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1
Peck, Gregory, Megan McGuire, Thomas Boudreau, and Amanda Stewart. "Crop Load Density Affects ‘York’ Apple Juice and Hard Cider Quality." HortScience 51, no. 9 (September 2016): 1098–102. http://dx.doi.org/10.21273/hortsci10962-16.
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To assess the impact crop load has on hard cider chemistry, ‘York’ apple (Malus ×domestica Borkh.) trees were hand thinned to three different crop loads: low [two apples per cm2 branch cross-sectional area (BCSA)], medium (four apples per BCSA), and high (six apples per BCSA). Higher crop loads produced smaller, less acidic fruit that were slightly more mature. In juice made from fruit from these treatments, the total polyphenol content did not differ at harvest, but, after fermentation, the medium crop load had 27% and the high crop load had 37% greater total polyphenol content than the low crop load. Yeast assimilable nitrogen (YAN) concentration in juice made from fruit from the low crop load treatment had 18% and 22% greater than the medium and high crop load, respectively. YAN concentrations in juice from the medium and high crop load treatments were similar. Our results provide apple growers and hard cider producers with a better understanding of how apple crop load impacts YAN concentrations in juice and total polyphenol concentrations in juice and cider.
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Serra, Sara, Rachel Leisso, Luca Giordani, Lee Kalcsits, and Stefano Musacchi. "Crop Load Influences Fruit Quality, Nutritional Balance, and Return Bloom in ‘Honeycrisp’ Apple." HortScience 51, no. 3 (March 2016): 236–44. http://dx.doi.org/10.21273/hortsci.51.3.236.
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The apple variety, ‘Honeycrisp’ has been extensively planted in North America during the last two decades. However, it suffers from several agronomic problems that limit productivity and postharvest quality. To reduce losses, new information is needed to better describe the impact of crop load on productivity and postharvest fruit quality in a desert environment and the major region where ‘Honeycrisp’ expansion is occurring. Here, 7-year-old ‘Honeycrisp’ trees on the M9-Nic29 rootstock (2.5 × 0.9 m) were hand thinned to five different crop loads [from 4.7 to 16.0 fruit/cm2 of trunk cross-sectional area (TCSA)] to compare fruit quality, maturity, fruit size, elemental concentration, and return bloom. Fruit size distribution was affected by crop load. Trees with the highest crop load (16 fruit/cm2) produced smaller fruit. Index of absorbance difference (IAD) measurements (absorption difference between 670 and 720 nm), a proxy indicator of the chlorophyll content below the skin of fruit measured by a DA-meter, were made shortly after harvest (T0) and after 6 months of storage (T1). Fruit from the trees with the lowest crop load had lower IAD values indicating advanced fruit ripeness. The comparison between the IAD classes at T0 and T1 showed that fruit belonging to the lowest IAD class had significantly higher red-blushed overcolor percentage, firmness, dry matter, and soluble solid content than those in the “most unripe” class (highest IAD readings) regardless of crop load. The percentage of blushed color, firmness, titratable acidity (TA), soluble solids content, and dry matter were all higher in the lowest crop loads at both T0 and T1. Fruit calcium (Ca) concentration was lowest at the lowest crop load. The (K + Mg + N):Ca ratio decreased as crop load increased until a crop load of 11.3 fruit/cm2, which was not significantly different from higher crop loads. For return bloom, the highest number of flower clusters per tree was reported for 4.7 fruit/cm2 crop load, and generally it decreased as crop load increased. Here, we highlight the corresponding changes in fruit quality, storability, and elemental balance with tree crop load. To maintain high fruit quality and consistency in yield, careful crop load management is required to minimize bienniality and improve fruit quality and storability.
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Reginato, Gabino H., Víctor García de Cortázar, and Terence L. Robinson. "Predicted Crop Value for Nectarines and Cling Peaches of Different Harvest Season as a Function of Crop Load." HortScience 42, no. 2 (April 2007): 239–45. http://dx.doi.org/10.21273/hortsci.42.2.239.
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Several field experiments to assess the effect of tree size and crop load on fruit size and yield efficiency were conducted in cling peach and nectarine orchards of different harvest seasons in Chile. Trees were randomly selected in each orchard and then hand-thinned at the beginning of pit hardening to a wide range of crop loads. The fraction of above-canopy photosynthetically active radiation (PAR) intercepted by the canopy (PAR i) was determined at harvest. All fruits were counted and weighed and average fruit weight calculated. Crop load and yield were normalized by tree size measured by intercepted PAR i. For each orchard, the relationship between crop load and fruit size or crop load and yield efficiency was assessed by regression analysis. Fruit size distribution was calculated from fruit size adjusted for fruit load assuming a normal fruit size distribution and valued according to shipment date and price obtained from a Chilean export company. Using crop load as a covariate, fruit size adjusted for crop load was compared for nectarine and peach cultivars. Fruit size adjusted for fruit load and yield efficiency was greater with late season cultivars than the early or midseason cultivars. Predicted crop value (PCV), normalized in terms of PAR intercepted, was calculated for all the cultivars. Large differences in predicted crop value were found for early, midseason, and late ripening nectarines. Early and late ripening cultivars had the highest predicted crop value, especially at lower crop loads and larger fruit sizes. The early season cultivars had high crop value as a result of higher fruit prices, whereas the late season cultivar had high crop value as a result of higher production. With cling peaches, the early season cultivar ‘Jungerman’ had a lower predicted crop value than the late season cultivars ‘Ross’ and ‘Davis’. For cling peaches, the highest PCV was achieved at a relatively high crop load with high yield and small fruit size.
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Liu, Xiaoli, Qiuwen Chen, and Zhaoxia Zeng. "Study on nitrogen load reduction efficiency of agricultural conservation management in a small agricultural watershed." Water Science and Technology 69, no. 8 (February 11, 2014): 1689–96. http://dx.doi.org/10.2166/wst.2014.076.
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Different crops can generate different non-point source (NPS) loads because of their spatial topography heterogeneity and variable fertilization application rates. The objective of this study was to assess nitrogen NPS load reduction efficiency by spatially adjusting crop plantings as an agricultural conservation management (ACM) measure in a typical small agricultural watershed in the black soil region in northeast China. The assessment was undertaken using the Soil and Water Assessment Tool (SWAT). Results showed that lowland crops produce higher nitrogen NPS loads than those in highlands. It was also found that corn gave a comparatively larger NPS load than soybeans due to its larger fertilization demand. The ACM assessed was the conversion of lowland corn crops into soybean crops and highland soybean crops into corn crops. The verified SWAT model was used to evaluate the impact of the ACM action on nitrogen loads. The results revealed that the ACM could reduce NO3-N and total nitrogen loads by 9.5 and 10.7%, respectively, without changing the area of crops. Spatially optimized regulation of crop planting according to fertilizer demand and geological landscapes can effectively decrease NPS nitrogen exports from agricultural watersheds.
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Inglese, P., T. Caruso, G. Gugliuzza, and L. S. Pace. "Crop Load and Rootstock Influence on Dry Matter Partitioning in Trees of Early and Late Ripening Peach Cultivars." Journal of the American Society for Horticultural Science 127, no. 5 (September 2002): 825–30. http://dx.doi.org/10.21273/jashs.127.5.825.
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Effect of crop load on dry matter partitioning was studied on 3-year-old peach [(Prunus persica (L.) Batsch (Peach Group)] trees of the early ripening `Early May Crest' (EMC) grafted on `GF677' and Penta (Prunus domestica L.) rootstock and the late ripening `Flaminia' grafted on `GF677' rootstock [(Prunus persica × Prunus dulcis (Mill.) D. A. Webb] and grown outdoors in 230-L containers, for 2 years. Fruit thinning was carried out 10 days after fruit set to produce different crop loads. Trees were sampled destructively throughout two growing seasons and divided into above-ground and root components, for dry matter and carbohydrate analysis. At the end of the fruit development period, in the first year, total tree dry matter accumulation was related linearly to crop load even when the increase in crop load greatly decreased vegetative and root growth. Total dry matter accumulation was highest in EMC/`GF 677' at any specific crop load, and EMC trees on `GF677' allocated relatively more dry matter than EMC/`Penta' trees to vegetative and root growth, even under increasing fruit sink demand. Two consecutive years of heavy crops resulted in an inverse relationship between crop load and dry matter accumulation of trees, due to a major reduction of vegetative, root, and fruit growth. The percentage of dry matter partitioned to fruit decreased with the vigor of the rootstock, and EMC/`Penta' trees had the lowest harvest index at each specific crop load. The early ripening EMC/`GF677' trees which had twice the harvest index of `Flaminia'/`GF677' trees for any level of crop load. `Flaminia'/`GF677' trees had the largest canopy size. Starch content in the roots was lowest for cropping trees and depended on the rootstock and on the length of the fruit development period, being highest for the late ripening `Flaminia'/`GF677' trees. Individual fruit weight decreased with crop load, and the reduction of fruit size was related to rootstock and time of ripening.
