Experimental Orchard Research Articles

Viability and release of Neonectria ditissima ascospores on apple fruit in Brazil

AbstractDuring European canker monitoring in an apple experimental orchard, 14 mummified fruit (two and three trees with 10 and four positive records in 2018 and 2019, respectively) showed perithecia. Perithecium production on apple fruit, confirmation of pathogenicity of Neonectria ditissima isolated from mummified fruit, and ascospore release from fruit tissues has rarely been reported, and their role in the epidemiology of European canker has been largely overlooked. Thus, the objectives of our study were to (a) prove the presence of both conidia and ascospores of N. ditissima in mummified fruit in an experimental field, confirming pathogenesis in different apple cultivars, and (b) monitor production of the two types of inoculum in infected apple fruit over time. Canker incidence in this orchard was 47% of trees with symptoms in 2018 and 48% in 2019. Molecular and morphological tests confirmed that the fungus detected in the mummified apple fruit was N. ditissima. Apple fruit with sporodochia and perithecia washed immediately after collection from the orchard showed conidia but no ascospores of N. ditissima. However, after 4 days’ incubation, perithecia on mummified fruit showed many ascospore cirri. Koch's postulates were fulfilled on apple plants and mature fruit. Fruit inoculated with N. ditissima released spores for over a year under Brazilian field conditions. The release of both spore types peaked in May (Brazilian leaf fall) and October (spring); release of conidia also peaked in February (early harvest). These results support our hypothesis that fruit can serve as primary inoculum for European canker in Brazilian apple orchards.

Pre-harvest methyl jasmonate spray maintains postharvest quality of Kinnow mandarin (Citrus reticulata) fruits

The study was carried out at the experimental orchard of Indian Agricultural Research Institute, New Delhi (2019-20) to evaluate the pre-harvest effect of methyl jasmonate (MeJA) on postharvest quality of Kinnow mandarin (Citrus reticulata Blanco) under low temperature storage. Fruits were sprayed on tree with four concentrations of MeJA (0.1 mM, 0.3 mM, 0.5 mM, 0.7 mM) and control (distilled water) at 40 days and 20 days before commercial harvesting. The harvested fruits were stored consecutively at 2oC for 20 days followed by at 6oC for 20 days with 85-95% relative humidity. All the treatments showed significant results than control, but fruits treated with 0.5 mM MeJA retained higher moisture content (least water loss) and firmness with increase in TSS, acidity, total phenols, ascorbic acid, antioxidant and peroxidase enzyme activity during the storage period of 40 days. Therefore, pre-harvest spray @ 0.5mM MeJA could be an effective alternative to synthetic chemical use in maintaining the quality of Kinnow mandarin fruits during low temperature storage.

Early performance of several Prunus interspecific hybrid rootstocks for Redhaven peach in southern Ontario

A multi-year orchard experiment was established to measure the performance of Rootpac®-R, Rootpac®-20, Rootpac®-40, and Rootpac®-70 rootstocks using ‘Redhaven’ peach (Prunus persica var. persica) as the scion, compared with the ‘Bailey’ peach seedling rootstock, the current industry standard. Tree survival after five years was 79% on Rootpac-40, whereas the remaining rootstocks showed no tree mortality. Tree vigour and canopy height and width were influenced by rootstock genotype beginning the year of planting in 2016. For the first five years of production, Rootpac-70 consistently produced the largest trees based on truck cross-sectional area (TCSA) and by year five, all rootstocks produced trees with similar TCSAs, except for Rootpac-70, which was 38% larger than Bailey. By year five, cumulative yields were greatest on Rootpac-70, which were 10% higher than Bailey; cumulative yields of Rootpac-R, Rootpac-20, and Rootpac-30 were 98%, 89%, and 84% that of Bailey, respectively. Cumulative yield efficiency was significantly influenced by rootstock although the magnitude of the differences was small and likely of insignificant commercial importance. Rootpac-40 consistently produced the largest fruit. These results are only reflective of the orchard establishment years and additional data are required before peach producers can make fully informed decisions concerning the rootstocks evaluated in this study for their orchard systems. However, at this juncture, all the Rootpac rootstocks evaluated in this study are likely to impart excessive vigour to be used in a higher density system and offer little advantage over Bailey.

