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Terence L. Robinson and Warren C Stiles

A field experiment was established in 1992 with `Empire' apple trees on either M.7 or M.9 rootstock. Preplant fertilization with NPKB plus lime compared to the lime only control did not increase tree growth during the first 4 years, but did increase cumulative yield (10%) and average fruit size (7%). The addition of annual applications of ground-applied NKB after planting increased total shoot growth 17%, as well as yield (26%) and fruit size (14%) compared to the lime only control. Trickle irrigation significantly increased trunk cross-sectional area (17%), shoot growth (16%), yield (18%), fruit size (5%), and yield efficiency (7%). The interaction of ground fertilization and trickle irrigation showed that trickle irrigation increased the benefits of ground applied fertilizers. Without trickle irrigation, ground-applied fertilizers increased shoot growth only 6% and yield 14% compared to the unfertilized controls, but, with the addition of trickle irrigation, the ground-applied fertilizers increased shoot growth 21% and yield 21% over the irrigated but unfertilized control. Ground fertilization increased yield efficiency and fruit size by the percentage by whether or not trickle irrigation was present. Fertigation gave similar results as the trickle plus ground fertilizer treatment on tree growth, yield, fruit size, and yield efficiency. Our results indicate that trickle irrigation in the eastern United States can improve tree growth, yield, and fruit size in the first few years after planting. The addition of ground-applied fertilizer or fertigation can improve tree performance even more. However, in the humid New York climate, there does not appear to be a significant benefit from injecting the fertilizer into the trickle water compared to applying the fertilizer on the ground.

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Ian A Merwin and John A. Ray

Temporal and spatial combinations of tree-row weed suppression treatments were evaluated during 5 years in a New York apple (Malus domestica Borkh. cv. Imperial Gala on Malling 26 rootstocks) orchard planted in Apr. 1991, and provided with trickle irrigation. Twenty-eight factorial treatment combinations [0, 2, 4, and 6 m2 weed-free areas (WFAs); and May, June, July, August, May + June, June + July, May + June + July, and June + July + August weed-free times (WFTs)] were maintained from 1991 to 1995 by postemergence paraquat herbicide applications in tree-row strips. Trunk cross-sectional area (TCA) growth and yield were monitored annually, and few differences were observed as WFA increased from 2 to 4 to 6 m2 per tree. However, WFT substantially influenced TCA, fruit production, and yield efficiency. Early summer WFTs increased TCA during the first two growing seasons, compared with late summer treatments. When trees came into production in 1993-94, yields increased as the duration of WFT increased, but where similar periods of WFT had been established later during the growing season, annual yield, cumulative yield efficiency, and the ratio of crop value to weed-control costs were all reduced. Groundcover species distribution was evaluated each year in September, and graminaceous weeds were more prevalent in the early and midsummer WFTs, while herbaceous broadleaf weeds dominated in the August treatments. A quadratic model regressing cumulative yield efficiency on WFTs grouped into 30-, 60-, and 90-day categories showed that efficiency peaked between 60 and 90 days of WFT. It appeared that timing of weed suppression may be as important as the area of suppression beneath trees in comparable apple orchards, that early summer weed control was especially important for newly planted trees, and that drip irrigation allowed reductions in the area and amount of tree-row herbicide applications, without significant losses in apple tree growth or crop value.

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Kevin R. Day and R. Scott Johnson

Minimal dormant pruning after the first and second growing seasons, followed by standard pruning thereafter, improved total tree yield in the 3rd, 4th, and 5th years after planting. Trees that were pruned in accordance with standard local practice had ≈50% yield compared to minimally pruned trees in years 3 through 5. Fruit from minimally pruned trees was sgnificantly smaller, but mathematical adjustment of crop load indicated that overall yield efficiency was improved in the 3rd and 4th years for trees receiving minimal pruning.

