Shoot Thinning Research Articles

Impact of planting density and shoot thinning on alstroemeria flowering, soil attributes and cost economics

A field experiment was conducted to assess the impact of various planting densities and levels of shoot thinning on cut flower yield, quality, soil chemical properties and cost economics in the commercially cultivated alstroemeria cultivar 'Capri'. The experiment involved three planting densities (4, 6 and 8 plants/m2) along with three shoot thinning levels (10 %, 20 % and 30 %). It was observed that higher planting density (4 plants/m2) promoted the length of cut stem, early bud formation, and flowering, optimal quality parameters, including maximum stem thickness, cut stem weight, floret quantity/stem, floret size, number of flowering stems/plant (yield) and vase life. Exclusive use of higher vegetative mass removal (30 % shoot thinning) was found to improve quality parameters such as the length of cut stem, number of flowering stems, stem thickness, weight of cut stem, floret quantity/stem, floret size, vase life, and early flowering. Soil samples were collected from each treatment and the consequent lab analysis revealed that the lower planting density and shoot thinning level resulted in maximum soil organic carbon, nitrogen, phosphorous and potassium content. In conclusion, planting density of 4 plants/m2 and 30 % shoot thinning emerged as the optimal combination for enhancing quantitative parameters in commercial alstroemeria cultivation. The study underscores the importance of strategic planting practices and vegetative mass management for maximizing yield and quality in alstroemeria production, along with ensuring higher economic returns.

Automated System for Continuous Green Shoot Thinning in Vineyards

Highlights An automated green shoot thinning system was developed by integrating machine vision and mechanical systems. Mask R-CNN used for segmenting cordons at different shoot growth stages. Point cloud registration used to accurately stitch cordon trajectories for continuous thinning operation. Field and lab tests demonstrated the integrated system can efficiently automate green shoot thinning operation. Abstract. Mechanized green shoot thinning in vineyards has helped reduce labor and associated costs. However, high variability in the thinning efficiency has been observed with the current machines in non-selective thinning due to challenges faced by the operators to precisely position thinning end-effectors along the cordon trajectories. In this study, an automated green shoot thinning system is proposed for cordon-trained grapevines to enhance the precision and efficiency of mechanical thinning operation. The automated system consisted of (1) a machine vision system for estimating cordon trajectories and (2) a mechanical system to position thinning rollers along the estimated trajectories during the real-time thinning operation. The vision pipeline used a Mask R-CNN model to determine cordon profiles at different shoot growth stages and a depth image to estimate the 3D cordon trajectory. In addition, point-cloud registration estimated transformation matrices for accurately stitching adjacent cordon trajectories and generating a long map of trajectory for the thinning rollers to follow. An image processing-based calibration method was used to obtain transformation parameters that transformed the estimated trajectories from the camera coordinate space to the thinning-roller coordinate space required for trajectory following. Lab tests, conducted using simulated cordons, showed the integrated system can precisely position the thinning rollers with root mean square errors (RMSE) of 2.0 cm and 1.7 cm for vertical and lateral positions, respectively. To quantify the thinning performance of the integrated system in the field, shoot thinning efficiency (the percentage of target shoots impacted) was determined. From the field evaluation, shoot thinning efficiency of 76% and 85% were achieved for two rows of grapevines, with an overall shoot thinning efficiency of 80%. The favorable test results demonstrated that the proposed integrated system is capable of effectively automating green shoot thinning operations, which has the potential to improve shoot thinning performance in vineyards. Keywords: Automated green shoot thinning, Cordon trajectory estimation, Mask R-CNN, Vineyard canopy management.

Summer pruning in Mediterranean vineyards: is climate change affecting its perception, modalities, and effects?