Detecting tree water stress using a trunk relative water content measurement sensor

Irrigation water management in tree crops requires timely and accurate determination of crop water status for making irrigation scheduling decisions. However, commonly used techniques for measuring tree water statuses, such as stem water potential measured with pressure chambers or leaf stomatal conductance measured with porometers, are manually operated and lack the timeliness for making irrigation decisions in real-time. The objective of this research was to develop and field test a new electronic sensor system capable of continuously monitoring tree trunk relative water content. Replicated sensors were installed in experimental orchards planted with pomegranate and nectarine trees. Data collected from the sensor readings were compared with periodic trunk diameter, stem water potential, and leaf stomatal conductance measurements. Strong linear correlations were observed between sensor readings and tree trunk diameter variations but with a 3–4-hour phase lag. Sensor readings were also strongly correlated to stem water potential (R2 = 0.58-0.85) and leaf stomatal conductance (R2 = 0.60-0.84) for both pomegranate and nectarine trees. The next step is to further validate the sensors in commercial orchards and apply the sensors for making real-time irrigation water management decisions.

Integrated rearing system proposal for Cantareus aspersus in experimental orchards: Growth models.

An integrated rearing system for Cantareus aspersus under environmental conditions in an experimental orchard is proposed. In this study, the natural behaviour, circadian rhythms and suitable rearing conditions of the edible snail were optimised to produce homogeneous growth and low variability. The growth was standardised, and growth pattern fit was assessed with various models. One thousand fry were cultured in the orchard, and a random sample of 100 snails were measured weekly for 23 weeks. The rearing system had the following characteristics: snails and earthworms were included in the experimental rearing orchard; a homogeneous group of juvenile snails of the same age and size and high rearing density (500 snails/m2) was used; snails were fed with layers mash ad libitum; and mixed and fringes vegetation was planted in the orchard. A commercial size of 60% of snails was achieved in 21 weeks and 95% in 23 weeks. The different models showed a good fit, and the quadratic model obtained the best fit. This experimental snail orchard proposal can be extended to other areas, although it must be corrected according to different environmental conditions and fit to other species of interest. This experimental model could constitute a viable alternative to traditional models of animal experimentation with mammals, and given its high adaptability, it could be applied in different fields of science.

Use of alpha-naphthylacetic acid in ovary thinning and preharvest fruit drop reduction in apple trees

Chemical thinning of apple ovaries in intensive orchards is highly relevant. This farming practice reduces manual labour, decreases the fructification interval and improves apple quality. Growth regulators, including alpha-aphthylacetic acid, also reduce preharvest fruit drop allowing for an optimal harvest capacity. The research aimed to study the impact of different alpha-naphthylacetic acid application rates on ovary thinning and preharvest fruit drop. Assays were conducted in 2019—2020 in a leached-chernozem experimental apple orchard of the Michurin Federal Research Centre in Tambov Region. Assay 1 studied the treatment impact on apple tree thinning at rates 100, 200, 300 and 400 ml/ha in 8—12 mm fruits, assay 2 (treatment 2 weeks prior to expected harvest) — on reducing preharvest apple drop at rates 200, 300 and 400 ml/ha. The treatments significantly reduced the number of ovaries in the Zhigulevskoe/62-396 cultivar and increased mean apple fruit weight. Such increase was an important yield-rising factor in the 300 and 400 ml/ha treatments. Alpha-naphthylacetic acid treatments in 8—12 mm fruits had a significant lowering impact on total leaf nitrogen content. The treatments also induced a significant reduction in preharvest apple fruit drop, with the best effect at rate 300 ml/ha. No explicit impact of alpha-naphthylacetic acid on fructification interval was observed in the study period.

