Mg concentration and browning of blossom end part of 'Fuyu' sweet persimmon during MA storage

This study was conducted to investigate the relationships between fruit Ca, K, and Mg concentrations and browning of blossom end part (BBEP) of the 'Fuyu' persimmon during modified atmosphere (MA) storage. Calcium concentration of the soils and stem bark were significantly lower in an orchard where the browning of persimmon fruit occurred than in an orchard producing normal fruit. However, K and Mg concentration of the soils and stem bark were not different between the two orchards. Calcium concentration of the flesh and peel was lowest in the blossom end part of the fruit (BEP) where the browning symptoms were most severe. The severity of BBEP of the fruit appeared to be directly related to the Ca concentration of peel and flesh. The Ca/K+Mg ratio of fruit also had a relationship to the BBEP. There were negative correlations between Ca/K, Ca/Mg, and Ca/K+Mg in fruit peel and flesh. Accordingly, low Ca concentration in the fruit appeared to be a major factor inducing the browning symptoms in the BEP of the 'Fuyu' persimmon during MA storage at low O 2 and high CO 2 .

“JONAGOLD” APPLE FRUIT QUALITY AS INFLUENCED BY FALL SPRAYS WITH CALCIUM CHLORIDE AT HIGH RATES

The aim of the experiment was to examine the effects of fall sprays with calcium (Ca) as calcium chloride at high rates on ‘Jonagold’ apple (Malus domestica Borkh.) fruit quality. Trees were sprayed with Ca both in summer (9, 7, 5, and 3 weeks before fruit harvest) at a rate of 3 kg Ca ha−1and in fall (one week before fruit harvest) at rates of 8, 16, or 24 kg Ca ha−1. Fall Ca sprays resulted in leaf injuries and defoliation; however they had no effect on cold hardiness of one-year-old shoots. Fruit yield, weight, maturity at harvest, surface condition, and color were not influenced by Ca sprays during three consecutive years. Fruit Ca concentration corresponded with amount of Ca applied. In two of three years, summer Ca sprays decreased sensitivity of apples to bitter pit. Fruit sprayed with Ca both in summer and in fall had higher firmness and titratable acidity after storage and were more resistant to bitter pit and internal breakdown than controls and fruit sprayed only with Ca in summer. Apples sprayed with Ca in summer and in fall at the highest rate were the least sensitive to bitter pit and internal breakdown and were more resistant to decay than control fruit.

EFFECT OF CALCIUM CHLORIDE SPRAYS AT DIFFERENT WATER VOLUMES ON “SZAMPION” APPLE CALCIUM CONCENTRATION

The aim of the study was to examine the effect of calcium chloride sprays at different water volumes on ‘Szampion’ apple calcium (Ca) concentration. Apple trees were sprayed with CaCl2at a rate of 7 kg ha−1 using 250, 500, 1000, and 1500 L of water which represents: 2.8, 1.4, 0.7 and 0.5% CaCl2 solution, respectively. Sprays with CaCl2 were applied 6, 4, and 2 weeks before fruit harvest by a directed air-jet sprayer with radial fan. Fruit Ca concentrations were determined from the bottom (to 1.5 m height), middle (from 1.6 to 2.3 m height) and top (from 2.4 to 3.0 m height) of tree. The trees unsprayed with Ca served as a control. The study showed that such treatments did not injure leaves and fruit. Efficacy of CaCl2 sprays at studied water rates in increasing fruit Ca concentration was similar. Apples sprayed with Ca from the middle and bottom of tree canopy had higher Ca concentrations than control fruit. Leaf Ca applications at all water volumes had no effect on fruit Ca concentration from tree canopy top, however, laboratory study indicated that apples from this zone had ability to take up exogenous Ca. It was also found that young ‘Szampion’ fruitlets took up clearly less exogenous Ca as compared to mature fruit, which suggests that Ca sprays of this cultivar should be performed mainly at late apple development stages.

Study of Apple Cultivars on Dwarfing Rootstocks in North Mississippi

This study was established to determine the influence of scion/stock combination on leaf area, yield efficiency, and fruit quality attributes in effort to identify the most suitable scion/stock combination for Mississippi. Twenty-nine scion/stock combinations were grown at the Pontotoc Ridge-Flatwoods Research and Extension Center, North Mississippi. The treatments were arranged in a completely randomized design (CRD) with six single tree replications. `Jon-A-Red' on Mark produced the smallest leaf area, while the largest leaf area was produced by the combination of `Royal Gala' on MM106 and `Blushing Golden' on M7A. Scion/stock combinations significantly affected yield efficiency, fruit yellow pigment dvelopment, firmness and fruit mineral composition. Scion cultivars on Mark resulted in the highest yield efficiency, except `Empire'. `Ultra Gold' and `Braeburn' on Mark and `Blushing Golden' on MM111 led to yellow pigmentation in the highest category. Meanwhile, `Braeburn' on Mark was among the scion/stock combinations that produced the firmest fruit. And fruit from trees on Mark consistently had high calcium (Ca) levels. After 7 years, `Royal Gala' on Mark produced the highest yield efficiency. `Braeburn' on Mark resulted in both the firmest fruit and the highest fruit Ca concentration.