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Anthony, Brendon, Sara Serra, and Stefano Musacchi. "Optimizing Crop Load for New Apple Cultivar: “WA38”." Agronomy 9, no. 2 (February 22, 2019): 107. http://dx.doi.org/10.3390/agronomy9020107.
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Crop load management is growing increasingly important as a factor related to biennial tendencies, post-harvest disorders, and inconsistent fruit quality in apples like “Honeycrisp”. Washington State University released a new apple cultivar, called “WA38”, in 2017. Limited literature is available about the productive characteristics of this new cultivar. An experimental trial evaluating the effect of crop load on leaf area, fruit quality, mineral composition, and return bloom of “WA 38” was conducted for two consecutive years (2017 and 2018) to determine an optimal crop load. Trees were trained as a spindle and grafted on Malling-9 Nic29 (Nic29) rootstocks. Crop loads were adjusted to 2, 4, 6, and 8 fruits/cm2 of trunk cross-sectional area (TCSA). Crop load had a significant effect on production, with yields ranging from 28 to 83 MT/ha in 2017. Fruit quality was impacted by increasing crop load, with a reduction in fruit weight, soluble solid content, firmness, dry matter, titratable acidity, and a delay in maturity. Leaf-to-fruit ratios were higher in lower crop loads. Relatively consistent flower bud formation was seen at the 6 and 8 fruits/cm2 categories. A possible threshold for optimal fruit quality and consistent bloom was identified around 6 fruits/cm2 TCSA.
7
Einhorn, Todd C., Debra Laraway, and Janet Turner. "Crop Load Management Does Not Consistently Improve Crop Value of ‘Sweetheart’/‘Mazzard’ Sweet Cherry Trees." HortTechnology 21, no. 5 (October 2011): 546–53. http://dx.doi.org/10.21273/horttech.21.5.546.
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The effect of crop load level on vegetative growth, fruit growth, yield, fruit quality, surface pitting, crop value and return bloom was studied over a 2-year period on 9- and 10-year-old ‘Sweetheart’/‘Mazzard’ sweet cherry (Prunus avium) trees. In early spring, whole-tree crop loads were adjusted to two different levels by removal of reproductive buds (either 50% or all but one) from spurs and compared with an unthinned control. In 2009, heavy crop loads of unthinned trees reduced fruit size by 30 days after full bloom (DAFB). At harvest, fruit diameter of thinned treatments was increased 22% and 27% compared with unthinned fruit. Fruit quality attributes [soluble solids concentration (SS), fruit firmness, and total acids (TA)] were significantly greater for thinned treatments. Thinned treatment yields were reduced 40% to 54% relative to unthinned trees, with greater percentages of fruit in large size classes. Despite significantly fewer fruit per tree, moderately thinned trees had a higher estimated crop value ($142 per tree) than unthinned trees ($125 per tree). Crop value was lowest for the heavily thinned treatment ($107 per tree), reflecting overthinning. In 2010, shoot growth was negatively related to crop load level. Fruit growth of unthinned trees was not significantly affected by higher fruit density until 89 DAFB. Yield of 2010 unthinned trees was 87% of 2009, while thinned tree yields were similar between years. Improved fruit quality and greater percentages of large fruit were observed for thinned treatments in 2010; however, crop value was highest for unthinned trees ($190 per tree), even though 18% of the fruit were too small for fresh market sale. Surface pitting was unaffected by crop load level in either year. Return bloom (flowers per reproductive bud and reproductive buds per spur) was significantly, negatively related to the prior season's crop load in 2010 and 2011. In the current sweet cherry pricing structure, higher crop value is associated with large volumes of medium-sized fruit. Thinning to manage crop load of low-medium density, productive ‘Sweetheart’/‘Mazzard’ trees will not be an annual requirement, though in heavy fruit set years crop load management will improve crop value.
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van Vliet, L. J. P., B. J. Zebarth, and G. Derksen. "Effect of fall-applied manure practices on runoff, sediment, and nutrient surface transport from silage corn in south coastal British Columbia." Canadian Journal of Soil Science 82, no. 4 (November 1, 2002): 445–56. http://dx.doi.org/10.4141/s01-041.
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Runoff from manured cropland during the wet fall and winter season, when 70% of the annual rainfall occurs, is a surface water quality concern in the Lower Fraser Valley of British Columbia. This study compares different fall-manure application strategies on runoff and contaminant transport from silage corn (Zea mays) land. The treatments were (i) a control, which did not receive manure in the fall; (ii) manure broadcast in the fall on corn stubble; and (iii) manure broadcast in the fall on corn stubble with an established relay crop. Runoff, solids, and nutrients loads from natural precipitation were measured on replicated experimental plots (0.0125 ha) from 1996 to 1998. Fall-applied manure on 3–5% sloping silage cornland without a relay crop resulted in a high risk to surface water quality, due to high suspended solid loads of between 7 and 14 Mg ha-1 yr-1 and high nutrient transport with mean annual total Kjeldahl N (TKN) P, and K loads of 98, 21, and 63 kg ha-1, respectively. Compared with no relay crop, intercropping silage corn with a relay crop of Italian ryegrass (Lolium multiflorum) reduced the mean annual runoff and suspended solid load by 53 and 74%, respectively, TKN load by 56%, P load by 42%, K load by 31%, and Cu load by 57%. Even though total nutrient loads were lower with the relay crop treatment, all fall manure treatments including the relay crop resulted in nutrient loads above guidelines for the first three runoff events immediately following application. Key words: Runoff, suspended solids, nutrient loads, relay crop, cover crop, silage corn, manure
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Maas, F. M., and P. A. H. van der Steeg. "CROP LOAD REGULATION IN 'CONFERENCE' PEARS." Acta Horticulturae, no. 909 (October 2011): 367–79. http://dx.doi.org/10.17660/actahortic.2011.909.41.
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Francescatto, P., J. Lordan, and T. L. Robinson. "Precision crop load management in apples." Acta Horticulturae, no. 1281 (June 2020): 399–406. http://dx.doi.org/10.17660/actahortic.2020.1281.53.
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Taylor, J. A., J. L. Dresser, C. C. Hickey, S. T. Nuske, and T. R. Bates. "Considerations on spatial crop load mapping." Australian Journal of Grape and Wine Research 25, no. 2 (December 19, 2018): 144–55. http://dx.doi.org/10.1111/ajgw.12378.
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Sidhu, Ramandeep Singh, Sally A. Bound, and Ian Hunt. "Crop Load and Thinning Methods Impact Yield, Nutrient Content, Fruit Quality, and Physiological Disorders in ‘Scilate’ Apples." Agronomy 12, no. 9 (August 23, 2022): 1989. http://dx.doi.org/10.3390/agronomy12091989.
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Most apple cultivars produce too many flowers to enable consistent yields of high-quality fruit, thus, crop load management (thinning) is an integral part of orchard management in modern apple cultivation. Crop load is managed by thinning excess flowers and/or fruit from a tree, however ideal targets vary between cultivars. In this two-year study, the effect of thinning methods at different levels of crop load on fruit quality and production, post-harvest storability and physiological disorders, and fruit and leaf nutrient content in ‘Scilate’ apples were investigated in southern Tasmania, Australia. Two thinning methods, artificial bud extinction (ABE) and hand thinning (HT), were compared at three levels of crop load: 3, 6, or 12 fruit cm−2 limb cross-sectional area (LCSA), described as low, medium, and high, respectively. During the second season, all the ABE and HT treatments received additional chemical thinning (CT). The results demonstrated that ABE consistently outperformed HT in terms of improved fruit set, return bloom, and fruit weight. The fruit quality parameters, such as flesh firmness, total soluble solids, dry matter content, malic acid content, and fruit shape, were also improved under the ABE regime, with these positive effects being the clearest in the second season. In general, high-quality fruits were obtained from the low and medium crop loads, while the fruit quality was poor for the high crop load trees, but the low crop load fruit had a slightly higher incidence of internal flesh browning (predominantly radial) and fruit softening after regular atmosphere storage. The crop load also impacted on the fruit and leaf mineral nutrient content, where fruit N, Ca, Mn, and Zn, and leaf N, Fe, Zn, and Cu content increased while fruit and leaf K declined with a higher crop load. High crop load, irrespective of the thinning regime, and HT with a medium crop load, induced severe biennial bearing, whereas, the fruit yield was relatively consistent with ABE, even with a medium crop load. We conclude that ABE with a medium crop load (around six fruit cm−2 LCSA) is an effective method of managing crop load and optimizing the fruit quality in ‘Scilate’ apples.