Estimation of Fractional Photosynthetically Active Radiation From a Canopy 3D Model; Case Study: Almond Yield Prediction.

Canopy-intercepted light, or photosynthetically active radiation, is fundamentally crucial for quantifying crop biomass development and yield potential. Fractional photosynthetically active radiation (PAR) (fPAR) is conventionally obtained by measuring the PAR both below and above the canopy using a mobile lightbar platform to predict the potential yield of nut crops. This study proposed a feasible and low-cost method for accurately estimating the canopy fPAR using aerial photogrammetry-based canopy three-dimensional models. We tested up to eight different varieties in three experimental almond orchards, including California's leading variety of ‘Nonpareil’. To extract various canopy profile features, such as canopy cover and canopy volume index, we developed a complete data collection and processing pipeline called Virtual Orchard (VO) in Python environment. Canopy fPAR estimated by VO throughout the season was compared against midday canopy fPAR measured by a mobile lightbar platform in midseason, achieving a strong correlation (R2) of 0.96. A low root mean square error (RMSE) of 2% for ‘Nonpareil’. Furthermore, we developed regression models for predicting actual almond yield using both measures, where VO estimation of canopy fPAR, as a stronger indicator, achieved a much better prediction (R2 = 0.84 and RMSE = 195 lb acre−1) than the lightbar (R2 = 0.70 and RMSE = 266 lb acre−1) for ‘Nonpareil’. Eight different new models for estimating potential yield were also developed using temporal analysis from May to August in 2019 by adjusting the ratio between fPAR and dry kernel yield previously found using a lightbar. Finally, we compared the two measures at two different spatial precision levels: per-row and per-block. fPAR estimated by VO at the per-tree level was also assessed. Results showed that VO estimated canopy fPAR performed better at each precision level than lightbar with up to 0.13 higher R2. The findings in this study serve as a fundamental link between aerial-based canopy fPAR and the actual yield of almonds.

Study of energetic properties of different tree organs in six Olea europaea L. cultivars

Pruning is an important horticultural practice for the management of olive orchards (Olea europaea L.) that generates a considerable amount of residues every year. Olive orchards are increasingly expanding beyond the Mediterranean Basin to new growing Countries (Australia, California, Argentina, Chile and Uruguay) and this will certainly lead to larger availability of pruning material. Currently, the interest in use of olive tree pruning residues for energy purposes is increasing but unfortunately, the information on the differences among organs of the tree, in terms of calorific value and ash content, is scarce. Another unknown aspect is the effect of cultivar vigour on dry matter partition among different tree organs, these are important traits to establish the energetic quality of pruning residues. The aim of this research was to study energetic aspects of six olive cultivars, largely grown in the Sicilian olive industry and characterized by different vigour. The trees taken into consideration in the study were selected in an experimental orchard to avoid any effect due to differences in environmental conditions and management. The energetic characteristics, calorific value and ash content, were evaluated for the various tree organs particularly shoots, leaves and branches; also root system was evaluated, although the roots can only be used once the trees are uprooted. Significant differences were observed in the calorific values among the different tree organs and the cultivars. Regarding the ash, shoots and leaves showed the highest content with respect to the other organs, thus causing a possible tendency in slagging with fouling and corrosion of boiler components.

Proximity to natural habitat and flower plantings increases insect populations and pollination services in South African apple orchards