Summer pruning encompasses a series of operations typically performed on the grapevine during the growing season. This review provides an update on the research conducted over the last 20 years on the modalities and strategies of main summer pruning operations, which include shoot positioning and thinning, shoot trimming, leaf removal, and cluster thinning, with a special focus on their adaptation to climate change occurring in Mediterranean areas. Three main novelties emerged from the survey. First, due to a common need to shelter clusters against overheating and sunburn-related damages, shoot thinning and leaf removal are practices that are now being applied in a much more cautious and conservative manner. Second, the meaning of summer pruning is evolving because operations are being used as precious tools to direct ripening toward a desired direction rather than being received passively. Third, some operations, such as leaf removal, have disclosed very high plasticity, which means that, depending on the timing and modalities of the intervention, yield can be either increased or decreased and ripening anticipated or postponed. In an era where economic and environmental sustainability have to find a good compromise, cluster thinning is increasingly being depicted as an extraordinary operation that should be left to occasional occurrences of overcropping. Moreover, summer pruning is a tool through which growers can, to an extent, exploit the potentialities offered by climate change. For instance, the crop-forcing technique, under the different configurations of single and double cropping within the same season, has been trialed promisingly in several regions and cultivars. The principle of forcing is to unlock the dormant bud during the first year by removing at least the young organs present on the shoot within a time window between the end of the flowering and pea-size stages. In particular, when it is applied in a double-cropping mode, the preliminary results related to Pinot noir, Grenache, Tempranillo, and Maturana tinta indicate that two harvests separated by 30-50 days can be obtained, with the latter having superior quality in terms of a lower level of pH and higher levels of acidity, anthocyanins, and phenolics.

Evaluating the Effects of Early Pruning, Leaf Removal, and Shoot Thinning on ‘MidSouth’ Grapes over Two Consecutive Vintages in South Mississippi

Yield components and fruit composition of ‘MidSouth’, an interspecific hybrid bunch grape (Vitis spp.) with relatively low total soluble solids and high titratable acidity, was evaluated in south Mississippi to determine if treatments consisting of early pruning, early pruning with pre-bloom leaf removal, normal pruning with post-fruit set leaf removal, or normal pruning in one study, or post-fruit set leaf removal, post-fruit set shoot thinning, or neither leaf removal nor shoot thinning in a second study could improve these qualities. Early pruning with leaf removal reduced berries per cluster, cluster weights, yields, and Ravaz index. Early pruning treatments had inconsistent results from year to year, and normal pruning treatments were not often significantly different. Shoot thinned vines had lower yields and Ravaz index and higher total soluble solids. Second study leaf removal vines had lower juice pH in 2020 and lower yield per vine in 2021. These findings show that ‘MidSouth’ can be altered by these practices, but they did not appear to sufficiently alter ‘MidSouth’ quality. Thus, early pruning with or without leaf removal, normal pruning with leaf removal, and shoot thinning are not recommended for ‘MidSouth’ in south Mississippi, and normal pruning without these practices should be continued.

Severe Shoot Trimming and Crop Size as Tools to Modulate Cv. Merlot Berry Composition.

Viticulture production is challenged by climate change and the consequent higher accumulation of carbohydrates in grapevine berries, resulting in high-alcoholic wines. This study investigates the application of severe shoot trimming performed at three different stages and crop size management as tools for the modulation of cv. Merlot berry composition, aimed at reducing the sugar content in the berry. In the first study, the effects of severe shoot trimming carried out at three different phenological stages were studied. In the second study, late severe shoot trimming was combined with two crop sizes and regulated by shoot thinning. The obtained results demonstrated that severe shoot trimming in earlier stages of berry development limited the accumulation of both sugars and anthocyanins as compared to the control treatment. However, when severe shoot trimming was performed at late veraison (at approximately 14 Brix), it decreased only the accumulation of sugars, without affecting the accumulation of anthocyanins. The results of the second study showed that the modification of crop size by shoot thinning significantly affected the measured yield parameters, whereas the effect on Brix and anthocyanins was seasonally dependent. It was concluded that among the studied techniques, severe shoot trimming at late veraison is the most effective way to reduce sugar content in the berry without affecting the accumulation of anthocyanins.