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Wünsche, Jens N., John W. Palmer, and Dennis H. Greer. "Effects of Crop Load on Fruiting and Gas-exchange Characteristics of `Braeburn'/M.26 Apple Trees at Full Canopy." Journal of the American Society for Horticultural Science 125, no. 1 (January 2000): 93–99. http://dx.doi.org/10.21273/jashs.125.1.93.
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Effect of crop load on tree growth, leaf characteristics, photosynthesis, and fruit quality of 5-year-old `Braeburn' apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] trees on Malling 26 (M.26) rootstock was examined during the 1994-95 growing season. Crop loads ranged from 0 to 57 kg/tree [0 to 1.6 kg fruit/cm2 trunk cross sectional area (TCA) or 0 to 8.7 fruit/cm2 TCA]. Fruit maturity as indicated by background color, starch/iodine score, and soluble solids was advanced significantly on low-cropping trees compared to high-cropping trees. Whole-canopy leaf area and percentage tree light interception increased linearly with a significant trend as crop load decreased. From midseason until fruit harvest, leaf photosynthesis decreased significantly on lighter cropping trees and similarly, a positive linear trend was found between whole-canopy gas exchange per unit area of leaf and crop load. Leaf starch concentration in midseason increased linearly as crop load decreased, providing some explanation for the increased down-regulation of photosynthesis on trees with lower crop loads. After fruit harvest, the previous crop loads had no effect on leaf photosynthesis and preharvest differences in whole-canopy gas exchange per unit area of leaf were less pronounced. At each measurement date, daily whole-canopy net carbon exchange and transpiration closely followed the diurnal pattern of incident photosynthetic photon flux. The photochemical yield and electron transport capacity depended on crop load. This was due mostly to reaction center closure before harvest and an increased nonphotochemical quenching after harvest.
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Schmidt, Tory, Don C. Elfving, James R. McFerson, and Matthew D. Whiting. "Crop Load Overwhelms Effects of Gibberellic Acid and Ethephon on Floral Initiation in Apple." HortScience 44, no. 7 (December 2009): 1900–1906. http://dx.doi.org/10.21273/hortsci.44.7.1900.
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Potential strategies against biennial bearing in apple [Malus × sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] include promotion of return bloom with an “on”-year application of ethephon or inhibition of return bloom with an “off”-year application of gibberellic acid (GA), but the influence of initial crop load on the efficacy of these bioregulators is poorly understood. In 2004 and 2005, six total trials were initiated in which whole trees were manually adjusted shortly before anthesis to one of three levels of crop load (100%, 50%, 0%) in ‘Cameo’, ‘Honeycrisp’, and ‘Fuji’; GA4 + 7 was overlaid on trees of each crop level in four trials and ethephon in two. In all trials, initial crop load was the primary determinant of return bloom; proportional influence on flower density, fruit density, and yield was generally most pronounced at the 50% crop level. GA4 + 7 consistently reduced floral initiation, whereas ethephon promoted it. Flowering responses from a historically alternating ‘Cameo’ trial site showed greater sensitivity to ethephon and less sensitivity to GA4 + 7 than did responses from parallel trials established in an annually bearing ‘Cameo’ block, suggesting a predilection of nascent buds to a specific fate before the influence of exogenous bioregulators or gibberellins from seeds produced in developing fruit. Light crop loads and GA4 + 7 applications generally promoted shoot extension, whereas heavy crops and ethephon had the opposite effect.
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Barden, John A. "CROP LOAD AND LIMB GIRDLING AFFECT APPLE FRUIT SIZE, COLOR, AND QUALITY." HortScience 27, no. 6 (June 1992): 625d—625. http://dx.doi.org/10.21273/hortsci.27.6.625d.
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In 1990, 15-yr-old `Smoothee Golden Delicious' trees on M.9, M.9/MM.111, and MM.111 were used. On each of 4 trees per rootstock, 3 branches (1.0-1.7 cm dia) were selected. On 7 June (45 DAFB), crop loads were adjusted to 3, 5, or 7 fruit per cm2 branch cross sectional area (BXSA), and each branch was girdled. On 6 Sept all fruit were harvested; fruit weight, ground color, percent blush, soluble solids, starch, and firmness were regressed against crop load. Each was negatively related to crop load, most strongly for soluble solids, ground color and blush. Rootstock influenced several factors and some interaction with crop load occurred. In 1991, heavily cropping 10-yr-old trees of Empire/M.7A were used. One each of 7 trees, branches (1.2-2.0 cm dia) were thinned to 4, 8, or 12 fruit/cm2 BXSA on 5 June (40 DAFB). One branch per crop load per tree was girdled on 5 June. On 29 Sept fruit were harvested for evaluation. ANOVA indicated significant interactions between crop load and girdling for fruit weight, firmness, soluble solids and starch. Each showed a significant negative linear regression with crop load on girdled branches; on ungirdled branches none of the regressions were significant.
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Naor, A., I. Klein, I. Doron, Y. Gal, Z. Ben-David, and B. Bravdo. "Irrigation and Crop Load Interactions in Relation to Apple Yield and Fruit Size Distribution." Journal of the American Society for Horticultural Science 122, no. 3 (May 1997): 411–14. http://dx.doi.org/10.21273/jashs.122.3.411.
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The interaction between irrigation and crop load with respect to fruit size distribution was investigated in a `Golden Delicious' apple (Malus domestica Borkh) orchard located in a semi-arid zone. Irrigation levels during the main fruit expansion phase ranged from 0.42 to 1.06 of the Class A pan evaporation coefficient. Crop load was adjusted to 100 to 450 fruit/tree in the 1250 trees/ha orchard by hand thinning. Total yield was not affected by irrigation level up to a crop load of 200 fruit/tree. Yield of all grades >65 mm was affected by irrigation level for higher crop densities. The yield of fruit of diameter <75 mm was not affected by increasing the Class A pan evaporation coefficient above 0.75. Our data indicate that availability of assimilates may limit the size of fruit with potential to grow larger than 70 mm in diameter at all crop loads higher than 200 fruit/tree. This limitation increases with decreasing irrigation level. The volumetric relative growth rate (VRGR) increased with irrigation level and with decreasing crop load. VRGR was more affected by crop load than by irrigation level in the ranges studied.
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Haouari, Afef, Marie-Christine Van Labeke, Kathy Steppe, Fethi Ben Mariem, Mohamed Braham, and Mohamed Chaieb. "Fruit thinning affects photosynthetic activity, carbohydrate levels, and shoot and fruit development of olive trees grown under semiarid conditions." Functional Plant Biology 40, no. 11 (2013): 1179. http://dx.doi.org/10.1071/fp13094.
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Olive (Olea europaea L.) production is marked by annual oscillations as trees alternate from high to low crop loads in successive years. Gas exchanges and carbohydrate content of leaves and fruits in olive tree (O. europaea cv. Besbassi) were monitored at pit hardening and fruit ripening. After fruit set, three crop loads were applied (100%, 50% and 25% of the initial fruit load) by manual thinning. Severe fruit thinning reduced photosynthesis, stomatal conductance and intercellular CO2 concentration. Crop load had no significant effect on chlorophyll fluorescence parameters. The reduction of 75% of the initial crop load favoured the accumulation of starch in leaves and soluble sugars in leaves and fruits. The reduction in initial fruit load had a significant positive effect on the current year’s shoot elongation and on inflorescence number the following spring. To increase the fruit size, a strong thinning (75%) was necessary, which coincided with the highest shoot vigour. Moderate thinning (50%) hardly affected leaf carbohydrate content and fruit size, but photosynthetic capacity was only limited at fruit ripening.
