Dormant Pruning Research Articles

Pruning terms and techniques affect vigour and flower formation of Ukrainian sweet cherry trees

Excessive tree vigour and late entrance into full production, inherent to sweet cherry trees, are major challenges in the intensive cultivation of this crop. Possible ways to reduce the vigour and stimulate flower induction include shifting the term of pruning and reducing its severity. However, the reaction of the trees may differ depending on specific cultivar, soil and climatic conditions. Therefore, the aim of the study was to determine the effect of various techniques and terms of pruning on young sweet cherry trees in order to adapt the intensive cultivation technology to the arid conditions of southern Ukraine. The results showed a strong cultivar-specific reaction to various pruning treatments. Pruning young sweet cherry trees in late summer contributed to a reduction of trunk and canopy indices by 11-22% on one of the cultivars and an increase in the number of flowers per tree by 1.4-1.7 times on both cultivars, compared to dormant pruning. Low severity pruning reduced 1-year-old shoot length by 9-25% and increased the number of flowers by 1.5-2.5 times compared to more aggressive pruning. The effect of pruning treatments on tree vigour was more pronounced during the first and second year of their application.

Seasonal Susceptibility of Sweet Cherry Pruning Wounds to Calosphaeria pulchella, Cytospora sorbicola, and Eutypa lata.

Fungal canker pathogens commonly infect trees at pruning wounds leading to branch dieback and loss of productivity in sweet cherry orchards. However, the seasonal susceptibility of sweet cherry pruning wounds to Calosphaeria pulchella, Cytospora sorbicola, and Eutypa lata is not well understood. This study compared the susceptibility of sweet cherry pruning wounds made during the dormant season (January) and the postharvest season (late May to June) to infection by main canker pathogens in California. Field trials were conducted in three cherry orchards and trees were pruned at the different periods over 2 years. Fresh pruning wounds were inoculated with spores of each pathogen, and pathogen recovery was assessed through microbiological isolations at 3 to 4 months after inoculations. Pruning wounds made in late May and June resulted in significantly higher infection by Cal. pulchella compared to pruning wounds made in January. Pruning wounds made during both seasons were generally equally susceptible to Cyt. sorbicola and E. lata infections. However, there was one orchard where dormant pruning wounds were more susceptible to infection by E. lata and there was one particularly cold winter where Cyt. sorbicola did not infect pruning wounds. Overall, our findings suggest that Cal. pulchella infections of cherry pruning wounds are more likely to occur during periods of warm temperatures such as late spring and early summer. However, infections by Cyt. sorbicola and E. lata can occur year-round if inoculum is present and if winter temperatures are not abnormally low for California. Finally, our results suggest that the emergence of Cal. pulchella as a major canker pathogen of sweet cherry in California may be the result of a shift from dormant to after-harvest pruning of sweet cherry trees.

Studies on physiological and productive effects of multi-leader training systems and Prohexadione-Ca applications on apple cultivar 'WA 38′

