Non-thinned Control Research Articles

Effect of Crop Load on Yield and Quality Parameters in Apple cv. Gala Redlum

The present study was conducted at the experimental field of the Division of Fruit Science, Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir during the year 2021-2022. The primary objective of this study was to assess the impact of varying crop loads on the growth, yield, quality, and return bloom of Gala Redlum apples, with specific emphasis on trunk cross-sectional area (TCSA). The experimental design involved a Randomized Complete Block Design (RCBD) with three replications, utilizing 4-year-old Gala Redlum plants. The trees were subjected to manual thinning, resulting in crop loads of 4, 6, 8, 10 fruits per cm² of TCSA, with a non-thinned control group. Notably, the maximum fruit yield (18.52 kg/tree) was observed in the control group (no thinning), while the minimum yield (7.57 kg/tree) was recorded in the C2 group (4 fruits per cm² of TCSA), followed by C3 (11.03 kg/tree). Furthermore, the impact of different TCSA ranges on fruit yield was statistically significant. The maximum fruit yield (14.45 kg/tree) was observed in the S2 group (10-12 cm² TCSA), while the minimum yield (12.16 kg/tree) was noted in the S1 group (8-10 cm² TCSA). Yield efficiency, measured as yield per unit of TCSA, reached its highest (1.838 kg/cm²) in the control group and is lowest (0.766 kg/cm²) in the C2 group (4 fruits per cm² of TCSA). The results further revealed that the C2 group (4 fruits per cm² of TCSA) exhibited the maximum Total Soluble Solids (TSS) content (14.73 °Brix), total sugars (11.62%), and TSS: Acid ratio (61.45). Similarly, the C3 group (6 fruits per cm² of TCSA) demonstrated elevated TSS (14.20 °Brix), total sugars (10.99%), and TSS: Acid ratio (54.66). Additionally, the S2 group (10-12 cm² TCSA) recorded the highest TSS (13.75 °Brix), total sugars (10.51%), and TSS: Acid ratio (50.53). The combination of C2S2 and C3S2 treatments exhibited superior results, with the highest TSS (14.82 °Brix), total sugars (11.77%), and TSS: Acid ratio (62.64). Fruit firmness (8.81 kg/cm²) and fruit acidity (0.327%) were maximized in the C1S1 treatment combination.

Fruit Thinning Improves Fruit Size, Yield and Return Flowering in ‘Washington Navel’ Orange (Citrus sinensis L. Osbeck)

ABSTRACT “Washington Navel” orange is the principal mid-season maturing cultivar grown in south-eastern Australia. The cultivar has strong export potential and earns high returns for citrus growers. However, trees bear a large number of small-sized fruit in an on-year followed by a small number of large-sized fruit the next year if crop load is not properly managed. Thinning can be used as a crop management strategy to adjust crop load. A thinning experiment was conducted, and crop loads were adjusted on a whole tree basis to 2, 4, 6 or 8 fruit/0.125 m3 canopy volume (CV), removing 46%, 30%, 20% and 8% of the crop respectively, and compared to non-thinned control trees. Fruit diameter was measured at regular intervals from February to July. Fruit yield and number were recorded for two consecutive seasons. Return bloom after thinning was also recorded. Thinning treatments 2, 4 and 6 fruit/0.125 m3 CV resulted in higher fruit growth rates of 24%, 9% and 14% compared to the control. Thinning to a crop load of 6 fruit/0.125 m3 CV produced the best results for fruit size and yield during the treatment year. The following year return bloom was increased in the 2, 4 and 6 fruit/0.125 m3 CV compared to the control. The 6 fruit/0.125 m3 CV treatment resulted in a higher cumulative yield of 169 kg/tree over two cropping seasons and 42% fruit in the size class > 75 mm diameter compared to the control. Economic analysis revealed that 6 fruit/0.125 m3 CV could generate an extra $4,240/ha of income for citrus growers. It was concluded that a fruit load of 6 fruit/0.125 m3 CV was required to produce high yields and large fruit size over two cropping seasons.

