High-density Orchards Research Articles

Fruit canopy positioning affects fruit calcium and potassium concentrations, disorder incidence, and fruit quality for ‘Honeycrisp’ apple

One advantage of high-density apple orchard systems is homogeneity in fruit maturity and quality. However, even in modern orchard systems, variation in fruit quality occurs. ‘Honeycrisp’ apple is susceptible to numerous disorders including bitter pit, soft scald, and poor colour development. Heterogeneity in fruit quality and nutrient distribution can lead to variation in fruit storability. Here, we tested the effect of within-canopy position on fruit calcium and potassium concentrations, quality, and disorder development for fruit across nine representative high-density orchards. Calcium concentrations were greater in the upper part of the canopy compared with the lower part. Potassium was more evenly distributed within the canopy. Calcium concentrations and potassium-to-calcium ratios were significantly correlated with mean bitter pit incidence, which was between 20% and 30% in the lower half of the tree and <15% in the upper half. Fruit quality was significantly affected by the position in the canopy and was not constrained to only colour, but also other quality metrics such as dry matter, size, and firmness. Additionally, the internal ethylene concentrations (IECs) of fruit in the upper canopy were approximately 50% of the IECs for fruit from the lower canopy. With an increased emphasis on uniformity and predictability of fruit for long-term storage, these results underscore the importance of understanding variation within the canopy. Even for high-density systems, significant variation in fruit quality can occur and fruit from the upper canopy has lower disorder incidence and higher fruit quality than fruit from the lower canopy.

Five-year nutritional study of apples in commercial high density orchards

Five-year nutritional study of apples in commercial high density orchards

Long-term evaluation of growth and production of olive cultivars in super high-density orchard under cold-weather conditions

Hedgerow olive orchards are being established in all olive-producing countries. Little information is available, however, concerning adaptation of olive cultivars to cold conditions. For this reason, nine olive cultivars were trained in hedgerows and evaluated during nine years in the cold area of central Spain (Toledo). Three of them (‘Arbequina’, ‘Arbosana’ and ‘Koroneiki’) are the most widely cultivated in hedgerow orchards. ‘Cobrançosa’, ‘Cornicabra’ and ‘Manzanilla cacereña’ are cultivated in cold weather conditions, and ‘Sikitita’ is a new cultivar, so far evaluated only in warm areas. Vegetative growth (tree height and trunk diameter) was measured annually until individual hedgerows were formed. In most cultivars, hedgerows that occurred by the 5th year after planting. At that time, hedgerow architectures were described. Fruits were machine-harvested from the 3rd year. ‘Koroneiki’ showed the highest growth rate from the first year and very few trees were damaged by harvesting. In the 7th year, the most vigorous cultivars were ‘Koroneiki’, ‘Arbequina’ and ‘Cornicabra’ and the least were ‘Arbosana’ and ‘Sikitita’. Regarding hedgerow architecture, ‘Koroneiki’ and ‘Arbosana’ hedgerows were narrow while ‘Arbequina’ and ‘Manzanilla cacereña’ were wide. Neither vegetative growth nor hedgerow size were related with oil production. After 9 years 63% of the ‘Cobrançosa’ trees were severely damaged by harvesting. ‘Arbosana’, ‘Koroneiki’ and ‘Arbequina’ produced the greatest number of fruits and most oil. After 7 years they remained the most productive cultivars but by then oil yields of ‘Cornicabra’ and ‘Sikitita’ were comparable. These latter two cultivars produced fewer fruits of higher oil content. ‘Manzanilla cacereña’ and ‘Cobrançosa’ are not recommended for hedgerow orchards because of high alternate bearing, low production and susceptibility to damage during machine harvesting. ‘Cornicabra’ and ‘Arbosana’ are of questionable use in cold conditions because of high susceptibility to Pseudomonas savastanoi. Considering all agronomic aspects, ‘Koroneiki’, ‘Sikitita’ and ‘Arbequina’ can be recommended for hedgerow production in similarly cold environments.