The release of new apple varieties able to improve consumer satisfaction provides the opportunity to modernize orchards and transition them away from unlucrative plantings towards highly productive, high-value cultivation systems. Top-working an existing, unprofitable mature orchard by grafting a new variety allows the orchardist to take advantage of an existing root system to achieve early bearing and reduce the establishment cost. Often, the scion in a new top-grafted orchard can present excessive vigor in the years following the grafting due to the abundance of reserves stored in the mature root system that become available for the new variety at the beginning of the season. This case study focuses on ‘WA 38′, an apple variety released in 2017 to Washington State growers. ‘WA 38′ can show variable vigor levels depending on the choice of rootstock, training system, planting density, pruning technique, water availability, and soil characteristics. Prohexadione-calcium (Pro-Ca, Apogee®) has been utilized for years in apple and other crops as a growth regulator with inhibitory activity on gibberellin synthesis, with the common effect of reducing shoot growth and canopy development and other potential physiological effects depending on genetics of the variety, timing, and rate of applications. This study investigated the physiological responses of ‘WA 38′ scion top-grafted on an 8-year-old Granny Smith/M.9 orchard and then trained to 1, 2, and 3-axis systems—suitable for modern mid-high-density planting—with and without the application of Pro-Ca for two consecutive years. The growth regulator was applied in post-bloom at a 250 ppm rate, starting at approximately 12-cm shoot length for three sprays per season. The parameters assessed to evaluate the impact of Pro-Ca on the variety in three training systems were: one-year-shoot length, internode length, dormant pruning weights, number of flower clusters per tree, photosynthetic carbon assimilation rate, stomatal conductance, intercellular CO2 concentration, transpiration rate, chlorophyll determination (by SPAD and chemical extraction), leaf mineral analysis (macro and micro-nutrients), yield per tree, fruit size distribution and packout. The present results confirmed the effectiveness of the Pro-Ca in reducing the canopy growth and vigor in ‘WA 38′, with diminished internode length, total shoot length, and lower amount of pruned material. Leaf gas exchange parameters and chlorophyll quantification highlighted an alteration of tree physiology by Pro-Ca application with increased transpiration, stomatal conductance, intercellular CO2 concentration, and higher concentrations of chlorophyll a and b with respect to untreated trees. Pro-Ca-treated- ‘WA 38′ trees did not show any negative effect on productivity; rather, an increased average fruit mass and an enhanced proportion of apples in the extra-large size category compared to control. Fewer significant differences were found in the comparison between the training systems. Overall, the 3-axis system showed a higher yield and greater number of flower clusters per tree with a lower average area of each leader in comparison to 1-axis. Further investigations will shed light on ‘WA 38′ tree performance, productivity, and fruit quality after multiple years of Pro-Ca treatment to offer orchard management recommendations for a modern, top-worked, machine-friendly orchard.

Skeleton extraction and pruning point identification of jujube tree for dormant pruning using space colonization algorithm.

The dormant pruning of jujube is a labor-intensive and time-consuming activity in the production and management of jujube orchards, which mainly depends on manual operation. Automatic pruning using robots could be a better way to solve the shortage of skilled labor and improve efficiency. In order to realize automatic pruning of jujube trees, a method of pruning point identification based on skeleton information is presented. This study used an RGB-D camera to collect multi-view information on jujube trees and built a complete point cloud information model of jujube trees. The space colonization algorithm acts on the global point cloud to generate the skeleton of jujube trees. The iterative relationship between skeleton points was represented by constructing a directed graph. The proposed skeleton analysis algorithm marked the skeleton as the trunk, the primary branches, and the lateral branches and identified the pruning points under the guidance of pruning rules. Finally, the visual model of the pruned jujube tree was established through the skeleton information. The results showed that the registration errors of individual jujube trees were less than 0.91cm, and the average registration error was 0.66cm, which provided a favorable database for skeleton extraction. The skeleton structure extracted by the space colonization algorithm had a high degree of coincidence with jujube trees, and the identified pruning points were all located on the primary branches of jujube trees. The study provides a method to identify the pruning points of jujube trees and successfully verifies the validity of the pruning points, which can provide a reference for the location of the pruning points and visual research basis for automatic pruning.

The Effect of Spur Position and Pruning Severity on Shoot Development

Adjusting yearly pruning severity is a common vineyard management practice employed to manipulate vegetative and reproductive growth in grapevines. Although the effects of pruning on total vegetative growth are well documented, there is little research on the effects of adjusting shoots meter−1 via dormant season pruning on addressing mid-cordon shoot weakness and developmental delays. Cordon-trained, spur-pruned vines are thought, by many growers, to be especially prone to weaker positions and delayed development at mid-cordon positions. This phenomenon is also thought to become more exaggerated as the vine ages. Therefore, the effects of shoot density manipulation, implemented via dormant pruning practices, to homogenize shoot and cluster development along the length of the cordon were examined. In this research, Cabernet Sauvignon grapevines were pruned to either 5.5 shoots meter−1 (5.5) or 11.1 shoots meter−1 (11.1). To control for variations in light interception into the fruiting zone, a control of 11.1 shoots meter−1 with sensor guided leaf thinning (11.1LT) was implemented at full berry set to match the canopy light of the 5.5 shoots meter−1 treatment. It was found that individual shoot growth and yield were directly impacted by manipulation of pruning severity. Shoot growth response varied primarily by growing season, including shoot length and internode length. Yield components were significantly lower in the 5.5 treatment during the first two years of the study but were not significantly different during the last year of the study. The 5.5 treatment resulted in the highest pH and total soluble solids at harvest in 2016 and 2017.