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Vizzari, Marco, Sara Antognelli, Mariano Pauselli, Paolo Benincasa, Michela Farneselli, Luciano Morbidini, Piero Borghi, Giacomo Bodo, and Alessandra Santucci. "Potential Nitrogen Load from Crop-Livestock Systems." International Journal of Agricultural and Environmental Information Systems 7, no. 3 (July 2016): 21–40. http://dx.doi.org/10.4018/ijaeis.2016070102.
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The EU “Water” Directive establishes a common European framework for the environmental protection of inland, coastal and marine waters. One of the major environmental concerns about water quality is certainly the N loads from agro-livestock systems. In this study, carried out in Umbria region, Italy, a novel spatial database for a multi-scale and multi-level analysis was designed and implemented integrating different agricultural and livestock farming datasets related to agro-livestock system. This database allows the calculation of different descriptive indicators about agricultural and livestock farming systems at different scales of investigation (NVZ, sub-basins, bodies of ground water, cadastral sheets, municipalities, provinces, entire region). Moreover, three relevant spatial indicators (potential nitrogen crop supply, potential nitrogen availability from livestock manure, and total potential nitrogen loads) were calculated applying an assessment model developed in the study. All this information appears very significant to support decision making at the various administrative levels and to pursue the environmental objectives established by EU and national regulations.
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Stefanelli, D., T. Plozza, H. Flachowsky, and J. N. Wünsche. "Young apple tree responses to crop load." Acta Horticulturae, no. 1229 (December 2018): 221–28. http://dx.doi.org/10.17660/actahortic.2018.1229.34.
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Johnson*, Holly A., Steven A. Weinbaum, and Theodore M. DeJong. "Crop Load Effects on Subsequent Peach Floral Development, Pistil Size at Anthesis and Fruit Size at Maturity." HortScience 39, no. 4 (July 2004): 851C—851. http://dx.doi.org/10.21273/hortsci.39.4.851c.
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The effects of low and high crop loads in 2002 on floral development (Summer 2002), pistil size at anthesis (Spring 2003), and subsequent season fruit size at maturity (Summer 2003) were studied. Trees were all thinned to the same crop load in 2003. Three peach cultivars (Elegant Lady, O'Henry and Fairtime) with different ripening times (mid-July, mid-August, and early-September, respectively) were used to assess the effects of current season crop on floral development for the subsequent season. Based on previous literature, we reasoned that the maximum competition for carbohydrates between maturing fruit and developing buds is likely to occur at fruit maturity, especially under heavy crop loads. In 2003, individual fruit were harvested and weighed at maturity. In all three cultivars, a heavy crop load reduced the percentage of floral buds initiated and delayed floral differentiation. A heavy crop load also reduced pistil size at anthesis and fruit size at maturity in the subsequent season. These data support the practice of vigorous pruning to annually renew fruiting wood in peach to minimize the influence of crop in the previous season on the subsequent season's fruit and maintain large fruit sizes.
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Li, Kuo-Tan, Jim Syvertsen, and Jill Dunlop. "(463) Grapefruit Crop Load Affects Net Gas Exchange of Leaves, Tree Growth, and Fruit Quality." HortScience 40, no. 4 (July 2005): 1048A—1048. http://dx.doi.org/10.21273/hortsci.40.4.1048a.
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Effects of crop load on leaf characteristics, shoot growth, fruit shape, fruit quality, and return bloom were investigated in 13-year-old `Ruby Red' grapefruit (Citrus paradisi Macf.) on `Swingle' citrumleo rootstock. Trees were hand thinned in June 2003 and 2004 at the end of physiological fruit drop to establish three to four levels of crop load ranging from normal (high crop load without thinning) to extremely low (near 90% fruit removal). Leaves on high crop load trees had higher net assimilation of CO2 (ACO2) than those on low crop load trees. Crop load enhancement of ACO2 continued until harvest. In 2004, however, the effects were diminished in October just prior to the beginning of the harvest season, after leaf and fruit loss from three consecutive hurricanes. There was no difference in leaf dry weight per leaf area and leaf nitrogen among treatments. Nonfruiting branches of high crop load trees produced fewer, but longer, summer flushes than those of low crop load trees. Fruiting branches generally produced few summer flushes with similar shoot lengths among treatments. High crop load trees developed a greater percentage of vegetative shoots, whereas low crop load trees developed more inflorescences. Crop load adjustments did not affect fruit size and total soluble solid content, but low crop load trees produced a higher percentage of irregular shape (sheepnosed) fruit with high acidity.
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Rohla*, Charles T., Michael W. Smith, Niels O. Maness, and William R. Reid. "Crop Load and Shoot Type Affect Return Bloom of Pecans." HortScience 39, no. 4 (July 2004): 814A—814. http://dx.doi.org/10.21273/hortsci.39.4.814a.
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Trees with about the same crop load were hand thinned to 1, <2, or <3 fruit per cluster or not thinned while the ovule was about one-half expanded. Treatments were replicated three times. Vegetative, and bearing terminal, lateral and shoots with secondary growth were tagged in October, and flowering was determined the following year. Shoots and roots were sampled during dormancy and analyzed for organically bound N, and K. Results indicated that branches with secondary growth produced substantially more shoots and flowers than other branch types. The unthinned trees produced fewer total flowers per branch, had a lower percentage of branches with flowering shoots, and smaller flower clusters than thinned trees. Organically bound N in the roots and shoots was not affected by crop load. Crop load appeared to be negatively related to K concentration in roots <1 cm in diameter, but not in roots >1 cm in diameter. The data suggest that neither N nor K were limiting in trees with large crops.
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Hama, T., T. Aoki, K. Osuga, S. Sugiyama, and D. Iwasaki. "Nitrogen and phosphorus effluent loads from a paddy-field district adopting collective crop rotation." Water Science and Technology 66, no. 5 (September 1, 2012): 1074–80. http://dx.doi.org/10.2166/wst.2012.292.
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Japanese paddy rice systems commonly adopt the rotation of vegetables, wheat and soybeans with paddy rice. Crop rotation may, however, increase the nutrient load in effluent discharged from the district because more fertilizer is applied to the rotation crops than is applied to paddy crops. We investigated a paddy-field district subject to collective crop rotation and quantified the annual nutrient load of effluent from the district in three consecutive years. The total annual exports of nitrogen and phosphorus over the investigation period ranged from 30.3 to 40.6 kg N ha–1 and 2.62 to 3.13 kg P ha–1. The results suggest that rotation cropping increases the effluent nutrient load because applied fertilizer is converted to nitrate, and surface runoff is increased due to the absence of shuttering boards at the field outlets.
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Crisosto, Carlos H., Vanessa Bremer, Maxwell Norton, Louise Ferguson, and Todd Einhorn. "Preharvest Ethephon Eliminates First Crop Figs." HortTechnology 20, no. 1 (February 2010): 173–78. http://dx.doi.org/10.21273/horttech.20.1.173.
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Most fig (Ficus carica) cultivars have potentially two crops; fruit from the first crop are called brebas. This crop is commercially important in some Mediterranean area cultivars. The second or main crop, called figs, is the commercially important crop for most fig cultivars. Due to labor cost increases, harvest of the breba crop, with its low production and lower quality fruit, has become economically unviable in some cultivars. Unharvested brebas are potential sites for fungal pathogens and they attract insects. Spring ethephon applications of 250 to 500 ppm applied before full leaf expansion, when the largest fruit are about 1.5 to 2 cm in diameter reduced the breba crop load (≈92%) without adverse side effects. The use of early fall ethephon applications of 500 ppm also resulted in breba crop load reductions (≈30%), but with significantly lower efficacy than spring treatments. These fall and/or spring ethephon treatments did not affect the percentage of vegetative budbreak, breba weight, breba soluble solids concentration, fig crop load, fig weight, or ethephon residues. Thus, early spring ethephon application at 300 ppm (0.22–0.36 kg·ha−1), when breba fruit and leaves are just starting to develop and figs are not present, was a safe, effective and inexpensive way (about $16 per hectare) to reduce the breba crop. Currently, ethephon is included in the federal IR-4 program, and residue studies are ongoing as a protocol for future registration.
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Lawes, Roger, and Michael Renton. "The Land Use Sequence Optimiser (LUSO): A theoretical framework for analysing crop sequences in response to nitrogen, disease and weed populations." Crop and Pasture Science 61, no. 10 (2010): 835. http://dx.doi.org/10.1071/cp10026.