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Esmaeil Fallahi, Brenda R. Simons, John K. Fellman, Mark A. Longstroth, W. Michael Colt, and Delmer O. Ketchie

Twenty-six strains of `Delicious' apple (Malus domestica Borkh.) were evaluated over several years for growth, yield, and fruit quality at harvest and after 6 months of storage. `August Red', `Rose Red', and `Sharp Red' had larger trunk cross-sectional area (TCSA) 3 and 18 years after planting compared to most other strains. `August Red' and `Starking' had larger TCSA and cumulative yield. `Apex,' `Improved Ryan Spur', `Silverspur', `Starkrimson', and `Wellspur' were also among strains with high cumulative yields and yield efficiencies. `Hardi-Brite Spur' and `Red King Oregon Spur' had moderately high yields and small TCSAs, thus, high yield efficiencies. `Atwood', `Hardispur', `Imperial', `Improved Ryanred', `Starkspur Supreme', and `Topred' had low cumulative yields. `Ace' and `Improved Ryanred' had low yield efficiencies. `Ace', `Imperial', `Red King Oregon Spur', `Rose Red', `Starking', and `Wellspur' had heavier fruit, while fruit weight in `August Red', `Hardispur', and `Starkrimson' was lighter than that in most other strains. `Redspur' and `Starkspur Supreme' had the largest length to diameter (L/D) ratios. `Early Red One' had a similar red skin color rating as `Rose Red.' The red skin color rating of `Early Red One' was significantly higher than that of all other strains. `Hi-Early', `Improved Ryanred', `Redspur', and `Starking' had the poorest skin color ratings. `Hardispur', `Nured Royal', `Silverspur', and `Starkrimson' had high soluble solids concentrations (SSCs) at harvest and after storage. `Early Red One', `Imperial', `Improved Ryan Spur', and `Red King Oregon Spur' had lower SSCs at harvest and after storage. Fruit of `Apex' and `Redspur' had relatively high firmness at harvest, while `Hardispur', `Silverspur', `Starkrimson', and `Starkspur Supreme' had firm fruit at harvest and after storage. `Hardi-Brite Spur' had the softest fruit after storage, and fruit from `Rose Red' had a lower firmness than most other strains at harvest and after storage. Considering cumulative yield, yield efficiency, or some quality parameters, `Apex', `Classic Red', `Improved Ryan Spur', `Red King Oregon Spur', `Silverspur', and `Wellspur' had satisfactory overall performance. Strains are also suggested for planting depending on the market situation and the demand for a particular quality factor. `Hardispur' and `Sturdeespur' (Miller) are not recommended for planting under climatic conditions similar to those of this experiment.

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C.G. Embree, B.H. Lesser, and A.D. Crowe

The 30 apple (Malus domestica Borkh.) rootstock candidates selected for cold hardiness, known as the Kentville Stock Clone (KSC), with `McIntosh' and `Delicious' as scion cultivars, were compared at 11 years of age for tree size, weight, fruit yield, and crop efficiency under field conditions. Trunk cross-section area and tree weight were highly correlated. Tree size was similar for the two cultivars in most cases and ranged in size from semidwarf to very vigorous. Cumulative yield efficiencies varied by nearly two-fold and were not correlated with tree size. The most efficient rootstocks were KSC 28, KSC 7, and KSC 6 in the semidwarf, semivigorous, and vigorous size classifications, respectively.

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David C. Ferree

The apple (Malus ×domestica Borkh.) cultivars Starkspur Supreme Delicious and Melrose were planted in 1987 on eight apomictic apple rootstock selections made in Germany by Dr. Hanna Schmidt and on M.7. Selections 2 [M. hupehensis (Pamp.) Rehd. parentage] and 8 [M. sieboldii (Regel) Rehd. parentage] were similar to M.7 in precocity, cumulative yield per tree, and yield efficiency, while the other selections with M. sargenti Rehd. in their parentage were slower to flower and had lower yields and yield efficiencies. Selections 2 and 8 tended to result in larger trees than M.7, while the selections with M. sargenti parentage were generally similar to M.7 in size. Except for trees on M.7 and selection 2, `Starkspur Supreme Delicious' developed more severe symptoms of internal bark necrosis (IBN) than did `Melrose', which normally does not show IBN. However, `Melrose' showed IBN symptoms on selections with M. sargenti parentage. IBN symptoms were positively correlated with leaf Mn concentrations. Influence of rootstocks on other nutrient elements, although significant, were small compared to the effect on Mn. A significant interaction occurred between cultivar and rootstock in their effects upon branch morphology, mostly because fewer flowering spurs and more vegetative spurs were observed on `Melrose' than on `Starkspur Supreme Delicious' when grafted on Selection 2. These apomictic selections offered no advantage over M.7 as rootstocks for apples.

