Blueberry (Vaccinium corymbosum L.) stands out among fruit in terms of three open physiological questions about its climacteric character, CO2 uptake, and the absence or presence of stomata on its ...floral organs. The objective of the present study was to examine the structures of blueberry flowers and fruit to explain their contribution to CO2 exchange and transpiration in order to clarify these discrepancies. Blueberries were dewaxed and the sepals/corolla removed for stomata counts, and their micromorphology was studied via LT-SEM. The fruit has stomata, contrary to beliefs in the literature, possibly because the stomata are occluded by the dense wax cover or ‘bloom’ and hidden on the distal part of the ovary in between and underneath the corolla. However, stomata were located on the distal part of the fruit surrounded by the sepals (calyx) and found predominantly on the abaxial sepals, while the adaxial side of the sepals and the proximal part of the ovary lacked stomata. The petals were devoid of stomata, trichomes, and chlorophyll and abscised after anthesis. In contrast, the sepals remained until maturity, contributing 5–7% to the berry surface but contributing to the majority of fruit stomata and chlorophyll. With 59–71% of the fruit’s chlorophyll, sepals were a significant source of the CO2 uptake. Similarly, with 95% of the berry stomata, sepals were a significant source of water loss, measured via porometry of fruit with and without sepals. Overall, this study identified the ovary as a minor source and sepals as the dominant source of CO2 and H2O exchange in blueberries.
The use of plastics in horticulture is reviewed with respect to its sustainability based on the traditional criteria of triple Rs (reduce, reuse, and recycling) plus a re-place strategy, taking into ...account possible alternatives. Hail (and insect) nets made of HD-PE, with their long-term use mostly on apple and polytunnels of LD-PE for cherry and strawberry as well as solarisation mulches (reuse), were found to be relatively sustainable solutions for their needs and are currently without alternatives. In contrast, standard black mulch, with its largest share among horticultural plastics, had the widest range of sustainable alternatives, ranging from biodegradable to spray mulch; few sustainable alternatives are available for fleeces and reflective mulches. For the third sustainable option, pilot recycling schemes were examined, such as PolieCoTM (Italy), MAPLATM (Spain), and ERDETM (Germany); they collect 30–50% of the agricultural plastics used in their respective areas, with a successful retrieval growth rate of ca. 20% per year in the case of ERDETM. For the fourth new R option (replace), future sustainability perspectives for the predominant black mulch are research into and development of better, biodegradable, non-fossilbased plastics, sprayable mulch; microbes for the digestion of deployed polyolefins and, for a certain limited range (on shade tolerant crops or in high-light intensity environment), hail nets and polytunnels that are equipped/substituted by/with solar panels (“agri pv”) for the concomitant sustainable production of green renewable energy.
Most trees from temperate climates require the accumulation of winter chill and subsequent heat during their dormant phase to resume growth and initiate flowering in the following spring. Global ...warming could reduce chill and hence hamper the cultivation of high-chill species such as cherries. Yet determining chilling and heat requirements requires large-scale controlled-forcing experiments, and estimates are thus often unavailable. Where long-term phenology datasets exist, partial least squares (PLS) regression can be used as an alternative, to determine climatic requirements statistically. Bloom dates of cherry cv. ‘Schneiders späte Knorpelkirsche’ trees in Klein-Altendorf, Germany, from 24 growing seasons were correlated with 11-day running means of daily mean temperature. Based on the output of the PLS regression, five candidate chilling periods ranging in length from 17 to 102 days, and one forcing phase of 66 days were delineated. Among three common chill models used to quantify chill, the Dynamic Model showed the lowest variation in chill, indicating that it may be more accurate than the Utah and Chilling Hours Models. Based on the longest candidate chilling phase with the earliest starting date, cv. ‘Schneiders späte Knorpelkirsche’ cherries at Bonn exhibited a chilling requirement of 68.6 ± 5.7 chill portions (or 1,375 ± 178 chilling hours or 1,410 ± 238 Utah chill units) and a heat requirement of 3,473 ± 1,236 growing degree hours. Closer investigation of the distinct chilling phases detected by PLS regression could contribute to our understanding of dormancy processes and thus help fruit and nut growers identify suitable tree cultivars for a future in which static climatic conditions can no longer be assumed. All procedures used in this study were bundled in an R package (‘chillR’) and are provided as
Supplementary materials
. The procedure was also applied to leaf emergence dates of walnut (cv. ‘Payne’) at Davis, California.