Semantics-guided skeletonization of upright fruiting offshoot trees for robotic pruning

Dormant pruning for fresh market fruit trees is a relatively unexplored application of agricultural robotics for which few end-to-end systems exist. One of the biggest challenges in creating an autonomous pruning system is the need to reconstruct a model of a tree which is accurate and informative enough to be useful for deciding where to cut. One useful structure for modeling a tree is a skeleton: a 1D, lightweight representation of the geometry and the topology of a tree. This skeletonization problem is an important one within the field of computer graphics, and a number of algorithms have been specifically developed for the task of modeling trees. These skeletonization algorithms have largely addressed the problem as a geometric one. In agricultural contexts, however, the parts of the tree have distinct labels, such as the trunk, supporting branches, etc. This labeled structure is important for understanding where to prune. We introduce an algorithm which uses topological and geometric priors about Upright Fruiting Offshoot (UFO) trees to produce such a labeled skeleton. We test our skeletonization algorithm on point clouds from 29 UFO trees and, using an accuracy metric based on the number of correctly reconstructed and labeled skeleton segments, demonstrate a median construction accuracy of 70% with respect to a human-evaluated gold standard. We also make point cloud scans of 82 UFO trees open-source to other researchers. Our work represents a significant first step towards a robust tree modeling framework which can be used in an autonomous pruning system.

Automatic branch detection of jujube trees based on 3D reconstruction for dormant pruning using the deep learning-based method

Pruning is a time-consuming and labor-intensive practice for managing of dormant jujube orchards, in which dormant pruning is still mainly dependent on manual operation. Automated pruning using a robotic platform could be a better solution to overcome the skilled labor shortage and increased labor costs. With the development of dwarf and dense planting of jujube trees, the tree architectures are suitable for robotic pruning. This study concentrated on the detection and identification of pruning branches, which was a critical step for automating pruning operations. The method in this study mainly consisted of three steps: first, present a vision system based on two synchronous consumer-level RGB-D cameras to obtain the high-quality 3D point cloud in filed; second, propose the reconstruction pipeline for the desired three-dimensional model (basically a complete 3D model) using only two perspectives; and third, automatically segment the trunks and branches based on deep learning method (SPGNet), and then apply the DBSCAN clustering algorithm for estimating branch counts of jujube trees. For the reconstruction of jujube tree, registration errors II (0°-180°) were greater than errors I (0°-55°), and registration errors I (0°-55°) were less than 1 mm under different light conditions. Experimental results demonstrated that trunks and branches were segmented successfully with class accuracies of 0.93 and 0.84, and another metric intersection-over-union (IoU) was 0.85 and 0.76, respectively; the coefficient of determination (R2) values analyzed between the ground-truth and cluster results were 0.83, 0.88, and 0.89 in sunny, cloudy, and night conditions, respectively. These results showed that the proposed method for detecting branches could be utilized to generate substantial information, such as the diameter length and diameter of the branch, which was critical for the automated dormant pruning of jujube trees in the future orchard field.