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The break crop effect, where a non-cereal crop provides relief from soil pathogens, may increase soil nitrogen reserves for a cereal and help minimise populations of herbicide resistant weeds. It is widely used in agriculture to maximise the economic return and yield of cereal crops. In Western Australia, cereal crops are being grown with increasing frequency, at the expense of less profitable break crops and we have developed a land use sequence optimiser (LUSO) to analyse strategic break crop decisions across a suite of price, yield, nitrogen fertiliser cost, soil borne disease load and weed load thresholds. The model is flexible and can easily be parameterised for a wide range of economic, edaphic and biotic parameters. We demonstrate its use in a strategic sense to determine economic and biotic thresholds that force a rotation change in a typical Western Australian cropping system.
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Ferguson, I. B., and C. B. Watkins. "Crop Load Affects Mineral Concentrations and Incidence of Bitter Pit in `Cox's Orange Pippin' Apple Fruit." Journal of the American Society for Horticultural Science 117, no. 3 (May 1992): 373–76. http://dx.doi.org/10.21273/jashs.117.3.373.
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Apple fruit (Malus domestics Borkh. cv. Cox's Orange Pippin) were harvested in four orchards from trees growing under the same conditions but differing in crop load. Regardless of fruit size, apples from light-cropping trees had lower Ca and higher K concentrations and more bitter pit than did fruit from trees with heavy crop loads. The inverse relationship between Ca concentration in the fruit and the incidence of bitter pit also varied according to crop load and could affect the ability to predict incidence of bitter pit from Ca measurements. Differences in fruit maturity that would influence bitter pit incidence were not associated with crop load. The enhanced susceptibility to storage disorders, such as bitter pit, in fruit of all sizes from light-cropping trees suggests the need to handle fruit from such trees differently for postharvest storage.
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Garriz, P. I., G. M. Colavita, and H. L. Alvarez. "166 Influence of Crop Level on Growth and Quality of `Braeburn' Apple Fruit." HortScience 35, no. 3 (June 2000): 418E—419. http://dx.doi.org/10.21273/hortsci.35.3.418e.
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Crop load and the genetic biological carrying capacity (source–sink relationships) determine the potential for fruit size development on apple; however, the environment within which the fruit grows attenuates this potential. The effects of different crop loads on the growth pattern and the progress of maturity in apples were evaluated at the Comahue National Univ., Argentina (lat. 38 56'S long 67 59'W), during the 1998–99 growing season. Our experiment was conducted on 6-year-old `Braeburn'/Malling Merton 111 apple (Malus domestica Borkh.) trees spaced 4.0 × 2.3 m and trained to palmette leader. Treatments were 1) light crop load (LC), 2.5 fruit/cm2 trunk cross-sectional area (TCSA), 2) moderate crop load (MC), 6.5 fruit/cm2 TCSA (standard commercial crop load) and 3) high crop load (HC), minimum 8 fruit/cm2 TCSA, no fruit removed from tree. Whole trees were hand-thinned 19 days after full bloom (DAFB). Fruit diameter (FD) was taken at two weekly intervals (n = 24 per date and treatment) and maturity indexes were determined at harvest. Analysis of variance was used and mean separations were computed with Student's t test. From 38 DAFB until harvest, fruit size was significantly reduced (P < 0.01) in the HC trees, indicating that they were source-limited during growth. At 166 DAFB, FD was 7.48, 7.14, and 6.89 cm for the LC, MC and HC treatments, respectively. Adequate carbon was apparently available to support a commercial crop load since no differences were found between LC and MC trees. Crop level influenced flesh firmness; at 173 DAFB, it was significantly lower in HC trees than MC and LC trees (84.33, 92.51, and 91.57 N, respectively). These results suggest some goals of thinning for ensuring sizable `Braeburn' fruit.
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Snyder-Leiby, Teresa Eileen, and Shixiong Wang. "Role of Crop Load in Chloroplast Ultra-structure and Zonal Chlorosis, a Physiological Disorder in ‘Honeycrisp’ Apple Trees." HortScience 43, no. 6 (October 2008): 1819–22. http://dx.doi.org/10.21273/hortsci.43.6.1819.
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‘Honeycrisp’ is a relatively new apple cultivar (Malus ×domestica Borkh.) with a unique crisp fruit texture that makes it highly desirable. However, the leaves often develop a zonal chlorosis that resembles potato leafhopper damage. Other researchers have determined that the symptoms correlate with decreasing crop load rather than leafhopper damage. This study investigates the possibility that the zonal chlorosis is related to the buildup of starch grains causing rupture of chloroplasts. Transmission electron microscopy was used to document ultrastructural changes in chloroplasts in trees with three different crop loads from the beginning of the season to the end of the season. In trees with extremely low crop loads, we observed abnormalities of chloroplast membrane structure and accumulation of larger and more numerous starch grains. These appear before the appearance of chlorotic symptoms. By early August, the chloroplasts from chlorotic regions of leaves on trees with light crop loads are completely disrupted and abnormally large starch grains are found in place of chloroplasts. As the season progresses, trees with moderate and heavy crop loads showed less severe chloroplast disruption and smaller starch grain accumulation than trees with light crop load.
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Blanco, Victor, Pedro J. Blaya-Ros, Roque Torres-Sánchez, and Rafael Domingo. "Irrigation and Crop Load Management Lessen Rain-Induced Cherry Cracking." Plants 11, no. 23 (November 26, 2022): 3249. http://dx.doi.org/10.3390/plants11233249.
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The combined effects of deficit irrigation and crop load level on sweet cherry (Prunus avium L.) physiological and agronomic response were evaluated during the 2019 season in a commercial orchard located in southeastern Spain. Two irrigation treatments were imposed: (i) control treatment (CTL) irrigated above crop water requirements at 110% of crop evapotranspiration (ETC) and (ii) a deficit irrigation treatment (DI) irrigated at 70% ETC. Within each irrigation treatment, crop load was adjusted to three levels: 100% (natural crop load—high), 66% (medium crop load), and 33% (low crop load). The water relations results were more affected by the irrigation strategies applied than by the crop load management. The deficit irrigation strategy applied reduced soil water availability for DI trees, which led to a continuous decrease in their gas exchange and stem water potential. At harvest, the fruit water potential and osmotic potential of cherries from the DI treatment resulted in significantly lower values than those measured in cherries from CTL trees. On the other hand, both the irrigation strategies imposed and the crop load management used impacted fruit quality. Trees with the lowest level of crop load had fruits of greater size, regardless of the irrigation treatment assayed, and in the DI treatment, cherries from the trees with the lowest crop load were darker and more acidic than those from the trees with the highest crop load. Our results emphasize the different effects that rainfall before harvest has on mature cherries. Thus, cracked cherries at harvest represented 27.1% of the total yield of CTL trees while they were 8.3% of the total yield in DI trees. Cherries from CTL trees also showed a greater cracking index than those from DI trees. Moreover, a linear relationship between crop load and fruit cracked at harvest was observed, particularly for the CTL treatment; thus, the lower the crop load, the greater the proportion of cracked cherries.
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Reginato, Gabino, Terence Robinson, and Victor Garcia de Cortazar. "Predicted Crop Value for a Cling Peach and Three Nectarines of Different Harvest Seasons as a Function of Crop Load." HortScience 41, no. 4 (July 2006): 995C—995. http://dx.doi.org/10.21273/hortsci.41.4.995c.
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Several field experiments to assess the effect of tree size and crop load on fruit size and yield were conducted in a `Ross' cling peach orchard and in three nectarine orchards of different harvest seasons in Chile. Trees were randomly selected in each orchard and then hand-thinned at the beginning of pit hardening to a wide range of crop loads. The fraction of above-canopy photosynthetically active radiation intercepted by the canopy (PARi) was determined at harvest and all fruits were counted, weighted, and average fruit weight calculated. Cropload and yield were expressed in terms of fraction of PARi. Data on farm gate prices for export fruit of different sizes and export dates were obtained from a Chilean export company. For each orchard, the relationship between cropload and fruit size or cropload and yield efficiency was assessed by regression analysis. Fruit size distribution was calculated from adjusted fruit size assuming a normal fruit size distribution and valued according to shipment date and price. Using crop load as a covariate, fruit size adjusted for cropload was calculated for each nectarine orchard. Differences in adjusted fruit size and yield efficiency were detected among cultivars. Predicted crop value, normalized in terms of PARi intercepted, was calculated for all the cultivars. Large differences in predicted crop value were found for early, mid-season, and late-ripening nectarines. The early and late ripening cultivars showed the highest predicted crop value, especially at lower crop loads and larger fruit sizes. On the other hand, `Ross' cling peach showed its highest crop value at a medium crop load with high yield and relatively small fruit size. (Funded by FONDECYT grant 1930695.)