The Impact of Vineyard Mechanization on Grape and Wine Phenolics, Aroma Compounds, and Sensory Properties

Grapes are one of the most valuable fruit crops in the United States and can be processed into a variety of products. The grape and wine industry contributes to and impacts the U.S. agricultural economy. However, rising labor costs and global competition pose challenges for the grape and wine industry. Vineyard mechanization is a promising strategy to increase efficiency and address the labor shortage and cost issues. Recent studies have focused on the impact of vineyard mechanization on general grape and wine quality. Wine phenolics, aroma compounds, and sensory characteristics are the key indicators of wine quality and consumer preference. This article aims to review the impact of vineyard mechanization, specifically mechanical harvesting, mechanical leaf removal, mechanical shoot thinning, cluster thinning, and mechanical pruning on grape and wine phenolics, and aroma compounds and sensory profile. Studies have shown that vineyard mechanization significantly affects phenolic and aroma compounds, especially grape-derived aroma compounds such as volatile thiols, terpenes, C13-norpentadiene, and methoxypyrazine. Mechanically processed grapes can produce wines of the same or better quality than wines made from hand-operated grapes. Vineyard mechanization could be a promising strategy for grape growers to reduce operating costs and maintain or improve grape and wine quality. Future research directions in the area of vineyard mechanization were discussed. It provides a comprehensive view and information on the topic to both grape growers and winemakers in the application of vineyard mechanization.

Advancement in Knowledge and Adoption of Grape Growing Farmers in Theni District of Tamilnadu

Grape (Vitis grape L.) could be a temperate fruit crop and conjointly cultivated beneath tropical and climatic zone regions within the world. This study on improved grape knowledge and adoption of recommended grape practices among farmers was conducted in the Theni district of Tamil Nadu by employing a combination of purposive and proportionate random sampling methods with 120 grape growers. The data were collected with the help of a well-structured and pretested interview schedule during July to August 2020-21. The district contributes significantly to the state's area of production in grapes. The area of cultivation of grapes to the state is substantial (79.80%). In the study it was concluded that cent percent of the grape growers had correct knowledge about soil type, planting, gap-filling, recut, supporting, weeding, irrigation type, training, pruning time, bud dormancy breaking chemical, micronutrient mixtures, fertigation, shoot thinning, subcane development, training the shoots, tipping, cluster and berry thinning, mealybug control, and downy mildew control. About 60.83 per cent of the grape growers belonged to medium level of knowledge about recommended practices of grape cultivation. The results showed overall adoption of the grape growers wasmedium level of adoption (71.67%). This study explores the keen view of the advancement in knowledge and adoption followed by grape cultivators in Theni District.

Joint effects of patch edges and habitat degradation on faunal predation risk in a widespread marine foundation species.

Human activities degrade and fragment coastal marine habitats, reducing their structural complexity and making habitat edges a prevalent seascape feature. Though habitat edges frequently are implicated in reduced faunal survival and biodiversity, results of experiments on edge effects have been inconsistent, calling for a mechanistic approach to the study of edges that explicitly includes indirect and interactive effects of habitat alteration at multiple scales across biogeographic gradients. We used an experimental network spanning 17 eelgrass (Zostera marina) sites across the Atlantic and Pacific oceans and the Mediterranean Sea to determine (1) if eelgrass edges consistently increase faunal predation risk, (2) whether edge effects on predation risk are altered by habitat degradation (shoot thinning), and (3) whether variation in the strength of edge effects among sites can be explained by biogeographical variability in covarying eelgrass habitat features. Contrary to expectations, at most sites, predation risk for tethered crustaceans (crabs or shrimps) was lower along patch edges than in patch interiors, regardless of the extent of habitat degradation. However, the extent to which edges reduced predation risk, compared to the patch interior, was correlated with the extent to which edges supported higher eelgrass structural complexity and prey biomass compared to patch interiors. This suggests an indirect component to edge effects in which the impact of edge proximity on predation risk is mediated by the effect of edges on other key biotic factors. Our results suggest that studies on edge effects should consider structural characteristics of patch edges, which may vary geographically, and multiple ways that humans degrade habitats.