Effect of calcium sprays, time of harvest, cold storage, and ripeness on fruit quality of ‘anjou’ pears1

Calcium chloride (CaCl2), increased Ca concentrations in fruit cortex and peel of ‘Anjou’ pears (Pyrus communis L.). Calcium sprays reduced the fruit disorders: brown core, cork spot and superficial scald. Fruit size (weight) increased while fruit Ca concentrations decreased with fruit at the later harvest dates. The earliest harvest date was associated with a lower incidence of fruit disorders. Superficial scald increased in fruit held longer in cold storage and in ripened fruit. Shelf‐life and fruit quality of Ca‐sprayed fruit was improved due to higher Ca concentrations in fruit peel and cortex resulting in overall enhancement of fruit appearance, and in improvement in the control of the incidences of cork spot, scald, brown core, and external and internal rots, and in amelioration of fruit juiciness and fruit color.

541 Effect of Supplemental Calcium on Watermelon Yield, Fruit Weight, Soluble Solids, and Calcium Content of Leaves and Fruit

Inadequate available Ca can cause blossom end rot in watermelons. Many products and materials are marketed to try and help reduce this problem. A 3 X 3 factorial was set up with three soil Ca treatments (none, 1120 kg/ha of dolomite and 1120 kg/ha of qypsum) and three foliar Ca treatments (none, Liqui-Cal at 9.35 L/ha and Foli-Cal at 4.67 L/ha) using both a seeded (2N) and seedless (3N) cultivar. Mehlich-1Ca level prior to planting was 305 ppm. None of the Ca treatments affected leaf or fruit Ca levels. Applied Ca treatments did not affect total yields, fruit weight, or percent soluble solids of the seedless cultivar (Crimson Trio). Yield of `Royal Flush' (2N) was reduced by application of Foli-Cal, but none of the other parameters were affected by the other Ca treatments. Leaf Ca level of `Royal Flush' (3.05%) was almost twice that of `Crimson Trio' (1.59%), while fruit Ca content of `Royal Flush' (0.26%) was lower than that of `Crimson Trio' (0.32%).

Calcium sprays, time of harvest, and duration in cold storage affects fruit quality of d'Anjou pears in a critical year

Calcium chloride (CaCl2) sprays increased calcium (Ca) concentrations in d'Anjou fruit (Pyrus communis L.), reduced the incidence of cork spot and improved shelf‐life by increasing fruit firmness in a critical year that had lower fruit Ca concentrations due to record high spring and late season temperatures. The third and final harvest in late September resulted in larger fruit size, lower fruit Ca concentrations, higher incidence of cork spot, more extractable juice and yellow fruit skin color, higher soluble solids and sucrose concentrations, but lower acidity than earlier harvested fruits. Fruit held longer in cold storage (145 days) had higher concentrations of fruit Ca, lower concentrations of carbon dioxide (CO2) and ethylene (C2H4), less fruit firmness, soluble solids and acidity, lower concentrations of sucrose, glucose and fructose, and less green color of fruit skin than short term storage (45 days). Shelf‐life of CaCl2‐sprayed fruit was improved because of higher concentrations of fruit Ca that resulted in a lower incidence of cork spot and brown core, fruit firmness was higher, levels of CO2 and C2H4 were lower, and soluble solids, acidity, and extractable juices were affected less for ripened fruit.

565 Evaluation of the Massive Use of Magnesium Infiltration to Predict Bitter Pit in Apples

Bitter pit (BP) is the main physiological disorder of apples in Chile. Its incidence affects pre- and postharvest handling of the fruit and the profitability of this species. Since 1991, its control and prediction have been studied by this research team through field and laboratory trials. The BP incidence is linked to the fruit Ca concentration; however, fruit Ca analysis has not adequately predicted BP incidence in postharvest. Several authors have proposed Ca/Mg antagonism, which has been the basis to develop a predictive method through fruit Mg infiltration (IMG) 40 days before harvest. IMG has been massively used for two seasons in Chile, with 375 samples processed in 1997 and 1170 in 1998. The industry has been increasing its proportion of the samples processed, from 22% in 1997 to 71% in 1998. The most prominent varieties are `Granny Smith' (GS) > `Braeburn' (BR) > `Royal Gala' (RG) > `Red King Oregon' (RKO). The massive use of IMG has obtained predictive capacities (r2 between BP predicted and BP after 3 months regular cold storage) of 0.8 for `Fuji'; 0.7 for GS, BR, and RG; and 0.58 for RKO. (This reduction in the predictive capacity with regards to the previous research under controlled conditions would, in part, be due to problems in obtaining fruit samples: non-uniform fruit size, inadequate sampling dates, diverse fruit numbers, etc.) Developments are underway to increase the geographical coverage of the service, the predictive capacity of the method for certain cultivars and productive areas and the number of samples processed.

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

SummaryFruit 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.