Precommercial thinning increased diameter growth while maintaining mixedwood stands composition, 15 years after treatment

Precommercial thinning could be a valuable tool for climate change adaptation, as it can promote stand diversity while increasing productivity. Softwood and hardwood stands are usually thinned following different methods, and we lack recommendations for application in mixedwood stands. We evaluated the effects of precommercial thinning on the growth and composition of balsam fir ( Abies balsameaL.)–birch stands dominated by paper and yellow birch ( Betula papyrifera Marsh. and Betula alleghaniensis Britt.), comparing methods and production objectives (systematic release-softwood, systematic release-mixedwood, crop-tree release-mixedwood, and crop-tree release-hardwood) in Québec (Canada). Precommercial thinning increased tree-level and stand-level growth, especially for both birches. Compared to the non-thinned control, thinning increased tree diameter at breast height annual increments by 60%–107%, with similar results among modalities. Thinning changed initial stand composition, but mixedwood production plots composition was similar to that of the control 15 years after treatment. Promoting diversity is often perceived to be made at the expense of wood production. Our results suggest that we can obtain both increased growth and maintain diversity. Precommercial thinning is currently suggested as an adaptation tool that can foster drought resistance. Based on our study, we suggest it could serve another purpose in climate-adapted forest management, that is, maintaining diversity and thus increasing resilience to disturbances.

השפעת מועד דילול האשכולות בכרם יין על הגפן, ואיכות הענבים והיין

In the current practice among vineyards, it is customary to regulate the vines' crop in order to achieve the required quality. Many studies have shown a correlation between low crop levels and increased grape and wine quality. The aim of this work is to examine the effect of relatively late grape bunch thinning on crop parameters and wine quality, as well as their effect on the expression of genes in the phenylpropenoid pathway. Thinning treatments were executed during (1) an early stage of berry growth, the veraison phase (color change), and (3) the "harvest eve" phase – about two weeks before the harvest. The research work took place for several years at vineyards in Gush Etzion and Mevo Horon, Israel. In this paper, we present the research that took place in 2018 at the Mevo Horon vineyard, using Shiraz and Merlot wine varieties. The results show that there was an improvement in the indices of acid, polyphenols, and color in the thinned plots compared to the non-thinned control plots. In most indices, an improvement was found in grapes treated by late thinning over that of non-thinned. Thus, it may be concluded at this stage that even a thinning treatment conducted 10 days before harvest has a significant positive influence on wine quality compared to the maintenance of high yields until harvest time. An analysis of the expression level of central genes involved in the formation of anthocyanins (color) showed that the early thinning treatments caused an increase in their expression level. The results of this experiment may present the basis for further examination of a new cultivation practice in which high yield will be maintained and thinning will be carried out late in the season. The clusters removed during thinning may be used to produce rose wines, given adequate compensation to the farmer and winery for this costly operation.

Shoot thinning of Semillon in a hot climate did not improve yield and berry and wine quality

Aim: Shoot thinning is a common canopy management practice used to obtain a desired shoot density and to improve canopy microclimate. Since thinning is often carried out manually, the cost can be high. In this study the effect of severe shoot thinning (50 % of shoots removed) applied at EL 15 was investigated by comparing yield components, canopy size, berry and wine chemistry, and sensory attributes to a non-thinned control for the variety Semillon. The objective was to determine whether shoot thinning could change canopy architecture and lead to improved fruit and wine chemistry and sensory characteristics.Methods and results: The trial was carried out over four consecutive growing seasons (starting in 2014-15) in the Semillon block of the Coombe vineyard (Waite Campus, the University of Adelaide). Canopy architecture was monitored at key phenological stages in each season and yield components were assessed at harvest. The harvested fruit was used for chemical and sensory analysis of the berries. Wines were made and their chemistry and sensorial attributes assessed. Shoot thinning reduced the total leaf area in only two of the four seasons, but single shoot leaf area and cane weight were higher in shoot-thinned vines in all seasons. Shoot thinning did not reduce yield, despite a large reduction in bunch number, because of increased bunch weight. Shoot thinning did not change berry and wine chemistry. Similarly, little differences were observed in the sensory profile of berries and wines, and the assessors preferred the wines obtained from shoot thinned vines in the last season only.Conclusions: In this study, shoot thinning increased the leaf area per shoot and the cane weight, but yield and grape and wine chemistry were unaffected. The vine balance indices leaf area/yield and yield/pruning weight were also unaffected by the treatment, despite its intensity (50 % of shoots removed).Significance and impact of the study: The practice of shoot thinning when applied at EL stage 15 (8-9 leaves separated) was not effective as a technique to improve canopy microclimate and berry and wine chemistry for the white variety Semillon in a hot Australian climate. By not applying shoot thinning growers could potentially make significant savings without affecting yield or wine properties. Further research is needed to explore the effect and timing of shoot thinning on other varieties and in different environments.