Semi-Minimal-Pruned Hedge (SMPH) as a Climate Change Adaptation Strategy: Impact of Different Yield Regulation Approaches on Vegetative and Generative Development, Maturity Progress and Grape Quality in Riesling

The training system Semi-Minimal-Pruned Hedge (SMPH) blends features of traditional Vertical Shoot Positioning-type (VSP) trellising systems with the concept of minimal pruning. While saving labor, this training system results in relatively high crop load and a poor leaf area to fruit weight-ratio (LFR), and thus, needs to be able to ripen grapes in a cool to moderate climate. For these reasons the impact of yield regulation strategies, including (i) shoot thinning (Darwin-Rotor), (ii) biotechnological thinning (Gibberellic acid), and (iii) bunch thinning (harvest machine) were trialed in a three year study at Geisenheim, Germany between 2017 and 2019 using Riesling (Vitis vinifera L.). The average yield per vine in SMPH (5.34 ± 1.10 kg) was 61.1% higher with a narrower LFR (14.01 cm2 g−1), compared with VSP (3.32 ± 1.02 kg, LFR: 16.99 cm2 g−1). The yield was successfully reduced and LFR simultaneously increased with shoot thinning (−33.1%, LFR: 19.04 cm2 g−1), biotechnological thinning (−18.3%, LFR: 16.69 cm2 g−1) and bunch thinning (−37.3%, LFR: 21.49 cm2 g−1). Ripening was delayed in SMPH. On average, two maturity thresholds (14.1 °Brix and 18.2 °Brix) were achieved 129 GDD (seven days according to the recorded daily mean temperatures, respectively) and 269 GDD (16 days) later in non-thinned SMPH, compared to VSP. All thinning treatments accelerated maturity progress ranging from 27 GDD (two days) to 58 GDD (three days) for 14.1 °Brix and 59 GDD (three days) to 105 GDD (six days) for 18.2 °Brix. Apart from immediate benefits on the economic efficiency, the adaption of the leaf area to fruit weight ratio using SMPH holds high potential to, (i) produce grapes targeting specific wine profiles and/or (ii) reducing the velocity of ripening under conditions of climatic change.

Development and performance evaluation of a machine vision system and an integrated prototype for automated green shoot thinning in vineyards

AbstractGreen shoot thinning in vineyards is an essential, perennial operation for maintaining canopy health and optimizing yield and quality of wine grapes. Use of mechanized thinning system, which is essential to reduce labor dependency and associated cost, causes high variability in shoot removal efficiency due to difficulty in precisely positioning the thinning end‐effector along cordon trajectories. Automated/robotic solution for precise positioning of the thinning end‐effector could significantly improve the performance and efficiency of mechanical green shoot thinning. This study presents: (i) a machine vision‐based cordon detection system that can estimate cordon trajectories at different shoot growth stages in a vineyard; and (ii) evaluation of an integrated green shoot thinning system capable of automatically positioning the thinning end‐effector following vine cordon trajectories. The developed machine vision system uses deep learning‐based techniques that could accurately estimate cordon trajectories with root mean square error (RMSE) of 7.3, 10.3, and 16.1 pixels for canopy images captured in 2–4 weeks of shoot growth, respectively. Then, a control strategy was presented for the integrated system, which receives the computed cordon trajectories from machine vision system to automatically position the thinning end‐effector to cordon trajectories. Field evaluations in a research vineyard showed that the integrated system can achieve an RMSE of 1.47 cm in following the cordon trajectories at 6.6 cm·s−1forward speed. Future work will incorporate additional sensing system to detect individual shoot on cordon and integrating it with an existing system to achieve higher level of precision in green shoot thinning.

Impacts of leaf removal and shoot thinning on cumulative daily light intensity and thermal time and their cascading effects of grapevine (Vitis vinifera L.) berry and wine chemistry in warm climates

Leaf removal (LR), shoot thinning (ST) and their combination (LRST) are known to increase berry solar exposure affecting berry composition and consequently improving wine quality and antioxidant properties. We hypothesized that LR, ST or their combination (LRST) would affect flavonoid content during berry ripening by means of changes of the berry microclimate (light and temperature) as well as wine composition, quality, and antioxidant properties. Thermal time and sum of light intensity thresholds were different to achieve the maximum berry anthocyanin and flavonol contents. ST mostly affected wine characteristics by increasing alcoholic content, acidity, hue and phenolic substances. Wine antioxidant capacity decreased in ST wines likely by decreases in catechin and quercetin contents. ST and LRST increased proanthocyanidin polymerization and decreased monomeric flavan-3-ols, which may reduce wine bitterness and enhance astringency. Therefore, the management of canopy should take into account the warming trends in viticulture regions, rather than being applied preemptively.