A large literature has documented the effects of weather on agricultural yields. However, weather not only impacts the quantity produced, but also the quality of the product. Due to data limitations, ...the quality effects have primarily been studied using lab experiments for specific attributes, and the financial implications for farmers of a quality effect are less clear. Using a unique longitudinal micro-level data set of Swiss apple orchards that include information on both the quantity produced as well as the quality, we show that the latter can have an even larger effect on farm revenue. Ignoring the quality of the harvested product substantially biases the impact of weather extremes on agricultural income and the potential effects of climate change. Our quality measure is the orchard-year specific price shock. If an orchard gets a lower price for its specific apple variety compared to previous years and compared to other orchards in the same year, we observe the market's valuation of its inferior quality accounting for overall price movements (other orchards growing same variety that year) as well as orchard specific factors (orchard fixed effects). We find that spring frost events induce farm gate price drops and thus revenue reductions of up to 2.05% per hour of exposure.
This concept paper summarizes key "hotspots" for waste generation along the food supply chain and identifies a range of existing solutions/measures that can help producers, retailers and consumers ...reduce the amount of food that is wasted. The majority of food waste of 71-92 kg/head/year in Western Europe was found to originate from private households (61%), followed by restaurants and canteens (17%) and then supermarkets (5%); 59%-65% (of this food waste (71-92 kg) can be avoided and 54% thereof are fruit and vegetables. Since ethylene accelerates fruit ripening and its accumulation can lead to fruit decay and waste and new portable instruments now enable continuous in-situ determination of ethylene along the food chain, there is a possible key to reducing food waste of perishable, fresh produce. Hence, suggested countermeasures at the field level are use of ethylene inhibitors (AVG as "Retain" or MCP as "Harvista"), the former prevents pre-mature fruit drop in pome fruit, incentives for processing fruit of industrial grade and whole crop purchase ("WCP"). Along the supply chain, applications of ethylene inhibitors (e.g., 1-MCP as "SmartFresh") absorber strips (e.g., "It's Fresh", Sensitech), bags (e.g., "Peakfresh") as well as simply cooling and venting, and shading to avoid sun exposure. Countermeasures also include superstores no longer promoting multi-packs, e.g., "two strawberry punnets for the price of one", abandon the "Display until" or "Sell by" date, conservative consumer shopping behavior, and sale of class II produce ("Wunderlinge" in Billa or "Kleine Äpfel" in REWE, "Ünique" in Coop), collection (rather than wasting) of perishable food by volunteers ("Die Tafel"), or "Food Sharing" of private household left-over perishable on social media, or any combination of the above to aid reducing fresh produce waste.
•Partial Least Squares regression can illustrate tree responses during dormancy.•Phenology responses to chill and heat accumulation rates vary by species and site.•Walnuts in California responded to ...variation in chill accumulation.•Heat accumulation was more important for cherries and chestnuts in cold-winter sites.•Delayed phenology in warm years may indicate vulnerability to climate change.
Temperate-zone trees must fulfill cultivar-specific chilling and heat requirements during the dormant period, in order to produce leaves and flowers in the following growing season. Timing and accumulation rate of chill and heat are understood to determine the timing of spring events, but both processes are difficult to observe in dormant tree buds. Where long-term phenological observations are available, Partial Least Squares (PLS) regression offers a statistical opportunity to delineate phases of chill and heat accumulation and determine the climatic requirements of trees. This study uses PLS regression to explore how the timing of spring events of chestnut in China, cherry in Germany and walnut in California is related to variation in the daily rates of chill and heat accumulation, as calculated with horticultural models. Dependent variables were 39 years of flowering dates for chestnuts in Beijing (China), 25 years of cherry bloom in Klein-Altendorf (Germany) and 54 years of walnut leaf emergence in Davis (California, USA). These were related to daily accumulation rates of chill, calculated with the Dynamic Model, and heat, calculated with the Growing Degree Hours Model. Compared to an earlier version of the procedure, in which phenological dates were related to unprocessed temperature data, delineation of chilling and forcing phases was much clearer when using horticultural metrics to quantify chill and heat. Chestnut bloom in the cold-winter climate of Beijing was found to depend primarily on the rate of heat accumulation, while cherry bloom in the temperate climate of Germany showed dependence on both chill and heat accumulation rates. The timing of walnut leaf emergence in the mild-winter climate of California depended much more strongly on chill accumulation rates. Chilling (in Chill Portions=CP) and heat (in Growing Degree Hours=GDH) requirements determined based on PLS regression were 79.8±5.3 CP and 13,466±1918 GDH for chestnut bloom in Beijing, 104.2±8.9 CP and 2698±1183 GDH for cherry bloom in Germany, and 37.5±5.0 CP and 11,245±1697 GDH for walnut leaf emergence in California. Spring phases of cherry in Klein-Altendorf and especially chestnut in Beijing will likely continue to advance in response to global warming, while for walnut in California, inadequate chilling may cause delays in flowering and leaf emergence. Such delays could serve as an early-warning indicator that future productivity may be threatened by climate change. The R package ‘chillR’ makes the method used in this study available for wider use.