Multi-year study of the effects of cluster thinning on vine performance, fruit and wine composition of Pinot noir (clone 115) in California’s Edna Valley AVA (USA)

A three-year study was conducted at a commercial vineyard site in California’s Edna Valley AVA to evaluate the physiological and agronomical effects of the timing of cluster thinning on Pinot noir (clone 115) grapevines. Vines were thinned to one cluster per shoot at three selected time-points during the growing season (bloom + 4 weeks, bloom + 8 weeks and bloom + 12 weeks), and fruit from each treatment was harvested and made into wine. Across all growing seasons, yield decreased 43% in thinned vines relative to non-thinned control vines. No effect of cluster thinning or interaction with growing season was found in vine shoot diameter, internode length, fruit zone light level, or cluster weight. The growing season significantly affected more fruit and wine parameters than did cluster thinning treatment, with interactions between treatment and growing season found in fruit Brix, titratable acidity, and anthocyanins, as well as wine anthocyanins and wine b* (yellow component). For example, bloom + 8 and bloom + 12 thinning treatments advanced Brix in 2017 but had no effect in 2018. Cluster thinning treatments respectively increased berry anthocyanins and total phenolics by 43% and 87% in 2017 and by 103% and 140% in 2018 relative to the non-thinned control, with no significant differences found between the different thinning treatments. However, the resulting wines from cluster thinning treatments showed no differences in the levels of anthocyanins and total phenolics. The fact that different cluster thinning treatments resulted in nil or minor effects on fruit and wine suggests that the vines tested were at or below a balanced crop load prior to the application of cluster thinning. Edna Valley AVA Pinot noir grapes could likely support crop loads (expressed as the Ravaz index) higher than 3.2 without negatively impacting fruit or wine composition and reducing crop load below that level is unlikely to increase fruit or wine quality.

Agronomical and Chemical Effects of the Timing of Cluster Thinning on Pinot Noir (Clone 115) Grapes and Wines

A two-year study was performed to evaluate the effects of the timing of cluster thinning on Pinot noir grapes and wines in the central coast of California. Vines were thinned to one cluster per shoot at three selected time-points during the growing season, and fruit was harvested and made into wine. No consistent effect of cluster thinning was found in wine phenolic profile or color across a cool (2016) and a warm (2017) growing season. The growing season had a more significant effect than the cluster thinning treatment for most parameters measured. There was no detectable overall sensory difference between the non-thinned control wines and any of the thinned treatment wines. Based on current results, Pinot noir vineyards on the central coast of California can support crop loads that result in Ravaz Index values from 3 to 6 without concern for impacting ripening potential or negatively affecting fruit composition.

Evaluation of 10-year temporal and spatial variability in structure and growth across contrasting commercial thinning treatments in spruce-fir forests of northern Maine, USA

Detailed measures of growth pattern and structural heterogeneity applied in this study helped to quantify the immediate effects of various thinning regimes on forest structure and the resulting alterations in tree size as well as observed longer term stand dynamics. Forest management, stand structure, and tree growth are highly inter-correlated. Prior analyses, however, have resulted in mixed outcomes with limited success in revealing ecological mechanisms. The study aimed at evaluating the relationship between forest structure and stand dynamics by applying several sophisticated measures of growth pattern and structural heterogeneity. Data from a controlled and fully stem-mapped commercial thinning experiment with seven contrasting treatments including a non-thinned control at six locations across the Acadian Forest of Maine, USA, was used. Stand-level attributes examined included tree size and growth heterogeneity, spatial tree distribution, and growth dominance. Thinning generally reduced stand structural heterogeneity compared to the non-thinned control. In addition, the spatial arrangement of trees changed from fully random (non-thinned control) to a more clustered (removal of dominant and co-dominant individuals) or regular distribution (removal of intermediate and suppressed individuals). Overall, stand growth exhibited increasing (non-thinned control, removal of intermediate and suppressed individuals) or decreasing growth dominance of large trees (removal of co-dominant competitors). Forwarder trails increased basal area growth of individual trees up to a distance from the trail of approximately 5 m. Findings of this study validate an earlier insight according to which interactions between management practices, forest structure, and tree growth form a permanent feedback loop.