Effects of irrigation and shoot thinning on the size and phenolics content of developing grape berries (Vitis vinifera L. cv. Tempranillo)

Aim of study: The concentration of phenolics in the grape berries can be influenced by cultural practices such as irrigation or thinning. The main objective of the present study was to evaluate the effect of combinations of these practices on grape size and phenolics content. Area of study: The trial was carried out in an experimental cv. Tempranillo vineyard located in Extremadura, Spain. Material and methods: Two irrigation regimes were considered: rainfed vines (non-irrigated, NIr), and 100% ETc irrigated vines (Ir). For each irrigation treatment, two cropping levels were studied: low shoot-thinning (LT) vs high shoot-thinning (HT) implemented in winter and spring, respectively. Berry weight, and total phenolics, proanthocyanidin, and anthocyanin concentrations were determined at eight stages of berry development in three consecutive years (2014, 2015, and 2016). Main results: Specific weather conditions of each year affected phenolics accumulation differently. In 2014, where maximum temperatures were low and an important rainfall occurred at Stage II, both the NIr-LT and NIr-HT treatments led to the greatest concentrations of total phenolics, proanthocyanidins, and anthocyanins. In 2015, where a little rainfall was registered at Stage II, the berries from the NIr-HT and Ir-HT treatments accumulated the greatest total phenolics and proanthocyanidin contents, but the NIr-LT and NIr-HT treatments led to the greatest accumulation of anthocyanins. Finally, in 2016, where high maximum temperatures and scarce rainfall were registered, the Ir-LT and Ir-HT treatments presented the greatest concentrations of total phenolics, proanthocyanidins, and anthocyanins. Research highlights: A significant effect of irrigation and thinning was observed on berry size and phenolic content, as well as year × thinning interaction.

Estimating the trajectories of vine cordons in full foliage canopies for automated green shoot thinning in vineyards

Green shoot thinning in vineyards is carried out annually aiming to produce high-quality grapes. Recently, mechanical machines are used for green shoot thinning to reduce labor costs which causes 10–85% variation in shoot removal efficiencies due to the difficulty in precisely positioning the thinning end-effector to cordon trajectories. Automatically controlling the position and orientation of thinning end-effector to follow the cordon trajectories is expected to increase the performance and efficiency of these machines. However, during most of the green shoot thinning season (between first week of bud opening to the fourth week of shoot growth), cordons are occluded by shoots/leaves making it extremely challenging to determine the trajectories of cordons. In this study, we presented a deep learning based novel approach to estimate the trajectories of cordons during the thinning season in real field conditions. First, deep residual network (ResNet) and Faster region-based convolutional neural network was used to detect visible segments of full foliage grapevine canopies. Then, location information of detected visible segments were used to estimate the trajectories of cordons. This approach was evaluated using ground truth images collected from different growth stages of green shoots in real vineyard environment. The proposed approach achieved a correlation coefficient of 0.993, 0.991, and 0.987 in estimating cordon trajectories with the test dataset from weeks 2 to 4, respectively, of shoot growth.

Monitoring Vineyard Canopy Management Operations Using UAV-Acquired Photogrammetric Point Clouds

Canopy management operations, such as shoot thinning, leaf removal, and shoot trimming, are among the most relevant agricultural practices in viticulture. However, the supervision of these tasks demands a visual inspection of the whole vineyard, which is time-consuming and laborious. The application of photogrammetric techniques to images acquired with an Unmanned Aerial Vehicle (UAV) has proved to be an efficient way to measure woody crops canopy. Consequently, the objective of this work was to determine whether the use of UAV photogrammetry allows the detection of canopy management operations. A UAV equipped with an RGB digital camera was used to acquire images with high overlap over different canopy management experiments in four vineyards with the aim of characterizing vine dimensions before and after shoot thinning, leaf removal, and shoot trimming operations. The images were processed to generate photogrammetric point clouds of every vine that were analyzed using a fully automated object-based image analysis algorithm. Two approaches were tested in the analysis of the UAV derived data: (1) to determine whether the comparison of the vine dimensions before and after the treatments allowed the detection of the canopy management operations; and (2) to study the vine dimensions after the operations and assess the possibility of detecting these operations using only the data from the flight after them. The first approach successfully detected the canopy management. Regarding the second approach, significant differences in the vine dimensions after the treatments were detected in all the experiments, and the vines under the shoot trimming treatment could be easily and accurately detected based on a fixed threshold.