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Verdenal, Thibaut, Jorge E. Spangenberg, Vivian Zufferey, Ágnes Dienes-Nagy, Olivier Viret, Cornelis van Leeuwen, and Jean-Laurent Spring. "Impact of crop load on nitrogen uptake and reserve mobilisation in Vitis vinifera." Functional Plant Biology 47, no. 8 (2020): 744. http://dx.doi.org/10.1071/fp20010.
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Nitrogen deficit affects both crop production and composition, particularly in crops requiring an optimal fruit N content for aroma development. The adaptation of cultural practices to improve N use efficiency (NUE) (i.e. N uptake, assimilation and partitioning) is a priority for the sustainable production of high-quality crops. A trial was set on potted grapevines (Vitis vinifera L. cv. Chasselas) to investigate the potential of crop limitation (via bunch thinning) to control plant NUE and ultimately fruit N composition at harvest. A large crop load gradient was imposed by bunch thinning (0.5–2.5 kg m–2) and N traceability in the plant was realised with an isotope-labelling method (10 atom % 15N foliar urea). The results indicate that the mobilisation of root reserves plays a major role in the balance of fruit N content. Fertiliser N uptake and assimilation appeared to be strongly stimulated by high-yielding conditions. Fertilisation largely contributed to fulfilling the high fruit N demand while limiting the mobilisation of root reserves under high yield conditions. Plants were able to modulate root N reserve mobilisation and fertiliser N uptake in function of the crop load, thus maintaining a uniform N concentration in fruits. However, the fruit free amino N profile was modified, which potentially altered the fruit aromas. These findings highlight the great capacity of plants to adapt their N metabolism to constraints, crop thinning in this case. This confirms the possibility of monitoring NUE by adapting cultural practices.
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Embree, C. G., and D. S. Nichols. "Bio-regulators improve fruit size and c olour and reduce crop-load and annual bearing of Honeycrisp™ apples." Canadian Journal of Plant Science 85, no. 2 (April 1, 2005): 453–55. http://dx.doi.org/10.4141/p04-059.
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Honeycrisp™ [Malus × domestica (L.) Borkh.] can be a very profitable cultivar if fruit quality is high. Some crop-load bio-regulators were evaluated for improving fruit quality and annual flowering. Ammonium thiosulphate applied at full bloom reduced crop-load, increased fruit weight, fruit colour and return bloom. Fruitone N® combined with Sevin XLR® reduced the percent of fruit in the 40–60% colour category and also crop-load. Fruitone N® alone reduced crop-load. Key words: Honeycrisp™, fruit thinning, crop-load, return bloom
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Mattii, G. B., and F. Ferrini. "THE EFFECTS OF CROP LOAD ON ´SANGIOVESE´ GRAPEVINES." Acta Horticulturae, no. 689 (August 2005): 239–42. http://dx.doi.org/10.17660/actahortic.2005.689.27.
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Bound, Sally A. "Crop Load Management in Nashi Pear—A Review." Horticulturae 8, no. 10 (October 8, 2022): 923. http://dx.doi.org/10.3390/horticulturae8100923.
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Most nashi cultivars require heavy thinning, and this has traditionally been performed by the time and labour-intensive practice of hand thinning. Crop load management is a key cost driver for nashi production, but there are limited cost-effective options available for nashi growers compared to other pome fruit, especially apples and, to a lesser extent, European pears. There is, however, potential to adapt some of the thinning tools and techniques used in apples and European pears to reduce the labour requirements and high cost of thinning in nashi, thus improving industry profitability. Several chemical thinning agents have potential for nashi, and an understanding of the optimal application rates, times and weather conditions for each chemical, as well as the conditions/factors that impact the tree carbon balance, will improve the predictability of chemical thinning. However, it is difficult to target specific flowers/fruitlets within a cluster with chemicals, and the flowers that produce the preferred fruit shape and size are in the middle of the flower cluster. Mechanical thinning during the flowering period with either Darwin or BAUM-style string thinners has potential, particularly as these devices can be used as early as flower emergence. As for chemical thinning, the issue of non-selectivity needs to be addressed; however, the development of mechatronic systems should overcome most problems that occur with the currently available mechanical thinners. Shading at critical times is an avenue that could be explored further to ascertain the critical stage when developing fruit are susceptible to enable the determination of the optimal timing and duration of shading. Targeted pruning and bud thinning during the dormant winter period to reduce the floral bud numbers is a valuable option for the precise placement of fruit in optimal positions and to set up the required number of clusters. This review highlighted several tools/techniques that, with further work, can be incorporated into a systematic approach to crop load management in nashi while reducing the risk and cost.
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Robinson, T. L., P. Francescatto, and J. Lordan. "Advances in precision crop load management of apple." Acta Horticulturae, no. 1314 (June 2021): 133–38. http://dx.doi.org/10.17660/actahortic.2021.1314.18.
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Murri, G., F. Massetani, and D. Neri. "CROP LOAD AND FRUIT QUALITY OF 'FORTUNE' PLUM." Acta Horticulturae, no. 985 (April 2013): 213–19. http://dx.doi.org/10.17660/actahortic.2013.985.27.
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Whiting, Matthew D., and David Ophardt. "Comparing Novel Sweet Cherry Crop Load Management Strategies." HortScience 40, no. 5 (August 2005): 1271–75. http://dx.doi.org/10.21273/hortsci.40.5.1271.
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The development of novel crop load management techniques will be critical to the adoption and success of high density sweet cherry orchard systems based on new clonal rootstocks. Herein we report on a comparison of potential means of balancing crop load of `Bing' sweet cherry grown on the productive and precocious rootstocks `Gisela 5' and `Gisela 6'. In 2002, thinning treatments were applied to entire trees and consisted of an unthinned control (C), and manual removal of 50% of the blossoms (B) or 50% of 2-year-old and older fruiting spurs (S), throughout the tree. In 2003 all trees were left unthinned to characterize the carry-over effect of thinning treatment in 2002. In 2002, compared to C, thinned trees had 38% to 49% fewer fruit per tree, 22% to 42% lower yield, 8% to 26% higher fruit weight, and 2% to 10% larger fruit diameter. S and B treatments reduced yield by 42% and 22% on `Gisela 5' and by 40% and 31% on `Gisela 6', respectively. `Gisela 5'-rooted trees showed greater improvements in fruit quality than did trees on `Gisela 6'. Compared to C-, S-, and B-treated trees on `Gisela 5' yielded fruit that was 15% and 26% heavier, respectively. Yield of fruit ≥25.5 mm diameter was increased by 240% by S and 880% by B, though yield of this size fruit was still low (1.5 and 5.2 kg/tree, respectively). Neither technique had any beneficial carryover effect in the year following treatment despite S trees bearing about 25% fewer fruit than B and C trees. In both years, `Gisela 5'-rooted trees bore about 15% fewer fruit than trees on `Gisela 6'. Compared to `Gisela 5', `Gisela 6'-rooted trees were about 41%, 46%, and 24% more productive for C, S, and B, respectively. Number of fruit/tree in 2003 was within 4% and 8% of the previous year on `Gisela 6' and `Gisela 5', respectively. Crop value analyses suggest growers would be rewarded for producing high yields of medium size fruit (e.g., 21.5 to 25.4 mm) compared to low yields of high quality fruit.
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Cuevas, J., L. Rallo, and H. F. Rapoport. "Crop load effects on floral quality in olive." Scientia Horticulturae 59, no. 2 (October 1994): 123–30. http://dx.doi.org/10.1016/0304-4238(94)90079-5.
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Neilsen, Denise, Gerry Neilsen, Sunghee Guak, and Tom Forge. "Consequences of Deficit Irrigation and Crop Load Reduction on Plant Water Relations, Yield, and Quality of ‘Ambrosia’ Apple." HortScience 51, no. 1 (January 2016): 98–106. http://dx.doi.org/10.21273/hortsci.51.1.98.