Toward the valorization of olive (Olea europaea var. europaea L.) biodiversity: horticultural performance of seven Sicilian cultivars in a hedgerow planting system

An intense survey of the Sicilian’s olive growing areas for autochthonous germplasm, mainly represented by centennials olive trees (Olea europaea var. europaea L.) apparently older then III centuries, started at the beginning of the 1980s and resulted in the selection of more than 150 cultivars and accessions. This germplasm was propagated in a nursery, by grafting onto seedlings of Olea europaea L., and planted in an experimental orchard, in an olive district located in the South-west of the Island, where they were evaluated for over 30 years and selected for their early bearing, high and constant productivity, as well as high oil content of the fruits and excellent chemical (oleic acid and phenol content) and organoleptic profile of the oil. This paper reports data on the horticultural performances (production, vigor, crop efficiency and oil quality) of four cultivars (‘Kalat’, ‘Olivo di Mandanici’, ‘Abunara’ and ‘Minuta’), selected within the Sicilian’s autochthonous germplasm trained as 'Free Palmetta' and tested in a hedgerow planting system at three different planting densities: 500, 666 and 1000 trees ha-1. The cultivar ‘Nocellara del Belice’, ‘Cerasuola, and ‘Biancolilla’, widely cultivated in the area where the trial was carried out, were used as references.The outstanding performance of the cultivar ‘Kalat’ at planting density of 1000 trees ha−1, suggests that this cultivar can be a promising choice for the super high density orchards (SHD). The other cultivars tested did not performed as ‘Kalat’ and seem not suitable for SHD planting system due to their high vigor. The hedgerow planting system tested, in the first 6 years of planting, increaseed productivity of all cultivars compared to traditional olive orchard typical of the area where the trial was conducted. This hedgerow olive orchard may represent a valid solution to increase orchard productivity and to reduce harvest costs by mechanization, depending on tree high, with straddle or side by side canopy contact machines. Achieve higher yield and reducing management costs using autochthonous, resilient cultivars, could be a new strategy to counteract climate changes. The unique organoleptic profiles of the oils obtained from the cultivars tested, could improve the offer of tasty, flavored and nutraceutical extra virgin olive oils in the international markets. Results highlight the importance of preserving and valorizing biodiversity to increase productivity and resiliency of agricultural systems, facing continuous, fast and deep social and environmental changes.

Sweet cherry cultivars influenced the growth and productivity under HDP

In a field experiment, to identify the best sweet cherry varieties for high density orcharding, maximum canopy volume (18.94 cm3) was recorded in variety ‘Steela’ and minimum in ‘Lambert’ while, ‘Bigarreau Napoleon’ had maximum TCSA (213 cm2). Trees grown under HDP have lower TCSA in comparison to normal density. Primary and secondary branch girth were maximum in ‘Bigarreau Napoleon’ whereas, annual extension growth and shoot thickness were high in ‘Steela’. Yield, yield efficiency and cumulative yield efficiency were registered maximum in ‘Bigarreau Napoleon’ and ‘Bigarreau Noir Grossa’ cultivars. Largest fruit weight, fruit length and fruit diameter were found maximum (10.16 g/fruit), (25.51 mm) (25.20 mm) respectively in ‘Bigarreau Napoleon’. Total soluble solids were found maximum in ‘Bigarreau Noir Grossa’ (17.30 0Brix) among the studied cultivars. Correlation matrix showed that TCSA had positive correlation with canopy volume, primary branch girth and secondary branch girth and fruit weight showed positive correlation with fruit length and fruit diameter.