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.

Optimal Ranges and Thresholds of Grape Berry Solar Radiation for Flavonoid Biosynthesis in Warm Climates

In commercial wine grape production, canopy management practices are applied to control the source-sink balance and improve the cluster microclimate to enhance berry composition. The aim of this study was to identify the optimal ranges of berry solar radiation exposure (exposure) for upregulation of flavonoid biosynthesis and thresholds for their degradation, to evaluate how canopy management practices such as leaf removal, shoot thinning, and a combination of both affect the grapevine (Vitis vinifera L. cv. Cabernet Sauvignon) yield components, berry composition, and flavonoid profile. Three experiments were conducted in Oakville, CA, USA. First experiment assessed changes in the grape flavonoid content driven by four degrees of exposure. In the second experiment, individual grape berries subjected to different exposures were collected from two cultivars (Cabernet Sauvignon and Petit Verdot). The third experiment consisted of an experiment with three canopy management treatments (i) LR (removal of 5 to 6 basal leaves), (ii) ST (thinned to 24 shoots per vine), and (iii) LRST (a combination of LR and ST) and an untreated control (UNT). Berry composition, flavonoid content and profiles, and 3-isobutyl 2-methoxypyrazine were monitored during berry ripening. Although increasing canopy porosity through canopy management practices can be helpful for other purposes, this may not be the case of flavonoid compounds when a certain proportion of kaempferol was achieved. Our results revealed different sensitivities to degradation within the flavonoid groups, flavonols being the only monitored group that was upregulated by solar radiation. Within different canopy management practices, the main effects were due to the ST. Under environmental conditions given in this trial, ST and LRST hastened fruit maturity; however, a clear improvement of the flavonoid compounds (i.e., greater anthocyanin) was not observed at harvest. Methoxypyrazine berry content decreased with canopy management practices studied. Although some berry traits were improved (i.e. 2.5° Brix increase in berry total soluble solids) due to canopy management practices (ST), this resulted in a four-fold increase in labor operations cost, two-fold decrease in yield with a 10-fold increase in anthocyanin production cost per hectare that should be assessed together.

Effects of canopy management practices on grapevine bud fruitfulness

Background and aims: Bud fruitfulness is a key component of grapevine reproductive performance as it determines crop production for the following growing season. While canopy microclimate can impact bud fruitfulness, the effects of canopy management practices on bud fruitfulness are not well known. The objective of this study was to investigate the effects of common canopy management practices on bud fruitfulness and the relationships with shoot growth capacity, bud microclimate and bud carbohydrate level.Methods and results: Different canopy management practices, (shoot thinning, bunch thinning, leaf removal and lighter pruning) were applied to Semillon and Shiraz grapevines (Vitis vinifera L.). Light interception at the bud zone was measured after canopy management practices were applied. Bud fruitfulness at dormancy was assessed using bud dissection analysis. The number and size of inflorescence primordia, and the incidence of primary bud necrosis were recorded. The results were correlated with measurements of shoot growth capacity and carbohydrate content of buds and canes.Conclusions: Bud fruitfulness was mostly influenced by bud light interception, while the size of inflorescence primordia was positively correlated with shoot growth capacity and the carbohydrate level of buds. By altering canopy microclimate, canopy management practices can be used to manipulate bud fruitfulness and potentially bunch size.Significance and impact of the study: This study provides novel information on the impact of canopy management on grapevine bud fruitfulness and the size of inflorescence primordia. These findings can be used to make more informed vineyard management decisions for better yield control.