Impact of training system on ‘Blanc Du Bois’ vegetative growth, yield components and fruit composition

‘Blanc Du Bois’ (Vitisspp.) is the most widely grown Pierce’s disease tolerant white grapevine cultivar in Texas. As an interspecific hybrid, its growth habit is seimi-drooping, and 'Blanc Du Bois' is characterized as vigorous. This study evaluated the impact of training system (Mid-Wire Cordon with VSP, Mid-Wire Cane with VSP and Smart-Dyson, High-Wire Quadralateral, and Watson) on 'Blanc Du Bois' growth, yield components, and fruit composition at two locations in Texas. The first site was located in the Rio Grande Valley where the mean extreme minimum winter temperature is -1.1 to 1.7° C (USDA Cold Hardiness Zone 10a). As a result of climate and site conditions, vine size, determined by dormant pruning weight, was very large averaging from 3.71 to 5.56 kg per vine across training systems over a three-year period. At this site, the horizontally divided systems, High-Wire Quadrilateral and Watson were the highest yielding averaging 10.66 and 7.49 kg per vine, respectively, as a result of more shoots per vine, and higher fruitfulness. The Mid-Wire Cordon and Mid-Wire Cane Pruned Training Systems had lower yields in two out of three years, but fruit maturity indices soluble solids and pH reflected more advanced maturity at harvest. At the second site, located in the Central Gulf Coast of Texas (USDA Cold Hardiness Zone 8b), vines were less vigorous with pruning weights averaging 1.66 to 1.83 kg per vine across training systems over three years. Consistent differences in yield components, vine size, and fruit composition were not observed, and all the three training systems under study had acceptable growth and fruiting characteristics. The results of this research suggest that 'Blanc Du Bois’ vigor potential and growth habit makes it well-suited for horizontally divided canopy training systems, particularly on vigorous sites.

Evaluation of Grapevine Rootstocks on Slightly Acidic and Strongly Alkaline Texas Hill Country Soils

Summary Goals: Rootstock selection is usually dictated by vineyard site conditions such as pest and disease pressure, soil, and climate. This work evaluated the impact of rootstock on ‘Sangiovese’ vine size, nutritional status, and fruit composition at two sites in the Texas Hill Country, one with a slightly acidic (pH 6.58 ± 0.05) loamy fine sand soil and the other with a moderately to strongly alkaline (pH 8.48 ± 0.06) clay loam soil. Eleven rootstocks representing common rootstocks in Texas (‘Paulsen 1103’, ‘Kober 5BB’, ‘Teleki 5C’), nematode resistant rootstocks (‘UCD GRN-1’, ‘UCD GRN-2’, ‘UCD GRN-3’, ‘UCD GRN-4’ and ‘UCD GRN-5’), and rootstocks with possible tolerance to cotton root rot (Phymatotricopsis omnivora) (Ramsey, Dog Ridge, Florilush) were studied over a five-year period. Key Findings: At the Real County test site, in an alkaline clay loam soil, the rootstocks ‘Dog Ridge’ and ‘Teleki 5C’ maintained the most favorable nutrient status resulting in higher vine vigor and dormant cane pruning weights with pruning weights averaging 0.52 kg/vine and 0.37 kg/vine, respectively, versus 0.09 kg/vine for own-rooted ‘Sangiovese’. The rootstocks ‘Florilush’, ‘UCD GRN-1’, ‘UCD GRN-5’, and own-rooted ‘Sangiovese’ performed poorly at the Real County test site as a result of nutritional deficiency. At the Gillespie County site, in a slightly acidic loamy fine sand soil, all rootstocks performed acceptably with respect to vine size, nutrition, and fruit composition, although average dormant pruning weights over five years ranged across rootstocks from 0.52 to 0.87 kg/vine. Petiole potassium and magnesium were inversely correlated across rootstocks, with the strongest relationship (R2 = 0.58) observed in late summer at the Gillespie County site. Own-rooted ‘Sangiovese’ maintained the lowest petiole potassium and highest petiole magnesium concentrations over the study, as well as the lowest juice potassium and pH at the Gillespie County site. Juice potassium and pH were positively correlated (R2 = 0.57 and 0.76) across rootstocks in two out of three years of study at the Gillespie County site. Impact and Significance: This study demonstrated the importance of rootstock selection on a moderately to strongly alkaline soil versus a slightly acidic soil. Out of the eleven rootstocks tested, only ‘Dog Ridge’ and ‘Teleki 5C’ produced an acceptably sized (0.25 and 0.16 kg/m canopy) mature vine (fourth leaf) likely as a result of nutrition. All rootstocks under study resulted in petiole iron concentrations below recommended values, but the severity of shoot tip chlorosis, which is associated with iron deficiency, was highly rootstock dependent. The rootstocks with the lowest pruning weights and vigor ratings at the Real County site (own-rooted ‘Sangiovese’, ‘Florilush’, ‘UCD GRN-1’, and ‘UCD GRN-5’) generally expressed the most shoot tip chlorosis. Addressing this apparent nutritional deficiency with targeted fertilizer applications may have improved vine performance, but this research suggests that proper rootstock selection is a more viable option. The impact of rootstock was less apparent on slightly acidic loamy fine sand soil. All rootstocks and own-rooted ‘Sangiovese’, conferred acceptable pruning weights, nutritional status, and fruit composition. Basic juice chemistry did vary by rootstock while own-rooted ‘Sangiovese’ having the lowest juice potassium and pH, but the risks of growing own-rooted V. vinifera likely outweigh this potential benefit on sites where climate, soil conditions, pests, or disease may be limiting.