Influences of Conventional and Low-Density Thinning on the Lower Bole Taper and Volume Growth of Eastern White Pine

Abstract Throughout the northeastern United States, thinning is a common management practice in stands of eastern white pine (Pinus strobus L.), but foresters lack clear information as to whether conventional B-line or low-density thinning will best achieve their growth and financial objectives. Conventional management consists primarily of light crown thinning, whereas low-density management uses heavy crown thinning to isolate selected crop trees. To better inform silviculturists of the effects of these thinning regimes on volume growth and taper of white pine, we compared the lower bole taper—quantified as Girard form class (GFC)—and volume growth between the two thinning regimes and a nonthinned control. Over the 17-year study period, GFC increased among all treatments from an overall average of 0.77 — 0.01 (—SE) to 0.82 — 0.00. Trees under the B-line thinning regime had the most taper (lowest GFC), owing to a thinning-induced growth response at breast height but not at the top of the butt log. Low-density thinning, on the other hand, resulted in substantially larger, less tapered butt logs with significantly higher growth rates at both breast height and the top of the butt log. The volume growth of low-density trees was significantly higher than that of trees in the other treatments. At the stand level, however, the overall volume growth of the low-density treatment was significantly lower than that of the B-line treatment. Thus, this study reveals that when implementing low-density thinning, there is a tradeoff between overall stand growth and larger, less tapered individual trees.

Shoot thinning effects on seasonal whole-canopy photosynthesis and vine performance in Vitis vinifera L. cv. Barbera

Background and Aims: While shoot thinning is one of the most widely applied practices in the vineyard as a tool to regulate canopy density and/or crop level, its physiological bases are still fairly obscure and have been poorly investigated. Our aim was to assess seasonal modification of whole-canopy net CO2 exchange rate (NCER) in thinned and non-thinned grapevines, as well as establishing correlations with grape composition. Methods and Results: Potted, mature cv. Barbera vines were thinned (ST) to 10–15 shoots/m over the two trial years and compared with a non-thinned control (C). The data logged each season included whole-vine NCER monitored pre- and post-veraison for periods of variable lengths, vine growth, yield components and grape composition. While final leaf area per vine did not differ between treatments, ST showed reduced yield and improved berry colour and must sugar accumulation. In 2009, NCER/vine recovery in ST was 85% of C at verasion, whereas in 2010 full recovery was already reached around bloom. Conclusions: A load of 15 shoots/m maximised canopy efficiency by inducing the fastest recovery of whole-vine photosynthesis and markedly improved sugar, colour and phenolics. Retaining 10 shoots/m delayed NCER recovery while improving overall grape composition as compared to C. Significance of the Study: Direct assessment of the complex seasonal canopy NCER dynamics triggered by shoot thinning indicates that the source-sink balance evolves in ST towards a higher supply of assimilates per unit of crop than that available in non-thinned canopies during the veraison-to-harvest period.

Mechanical Thinning of Peach and Apple Trees Reduces Labor Input and Increases Fruit Size