Sweet cherry cultivars influenced the growth and productivity under HDP

In a field experiment, to identify the best sweet cherry varieties for high density orcharding, maximum canopy volume (18.94 cm3) was recorded in variety ‘Steela’ and minimum in ‘Lambert’ while, ‘Bigarreau Napoleon’ had maximum TCSA (213 cm2). Trees grown under HDP have lower TCSA in comparison to normal density. Primary and secondary branch girth were maximum in ‘Bigarreau Napoleon’ whereas, annual extension growth and shoot thickness were high in ‘Steela’. Yield, yield efficiency and cumulative yield efficiency were registered maximum in ‘Bigarreau Napoleon’ and ‘Bigarreau Noir Grossa’ cultivars. Largest fruit weight, fruit length and fruit diameter were found maximum (10.16 g/fruit), (25.51 mm) (25.20 mm) respectively in ‘Bigarreau Napoleon’. Total soluble solids were found maximum in ‘Bigarreau Noir Grossa’ (17.30 0Brix) among the studied cultivars. Correlation matrix showed that TCSA had positive correlation with canopy volume, primary branch girth and secondary branch girth and fruit weight showed positive correlation with fruit length and fruit diameter.

Growth and Feathering of Some Apple Cultivar-Rootstock Combinations in a Fruit-tree Nursery

The planting of well feathered trees are crucial in a high density orchard, than unbranched rods. Lateral bud-brake can be effectuated by several agro-technical methods in order to overcome apical dominance. Main targets of the researches were to investigate the feather induction by removing the apical leaves and to study a proper basic and foliar fertilization scheme. The highest mean height of the trees with significant differences was achieved by untreated Florina, followed by variants of Florina treated with Solfert, untreated control Idared and Florina with NPK and Fertitel. The number of feathered trees was higher in Florina than in Idared. The best results were obtained with Solfert and NPK followed by Fertitel. The growth in height was not affected by the lack of fertilizers in the control variants, but in other fertilization variants where branching was observed the height of the trees was reduced.

Phenotypic Association of Multi-scale Architectural Traits with Canopy Volume and Yield: Moving Toward High-density Systems for Macadamia

The vigorous growth and large canopy size of commercial macadamia (Macadamia integrifolia, M. tetraphylla, and hybrids) cultivars generally restricts macadamia orchards to low-density planting. Little is known of the detailed interactions between plant architecture and yield components specific to macadamia. This chapter examines how dependent traits such as canopy size and yield might be determined by direct and indirect interactions between traits at different scales within the canopy. Fifteen genotypes (n = 3) were phenotyped in two growing seasons for architectural and reproductive traits, around the age of their transition from juvenility to maturity. Genotypes varied in canopy volume, cumulative yield, and canopy efficiency, and particular genotypes with low canopy volume and high yield were considered potentially useful for future high-density orchard systems. There was high variability in architectural, floral, and yield traits at multiple scales. Direct and indirect effects of architectural traits on the variability of yield and tree size were quantified using path coefficient analysis. Canopy volume was subject to positive direct effects from trunk cross-sectional area (TCA; 0.72), lateral branching (0.24), and branch unit (BU) length (0.24). Other traits showed significant indirect effects with canopy volume via TCA, such as branch cross-sectional area (BCA; 0.43), BU length (0.40), lateral branching (0.35), and internode length (0.32). Branch angle had a significant indirect negative effect on canopy volume via BU length (−0.11). Nut number had the strongest direct effect on yield (0.97), and this relationship was significantly indirectly influenced by raceme number (0.47), raceme length (0.50), nut number per raceme (0.33), canopy volume (0.37), and branch angle (0.35). In these relatively young trees, early yield was directly and positively influenced by canopy volume (0.12), presumably due to increased early light interception, which suggests that early canopy vigor contributes to early yield. This study suggests that yield and canopy size are determined by complex phenotypic interactions between architectural traits at different scales. Therefore, preplanting (i.e., scion and rootstock selections) and postplanting (i.e., pruning and training) manipulations that specifically manage architectural traits such as shoot length, branching, branch angle, raceme length, and nuts per raceme may result in the creation of efficient macadamia canopies.

Side Appel Amenability to Ontario

My thesis research involves an evaluation of apple production for the rapidly expanding Ontario cider industry. This entails several experiments that provide an analysis of several apple cultivars. These include apples from traditional global cider regions, established Ontario varieties, and novel crab-derived varieties. Firstly, a report on the cider-centric sensory characteristics of these apples will be published. Additionally, the winter hardiness of varieties with historic use in cider making will be established using microscopy methods. This will provide a minimum cultivation temperature for use in planting decisions throughout Ontario’s apple growing regions. A major concern of Ontario apple grower’s is the cost of harvest labour. For this purpose, I am evaluating the economics of mechanical harvesting in high-density orchards. Lastly, I am exploring the suitability of ice cider production in Ontario to provide methodology recommendations. My project seeks to support the expanding Ontario cider industry through providing localized guidelines.

