This project evaluated the leaf and fruit nutrient content of two apple cultivars, Buckeye Gala and Aztec Fuji, on four dwarfing rootstocks, G.935, G.41, G.11 and M.9 NAKB T-337 in 2016 and 2017. The trees were planted in 2014 and produced their first commercial crop in 2016. The study was conducted in a commercial orchard located in Biglerville, PA. Six replicated samples of both leaves and cortical peels were collected from each of the rootstocks and cultivars in both years and analyzed by the Penn State University Agricultural Analytical Services Lab. Four replicated leaf samples consisting of leaves from current season’s growth were collected for plant sap analysis by Crop Health Labs in 2016 from both cultivars on the four rootstocks. In 2017 plant sap analysis samples were only collected for the Fuji trees on the four rootstocks. There was a significant cultivar x rootstock interaction for both leaf and fruit peel tissue analysis. All fruit peel nutrient levels were lower than corresponding nutrient levels in the leaf tissue. Leaf N was highest for both cultivars on G.41. Leaf P was lowest for both cultivars on G.11 rootstock Leaf Ca on Fuji/G.41 and Gala/G.11 were the lowest for the different rootstocks. Leaf nutrient levels for K, Ca and Mg were different by rootstock but there was no distinctive pattern of one rootstock being significantly higher or lower than another. Leaf N/Ca ratio was greatest on Fuji/G.41 and Gala/G.11 which potentially may result in greater susceptibility to bitter pit on these rootstocks. Bitter pit presence in 2016 was significantly higher for fruit from Fuji/G.11 than that on M.9T337, and G.935 while fruit from G.41 was similar. In 2016 on Gala and both cultivars in 2017 had no difference in percent fruit with bitter pit.
In summary, there does not appear to be any distinct trend showing consistent differences in nutrient uptake/accumulation in this study as influenced by rootstock. However, it should be noted that this was only a two year study with two distinctively different growing seasons. The 2016 growing season was characterized by unusually dry and particularly in the August through September time frame. Since Ca can only move in the tree via the xylem and through the xylem tissues lower levels of Ca probably explain the presence of bitter pit in the Fuji after storage in 2016. The 2017 growing season had more normal precipitation and no fruit showed any evidence of bitter pit.
Outreach at the Penn State Fruit Research and Extension Center field day July 11, 2018 reached many farmers and the results have been incorporated into the updated 2018 Penn State Fruit Production Guide.
Leaf analysis is an underutilized technique in orchards and generally is not used to sample specific root stock scion combinations. Sap analysis has not been used at all and is a new methodology in tree fruit production. This project will demonstrate the value and importance of the use of nutritional monitoring of orchards to reduce fertilizer inputs and as a tool to monitor fruit quality. Questions that can be answered are: 1) Are different root stocks are more efficient in nutrient uptake; 2) Can nutrient sap analysis be related to leaf analysis results; 3) Can cortical fruit peel analysis be related to both leaf and sap analysis. 4) If differences in nutrient uptake by root stock exists can root stock selection help reduce fertilizer applications and reduce contamination in Chesapeake watershed.
Apple rootstocks are the primary means of controlling tree size. Although the exact nature of the process is not completely understood many possible mechanisms have been suggested (Jackson, 2003). Several studies have shown that scion nutrient uptake and content can be influenced by rootstock (Crassweller & Ferree, 1984; Fallahi et al., 2013, Reighard et al., 2013)
The apple rootstock situation has changed dramatically in the last ten years. The introduction of the new Geneva series of rootstocks developed at Cornell University has resulted in changes in planting densities, training techniques and production systems (Fazio et al. 2013). The new rootstocks have shown the ability to alter gene expression in the scion, growth habit, root architecture (Jensen et al., 2010). Recently, Fazio et al. (2014) has also noticed difference in nutrient uptake and content of the rootstocks that can be determined through the existence of genetic markers.
Fruit quality is also influenced by nutrient content and uptake. Bitter pit which is a disorder due to low fruit calcium can severely affect fruit quality. It has been suggested that the incidence of the this disorder may depend upon the interrelationship of nitrogen, calcium, potassium and magnesium and samples of the apple fruit peel can indicate the potential for bitter pit development (Baugher et al., 2015). Korban and Swiader (1984) demonstrated that nutrient leaf analysis may also provide some indications of the potential for bitter pit susceptibility. A relatively new methodology of plant sap analysis has been utilized in orchards to help determine nutrient status of high density orchards (Scott, 2013) The purpose of this study is to look at nutrient levels of two cultivars, Aztec Fuji and Buckeye Gala, in a grower’s orchard that are planted on the new Geneva rootstocks G.935, G.41, G.11 and a standard dwarfing rootstock M.9 NAKB T-337.