Hand thinning is a necessary but costly management practice in peach (Prunus persica) production. Organic apple (Malus ×domestica) production also may require hand thinning to adjust crop load. Mechanical devices to aid in thinning have been developed, but none has proven highly efficient and capable of completely replacing hand thinning. Narrow canopy training systems and novel peach tree growth habits offer new opportunities to examine mechanical methods for thinning peach and apple trees. Our studies evaluated mechanical thinning devices on peach and organically grown apple trees. In 2005 and 2006, a U.S Department of Agriculture-designed spiked-drum shaker was used to thin pillar (columnar) peach trees at 52 to 55 days after full bloom. The drum shaker, driven at two different speeds in the orchard, reduced crop load an average of 58% and follow-up hand thinning time by 50%, and increased fruit size by 9% at harvest compared with conventional hand-thinned or nonthinned control trees in 2005. In 2006, the shaker was driven at one speed but operated at two different frequencies. At 260 cycles/minute, the drum shaker removed more fruit and reduced crop load to a greater extent than when operated at 180 cycles/minute, however, fruit size at harvest did not differ between the two operating frequencies. The drum shaker reduced follow-up hand thinning time between 54% and 81%. Horticultural and economic evaluations of the drum shaker and/or a German-designed blossom string thinner were conducted in 2007 in four commercial peach orchards trained to a perpendicular V or quad V system and an organic apple block trained to a narrow vertical axis system. Mechanical thinners reduced peach crop load by an average of 36%, decreased follow-up hand thinning time by 20% to 42%, and increased fruit in higher market value size categories by 35%. The net economic impact of mechanical thinning versus hand thinning alone ranged from $175/ha to $1966/ha. Mechanical thinning at 20% full bloom resulted in more fruit in the large size categories (2.75 inches in diameter and larger) than thinning at 80% full bloom. Detailed counts of flowers on branches with different orientations indicated that pruning may be adjusted to improve thinner performance. The string thinner effectively thinned dwarf apple trees trained to a vertical axis system in a certified organic orchard, resulting in a reduction in hand thinning time and an increase in fruit size. Based on our tests, mechanical thinning appears to be a promising technique for supplementing hand thinning in apple and peach trees.

Magnitude of Viticultural and Enological Effects. II. Relative Impacts of Cluster Thinning and Yeast Strain on Composition and Sensory Attributes of Chardonnay Musqué

Chardonnay Musqué vines were subjected to six crop levels (nonthinned control and cluster thinned at late bloom/early set, early stage I of berry growth, late stage I, lag phase, veraison) over four years (1999 to 2002). Wines were made from these treatments using yeast strain VL1 (<i>Saccharomyces cerevisiae</i>). Additional fruit from nonthinned vines was subjected to several enological treatments: EC1118 strain (<i>S. bayanus</i>) ± pectinase preparation Cinn-Free and VL3 strain (1999) and EC1118 ± Cinn-Free and AR2000 enzymes, and CY3079, D47, and VL3 strains (2000 and 2001). Enological treatments were compared chemically and sensorially and to the viticultural treatments. Thinning decreased yields and clusters per vine regardless of timing. Both berry and cluster weights decreased as time of thinning was delayed, suggesting yield compensation. Thinning at/after early stage I led to higher Brix, pH, and potentially volatile terpenes (PVT) relative to the control; titratable acidity (TA) decreased with later thinning; and free volatile terpenes (FVT) increased in some thinning treatments. There were substantial differences in wine pH, TA, and PVT among the different yeast strains and enzyme treatments. Use of prepress Cinn-Free led to increased TA and FVT, resulting from extraction of organic acids and terpenes from berry skins. VL1 increased wine TA and pH. VL1 and VL3 reduced wine PVT, perhaps because of enhanced β-glucosidase activity and/or biosynthesis/biotransformation of terpenes. Despite chemical composition differences among viticultural treatments, wines differed little sensorially. However, sensory differences did occur among yeast treatments, with VL1 wines being distinctive. Several sensory attributes that distinguished between yeast treatment wines were correlated with PVT.

Acclimation to irradiance of leaf photosynthesis and associated nitrogen reallocation in photosynthetic apparatus in the year following thinning of a young stand of Chamaecyparis obtusa

In order to quantify the effects of thinning on photosynthetic parameters and associated change in leaf nitrogen (N) contents, half of the trees in a 10-year-old Chamaecyparis obtusa (Sieb. et Zucc.) Endl. stand (36° 3'N, 140°7'E) were removed, giving a final density of 1 500 trees ha-1, in May 2004. Photosynthetic photon flux density (PPFD) and leaf N and carbon (C) contents in the lower (L), middle (M), and upper (U) crowns were monitored one, three, and five months after thinning in both the thinned stand and a non-thinned control stand. In addition, leaves' photosynthetic responses to CO2 concentration were simultaneously measured in situ to estimate the maximum rates of carboxylation (Vcmax) and electron transport (Jmax). Thinning increased PPFD in the L and M crowns but not in the U crown. Vcmax in both the L and M crowns of the thinned stand increased significantly in comparison with the same crown position of the control stand in the three and five months following thinning. In addition, the thinned stand exhibited an increase in N partitioned to ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) in the L and M crowns relative to the control stand three and five months after thinning, indicating that N had been redistributed within the photosynthetic machinery. Thinning did not affect N per unit area at any of the crown positions, but significantly increased the content of N as a fraction of the total leaf dry mass in the L and M crowns three and five months after thinning. This was a consequence of a decrease in leaf dry mass due to rapid shoot growth. Thus thinning did not cause a redistribution of N between leaves. Thinning improved irradiance in the L and M crowns of C. obtusa, leading to photosynthetic acclimation. Photosynthetic acclimation in the first year mainly occurred via redistribution of N within but not between leaves.