Cane- and Spur-Pruned Pinot noir Results in Similar Fruitfulness, Yield, and Grape Ripeness under Cool Climate Conditions

Summary Goals: Oregon Pinot noir growers prefer head training and cane pruning to cordon training and spur pruning, referred to herein as cane and spur pruning, respectively. With decreasing labor availability and increasing production costs, growers are interested in transitioning to spur pruning to improve vineyard economics because spur pruning requires less manual labor and is easier and more economical to mechanize than cane pruning. However, they are hesitant to adopt spur pruning because of fears of reduced and inconsistent yields, as they believe Pinot noir has unfruitful basal buds. We conducted a two-year field trial to compare Pinot noir cane- and spur-pruned vine productivity from dormancy to harvest in a vineyard trained to a unilateral Guyot training system where vines were head trained and cane pruned to one 10-node cane and one two-bud renewal spur or cordon trained and spur pruned to six spurs of two nodes per spur. Key Findings: Primary bud fruitfulness was no different between pruning methods. Node position was important for dormant compound bud fruitfulness. The first, second, and third count nodes from the base of a cane or spur were fruitful, but node positions 4 and 5 had 11% higher fruitfulness. There was higher compound bud fruitfulness and greater inflorescence primordia size in compound buds of dormant canes with greater weight and diameter, regardless of pruning method. Pruning method did not affect vine phenology, yield, or harvest grape ripeness (Brix, pH, and titratable acidity [TA]). Impact and Significance: Our study found no yield or grape ripeness differences between cane- and spur-pruned Pinot noir in a unilateral Guyot training system. Therefore, spur pruning is an option for producers who wish to reduce dormant pruning labor and who consider adopting mechanization for further cost savings. Additional shoot-thinning passes may be required in spur-pruned vineyards, since the older cordon wood resulted in greater growth of adventitious shoots in spring compared to cane-pruned vines.

Conversion to Mechanical Pruning in Vineyards Maintains Fruit Composition while Reducing Labor Costs in ‘Merlot’ Grape Production

A field study was conducted for three consecutive seasons in the hot climate of central California to assess the performance of ‘Merlot’ grapevine (Vitis vinifera) grafted onto ‘Freedom’ [Fresno 1613-59 × Dog Ridge 5 (27% V. vinifera hybrid)] during training system conversion to facilitate mechanization. The traditional head-trained and cane-pruned (CP) system was either retained or converted either to a bilateral cordon-trained, spur-pruned California sprawl training system (HP), or to a bilateral cordon-trained, mechanically box-pruned single high-wire sprawling system (SHMP). After the conversion, SHMP sustained greater yield with more clusters per vine and smaller berries without affecting the canopy microclimate. This was due to a higher number of nodes retained after dormant pruning. The SHMP canopies, compared with CP and HP; filled allotted canopy space earlier based on photosynthetically active radiation (PAR) transmitted through the canopies, populating the space allotted per vine, favoring higher production efficiency. There were no adverse effects of training systems on berry composition or flavonoid concentration, during or after conversion to mechanical management. However, experimental year effect was obvious on anthocyanin composition of ‘Merlot’ berries, increasing trihydroxylated (i.e., delphinidin-based) anthocyanins in the latter years of the experiment. Our results also provided evidence that earlier canopy growth coupled with sufficient reproductive compensating responses allowed for increased yields while reaching commercial maturity without a decline in anthocyanin content with the SHMP. Converting CP to SHMP reduced labor operations costs by 90%. Furthermore, the SHMP had greater gross revenue and resulted in greater net income per acre even when the conversion year was taken into account. Therefore, SHMP is recommended for growers within the hot climate of the central San Joaquin Valley as a means to maintain productivity of vineyards while not sacrificing berry composition at the farm gate.