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Uncertain water supplies resulting from changing climatic conditions in western North America led to this investigation of the role of crop load reduction in maintaining performance of high-density ‘Ambrosia’ apple (Malus ×domestica) on M.9 rootstock. A split-plot experimental design was imposed for three growing seasons (2007–09) with six replicates of four main plot irrigation treatments and three crop load subplots comprised of three trees. Four season-long irrigation (Irr) treatments were applied through 2 × 4 L·h−1 drip emitters per tree and included Irr1) control [100% evapotranspiration (ET) replacement], Irr2) 50% ET replacement, Irr3) 50% ET replacement to half the emitters, and Irr4) an increasingly severe treatment commencing at 50% ET replacement (once every 2 days) in 2007 and progressing to 25% and 18% ET replacement, 2008–09. Three target crop loads were established annually, 4–5 weeks after bloom as low (2.5, 3, and 3.75), medium (4.5, 6, and 7.5), and high (9, 12, and 15) fruit/cm2 trunk cross-sectional area (TCSA) 2007–09, respectively, by hand thinning around 4 weeks after bloom. Volumetric soil moisture contents generally reflected the amount of water applied and ranged from 20% for control (Irr1) to <10% for Irr4. Both irrigation and crop load treatments affected midday stem water potential more than leaf photosynthesis and stomatal conductance (gS). By the 2nd and 3rd year stem potential values for irrigation treatments ranged from a maximum of −1.0 to −1.3 MPa for Irr1 to minimums ≤-2.0 MPa for Irr4. gS decreased as midday stem potential decreased, but at any given stem potential value was greater at high crop loads, presumably in response to an increased demand for photosynthates. Fruit size decreased as crop load increased, but as irrigation deficits became more severe, fruit size was more closely correlated with stem water potential than gS. Consequently, fruit size was controlled by two mechanisms, competition for photosynthates and the effects of plant water status on gS. Negative linear relationships between crop load and average fruit size were used to determine the crop load required to produce an average fruit size of 200 g at different irrigation deficits. It was not possible to achieve adequate fruit size when applications were very low, as at 18% to 25% ET in Irr4. Crop load reduction around mid-June had no negative consequences for fruit quality, enhancing fruit color, and soluble solids concentration (SSC) and did not affect the incidence of sunburn, internal breakdown or bitter pit at harvest.
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Luby, J. J., and C. E. Finn. "Inheritance of Ripening Uniformity and Relationship to Crop Load in Blueberry Progenies." Journal of the American Society for Horticultural Science 112, no. 1 (January 1987): 167–70. http://dx.doi.org/10.21273/jashs.112.1.167.
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Abstract The intervals, in days, between 10%, 50%, and 90% ripened fruit, as well as crop load, were estimated over 2 years in progenies from a partial diallel cross among 17 blueberry (Vaccinium corymbosum L., V. angustifolium Ait., and V. corymbosum × V. angustifolium hybrids) parents. General combining ability (GCA) mean squares were highly significant for all ripening intervals and for crop load, while specific combining ability mean squares were nonsignificant, indicating a large proportion of additive genetic variance. Narrow-sense heritability estimates were about 0.50 for the three ripening intervals (10–50%, 50–90%, and 10–90%). Several parents had large positive GCA effects, indicating their contribution to a long ripening interval. Most progenies with large crop loads required >15 days between 10% and 90% ripened fruit. Despite the consistently positive relationship between ripening interval length and crop load, variation among families and the potential for within-family segregation suggest the possibility of obtaining genotypes with high yield potential and improved uniform ripening.
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Lakatos, T. "CROP LOAD AS A MODIFYING FACTOR IN CROP EVAPOTRANSPIRATION MODEL FOR IRRIGATION SCHEDULING." Acta Horticulturae, no. 618 (November 2003): 379–82. http://dx.doi.org/10.17660/actahortic.2003.618.44.
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Bates, T. R. "Mechanical crop control in New York ‘Concord’ vineyards target desirable crop load levels." Acta Horticulturae, no. 1177 (November 2017): 259–64. http://dx.doi.org/10.17660/actahortic.2017.1177.37.
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Stanley, C. J., and D. S. Tustin. "683 Contributions of Early Season Environment and Crop Load to Apple Fruit Development." HortScience 35, no. 3 (June 2000): 516D—516. http://dx.doi.org/10.21273/hortsci.35.3.516d.
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Many factors contribute to final apple fruit size. Researchers have studied these factors and have developed models, some very complex. Results from many New Zealand regions over several years suggest that early season temperature along with crop load are the key factors driving final fruit size. Accumulated growing degree days from full bloom to 50 days after full bloom (DAFB), accounted for 90% of the variance in fruit weight of `Royal Gala' apples at 50 DAFB under nonlimiting low-crop-load conditions. In turn, fruit weight at 50 DAFB accounted for 90% of the variance in final fruit size at harvest under the low-crop-load conditions. We hypothesise that a potential maximum fruit size is set by 50 DAFB, determined by total fruit cell number, resulting from a temperature-responsive cell division phase. Under conditions of no limitations after the cell division phase, we suggest that all cells would expand to their optimum size to provide the maximum fruit size achievable for that cell number. Factors which affect growth partitioning among fruits, e.g., higher crop loads, would reduce final fruit size, for any given cell number, when grown in the same environment. In Oct. 1999, four different crop loads were established at full bloom on `Royal Gala' trees (M9 rootstock) in four climatically different regions. In Hawkes Bay, similar crop loads were established at 50 DAFB on additional trees. Hourly temperatures were recorded over the season. Fruit size was measured at 50 DAFB and fruit will be harvested in Feb. 2000. These data should provide fresh insight and discussion into the respective roles of temperature and competition during the cell division fruit growth phase on apple fruit size.
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Bound, Sally A. "Managing Crop Load in European Pear (Pyrus communis L.)—A Review." Agriculture 11, no. 7 (July 8, 2021): 637. http://dx.doi.org/10.3390/agriculture11070637.
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Reducing levels of fruit set is often desirable in many European pear (Pyrus communis L.) cultivars. With a negative linear relationship between crop load and fruit size, crop load management early in the season minimises wastage of tree carbohydrate resources and provides maximum benefits in terms of fruit size and quality. There are several tools available for managing crop load including hand thinning, chemical thinning, photosynthetic inhibition through shading or application of chemicals, mechanical thinning and pruning. While hand thinning is the most accurate method of reducing excessive crop loads, there are some major drawbacks. With awareness that the early thinning offered by chemical thinning provides distinct advantages with regard to fruit size and other quality parameters, chemical thinning is gaining increasing acceptance in pear production. Some chemicals are used worldwide for thinning, but there are differences between countries and growing regions on recommended application timing and concentrations. The risks involved in chemical thinning can be mitigated by use of a structured approach, using a sequential spray program with both bloom and post-bloom thinners. Knowledge of conditions that impact the carbon balance of the tree and the ability to make use of carbon-deficit conditions are likely to improve the predictability of chemical thinning. Mechanical thinning has potential as a thinning tool, with advantages over chemical thinning in that it is environmentally friendly, can be used in organic production and is not weather dependent. Although artificial bud extinction has not been trialled on pears to date, it has been shown to be economically viable in apple. As it is a precision crop load management method that minimises tree resource wastage, it should be given serious consideration. As growers require large annual yields of high-quality fruit, the aim of this review was to examine current and potential crop load management methods for European pear cultivars and provide a portfolio of available options that can be integrated into a systematic approach for managing crop load.
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Hummell, Ann K., and David C. Ferree. "Influence of Crop Load and Cluster Microclimate on Yield and Fruit Quality in `Seyval Blanc'." HortScience 31, no. 4 (August 1996): 575a—575. http://dx.doi.org/10.21273/hortsci.31.4.575a.
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A 2-year field study was initiated in 1994 to examine the interactions between crop load and cluster exposure and their influences on the yield and fruit quality of mature, own-rooted `Seyval blanc' grapevines. Light, moderate, and heavy crop loads were established near bloom by cluster-thinning vines planted at 2.6 × 3.0-m spacing to around 20, 40, and 80 clusters per vine, respectively. At veraison, three clusters per vine were given one of three natural shaded treatments: fully exposed, partially shaded, and densely shaded. Vines with the heavy crop load produced higher yields per vine and lower cluster and berry weights. Heavy vine clusters tended to be more green in 1994 and possessed lower pH and soluble solid concentrations in both years compared to other crop loads. Compared to densely shaded clusters, fully exposed clusters had smaller average cluster and berry weights, lower titratable acidity, higher pH and soluble solid concentrations, and more yellow coloration. In 1994, no significant interactions were found for any fruit quality or yield characteristics. In 1995, significant interactions were found for soluble solids and hue angle, but not for yield, pH, or titratable acidity. These results suggest that the crop load of the vine and microclimate around the cluster, in addition to their individual effects, sometimes interact to affect fruit quality in `Seyval blanc' wine grapes.