Crop Load Reduction and Fruit Size Following Multi-step Thinning of 'Empire' Apple

Two years of field experiments were conducted in eastern New York to evaluate the efficacy of a multi-step thinning approach on reducing crop load (no. fruit per cm2 trunk cross-sectional area) and increasing fruit size of 'Empire' apple (Malus ×domestica Borkh.). Applications of Endothall (ET) at 80% bloom, NAA + carbaryl (CB) at petal fall (PF), and Accel™ + CB at 10 mm king fruitlet diameter (KFD), alone and in all combinations, were compared to a nonthinned control and to the application of NAA + CB at 10 mm KFD (commercial standard). In both 1996 and 1997, orthogonal contrasts indicated the multi-step treatment significantly increased fruit size, reduced cropload, and reduced yield compared to single applications. Effects on cropload of consecutive treatments were largely predicted by multiplying effects of individual treatments. Although all thinning treatments except for NAA + CB at PF in 1997 significantly reduced cropload, no single treatment thinned sufficiently to ensure good return bloom. Compared to NAA + CB at 10 mm KFD, multi-step thinning with NAA + CB at PF followed by Accel™ + CB at 10 mm KFD produced bigger fruits in both years, and resulted in a higher percentage of spurs carrying a single fruit in 1996. When fruit size was evaluated after removing the effect of cropload (cropload adjusted fruit weight), NAA + CB at PF, Accel™ + CB at 10 mm, and the two applied sequentially, resulted in greater cropload adjusted fruit weight than the nonthinned control in both years, whereas NAA + CB at 10 mm did not. Contrast analysis of treatments with and without ET showed no significant effect of including ET on fruit size, though total cropload was reduced at P = 0.10 and total yield was reduced (P = 0.03 in 1996 and P = 0.12 in 1997). No deleterious effects from multi-step treatments have been observed. All thinning treatments significantly increased return bloom in 1996 and 1997 compared to the control with little difference observed between treatments. Chemical names used: naphthalene acetic acid (NAA); 1-naphthyl-N-methylcarbamate [carbaryl (CB)]; 6-benzyladenine [BA (Accel™)]; 7-oxabicyclo (2,2,1) heptane-2,3 dicarboxylic acid [ET (Endothall™)]

The response of good and poor aspen clones to thinning

The response of good and poor clones of trembling aspen (Populus tremuloides Michx) to thinning was assessed 16 years after treatment. Prior to the thinning treatment, the clones had been assessed as either poor or good using a rating matrix that considered height, diameter, quality and vigour of the clones. Results indicate that the 250 largest DBH stems∙ha−1 did not respond to thinning, irrespective of clone rating. The growth of these dominant trees was unaffected by smaller competitors. Considering all trees, the non-thinned (control) good clones were indistinguishable from the thinned good clones in terms of top height, basal area, quadratic mean DBH, volume∙ha−1, and trees∙ha−1 16 years after treatment. For the good clones, 16 years of self-thinning yielded the same result as a single manual thinning. Due to a slower rate of self-thinning, the non-thinned poor clones retained some of the small stems longer and thus had a higher basal area and volume than the thinned poor clones. Thinning did not increase the piece size of the dominant trees so there was no associated increase in value.Thinning good and poor clones of trembling aspen did not increase the standing volume or piece size. Therefore, thinning is recommended only for good clones and only if it is profitable on its own. The literature on the benefits of thinning of aspen is contradictory. This may be due, in part, to undocumented clonal differences. Key words: trembling aspen, clones, thinning response, poplar, clonal rating

Determinação do peso do desbaste para florestas de &lt;i&gt;Eucalyptus grandis &lt;/i&gt;Hill ex Maiden, com base no índice de espaçamento relativo.