EARLY PERFORMANCE OF FOUR SWEET CHERRY CULTIVARS GRAFTED ON GISELA 5 AND COLT ROOTSTOCKS IN A HIGH DENSITY GROWING SYSTEM

Growing the sweet cherry on different vigor rootstocks, such as Colt and Gisela 5, in a high-density orchard, causes differences in growth and productivity and later imposes the need to change the growing system including pruning, flower and fruit thinning, irrigation and fertilization. In the present research, four sweet cherry cultivars (Summit, Kordia, Lapins and Regina) grafted on Colt and Gisela 5 rootstocks were assessed for morphological traits and productivity. The parameters investigated were: vegetative growth, bearing potential, fruit set, precocity, productivity, fruit growth habit and quality attributes. Compared to Colt, the trees on Gisela 5 had smaller TCSA and the length of two-year-old branches, in the fifth season after planting. Trees on Gisela 5 had a higher number of flower buds per may bouquet compared to Colt, which confirms that bearing potential is highly affected by the rootstock. Growing the sweet cherries on Gisela 5 induced a higher fruit setting in all cultivars except in Kordia. Fruit physical attributes were affected by the cultivar, growing system and experimental year. For all tested cultivars, the yield per tree was significantly lower on Colt compared to Gisela 5. Gisela 5 performed better than Colt, which suggests that Gisela 5 should be used as a rootstock in high density sweet cherry production systems.

Training systems for high-density cherry orchards in Trento province

In spring 2010, a high-density cherry trial was established comparing three training systems (TSs) (tall spindle axe (TSA) (2604 trees ha(-1)), bi-axis (2083 trees ha(-1)) and upright fruiting offshoot (UFO) (1736 trees ha-1)) with two sweet cherry (Prunus avium L.) cultivars (‘Kordia’ and ‘Regina’) grafted on two rootstock genotypes (GiSelA®5 (Gi5) and Piku1(S) (P1)). After 7 years, tree size, was similar among all the TSs. ‘Kordia’ had larger tree size than ‘Regina’. Among rootstock genotypes, tree size was larger with P1 compared to Gi5. Bi-axis trees had higher cumulative yield (CY) and cumulative yield efficiency (CYE) compared to trees trained as TSA and UFO systems. On a hectare basis, the TSA had similar CY to bi-axis, both significantly higher than UFO system. Trees on Gi5 had higher CY and CYE than trees on P1 and ‘Kordia’ had higher CY and CYE than ‘Regina’. TSs did not affect fruit weight. ‘Regina’ had bigger fruit size compared to ‘Kordia’ due to the significant lower number of fruits on the trees. Fruits on Gi5 had higher fruit weight compared to P1 despite having a significantly higher yield. ‘Kordia’ on Gi5 trained to a bi-axis system had the best combination of high yield and fruit size. Fruit soluble solids were higher with UFO than TSA and bi-axis systems. ‘Regina’ had higher soluble solids and firmness compared to ‘Kordia’, which is likely due to the lower CY obtained by ‘Regina’.

Validation of Fungicide Spray Schedule of Conventional Apple Orchards under High Density Apple Orchard System against Scab and Alternaria Leaf Blotch

The purpose of the study was to find out efficacy of phenological stage based recommended fungicide spray schedule comprising seven sprays used in conventional apple orchards (apple cultivars grafted on seedling rootstocks) for the management of scab and alternaria leaf blotch of apple in high density apple orchards (cultivars grafted on clonal rootstocks) of Kashmir valley. Its application under high density apple orchard (cv. Red Delicious on seedling roostock) system provided inadequate control as compared to the standard check. The application of fungicide sprays at different phenological stages under high density orchard system provided 70.07 to 74.27 and 63.96 to 79.97 per cent control in leaf scab incidence and intensity, as against 93.89 and 95.17 per cent recorded in conventional orchard system, respectively. The sprays exhibited 63.96 to 70.31 and 63.21 to 68.61 per cent control in fruit scab incidence and intensity in high density orchard system as against 92.31 to 90.04 per cent in conventional system, respectively. However, in case of Alternaria leaf blotch disease 67.48 to 82.16 and 83.84 to 88.15 per cent disease control in incidence and intensity was observed as against 82.16 and 88.15 per cent in conventional orchard system.

