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  • Author or Editor: Richard P. Marini x
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Average fruit weight from two apple-thinning experiments was estimated by sampling 20-fruit/tree or harvesting all fruit on three branches/tree. The estimated values were compared with the true average fruit weight calculated from the entire crop on a tree. The value of a fruit was calculated from packout data obtained from the two sampling methods and was compared to the true value obtained from the entire tree. Statistical techniques, typically used by biometritions in medical research, were used to assess the agreement between the values obtained with the estimation methods and the true values. Estimates of average fruit weight obtained from 20-fruit/tree may differ from the true value by about 13% and estimates obtained from weighing all fruit on three limbs/tree may be within about 11% to 19% of the true mean. Estimates of fruit value obtained from a 20-fruit sample may differ from the true value by about 4 cents per fruit and estimates from three limbs/tree may differ from the true mean by about 7 cents per fruit. Analysis of variance was performed on each data set and the resulting P values differed for the three methods of estimating fruit weight and fruit value. Thus, erroneous conclusions may result from experiments where fruit weight and fruit value is estimated from relatively small samples.

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`Norman' peach trees were trained to the central-leader or open-vase form and were planted at high (740 trees/ha) or low (370 trees/ha) density. A third density treatment was a high/low density, where alternate trees in high-density plots were removed after 6 years to produce a low-density treatment. Annual yield per hectare was ≈15% to 40% greater for high-density treatments than for low-density treatments, but tree form had little influence on yield. Fruit size tended to be greater for low-density than for high-density treatments, but cumulative marketable yield was greatest for high-density and lowest for high/low density treatments. After 9 years, cumulative crop value was higher for open-vase than central-leader treatments (P = 0.12), but tree density had less of an effect on crop value (P = 0.21). Cumulative costs were highest for high-density treatments, but were not influenced by tree form. Income minus costs was nearly $4500/ha higher for open-vase than for central-leader trees and net present value was more than $2000/ha higher for high-density than low-density trees (P = 0.20). Open-vase trees were more profitable than central leader trees and should be planted at densities of about 700 trees/ha in the mid-Atlantic region.

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For 2 years, 'Redchief Delicious' apple (Malus ×domestica Borkh.) trees were treated with combinations of NAA and oxamyl and 'Smoothee Golden Delicious' trees were treated with combinations of NAA and carbaryl. Oxamyl, at concentrations of 250 to 750 mg·L-1, but not NAA at concentrations of 1 to 6 mg·L-1, reduced fruit set, yield and crop value. NAA did not consistently affect average fruit weight or the percentage of small fruits on 'Redchief Delicious' trees. Carbaryl reduced fruit set and yield on 'Smoothee Golden Delicious' trees one of the two years. Fruit set and yield were negatively related to NAA concentration both years. In one of the two years the combination of NAA plus carbaryl was more effective than NAA alone. Treatments that provided adequate thinning tended to reduce crop value because the increase in fruit size did not compensate for the reduced yields. Chemical names used: 1-naphthyl-N-methylcarbamate (carbaryl); methyl N′,N′-demethyl-N [(methylcarbomoyl)oxy]-1-thiooxamimidate (oxamyl); 1-naphthaleneacetic acid (NAA).

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Three experiments were performed to determine if pruning treatments could reduce the need for peach [Prunus persica (L.) Batsch] fruit thinning without reducing average fruit weight. To determine if dormant shoot heading affected fruit size simply by reducing the number of flowers per tree, all 1-year-old shoots on `Cresthaven' trees were headed by 50% or blossoms were removed from the terminal half of each shoot. At 45 days after full bloom, all trees were hand-thinned to obtain predetermined crop densities. Average fruit weight was highest on trees with blossom removal, but crop value and net profit were highest for nontreated trees. To determine the influence of treatment severity on fruit weight, all shoots on `Cresthaven' trees were blossom-thinned or headed to remove blossoms on varying proportions of each shoot. Fruit set and the number of fruit removed during postbloom thinning decreased as the percentage of a shoot that was headed or blossom-thinned increased. Average fruit weight at harvest and crop value were higher for trees with blossom removal than for trees with headed shoots. Fruit weight and crop value were not affected by the percentage of the shoot treated. In the final experiment, all shoots on `Cresthaven' trees were headed by 50% or were not headed. Heading of shoots reduced fruit set, number of fruits removed at thinning, and thinning time per tree, but yield, crop density, and average fruit weight were not affected by heading. Profit was increased by shoot heading one of the 3 years. Results from this study indicate that heading peach shoots by 50% while dormant pruning can reduce thinning costs without reducing fruit size, but a similar level of labor-intensive blossom removal may reduce postbloom thinning costs and improve fruit size.

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Counting blossoms before treatment and collecting yield data for whole trees following thinning treatments arc expensive practices. Researchers often collect data on sample branches to reduce the time and expense of data collection. How accurate are these techniques? To generate discussion concerning sampling, results will he presented for several experiments where data were collected for whole trees vs. sample branches. Data will also be presented for different ways of assessing fruit size at thinning time. Fruit diameter, fruit weight and fruit volume were recorded for several cultivars over several seasons. I hope to generate discussion about the desirability of these different measures of fruit development.

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Abstract

In 2 cultivars of peach [Prunus persica (L.) Batsch] semihardwood cuttings of current season shoots rooted better from terminal than from basal portions. Rooting of basal and terminal cuttings was correlated with stem diameter.

Open Access

Abstract

Net gas exchange properties of green and red peach (Prunus persica L. Batsch) leaves were studied. Net photosynthesis, transpiration, and stomatal conductance were similar for both leaf types. Young leaves (about 60% fully expanded) had greater dark respiration rates than fully expanded leaves. Chlorophyll content was greater for green leaves than for red leaves, but did not change consistently as leaves aged. Red leaves contained more anthocyanin than green leaves. Anthocyanin content was similar for green leaves of different ages, whereas anthocyanin declined in red leaves as they aged.

Open Access