(1) Background: Plastic in fruit orchards represents an environmental issue due to large CO2eq emissions associated with its production from fossil fuel and disposal (often incineration). (2) ...Materials and methods: Apple cv. “Braeburn Hillwell” trees on M9 rootstocks under a hail net were used at Campus Klein-Altendorf (CKA), Germany (50 °N) in 2018. In order to reduce the use of plastics to improve the red colouration of fruit particularly under hail nets, three alternatives to the current use of reflective mulch in each alleyway between the tree rows were explored, with uncovered grass alleyways as control. About 2800 colour measurements were done in the four weeks prior to harvest on 720 attached fruit below and above 1 m height in the field, and ca. 6900 additional colour measurements were conducted at harvest. (3) Results: The underlying regulatory mechanisms contrasted between the diffusive reflection of the white woven ground cover (such as LumilysTM or ExtendayTM) in the alleyways and aluminium foil under the trees with regular (straight) light reflection. Good fruit colouring and a plastic reduction were achieved (a) through spreading the white woven ground cover in every other row, and (b) through substituting the white ground cover with aluminium foil (80% recycled). Both methods can reduce greenhouse gas (GHG) emissions (75–110 kg CO2eq/ha for the first option a). (4) Conclusion: Plastic use in fruit orchards can be reduced by multiple use of the material in the same or several years, spreading it in every other row or substituting it by another reflective material, a relevant step towards an environment-friendly sustainable horticulture.
(1) Background: Since early yield prediction is relevant for resource requirements of harvesting and marketing in the whole fruit industry, this paper presents a new approach of using image analysis ...and tree canopy features to predict early yield with artificial neural networks (ANN); (2) Methods: Two back propagation neural network (BPNN) models were developed for the early period after natural fruit drop in June and the ripening period, respectively. Within the same periods, images of apple cv. “Gala” trees were captured from an orchard near Bonn, Germany. Two sample sets were developed to train and test models; each set included 150 samples from the 2009 and 2010 growing season. For each sample (each canopy image), pixels were segmented into fruit, foliage, and background using image segmentation. The four features extracted from the data set for the canopy were: total cross-sectional area of fruits, fruit number, total cross-section area of small fruits, and cross-sectional area of foliage, and were used as inputs. With the actual weighted yield per tree as a target, BPNN was employed to learn their mutual relationship as a prerequisite to develop the prediction; (3) Results: For the developed BPNN model of the early period after June drop, correlation coefficients (R2) between the estimated and the actual weighted yield, mean forecast error (MFE), mean absolute percentage error (MAPE), and root mean square error (RMSE) were 0.81, −0.05, 10.7%, 2.34 kg/tree, respectively. For the model of the ripening period, these measures were 0.83, −0.03, 8.9%, 2.3 kg/tree, respectively. In 2011, the two previously developed models were used to predict apple yield. The RMSE and R2 values between the estimated and harvested apple yield were 2.6 kg/tree and 0.62 for the early period (small, green fruit) and improved near harvest (red, large fruit) to 2.5 kg/tree and 0.75 for a tree with ca. 18 kg yield per tree. For further method verification, the cv. “Pinova” apple trees were used as another variety in 2012 to develop the BPNN prediction model for the early period after June drop. The model was used in 2013, which gave similar results as those found with cv. “Gala”; (4) Conclusion: Overall, the results showed in this research that the proposed estimation models performed accurately using canopy and fruit features using image analysis algorithms.
PDF