Phytopigments, Proline, Chlorophyll Index, Yield and Leaf Nitrogen as Impacted by Rootstock, Training System, and Girdling in “Aztec Fuji” Apple

World overpopulation, scarcity of water and finite arable land mandate a more efficient use of these natural resources. To remain sustainable, modern-day apple (Malus domestica Borkh.) fruit production utilizes high-density orchards on semi-dwarfing, precocious rootstocks. Nonetheless, little attention has been paid to the use of size-controlling practices such as trunk girdling in these modern orchard systems. The impact of two rootstocks, two tree architecture (training) systems, and three levels of girdling (in spring) on chlorophyll index (CI), proline, chlorophyll content (Chl; a, b, a + b), carotenoids, anthocyanin, yield, fruit weight and leaf nitrogen (N) in “Aztec Fuji” were studied in 2015 and 2016. Trees on “Bud 9” had up to 5% higher chlorophyll indices in leaves on side branches than those on “Nic 29” at each sampling time in 2015 and 2016. However, trees on “Nic 29” had up to 5.5% chlorophyll index in terminal branches, 14% higher Chl b, 54% higher leaf proline in 2015, up to 5% higher leaf nitrogen (N) in 2015 and 2016, 82% higher yields in 2015, and up to 7% higher fruit weight in 2015 and 2016 than those on “Bud 9”. Trees trained into a central leader (CL) architecture had up to 6% higher chlorophyll index and 4% higher leaf N in terminal branches 2015 and 2016, 43% more terminal leaf proline content in 2015, but 13% less yield in 2016 than those with a tall spindle training (TS). Terminal leaves from trees receiving a bark girdling in 2015 (BG15) had up to 6.5% lower leaf N, 7% less chlorophyll index, and between 27% to 56% lower proline content than those from the ungirdled check and score girdled treatment in 2015 (SG15). Also, trees with BG15 and a bark girdling in both 2015 and 2016 (BG1516) treatments had significantly less leaf N concentration than all other treatments or the ungirdled check. Trees that were score girdled in 2015 and repeat score girdled in 2016 (SG1516) had 21% higher yield and 12% higher fruit weight than those that were ungirdled.

Evaluation of different mango (Mangifera indica) varieties for high density orchard in lateritic zone of eastern India

The present experiment was conducted under the semi-arid subtropical red lateritic zone of eastern India in West Bengal with seven years old popular mango (Mangifera indica L.) varieties grown at Horticulture Research Farm of Department of Horticulture and Postharvest Technology, Institute of Agriculture, Visva-Bharati, Sriniketan, West Bengal, India during 2015 and 2016. The varieties were evaluated for various morphological characters, yield and physicochemical quality of fruits. The results revealed that Kohinoor exhibited maximum tree volume (41.99 m3), fruit yield (21.03 kg/tree) and fruit weight (253.33 g/fruit). Whereas, Kohitoor exhibited maximum TSS (20.07 oB), TSS/acid ratio (100.35) and ascorbic acid (43.17 mg/100g) content of the fruits. Acidity content was found lowest (0.17%) in Gulab Khas. Regarding morphological characters, yield and physicochemical quality of fruits, the varieties Kohinoor, Kohitoor, Inayat Pasand are superior in quality and stand to promise for the small family farming orchard in the red lateritic zone of eastern India.