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Cheryl R. Hampson, Anita N. Azarenko, Rebecca McCluskey, and Jeffery Olsen

Many deciduous tree fruit species have a light requirement for floral induction. Floral induction of hazelnut has been reported to occur through the end of May into July. At the end of May, less than 5% full sun reaches the base of the canopy in a mature hazelnut orchard. Leaf area density was estimated to be 7.6. Six levels of shade (0, 30, 47, 63, 73, or 92%) were imposed on caged 7-year-old hazelnut trees (Corylus avellana L. cv. Ennis) to determine effects of shade on yield and nut quality. Shading reduced yield of nuts per tree from 3.43 kg in 0% shade to 0.62 kg in 92% shade and yield efficiency from 70.2 g/cm2 in full sun to 18.3 g/cm2 in 92% shade. Yield and yield efficiency decreased substantially in 30% shade. When shade exceeded 47%, nut and kernel size decreased sharply, but % kernel increased slightly. In comparison to trees in full sun, shaded trees had a higher incidence of moldy or shrivelled kernels and a lower incidence of blanks.

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B.H. Taylor, D. Geisler-Taylor, and F. Lenz

Beginning in 1986 in Bonn, trees growing in 120 liter lysimeters spaced 2.0 × 3.4 m apart were trained to either “V” - or spindle-shaped canopies. During the 4th and 5th leaf half of the trees in each training form were covered with shade fabric to reduce insolation to 42% of overhead PAR. In the 4th leaf both canopy shapes produced 26 mt apples/ha (1470 trees/ha, basis) in full sun, and shading reduced yields by 23%. But the 5th leaf yields reached 54 and 39 mt/ha under full sun in the “V”- and spindle-shaped canopies, respectively; furthermore the “V”-shaped trees under shade fabric had 25% greater yield efficiency than the spindle in full sun whereas the spindle trees under the same shade had 41% less yield efficiency than those in full sun. These differences in yield could be partially explained by differences measured in the pattern of distribution of shoots, wood and fruit in the canopies caused by tree training. Training to the “V”-shape increased dry matter partitioning to fruit on the shaded trees at the expense of the stem fraction in contrast to the opposite effect on spindle trees.

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Esmaeil Fallahi, W. Michael Colt, Bahar Fallahi, and Ik-Jo Chun

Tree fruit rootstocks are used to influence precocity, tree size, fruit quality, yield efficiency, mineral uptake, and to withstand adverse environmental conditions. In this paper, we will briefly discuss the history and literature of apple (Malus domestica) rootstocks and their effects on scion tree growth, yield, fruit quality, leaf mineral nutrition, and photosynthesis. Then, the results of our long-term study on the effects of rootstocks on tree growth, yield, fruit quality and leaf mineral nutrition, and one season of photosynthesis measurement in `BC-2 Fuji' will be presented and discussed. In this study, `Fuji' trees on `Malling 9 NAKBAT337' (M.9) rootstock had the smallest trunk cross-sectional area (TCA), highest yield efficiency, and were the most precocious followed by those on `East Malling-Long Ashton 26' (M.26 EMLA) and `East Malling-Long Ashton 7' (M.7 EMLA). Trees on M.7 EMLA often had larger fruit with less color than those on M.9 and M.26 EMLA. Trees on M.7 EMLA frequently had greater leaf K than those on other rootstocks. Trees on M.26 EMLA always had greater leaf Mg than those on other rootstocks. Leaves from the current terminal shoots (CTS) of trees on M.9 had higher net photosynthesis and transpiration than those on M.7 EMLA rootstock during 1998 growing season.

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Raymond L. Granger, Shahrokh Khanizadeh, and Yvon Groleau

In 1988 a randomized complete block design with five blocks was used to evaluate the performance of four cultivars (`Empire', `Cortland', `Summerland McIntosh' and `Lobo') grafted on four rootstocks {Budagovsky(Bud.)9, Malling(M.)7,Ottawa(O.)3 and Malling Merton(M.M.)111}. The sixteen cultivar-rootstocks combinations were planted randomly at 2.5m apart in the row. The distance between the rows was 5m. The trees have been trickle irrigated every year and came into bearing in 1990. On the basis of cumulative yield efficiency the combination `Lobo'/O.3 was significantly superior to all others. The second best performer was `Empire'/O.3 followed by `Lobo'/Bud9. `Empire'MM.111, `Summerland McIntosh'/M.M.111, `Cortland'/M.M.111, `Summerland McIntosh'/M.7 and `Empire'/M.7 had the least cumulative yield efficiency. Generally the cultivar `Lobo' was superior to others and O.3 was the best rootstock followed by Bud.9, M.7 and M.M.111.