Abstract Introducing areas of wildflower vegetation within crop fields has been shown to enhance pollinator activity and pollination services to crops, and findings in Europe showed an interaction effect between floral treatments and landscape context. Natural fynbos patches in the South African Cape Floristic Region (CFR) are potential reservoirs for beneficial insects that could enhance pollinator populations and crop pollination in commercial apple orchards. However, the effect of proximity to natural habitat and floral enhancement treatments on crop pollinators and yield are yet to be fully tested in southern temperate regions. To elucidate the impact of enhanced floral resources to apple flower visitors and crop yield, we established small experimental patches of flowers in non‐productive areas of commercial apple Malus domestica orchards in the CFR. Experimental orchards were embedded in landscapes with varying proportions of natural habitat within 1 km. We used pollinator exclusion experiments to determine the benefits of insect pollination on apple yield, quality and economic value. We found that the primary pollinator of apple flowers in the region is the endemic Cape honey bee, Apis mellifera capensis. Floral plantings enhanced overall pollinator abundance and honey bee flower visitation within the orchards, and positively affected apple size and economic value. Increased landscape complexity had a significantly positive effect on wild bees but not on honey bees. Synthesis and applications. We demonstrate that presence of floral plantings within orchards enhances pollinator activity within apple orchards and apple quality. This sustainable management practice may represent a profitable choice for growers, which could increase pollination services while reducing reliance on renting hives. These practices can indirectly contribute to increased landscape‐scale resilience and connectivity while also benefiting pollinators within the remaining natural habitat.

Monitoring of Emerging Water Stress Situations by Thermal and Vegetation Indices in Different Almond Cultivars

In recent years, the area dedicated to modern irrigated almond plantations has increased significantly in Spain. However, the legal irrigation allocations are lower than the maximum water requirements of the crop in most cases. Therefore, almond growers are forced to implement regulated deficit irrigation strategies on their farms, applying water stress in certain resistant phenological periods and avoiding it in sensitive periods. Given the need to monitor the water status of the crop, especially in the most sensitive periods to water stress, the objective of this work was to evaluate the sensitivity of two UAV-based crop water status indicators to detect early water stress conditions in four almond cultivars. The field trial was conducted during 2020 in an experimental almond orchard, where two irrigation strategies were established: full irrigation (FI), which received 100% of irrigation requirements (IR), and regulated deficit irrigation (RDI), which received 70% of IR during the whole irrigation period except during the kernel-filling stage when received 40% IR. The UAV flights were performed on four selected dates of the irrigation season. The Crop Water Status Index (CWSI) and the Normalized Difference Vegetation Index (NDVI) were derived from thermal and multispectral images, respectively, and compared to classical water status indicators, i.e., stem water potential (Ψstem), stomatal conductance (gs), and photosynthetic rate (AN). Of the four flights performed, three corresponded to mild water stress conditions and a single flight was performed under moderate water stress conditions. Under mild water stress, CWSI was not able to capture the differences between FI and RDI trees that were observed with Ψstem. Under moderate stress conditions, CWSI was sensitive to the water deficit reached in the trees and showed significant differences among both irrigation treatments. No differences were observed in the CWSI and NVDI response to water stress among cultivars. Although NDVI and CWSI were sensitive to water stress, the low signal intensity observed in NDVI makes this index less robust than CWSI to monitor crop water stress. It can be concluded that UAV-based CWSI measurements are reliable to monitor almond water status, although for early (mild) levels of water stress, Ψstem seems to be the preferred option.

The Effect of Mycorrhizal Fungi and PGPR on Tree Nutritional Status and Growth in Organic Apple Production

The desire to reduce the negative impact of crops on the environment, as well as the growing concern for consumer health, is increasing interest in organic fruit production. In this context, the development of new environmentally friendly agrotechnical methods which allows for reducing the use of organic fertilizers by improving the nutrient use efficiency and consequently decreasing the leaching of them is a task of a great importance. The main purpose of this study was to evaluate the effect of mycorrhizal arbuscular fungi (AMF) combined with plant-growth-promoting rhizobacteria (PGPR) on growth and nutritional status of apple trees cultivated on a silty-loam, rich in clay minerals and humus soil under organic farming conditions. Thus, a trial was established in an experimental orchard in Wilanów in Central Poland with three cultivars (‘Topaz’, ‘Odra’, and ‘Chopin’) and a promising clone, U 8869. Trees were or were not inoculated with AMF + PGPR within a split-block experimental design with four replicates. According to the results, mycorrhizal frequency obtained in the inoculated tree roots was on average two-fold higher than in the roots of the control plants. After four years of AMF + PGPR inoculation, 24% higher trunk cross-section area (TCSA) was observed, with the nitrogen and magnesium concentrations in leaves increasing, on average, by 7.8% and 64.2%, and phosphorus and potassium content decreasing by 37.2% and 46.5%, respectively. This study shows that using AMF + PGPR inoculum supports tree roots colonization by AMF. As a result, better nitrogen nutrition status is observed that promote vigorous growth of trees and more efficient uptake of magnesium from the bulk soil. On the other hand, lower phosphorus content in inoculated tree leaves might be explained by a dilution effect, and potassium decrease could occur as a result of fungus–plant competition in conditions of this element deficiency in soil.