The Hollabaugh Brothers Inc. orchard is located in Adams County at 545 Carlisle Rd., Biglerville, PA 17307. (www.hollabaughbros.com ). The orchard blocks to be used were planted in 2014 and consist of Aztec Fuji and Buckeye Gala on four different dwarfing rootstocks. Three are new Geneva rootstocks, G.935, G.11 and G.41. The other rootstock is the industry standard M.9 NAKB T337. There are the following number of trees on each rootstock that can be utilized Aztec Fuji – 1074 on G.935, 1026 on G.11, 624 on G.41 and 1325 on M.9 T-337. For Buckeye Gala there are 1121 trees on G.935, 1,100 on G.11, 1031 on G.41 and 1164 on M.9 T337. The trees will be divided up into 6 blocks and foliar and fruit peel samples will be collected from each block. Standard protocol of collecting leaf samples will be followed with collection occurring in early August. Cortical fruit peel samples will be collected approximately 3 weeks before anticipated harvest of each cultivar. Peel samples will consist of 3 cm diameter thin slices of the peel from the calyx end of 25 fruit. Leaf samples will consist of a composite sample from 25 trees each for a total of 50 leaves. All tissue samples will be dried prior to analysis. Analysis will be performed by Penn State University Ag. Analytical Service Lab ( http://agsci.psu.edu/aasl ). Nitrogen is analyzed by combustion with an Elementar Vario Max N/C analyzer, while P, K, Ca, Mg, Mn, Fe, Cu, B, Al, Zn, and S is done with acid digestion. Sap analysis will be performed by Crop Health Labs (http://crophealthlabs.com ). Twenty-five fruit from four replications will be collected. Fruit will be assessed for presence of bitter pit at harvest and stored in refrigerated storage for 40 days to be reassessed for development of bitter pit. An analysis of variance will be performed on all data and if it is significant mean separation tests will be utilized.
In the summer of 2016 trees located at the commercial orchard were selected base upon tree age and uniformity of growth and size. The cultivars were Aztec Fuji and Buckeye Gala all planted in 2014 and trained as tall spindles. Each cultivar was on M.9 NAKB T337, G.11, G.41 and G.935. Leaf samples were collected from Gala and Fuji on the four rootstocks for standard foliar analysis at PSU Ag Analytical Services Lab in late July in both years. Fruit samples from the same trees were collected approximately 3 weeks prior to estimated commercial harvest for each cultivar and placed into refrigerated storage for 90 days; removed and left at room temperature for 7 days when percent of fruit with bitter pit was determined. Nutrient analysis of leaf sap was collected from both cultivars in 2016 and from only the Fuji in 2017. Samples were collected at the same time as the fruit samples. These leaf samples were transported back to Penn State, the petioles were removed and the leaf blades shipped to NovaCrop by overnight air and the sap was extracted analyzed for nutrient concentration according to their proprietary methods. Data was analyzed by appropriate methods using SAS.
- Collected replicated foliar analysis samples of Gala and Fuji on the four rootstocks in early August of both years 2016 and 2017
- Collected fruit samples for storage and apple peel analysis for Gala in early August approximately 3 weeks before harvest
- Collected fruit samples for storage and apple peel analysis in late September approximately 3 weeks before harvest.
- Sap analysis samples for both cultivars were collected approximately 3 weeks before harvest in 2016 and for Fuji in 2017
- Storage samples were evaluated for bitter pit after 2 months of storage and 1 week after removal from storage
- Leaf and peel samples have been submitted to the Penn State Ag. Analytical Services Laboratory for nutrient level determination.
- Data for the two years was analyzed by appropriate techniques using SAS
Results: For the leaf and cortical peel tissue there was an interaction for N, P, K, Ca, Mg, B, and the ratios for N/Ca, K/Ca and K+Mg/Ca (Tables 1 & 2). Leaf N was significantly higher in leaves from both cultivars on G.41 rootstocks with no differences between the other rootstocks. For Fuji leaf P was highest on trees of G.935 and in Gala lowest on G.11 rootstocks. Leaf K levels were generally lower for all rootstocks on Fuji compared to results on Gala. The lowest mean leaf K for Fuji was on G.11 and for Gala was on G.41 rootstock. Leaf Ca and B levels for both cultivars was above the minimum suggested levels for all rootstocks with variation between rootstocks. Leaf N/Ca ratio for both cultivars varied by rootstock with the highest ratios for Fuji/G.41 and Gala G.11. K/Ca and K+Mg/Ca ratios were also variable by rootstocks.