Stub Length and Stub Angle Did Not Influence Renewal Shoot Number or Branch Angle of Tall Spindle ‘Gala’/Malling 9 Apple Trees

Renewal of limbs by pruning to leave a short, angled, upward-facing stub is common practice for spindle-type apple (Malus ×domestica) training systems. A short, beveled stub cut is thought to stimulate renewal growth from latent buds present underneath the base of the excised branch, and to stimulate smaller, more fruitful renewal limbs with wide crotch angles. We conducted trials over the course of 2 years that involved dormant pruning of ‘Buckeye Gala’ with renewal cuts to compare two stub lengths, 0.5 and 2 cm, and three stub orientations, upward facing, downward facing, and vertical facing, to determine the effects on renewal shoot number, position, angle, and length. We found no clear advantages with either stub length that we evaluated, and there was no improvement in renewal shoot quality with a bevel cut at any orientation. Stub length and stub angle did not influence limb renewal and may be unimportant for training orchard-pruning crews and for machine-learning and robotic pruning.

Flavonol Profile Is a Reliable Indicator to Assess Canopy Architecture and the Exposure of Red Wine Grapes to Solar Radiation.

Exposure to solar radiation is a determining factor of grape composition. Flavonol synthesis is upregulated by solar radiation leaving a fingerprint on flavonol profile. This study aimed to test the factors affecting flavonol accumulation and profile and their potential as an indicator to assess the overall exposure of red wine grape berry to solar radiation. We performed three experiments to study the response of flavonol accumulation and profile to (1) three different solar radiation exclusion treatments during berry development; (2) canopy porosity and leaf area index (LAI); and (3) spatial variability of water status, vigor and ripening and cultural practices in commercial vineyards. Results showed a strong relationship between global radiation, inverse dormant pruning weights or canopy porosity (inversely proportional to LAI) and % kaempferol or % quercetin. Furthermore, the increase in concentration of the above two flavonols was associated with a reduction of % myricetin. Total flavonol content, % kaempferol, % quercetin, and % myricetin had significant correlations with inverse dormant pruning weights, but these were less sensitive to over-ripening or water deficits. Flavonol profile was associated to site hydrology (wetness index) through changes in vigor, and to LAI; and responded to shoot thinning or fruit-zone leaf removal. These results support the reliability of the flavonol profile as an assessment parameter for studies aiming to discuss canopy architecture or the effect of solar radiation on grapevine berries.

Vegetative and Reproductive Responses of Mature Cabernet Sauvignon Grapevines Converted from Spur Pruning to Cane Pruning at Five-Foot In-Row Vine Spacing