Pomological and sensory properties of 8 different fig varieties in Croatia

The common fig (Ficus carica L.) is a fruit species traditionally cultivated in coastal Croatia. After some years of being of low commercial value, the interest in fig consumption and cultivation in this region seems to start following the increasing trend. One way of promoting fig consumption is to identify the varietal sensory properties, intending to match the consumer preferences. For this reason, the goal of this study was to evaluate sensory properties and pomological characteristics of fresh fruits of five dark (‘Šaraguja’, ‘Miljska’, ‘Crnica’, ‘Piombinese’, ‘Nero Rosso’) and three light-coloured (‘Petrovača bijela’, ‘Tiger’, ‘San Martino’) skin fig varieties, grown in Croatia. Figs were harvested from 5-years old trees in the fig experimental orchard located in Istria County (Croatia). Significant differences were observed for the properties of appearance, odour, flavour, and taste. Fresh fruits of varieties 'Šaraguja' and 'Tiger' reached the highest scores for the intensity of taste, fig odour, and flavour, compared to all the others. The highest values regarding fruit thickness and width were recorded from the variety 'Petrovača bijela', lenght from the variety 'Šaraguja', while 'San Martino' variety had the fruits of biggest weight. The variety 'Miljska' displayed the lowest values in all the observed pomological parameters. The importance of the pomological description and observation of sensory parameters of fresh figs lies in permitting the producers to decide the potential of each variety based on consumer preferences.

Prediction of Olive Tree Water Requirements under Limited Soil Water Availability, Based on Sap Flow Estimations

The forecast of irrigation requirements in commercial olive orchards in the era of climate change is at the forefront of scientific research. Simplified models that are based on monitoring soil and plant water status, along with microclimatic variables are well established. In the present study, an attempt was made to correlate the olive tree sap fluxes and the theoretical grass water losses, as expressed by reference evapotranspiration (ETo) in mild to moderate water-stress conditions. The water flow in the soil–plant–air continuum was monitored using soil water and thermal dissipation probes (TDP), which have a comparatively low cost and satisfactory reliability, while microclimatic variability was monitored by a meteorological station placed within the experimental orchard. The assessment of water stress was conducted via a stress coefficient (Ks), which was determined according to soil water availability, and validated with measurements of pre-dawn water potential and stomatal conductance. The results suggest the existence of an exponential correlation (R2 = 0.869) between daily plant transpirational losses and reference evapotranspiration, while the methodology’s applicability is verified by the validation process (R2 = 0.804 and RMSE = 0.579 L per day).