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Neilsen, Gerry H., Denise Neilsen, Sung-hee Guak, and Tom Forge. "The Effect of Deficit Irrigation and Crop Load on Leaf and Fruit Nutrition of Fertigated ‘Ambrosia’/‘M.9’ Apple." HortScience 50, no. 9 (September 2015): 1387–93. http://dx.doi.org/10.21273/hortsci.50.9.1387.
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Mature, fruiting ‘Ambrosia’/‘M.9’ apple [Malus ×sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] trees were subjected over three growing seasons to a split-plot experimental design involving four irrigation main plot treatments and three subplot crop load treatments with six replicates. This semiarid production region is traditionally irrigated 01 May to 01 Oct. during which time an average of ≈ 15 cm of precipitation occurs. Irrigation treatments were applied through 2 × 4 L⋅h−1 emitters per tree and included I1: daily application of 100% evapotranspiration (ET); or I2: 50% daily ET; or I3: 50% ET applied to one side; and I4: 50%, 25%, or 18% ET-application, applied every second day, 2007–09, respectively. Crop load treatments were imposed annually ≈4 to 5 weeks after full bloom to create low (2.5, 3, and 3.75 fruits/cm2 trunk cross-sectional area (TCSA), medium (4.5, 6, and 7.5 fruits/cm2 TCSA), and high crop loads (9, 12, and 15 fruits/cm2 TCSA), 2007–09, respectively. Leaf and fruit nutrient concentration was affected more by crop load than by any deficit irrigation strategy. Increased crop load increased concentrations of leaf nitrogen (N), calcium (Ca), and fruit Ca in 2 of 3 years and consistently decreased concentrations of leaf and fruit phosphorus (P) and potassium (K) and, in 2 of 3 years, fruit boron (B). Reductions in seasonal water applications (as with I4) reduced leaf P in 2 of 3 years. But, when significant, (usually only 1 of 3 year) increased fruit Ca, magnesium (Mg), P, K, and B concentrations. Crop load also had a dominant effect on fruit nutrient removal rates expressed as kilograms per hectare. High crop load increased removal of all measured nutrients in most years. In contrast, imposition of deficit irrigation strategies often (2 of 3 years) reduced fruit P, Mg, and B removal rates but had little effect on N, Ca, and K. Cumulative evidence suggests that deficit irrigation applied to N, P, K, and B fertigated high density ‘Ambrosia’ apple orchards in combination with crop load reduction to maintain fruit size should usually not create additional nutrient problems. However, low fruit Ca concentrations may occur if the crop is very low. Fertigation of 20 g K/tree/year was insufficient for older trees because inadequate K occurred in all treatments by the third year.
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Verdenal, Thibaut, Jorge E. Spangenberg, Vivian Zufferey, Ágnes Dienes-Nagy, Olivier Viret, Cornelis van Leeuwen, and Jean-Laurent Spring. "Corrigendum to: Impact of crop load on nitrogen uptake and reserve mobilisation in Vitis vinifera." Functional Plant Biology 47, no. 8 (2020): 769. http://dx.doi.org/10.1071/fp20010_co.
Full textAbstract:
Nitrogen deficit affects both crop production and composition, particularly in crops requiring an optimal fruit N content for aroma development. The adaptation of cultural practices to improve N use efficiency (NUE) (i.e. N uptake, assimilation and partitioning) is a priority for the sustainable production of high-quality crops. A trial was set on potted grapevines (Vitis vinifera L. cv. Chasselas) to investigate the potential of crop limitation (via bunch thinning) to control plant NUE and ultimately fruit N composition at harvest. A large crop load gradient was imposed by bunch thinning (0.5–2.5 kg m–2) and N traceability in the plant was realised with an isotope-labelling method (10 atom % 15N foliar urea). The results indicate that the mobilisation of root reserves plays a major role in the balance of fruit N content. Fertiliser N uptake and assimilation appeared to be strongly stimulated by high-yielding conditions. Fertilisation largely contributed to fulfilling the high fruit N demand while limiting the mobilisation of root reserves under high yield conditions. Plants were able to modulate root N reserve mobilisation and fertiliser N uptake in function of the crop load, thus maintaining a uniform N concentration in fruits. However, the fruit free amino N profile was modified, which potentially altered the fruit aromas. These findings highlight the great capacity of plants to adapt their N metabolism to constraints, crop thinning in this case. This confirms the possibility of monitoring NUE by adapting cultural practices.
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Schechter, Ido, J. T. A. Proctor, and D. C. Elfving. "THE EFFECT OF CROP LOAD ON FRUIT DRY WEIGHT AND DRY WEIGHT CONTENT, SPECIFIC LEAF WEIGHT, AND LEAF CARBON EXCHANGE." HortScience 27, no. 6 (June 1992): 625c—625. http://dx.doi.org/10.21273/hortsci.27.6.625c.
Full textAbstract:
Mature apple trees (Malus domestica Borkh.) were studied in the 1989 and 1990 seasons to explore the effect of differential crop load on fruit dry weight (DW), DW content, specific leaf weight, and leaf carbon exchange, using girdled and non-girdled limbs. Fruit DW and DW content decreased with heavier fruit loads, however, fruit on girdled limbs had higher fruit DW and DW content. Specific leaf weight did not differ in leaves on non-girdled limbs along the crop load gradient, but increased dramatically in leaves on girdled limbs with crop load lighter than one fruit per cm2 cross-sectional area. These leaves also had a low photosynthetic rate, high stomatal resistance, and high internal CO2 concentration. The results suggest a physiological limit for photoassimilate usage by the tree. Exceeding this limit by reducing sink strength resulted in excessive carbohydrate accumulation in leaves, causing physical damage to the photosystem.
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DELIĆ, Mersija, Fikreta BEHMEN, Saša MATIJAŠEVIĆ, Šaćira MANDAL, Saud HAMIDOVIĆ, and Senad MURTIĆ. "Influence of crop load on the yield and grape quality of Merlot and Vranac (Vitis vinifera L.) varieties in Trebinje vineyard." Acta agriculturae Slovenica 117, no. 4 (December 24, 2021): 1. http://dx.doi.org/10.14720/aas.2021.117.4.1601.
Full textAbstract:
<p class="042abstractstekst">The aim of this study was to study the impact of crop load on the yield and grape quality of ‘Merlot’ and ‘Vranac’ (<em>Vitis vinifera</em> L.) in Trebinje vineyard. The crop load levels studied in this trial were 9 buds (V1) and 12 buds (V2) per vine at each variety trained on Lenz-Moser bilateral cordon system. The impact was determined by measurements of yield per vine and grape quality characterized by the contents of total soluble solids, titratable acidity, total phenolics, total flavonoids and by total antioxidant capacity. The measured parameters of grape quality of ‘Merlot’ and ‘Vranac’ were not influenced significantly by crop load levels. V2, compared to the V1, showed the potential for increasing grape yield only for Merlot variety under experimental conditions. The results of this study also showed a positive correlation between total phenolics/flavonoids and total antioxidant capacity of grape berries in both varieties, regardless of crop loads applied.</p>
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Autio, Wesley R., and Duane W. Greene. "EFFECTS OF CROP LOAD AND HARVEST ON APPLE RIPENING." HortScience 25, no. 6 (June 1990): 624b—624. http://dx.doi.org/10.21273/hortsci.25.6.624b.
Full textAbstract:
Studies were conducted in 1989 to determine the effects of crop load and percent harvested on apple ripening. Twenty-seven `Golden Delicious' trees were selected and partitioned into 9 blocks. The crop load on one tree in each block was adjusted to 3.4, 6.9, or 15.0 fruit cm-1 trunk circumference in late June. Internal ethylene was measured in 6-fruit samples taken from each tree on 25 Sept., 2, 9, and 16 Oct. Increasing crop load had a significant linear effect on delaying ripening. Approximately 11 days separated the ripening of fruit from the 3.4 fruit cm-1 and the 15.0 fruit cm-1 treatments. In a second experiment, 18 `McIntosh' trees with similar crop load were partitioned into 6 blocks. Forty percent of the crop was harvested from 1 tree and 80% from another in each block on 7 Sept. Internal ethylene was measured on 7, 14, 21, and 28 Sept. Increasing the portion of the crop initially harvested linearly delayed subsequent fruit ripening. Approximately 6 days separated the ripening of fruit from the control and the 80%-removal treatments.