Flowering time of eleven olive cultivars in a high-density orchard in central Italy

Flowering time of eleven olive cultivars in a high-density orchard in central Italy

Assessment of olive transpiration derived from a remote sensing energy balance model compared with sap flow measurements

A remote sensing energy balance (R(SEB)) algorithm was used to estimate transpiration (TRSEB) from a high density and drip-irrigated olive (Olea europaea L. 'Arbequina') orchard, located in Pencahue Valley, Maule Region of Chile (35°23'S; 71°44'W). Meteorological variables over the orchard such as solar radiation, air temperature, relative humidity, wind speed and canopy temperature from zenith were recorded during the southern hemisphere summer, from January through February 2015. The RSEB model was evaluated using sap flow measurements obtained from compensation heat-pulse sensors. In 30-min intervals, the results showed that RSEB model estimated the olive transpiration with errors of 16%, presenting a root mean square error (RMSE) of 0.2 L h-1 and a mean absolute error (MAE) of 0.1 L h-1. On a daily basis, the RSEB model was able to predict the olive transpiration with RMSE and MAE values of 0.68 and 0.57 mm day-1, respectively. The overall analysis suggested that the model underestimates transpiration with errors of 10% on a daily basis.

Identifying vigour controlling rootstocks for mango

Vigour reduction in many tree crops is an essential element of highly productive, high density systems that is often achieved through rootstocks. Mangoes are large vigorous tropical trees that are traditionally grown at low density as suitable vigour reducing technologies are not commercially available. The aim of this work was to identify rootstock cultivars for mango that reduced scion vigour while maintaining or boosting yields. Ninety rootstocks are being evaluated for their ability to reduce vigour in two Australian mango scion cultivars from the National Mango Breeding Program (NMBP); ‘NMBP-1243’ and ‘NMBP-4069’. The evaluated rootstocks were sourced from a wide genetic range within Mangifera indica and related Mangifera spp. from the Australian National Mango Gene Bank and the Australian Mango Breeding Program. Rootstock-scion combinations were field planted at Walkamin, Queensland, Australia over three years, from May 2014 in randomised incomplete blocks. Tree height, canopy depth, canopy length (along the row), canopy width (across the row), rootstock trunk diameter (10 cm above the ground and 10 cm below the graft point) and scion diameter (10 cm above the graft) were measured every six months as indicators of tree growth and vigour. This is a report on the progress of 29 rootstocks from the May 2014 planting. There was a significant (p<0.05) effect of rootstock on tree height, canopy size and trunk diameter at 24 months. Seven rootstocks were consistently among the 13 lowest vigour trees for tree height, canopy length, canopy width and scion/rootstock trunk diameters, when ranked from lowest to highest vigour. These rootstocks show promise for high-density mango orchard systems. Evaluation is ongoing and will evaluate effect of rootstock on scion flowering and cropping.

Rootstock, Canopy Architecture, Bark Girdling, and Scoring Influence on Growth, Productivity, and Fruit Quality at Harvest in ‘Aztec Fuji’ Apple

The increasing scarcity of land and water for agriculture mandates an efficient use of these natural resources. Establishment of high-density orchards with the use of a size-controlling rootstock, in combination with a suitable canopy architecture, is an efficient method for fruit production. However, less attention has been paid to the use of size-controlling practices such as trunk girdling in these modern orchard systems. The impacts of two rootstocks, two tree architectures, and three levels of bark cambium cuts (girdling or scoring) on growth, yield, fruit quality attributes at harvest, and leaf nitrogen (N) in ‘Aztec Fuji’ apple (Malus domestica Borkh.) were studied in 2015 and 2016. Trees on Nic 29 had larger canopies, higher yields, and larger fruit, but lower fruit color, sunburn, and firmness than those on Bud 9. Trees with a tall spindle (TS) architecture had higher yield in 2016, higher fruit soluble solids and firmness in 2015, higher fruit russet in 2016, but shorter terminal growth in both 2015 and 2016 and lower leaf N in 2015 than did those with a central leader (CL) training system. Trees receiving a bark girdling in 2015 (BG15) or score girdling in 2015 and 2016 (SG1516) had significantly higher yield than trees on nongirdled trees (NOGD) in 2016. Bark girdling or score girdling in 2015 (BG15 or SG15) increased fruit weight (size), color, and firmness at harvest in the same year, although differences for score girdling were not always significant. However, BG15 or SG15 did not have a “carryover” effect and did not affect fruit size, color, or firmness at harvest in 2016. When bark scoring was repeated in 2016 (SG1516), fruit size was increased in 2016. On the basis of the results of this 2-year study, it appears that bark girdling in one year is sufficient to increase fruit size of the current year and the yield in the following year. If larger fruit size is the critical objective of fruit production, annual score girdling needs to be practiced. However, a further long-term study is needed to monitor the carryover effects of cambium girdling and scoring on tree performance and fruit quality attributes in the subsequent years.