Rootstocks Genotypes Impact on Tree Development and Industrial Properties of ‘Valencia’ Sweet Orange Juice

The low diversification of rootstock genotypes in orchards limits the expansion of the citrus industry, restricting increases in productivity and cost-saving via phytosanitary treatments and other horticultural practices. Therefore, the aim of this study was to assess the impact of rootstock genotypes on tree development and industrial properties of ‘Valencia’ sweet orange juice (Citrus sinensis). Twenty rootstock genotypes were evaluated by measuring tree growth and industrial properties of orange juices, including ‘Trifoliata’ hybrids with tangerine (citrandarins) and grapefruit (citrumelos), as well ‘Rangpur’ lime and other potential rootstocks. The experimental orchard was planted in Rancho Alegre, PR, Brazil, under clay soil and subtropical rainfed conditions. A randomized block design with four replicates was used. Trees grown on IPEACS–239 and IPEACS–256 citrandarins, and on ‘US–802’ pummelo hybrid had low vigor, high production efficiency and high industrial properties of orange juice, and are therefore potential alternatives for high-density plantings. The F.80–3 and F.80–5 citrumelos also had good dwarfing potential and high production efficiency, but lower industrial properties of juice compared to the other ‘Trifoliata’ hybrid rootstocks. Trees grown on ‘US–812’ citrandarin rootstock had low vigor, good productive performance, accumulated production and production efficiency similar to ‘Rangpur’ lime, and high industrial properties of juices. Although the ‘Rangpur’ lime and the ‘Florida’ rough lemon allowed high yields, the trees are very vigorous, with low-quality fruits. A Quick Reference Chart was created to provide practical and objective identification of the best rootstock alternatives for ‘Valencia’ orange trees in terms of tree development and industrial properties of juices.

Apple powdery mildew infestation detection and mapping using high-resolution visible and multispectral aerial imaging technique

Powdery mildew (PM) in apple orchards is a critical fungal disease that considerably reduces yield, harvested fruit quality, and orchard health. Rapid detection and mapping of resulting infestation at orchard scale is a challenge with existing laborious manual scouting approaches. Therefore, this study explored the feasibility of detecting and mapping PM infestation in an apple orchard block using high-resolution visible (red-green-blue [RGB]) and multispectral imaging technique. Imaging campaigns were conducted over an experimental orchard using small unmanned aerial systems (UAS) integrated with the above optical sensors. K-means classifier trained on individual snapshots of RGB imagery had mean disease detection accuracy of 77%. Eight multispectral vegetation indices also showed significant differences (p < 0.001) between healthy (Mean: 0.25–0.84) and infected (Mean: 0.01–0.25) leaves. Modified Simple Ratio-Red (MSRR), Modified Simple Ratio-Blue (MSRB), and Optimized Soil Adjusted Vegetation Index (OSAVI) showed the highest contrast (Mean: 0.46–0.79). Orchard block-scale mapping using RGB orthomosaic layer, classified with k-means and spectral angle mapper techniques had accuracies up to 73%. Overall, high resolution imagery in the visible and multispectral domain could sufficiently detect the infection and generate site-specific disease heat maps. These maps could be useful to apple growers in directing prescriptive resources ( pruning labor or fungicide application) for PM management.

Seasonal Abundance and Diversity of Egg Parasitoids of Halyomorpha halys in Kiwifruit Orchards in China.