Determining grapevine cordon shape for automated green shoot thinning using semantic segmentation-based deep learning networks

Canopy management practices are carried out annually in vineyards for establishing and maintaining healthy canopies. Green shoot thinning is an integral part of canopy management practices in wine grapes (Vitis vinifera), used to reduce crop load to desired level for optimizing wine quality. Mechanical thinning can reduce labor requirements by 25 times compared to manual operation. However, due to difficulty in adjusting position and orientation of thinning end-effector to the shape of the cordons, cluster removal efficiency with mechanical green shoot thinning varies from 10 to 85%. Automating mechanical thinning could help to substantially increase its efficiency and performance. For performing an automated operation, the first step is to determine the shapes of vine cordons. In this work, methods were investigated to accurately determine the cordon shapes using deep learning networks in natural environment of commercial vineyards. A color camera was used to acquire canopy images, and different deep learning-based semantic segmentation techniques (SegNet and FCN) were used to do this cordon detection and determination work. Results show that the FCN-based model initialized from VGG16 weights (FCN-VGG16) achieved the highest Boundary-F1 score compared to the same with other networks investigated (SegNet-VGG16, SegNet-VGG19, and FCN-AlexNet). Following the cordon segmentation, different mathematical models (Polynomial, Gaussian, Fourier, and sum of sines) were fitted on the cordon segments obtained from FCN-VGG16 network. The results showed that a polynomial model of 6th degree could fit about 80% of cordons trajectories with an R-square value of 0.98 and more. This model could be used to determine cordon trajectories in field operations when the cordons were heavily occluded by shoots/leaves to precisely position and orient thinning end-effectors/rollers for automated green shoot thinning.

In-row spacing and shoot thinning for ‘Chardonnay’ grapevines in the south of Minas Gerais, Brazil

ABSTRACT: The quality of sparkling wine reflects the climate and management of vineyard, since these factors affect grape development, berry composition, and base wine composition. ‘Chardonnay’ vines were subjected to five in-row spacing distances (0.5; 0.75; 1.0; 1.50; and 2.0 m) combined with and without shoot thinning. For each in-row spacing, vines were thinned to 5, 8, 10, 15, and 20 shoots per plant. Vegetative growth, yield, berry composition and base wine composition were analyzed for two years. Vines with decreased in-row spacing, presented fewer clusters and malic acid content in berries, mostly related to the shading effect. Shoot thinning increased bud fruitfulness and decreased leaf area per meter, leaf area per plant, and leaf layer number. In-row spacing from 1.5 m to 0.5 m showed promising results for the Southeast Brazil with higher yield per hectare and sufficient acidity to provide freshness in sparkling wines.

Thinning enhances stool resistance to an extreme drought in a Mediterranean Quercus ilex L. coppice: insights for adaptation

Mediterranean holm oak forests are subjected to chronic seasonal droughts coinciding with the warmest conditions during the summer. Importantly, climate change projections support increased frequency and intensity of droughts in the future. In order to evaluate whether thinning practices can be used as efficient adaptation strategies to climate change, we measured canopy cover as a surrogate of defoliation in 49 Quercus ilex L. subsp. ilex individual genets subjected to experimental ramet thinning. Canopy cover measurements were obtained before, during and after the exceptionally intense and prolonged drought of 2016. Our results show that intensity of basal area reduction determined higher resistance, but not resilience, to this intense-long drought period. Independently of shoot thinning intensity, every holm oak exhibited crown defoliation during the dry period but most of them recovered their leaves the next spring. Holm oaks subjected to thinning with more than over 50% of basal area removed, were less vulnerable to severe drought, however, and supported more leaves later on. Additionally, our results highlight the positive influence of canopy shading from neighbouring trees preventing defoliation after drought events. A greater canopy shading per stool led to a higher resistance in holm oak trees exposed to severe drought. These findings suggest that, in order to cope with concomitant climate change and to optimize genet-level stress tolerance, coppice selection should be done by removing shoots with fewer leaves per unit area, preferably those unexposed to shading from neighbouring trees until a reduction around 50% of basal area per stool is achieved.