O trabalho descreve a produção de um povoamento de Eucalyptus grandis Hill ex Maiden, submetido a 4 pesos de desbaste (tratamentos) realizados aos 96 meses e repetido aos 124 meses após o plantio e regulados em função da área basal da testemunha não desbastada (100%), e demais tratamentos com a manutenção de 60%, 50% e 40 % da área basal da testemunha. O experimento foi instalado segundo o delineamento de blocos casualizados com 2 repetições, em parcelas de 400m2. O índice de espaçamento relativo (S%) calculado para os três tratamentos de desbaste foi ajustado por regressão, o qual apresentou coeficientes angulares semelhantes, gerando retas paralelas. Por outro lado, os coeficientes de intercessão diminuiram com a redução do peso de desbaste. A variação da intercessão foi descrita por regressão, tendo como variável independente a percentagem de área basal mantida após o desbaste. Para a estimativa do Índice de Espaçamento foi definida a equação geral S% = - 10,95540 + 0,09561 Gmant - 0,001951 Gmant2 + 1,16672 h100 .

Lesquerella fendleri seed oil content and composition: harvest date and plant population effects

Yield losses of Lesquerella fendleri L. seeds, caused by shattering and seed oil content reduction by excessive desiccation could be minimized by the appropriate choice of harvest dates. However, no information is available on harvest dates to maximize economic returns at any planting density. This research was undertaken to study the effects of harvest dates and plant populations on oil yield and composition in L. fendleri. Mechanically seeded field plots of L. fendleri were thinned at 103 days after sowing (DAS) to density treatments of 250,000, 500,000, 750,000, 1,000,000, and an nonthinned control of 1,500,000 plants/ha. These plants were grown in 1993–1994 at The University of Arizona, Maricopa Agricultural Center in central Arizona, and were harvested at 203, 229, 243, and 264 DAS. Eight fatty acids, which make up 87–96% of mature seed oil, were investigated. These included palmitic (C16: 0), palmitoleic (C16: 1), stearic (C18: 0), oleic (C18: 1), linoleic (C18: 2), linolenic (C18: 3), lesquerolic (C20: 1-OH), and auricolic (C20: 2-OH) fatty acids. Generally, seed at the earliest harvest of 203 DAS had lower concentrations of palmitoleic, stearic, oleic, lesquerolic, and auricolic acids, and lower total oil content than those harvested at 229, 243, and 264 DAS. Also at 203 DAS, the 750,000 plants/ha treatment produced the highest fatty acid content yield, although both this oil and that from the 1,000,000 plants/ha treatment lacked auricolic acid. During this period, the major contributing fatty acids to oil content were oleic, linoleic, linolenic, and lesquerolic. Harvest at 229 DAS resulted in an increase in oil content for all treatments except the 750,000 plants/ha. Lesquerolic acid was the dominant oil for the nonthinned control. At 243 DAS, higher oil contents were observed in the 250,000, 750,000, and 1,000,000 plants/ha densities, with lesquerolic acid again the dominant fatty acid. At final harvest (264 DAS), lesquerolic acid content was virtually the same among the density treatments. No significant differences for seed yield, fatty acid composition or content were found among plant populations. The seed yield averaged over all population densities was 1344 kg/ha with a fatty acid content of 21.9%, giving an oil yield 267 kg/ha (calculated as total fatty acid content).

Effect of CPPU and NAA on Fruit Growth and Cropping of Redchief `Delicious'