Simple SummarySurveys of egg parasitoids of the brown marmorated stink bug, Halyomorpha halys, were conducted in 2018 and 2019 in green-fleshed ‘Hayward’ kiwifruit orchards in Mei County, Shaanxi Province, China, to assess the abundance and diversity of parasitoid communities under two different management systems. Parasitism occurred from June to August and from May to August across the two survey seasons, respectively. Five parasitoid species were recovered from successfully parasitized H. halys egg masses, where Trissolcus japonicus and Trissolcus cultratus were the predominant species. The abundance of T. japonicus varied throughout the season in both orchards in both survey seasons. Monthly T. japonicus abundance showed a unimodal distribution in 2018, peaking in July. There were two peaks (May–June and August) in the 2019 season. This study provides valuable information on the season-long abundance and diversity of egg parasitoids of H. halys in kiwifruit, and most importantly on the abundance and effectiveness, relative to other parasitoids, of T. japonicus in kiwifruit orchards.To develop effective and targeted biocontrol tactics for the brown marmorated stink bug, Halyomorpha halys, in crop habitats, a good understanding is essential of the abundance and diversity of its parasitoids in different crop habitats in its native range. To obtain information on the egg parasitoid communities of H. halys in kiwifruit, surveys using sentinel egg masses were conducted in 2018 and 2019. These assessed the species composition of egg parasitoids of H. halys in green-fleshed ‘Hayward’ kiwifruit orchards, and quantified their season-long abundances in orchards under two different management systems. Parasitism was observed from June to August 2018 (mean parasitism: 48%) and from May to August 2019 (mean parasitism: 29%) across the experimental orchards. In total, five different parasitoid species were found across the two surveys seasons in the kiwifruit orchards, Trissolcus japonicus, T. cultratus, T. plautiae, Anastatus japonicus, and Acroclisoides sp., where T. japonicus and T. cultratus were the predominant species. Monthly T. japonicus abundance data had a unimodal distribution in 2018, peaking in July. There were two peaks (May–June and August) in the 2019 season. Overall, T. japonicus was significantly more abundant in the organic orchard than the conventionally managed orchard only in 2018, and its monthly abundance differed significantly in the two orchards in the two survey seasons. Results and their implications for future classical biological control for H. halys in kiwifruit are discussed.

A parsimonious mechanistic model of reproductive and vegetative growth in fruit trees predicts consequences of fruit thinning and branch pruning.

Productivity of fruit tree crops depends on the interaction between plant physiology, environmental conditions and agricultural practices. We develop a mechanistic model of fruit tree crops that reliable simulates the dynamics of variables of interest for growers and consequences of agricultural practices while relying on a minimal number of inputs and parameters. The temporal dynamics of carbon content in the different organs (i.e., shoots-S, roots-R and fruits-F) are the result of photosynthesis by S, nutrient supply by R, respiration by S, R and F, competition among different organs, photoperiod and initial system conditions partially controlled by cultural practices. We calibrate model parameters and evaluate model predictions using unpublished data from a peach (Prunus persica) experimental orchard with trees subjected to different levels of branch pruning and fruit thinning. Fiinally, we evaluate the consequences of different combinations of pruning and thinning intensities within a multi-criteria analysis. The predictions are in good agreement with the experimental measurements and for the different conditions (pruning and thinning). Our simulations indicate that thinning and pruning practices actually used by growers provide the best compromise between total shoot production, which impacts next year's abundance of shoots and fruits, and current year's fruit production in terms of quantity (yield) and quality (average fruit size). This suggests that growers are not only interested in maximizing current year's yield but also in its quality and its durability. The present work provides for modelers a system of equations based on acknowledged principles of plant science easily modifiable for different purposes. For horticulturists, it gives insights on the potentialities of pruning and thinning. For ecologists, it provides a transparent quantitative framework that can be coupled with biotic and abiotic stressors.

Effect of foliar application of micronutrients and soil application of zinc sulphate on total chlorophyll and carotenoid content in sweet orange (Citrus sinensis) cv. blood red

The present investigation was carried out for two consecutive years of 2016 and 2017 at experimental orchard of Department of Horticulture, CCS HAU, Hisar to assess the performance of sweet orange cv. Blood Red to foliar application of micronutrients and soil application of zinc sulphate. In experiment I, the foliar application of micronutrients was done two times i.e. Ist spray was done on first week of april and 2nd spray on first week of july. The experiment comprises of thirteen treatments, viz., Zinc sulphate (ZnSO4) @ 0.25%, 0.50% &1.00%; Iron sulphate (FeSO4) @ 1.5%, 2.0% & 2.5%; Manganese sulphate (MnSO4) @ 0.25%, 0.50% & 1.00%; Boric acid (H3BO3) @ 0.1%, 0.2% & 0.3% and Control (No micronutrients). In experiment II, the soil application of zinc sulphate (ZnSO4) was done two times i.e. half dose in second fortnight of february and half dose in second fortnight of May. The experiment comprises of six treatments, viz., Zinc sulphate (ZnSO4) @ 50 g/plant, 100 g/plant, 150 g/plant, 200 g/plant, 250 g/plant and Control (No Zn application). Results indicated that foliar application of micronutrients and soil application of zinc sulphate affected significantly the chlorophyll and carotenoid content.