Nitrogen peel nutrient levels in this study were lower than reported in the study by Baugher et al. (2017) with Honeycrisp from orchards that had low incidence of bitter pit. Peel Ca levels were also higher in this study than reported in the previous study. By cultivar peel Ca was lower from Gala trees in comparison to Fuji trees but there was no real discernable trend as influenced by rootstock (Table 2).
Sap nutrient analysis levels are only presented for the 2016 growing season.There were no differences in N levels for either cultivar, any rootstock or a significant interaction (Table 3). Similarly there was no difference between cultivars for %P, %Mg, K/Ca ratio or K+Mg/Ca ratio. The latter two ratio means showing high variability. There was a cultivar x rootstock interaction for %K, %Mg, %Ca, and all three nutrient ratios.
Evaluation of fruit samples collected in both 2016 and 2017 showed that only the Fuji in 2016 showed evidence of bitter pit after storage (Table 4). This season was characterized as being drier and warmer than the 2017 growing season and most likely explains the observed differences in the incidence of bitter pit. Neither leaf nutrient nor calyx peel tissue levels appeared to explain the differences in bitter pit incidence by rootstock.
We were unable to obtain samples for sap analysis on the Gala in 2017 and the results from the 2017 season for the Fuji were of questionable accuracy. Levels of the 2017 Fuji samples were considerably higher by a factor of almost ten and we do not believe they were accurate. Difficulty in securing the leaf samples for a sap analysis and the need to ship the leaves to a laboratory in The Netherlands make the use of this test unreliable and we do not recommend it for tree fruit.
The following are comments on the 2016 growing season. Fuji — Besides sunburn and a bit of BMSB damage, fruit quality was excellent. The 935s seemed like they cracked worse than the other stocks. That was interesting because they had much more fruit on than the other trees. The ground is weaker (and drier this season) where the 935s were located, so perhaps the trees were drier/weaker as well. (Note that the planting has the same soil type throughout – Arendtsveille gravelly loam).
Gala — Quality was excellent however fruit size was very small. Fruit size was inversely proportionate to the amount of fruit on the trees. The M9s set and carried the least fruit — and therefore had the nicest, largest fruit at harvest. The 935s were thinned “normally” for 3rd leaf gala trees and carried an appropriate crop load however the fruit was nearly unmarketable due to small size. Certainly a result of our drought.
It does not appear to be any distinct trend showing consistent differences in nutrient uptake/accumulation in this study as influenced by rootstock. However, it should be noted that this was only a two year study with two distinctively different growing seasons. The 2016 growing season was characterized by unusually dry and particularly in the August through September time frame. Since Ca can only move in the tree via the xylem and through the xylem tissues lower levels of Ca probably explain the presence of bitter pit in the Fuji after storage in 2016. The 2017 growing season had more normal precipitation and no fruit showed any evidence of bitter pit.
Education & Outreach Activities and Participation Summary
In May of 2017 we hosted a twilight educational meeting at Hollabaugh Brothers Orchards were the attendees were able to look at the study block. We had a presentation describing the study, why it was undertaken, and what the preliminary results showed from the 2016 growing season. We will also have poster presentation at the Penn State Fruit Research and Extension Center field day to be held on July 11, 2018. The poster and discussion will relate the findings from this study to the attendees. Typical attendance at this semi-annual field day is usually in the neighborhood of 125 commercial fruit growers and related industry members.
Growers were made aware of the project and the possibility of apple rootstocks influencing nutrient uptake at a twilight meeting in May 2017 where they viewed the plantings. We had a discussion about why rootstocks could influence nutrient uptake and potential impacts on fruit quality. One of the important facts stressed was the importance of correct methodology in collecting leaf samples for nutrient analysis. We stressed the need for correct timing for leaf samples and the collection of the samples. Tree fruit leaf samples should be collected from mid-July to mid-August. Samples should be collected from uniform representative trees in a block. Leaf samples should be collected from a single cultivar on a single rootstock. Mixing cultivars in a single sample does not give a good representation of cultivar differences
The major stumbling block to this study was the fact that the planting was not set up as a true replicated study. While we had multiple samples the root stocks were not replicated within a block, but rather set up in blocks by rootstock and cultivar and the replications were taken within the blocks. This complicated the statistical analysis of the results. Sap analysis, while useful for vegetable crops during the active growing phase of the plants’ growing season is not very amenable to sampling tree fruit crops towards the end of the season. Additionally, the need to ship the samples overseas complicates the process and we believe lead to erroneous data in 2017. Sap analysis may eventually prove useful once the logistics of delivering the tissue to the analysis lab can be simplified.
I also believe that a study like this needs to be carried out over more than two growing seasons. This is especially true when dramatic differences can occur between one season and the next. A minimum of 3 to 5 years would be a better sampling period to help reduce the seasonal variability; unfortunately due to time limitations by the funding source we were limited to two year projects.