NAA is commonly used for fruit thinning of apples. However, with spur-type `Delicious' fruit, size may be less than expected based on the remaining crop load. Attempts to enhance fruit size on NAA-thinned trees with benzyladenine (BA) resulted in an interaction causing an increase in small (≤64 mm) fruit. CPPU [N-(2-chloro-4-pyridinyl)-N'-phenylurea], a highly active cytokinin in promoting parthenocarpy and growth of a number of fruit, was evaluated alone and with NAA for its effects on cropping and fruit growth in Redchief `Delicious'. High-volume sprays of CPPU were applied at 0, 2.5, 5, and 10 mg·L–1 to 13-year-old trees at 7.26 mm king fruit diameter. NAA was applied at 15 mg·L–1 with and without CPPU at 5 mg·L–1. Each treatment consisted of a single tree replicated four times. Response was evaluated by determining yield per tree and fruit size distribution at harvest. CPPU increased the amount of large (≥70 mm) fruit produced without significantly reducing yield. The amount of large fruit produced was 35, 71, 91 and 85 kg/tree for the nonthinned control (NTC) and CPPU at 2.5, 5, and 10 mg·L–1, respectively. NAA (15 mg·L–1) reduced yield by 39 kg/tree and increased amount of large fruit by 44 kg/tree. When CPPU (5 mg·L–1) was oversprayed with NAA (15 mg·L–1), yield was reduced by 30 kg/tree, and amount of large fruit was increased by 56 kg/tree compared to the NTC. The interaction was not significant for yield but was significant (P = 0.01) for amount of large fruit produced. Seed content was significantly reduced by NAA and CPPU, the effect being greater for NAA and in small (51 to 56 and 57 to 63 mm) than in large (76 to 82 mm) fruit. These data showing no significant inhibition of fruit growth with a combination of NAA and CPPU in Redchief `Delicious' are in contrast with findings for a related cytokinin, BA, where fruit growth was depressed significantly when combined with NAA.

Bloom Thinning `Loadel' Cling Peach with a Surfactant

Hand thinning fruit is required every season to ensure large fruit size of `Loadel' cling peach [Prunus persica (L.) Batsch] in California. Chemical thinning may lower costs of hand thinning. A surfactant, Armothin {[N,N-bis 2-(omega-hydroxypolyoxyethylene/polyoxypropylene) ethyl alkylamine]; AKZO-Nobel, Chicago; AR}, was sprayed at 80% of full bloom (FB), FB, and FB + 3 days. The spray volume was 935 liters/ha. Concentrations of AR were 1%, 3%, and 5% (v/v). An early hand thinning in late April, a normal hand thinning at 13 days before standard reference date (early May), and a nonthinned control were compared to bloom-thinned trees for set, yield, and fruit quality. AR resulted in no damage to fruit; however, slight leaf yellowing and burn and small shoot dieback were seen at the 5% concentration. Fruit set, and therefore, the number of fruit that had to be hand thinned, were reduced with 3% AR applied at 80% FB and 5% AR applied at all bloom phenophases (stages of bloom development). Thinning time was reduced by 37% (5% AR applied at 80% FB), 28% (5% applied at FB), and by 20% (3% applied at 80% of FB), compared to the normally hand-thinned control. Although AR resulted in early size (cross suture diameter and weight) advantages, at harvest there were no significant differences in fruit size among all AR treatments and the normally hand-thinned control. Total and salable yields of AR treatments and the normally hand-thinned control were equal. Armothin shows promise for chemical thinning of peach when used as a bloom thinner.

Flowering and fruiting in ‘Patterson’ apricot ( Prunus armeniaca) in response to postharvest application of gibberellic acid

In July or August of 1988 and 1989 which was approximately 2 or 6 weeks, respectively, after fruit harvest, cultivar ‘Patterson’ apricot ( Prunus armeniaca) trees were sprayed with a single spray of either 10, 50 or 100 p.p.m. gibberellic acid (gibberellin A 3, GA). GA sprays of 100 p.p.m. applied in early July reduced flower number per centimeter of limb length in the year following treatment. Flower number per centimeter of limb circumference was reduced by sprays of 50 and 100 p.p.m. GA applied in July. Fruit set was not affected by GA sprays. The yield and fruit number of hand thinned trees was equivalent to that found on trees treated with 50 and 100 p.p.m. GA sprays in July. Individual fruit weight (size) was increased by GA sprays of 50 and 100 p.p.m. in July compared to hand thinned trees. Fruit maturity was advanced when yields were reduced by GA sprays. In July, GA sprays of 10 p.p.m. resulted in increased individual fruit weight without reduced total yields per tree compared to non-thinned control trees. Results showed that the use of GA sprays the year before flowering (July) decreased flower numbers, eliminating the need for chemical or hand fruit thinning of ‘Patterson’ apricot.