Summary Goals: Once established, vineyards are generally constrained by vine and row spacing and trellis configuration, which restricts how these variables can be modified. Regardless, such post-planting modifications may be desirable. This project chronicles vine performance following the conversion of seven-yr-old, cordon-trained, spur-pruned vines (“spur-pruned”) to head training and cane pruning (“cane-pruned”) with vines spaced 5 ft (1.5 m) apart in the row. While there are both pros and cons with either system, head training and cane pruning has an operational advantage in that less labor is expended on shoot-thinning because of retention of far fewer basal buds with cane-pruned vines. At issue, though, is a perception or reality that relatively wide in-row vine spacing (e.g., ≥4 or 5 ft) leads to uneven shoot development and nonuniform fruit ripening on long canes. We hypothesized that nonuniformity of shoot growth and development would lead to increased variability of fruit maturity at harvest with the conversion from spur pruning to cane pruning, with mature vines planted 5 ft (1.5 m) apart in the row. Key Findings: In comparison to spur pruning, the cane-pruned vines exhibited: (i) delayed budbreak and bloom; (ii) fewer, but more fruitful shoots; (iii) lower cane-pruning weights; and (iv) similar canopy architecture, primary fruit chemistry at harvest, and uniformity of pruned cane weights. Impact and Significance: Although we hypothesized that a 5 ft (1.5 m) in-row vine spacing might lead to nonuniform shoot development and fruit ripening on bilateral canes, this proved not to be the case. Although there was variation in components of yield for cane-pruned vines compared to spur-pruned vines, fruit maturity indexed as soluble solids concentration was similar between the two systems in the four seasons after conversion. While spur pruning has some advantage from the standpoint of reduced or eliminated time to tie canes following dormant pruning, the disadvantage, at least with Cabernet Sauvignon, as used here, is the propensity of cordon training to produce abundant basal shoots, which add excess crop and canopy density or additional labor to remove those shoots. A closer in-row spacing might be advised for cane pruning in new vineyards; however, it is possible to effectively convert spur-pruned vines back to cane pruning even for mature vines spaced 5 ft (1.5 m) apart in the row should that conversion be desired for labor savings, anticipated fruit quality improvements, or other reasons.

Late dormant pruning affects split pit incidence in peach

Late dormant pruning affects split pit incidence in peach

Evaluating the use of harvesting systems and worker platforms in the South African deciduous fruit industry

The increasing cost of fruit production necessitates more cost-effective orchard practices on South African deciduous fruit farms. Increasing the productivity of labour is one of the components focussed on. Harvesting systems and worker platforms were tested in various production areas to evaluate the effect of these machines on worker productivity during harvesting, pruning and fruit thinning. The effect of harvesting systems on the incidence of harvest injuries was also assessed. The misalignment between typical South African deciduous fruit orchards and harvesting system design leads to a decrease in overall worker productivity during harvesting. Orchard actions where a lot of time is spent moving the ladder relative to the time spent working on the ladder showed the greatest productivity gains when performed with platforms, e.g., summer pruning and to a lesser extent dormant pruning. However, few South African orchards and operational systems are suited to the implementation of these machines and much optimization and investment will be needed to mechanize the harvesting process. Factors such as tree size, shape and uniformity, fruit distribution on the tree, fruit size and quality, orchard floor condition and aspect, labour team dynamics, harvesting incentives, bin condition, operational system employed and harvest logistics all affect the feasibility and ease of mechanization.

Prohexadione-calcium, ethephon, trinexapac-ethyl and maleic hydrazide reduce extension shoot growth of apple

Prohexadione-calcium (P-Ca) is widely used to reduce vegetative growth and labour costs associated with manual pruning. Orchard studies were conducted in 2012 and 2013 to determine the response of mature ‘Empire’/M.26 apple trees to individual or combined applications of P-Ca, ethephon (ETH), trinexapac-ethyl (TE), and maleic hydrazide (MH). Sprays were repeated three times at approximately 2-wk intervals starting at petal fall. All compounds reduced extension shoot growth, ranging from 40%–73% in 2012 and 26%–57% in 2013, relative to untreated controls. The greatest reduction in growth was achieved with ETH in one year and P-Ca + ETH and MH in another. The tank-mixed combination of P-Ca + ETH improved vegetative control compared with each compound applied alone. MH caused foliar phytotoxicity and damage to the apical meristem, resulting in the stimulation of lateral shoot growth. Reduction in shoot growth from any of the plant bioregulators (PBR) did not reduce dormant pruning times in the spring followi...