Cattle Horn Shavings: A Possible Nitrogen Source for Apple Trees

The circular economy concept promotes the recycling of agricultural waste. This study was aimed at investigating the effects of cattle horn shavings on apple tree nitrogen nutrition. Ligol apple trees on P 60 rootstock were the object of the study. The experiment was conducted in the experimental orchard of the Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry, from 2015 to 2018. Two fertiliser rates were tested: 50 and 100 kg/ha N. Horn shavings (14.1% N) were applied at the end of autumn or at the beginning of vegetation in the spring and in one treatment 100 kg/ha N rate was divided into two equal parts and applied both in autumn and spring. The effects of the horn shavings were compared with the effects of ammonium nitrate (34.4% N) and the unfertilised treatment. The lowest mineral nitrogen content was found in the unfertilised orchard soil and the soil fertilised with horn shavings in the spring at 50 kg/ha N equivalent. In all other cases, the fertilisers increased the soil’s mineral nitrogen content. The lowest leaf nitrogen content was found in apple trees that grew in the unfertilised orchard soil or soil fertilised in the spring with 50 kg/ha N of horn shavings (1.58–2.13%). In other cases, leaf nitrogen content was higher (1.77–2.17%). The apple trees with the lowest leaf nitrogen content produced the smallest average yield (34.5–36.6 t/ha). The highest yield was recorded from fruit trees fertilised with 50 kg/ha N of ammonium nitrate applied in spring or horn shavings applied in autumn (42.4 and 41.4 t/ha, respectively). The influence of horn shavings on the other studied parameters was similar to that of ammonium nitrate. Horn shavings, like nitrogen fertiliser, could facilitate nitrogen nutrition management in apple trees, especially in organic orchards, where the use of synthetic fertilisers is prohibited.

Linking Mineral Nutrition and Fruit Quality to Growth Intensity and Crop Load in Apple

Diagnostic of the nutritional status in fruit trees can be estimated using different models. However, these models usually do not fully match the character of the perennial crops and their accuracy needs to be improved. This study aimed at deepening the understanding of the aspects controlling mineral content of macro- and micronutrients and fruit quality of the apple trees with respect to the crop load and vegetative shoot growth. The focus was given on description of the nutrient content variability in time and space, its relation to important physiological events, and conditions altering their gradient in leaf and fruit. The evaluation was carried out with six years old ’Golden Delicious’ apple trees on M9, planted in an experimental orchard. Flowering rate, total yield, shoot growth intensity, mean fruit weight and quality along with mineral content of leaves, and fruit in different development stages were analysed according to intensity of natural or regulated flowering and fruit set, respectively. We found that aside of macroelements, iron, and manganese depended on the crop load. For nitrogen, phosphorus, and potassium content, their gradient increased up to 10–25% within the sufficiency range as the trees tried to maintain certain level of these nutrients in leaves and fruit simultaneously during deficit. In contrary, the higher content of Mg, Fe, and Mn related to the avoidance of deficit through up to 20–30% higher uptake in trees with higher crop load. Phosphorus, potassium, and calcium content in short fruiting shoots was more stage dependent, showing relation with the timing of cessation of particular meristematic growth activity. If no intense deficit occurred, the trees kept unrestricted initial investment of nutrients in the fruit during cell division stage whatever the crop load was. Their content at the later development stages appeared to be more dependent upon the consumption by particular sink. These findings allowed to improve the interpretation of the fruit trees nutrition status due to adaptation of the reference nutrient content in low cropping trees by a reduction of 5–10% N and P, 10–15% Ca, as well as by an increase of 15–20% K content in leaves at the stage with fruit size of 20 mm, and without change in P content at the stage of about 70% of final fruit size.