Effect of fertigation on yield and fruit quality of apple (Malus domesticaBorkh.) in high-density orchards on chernozems in Central Russia

The research was conducted in 2013-2015 in the experimental apple orchard of I.V. Michurin Federal Research Centre (Tambov region, Russia) with 'Zhigulevskoe' apple trees on B396 rootstock. The aim was to determine the optimal rates of nutrients by fertigation and foliar feeding efficiency. The soil was a leached meadow chernozem, low of humus, heavy loamy on sand with pseudofiber. There were recorded yield, main nutrient content in leaves and soil, as well as the humus content and soil pH, ascorbic acid, sugars and organic acids content in fruits. We applied N(10)P(10)K(10), N(20)P(15)K(20), N(25)P(20)K(25), N(25)P(20)K(30), N(30)P(25)K(30), N(35)P(25)K(35) rates (data are in kg ha(-1) of individual nutrient). Optimal fertigation rate for regions of the Central Chernozem Zone determined in our research was (in kg ha(-1)) N=25, P=20 and K=30. Excessive application of fertilizers through fertigation and also irrigation may led to soil degradation and deterioration of soil fertility, resulting in change of some physical and chemical parameters. The fertilizer rate determined during our research did not significant influence on the soil pH, humus content and cation exchange capacity. The content of ascorbic acid, sugars and titric acids of fruits at harvest was largely determined by the weather conditions of the growing year. Combination of fertigation and foliar fertilizing increased the productivity of apple trees.

New scion-rootstock combinations for diversification of sweet orange orchards in tropical hardsetting soils

Abstract Naturally occurring subsoil horizon restricting root development and a narrow genetic base of scion-rootstock combinations make the citriculture in Brazilian Northeast prone to biotic and abiotic stresses. The diversification of citrus orchards through the introduction of new scion-rootstocks combinations is an important strategy to reduce the risks associated with these constraints. Three experiments aiming at identifying appropriate scion-rootstock combinations for enhancing genetic diversification in citrus orchards under rainfed conditions in tropical hardsetting soils were established in Sergipe state in 2008. In each one, a different sweet orange (‘Sincora’, ‘Valencia Tuxpan’ and ‘Pineapple’) was grafted on six rootstocks (‘Santa Cruz’ Rangpur lime, ‘Red Rough’ lemon, ‘Orlando’ tangelo, ‘Sunki Tropical’ mandarin, HTR–051 and VKLxRPL–010 hybrids). After eight years the experiments were evaluated for plant development, yield performance and fruit quality. In general, all sweet oranges grafted on ‘Red Rough’ lemon showed great development and cumulative yield as does with ‘Santa Cruz’ Rangpur lime, with the later showing better fruit quality as an advantage. Inversely, HTR-051 hybrid displayed low yields despite high yield efficiency, for this rootstock induces dwarfism. ‘Sunki Tropical’ mandarin brought high yields of medium quality fruits, while the VKLxRPL-010 hybrid induced productive precocity, especially for ‘Sincora’ sweet oranges. Based upon these results, all tested scions grafted on ‘Red Rough’ lemon and ‘Santa Cruz’ Rangpur lime, followed by ‘Sunki Tropical’ mandarin are indicated for genetic diversification of groves, when planted at conventional density. On the other hand, the hybrid HTR-051 seems to have great potential for high density orchards, since it shows high yield efficiency and good quality of fruit.