Modeling Dormant Fruit Trees for Agricultural Automation

Dormant pruning of fruit trees is one of the most costly and labor‐intensive activities in specialty crop production. We present a system that solves the first step in the process of automated pruning: accurately measuring and modeling the fruit trees. Our system employs a laser sensor to collect observations of fruit trees from multiple perspectives, and it uses these observations to measure parameters needed for pruning. A split‐and‐merge clustering algorithm divides the collected data into three sets of points: trunk candidates, junction point candidates, and branches. The trunk candidates and junction point candidates are then further refined by a robust fitting algorithm that models as cylinders each segment of the trunk and primary branches. In this work, we focus on measuring the diameters of the primary branches and the trunk, which are important factors in dormant pruning and can be obtained directly from the cylindrical models. We show that the results are qualitatively satisfactory using synthetic and real data. Our experiments with three synthetic and three real apple trees of two different varieties showed that the system is able to identify the primary branches with an average accuracy of 98% and estimate their diameters with an average error of 0.6 cm. Although the current implementation of the system is too slow for large‐scale practical applications (it can measure approximately two trees per hour), our study shows that the proposed approach may serve as a fundamental building block of robotic pruners in the near future.

Automatic image-based determination of pruning mass as a determinant for yield potential in grapevine management and breeding

Background and Aims Vine balance is defined as a relation between vegetative (mass of dormant pruning wood) and generative (yield) growth. For grapevine breeding, emphasis is usually placed on the evaluation of individual seedlings. In this study, we calculated the mass of dormant pruning wood with the assistance of an automated image-based method for estimating the pixel area of dormant pruning wood. The evaluation of digital images in combination with depth map calculation and image segmentation is a new and non-invasive tool for objective data acquisition. Methods and Results The proposed method was tested on a set of seedlings planted at the Institute for Grapevine Breeding Geilweilerhof, Germany. All images taken in the field were geo-referenced, and the automated method was validated by manual segmentation. Together with additional yield parameters, the vine balance indices can be used to classify seedlings for breeding purposes. Conclusion The computed pruning mass obtained using image-based methods is an accurate, inexpensive and easy method to estimate pruning mass compared with the manual time-consuming measurements. Together with the yield parameters, it is a suitable method for seedling evaluation and can also be used in precision viticulture. Significance of the Study This study demonstrates an image-based evaluation of the pruning mass to be a highly valuable tool for grapevine research and grapevine breeding. Moreover, the tool might be used by industry to monitor vine balance. The key findings reported have the potential to increase grapevine breeding efficiency by using an accurate and objective phenotyping method.

Cover Crop and Root Pruning Impacts on Vegetative Growth, Crop Yield Components, and Grape Composition of Cabernet Sauvignon

Complete vineyard floor cover cropping (inter- and intrarow) and vine root pruning were evaluated as tools to restrict vegetative growth of Vitis vinifera cv. Cabernet Sauvignon grapevines. Treatments were arranged in a split-plot, randomized, complete block design with cover crop schemes as main plots and annual vine root pruning (RP), or not (NRP), as subplots. Five perennial grasses as complete floor cover crops were compared to a more conventional under-trellis herbicide strip combined with KY-31 fescue interrows. KY-31 fescue and orchardgrass each reduced shoot growth rate by >30% in 2006 and >20% in 2007, below that of the herbicide-strip control vines. Root pruning independently reduced shoot growth rates. The combination of cover crop and RP decreased dormant pruning weights more than did the additive effects of either factor applied alone. Pruning weights in 2010 were reduced 8% below the control by RP, by 15% by cover crop, but by 38% when both treatments were applied. Leaf petiole N concentration at bloom was ~11% lower in RP vines in two of three years evaluated, but did not differ among vines grown with different cover crops. Stem water potential (Ψstem) was not affected by treatments. Cover cropping did not reduce crop yield with the exception of reduced yield due to KY-31 fescue in 2006. Berry weights were slightly reduced by a RP × year interaction from 2007 to 2009 and by a year effect in 2011 compared to 2010. While complete vineyard floor cover cropping and root pruning were effective tools to reduce vine size and vigor, effects on canopy architecture and primary fruit chemistry were minimal and more influenced by seasonal variation.