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Thomas H. Yeager

Ilex vomitoria Ait. `Nana' root and-shoot growth increased as rate of fertilizer applied from a 6N-1P-3K solution increased from 0.5 to 2.5 g N/3-liter container during a 26-week experiment. Percentage of applied N, P, and Kin the plant and growth medium decreased as N applied increased. Dividing the fertilizer among one, two, or four applications per week resulted in similar use of applied N, P, and K. Shoot dry weights for the 0.5 g N/container treatment were less than for the Osmocote (18N-2.6P-10K) treatment (2.5 g N/container), but the percentage of applied N, P, and K in the plant and growth medium (55%, 42%, and 75%, respectively) was greater than for the Osmocote treatment (31%, 15%, and 27%, respectively).

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T.M. Gradziel and W. Beres

A single seedling exhibiting a semidwarf growth habit was found in an open-pollinated clingstone peach [Prunus persica (L.) Batsch] population. The growth habit was upright and open, with short, spur-like lateral branching. Tree size was about half that of its siblings as a result of shorter internodes. The total number of nodes on first-order branches was not significantly different from that on standard-sized trees. The semidwarf growth habit remained stable after vegetative propagation. Segregation in sexual progeny showed the trait to be highly heritable.

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Ronald L Perry*, Dario Stefanelli and Gail Byler

Trees of Gala were planted in 1994 on 18 rootstocks at the Clarksville Horticulture Experiment Station as one cooperating site of 26 North American sites organized by the NC-140 Regional Pome and Stone fruit rootstock committee. One tree each of seven rootstock treatments and two on B.9 and B.491 have died since establishment. Death has been caused by wind (brittle union) on most of the trees in replication one, on the western exterior of the plot which is exposed to strong wind. The most vigorous trees in this planting are those on V.1 and M.26 and least vigorous on M.27 and P.22. Cropping in 2003 was highest on Pajam 2, Ottawa 3 and M.9 NAKB 337, yielding an average of between 60 to 70 kg per tree. Cropping over the years has been highest on PJ.2, M.9 EMLA, and O.3. Cumulative yield efficiency in this plot is highest on P.16, followed by P.22 and B.491. Trees on M.26 are the least efficient over the years. Average fruit weight was highest in 2003 on V.1 and PJ.2. M.9 NAKB 337, the dominant international an national standard M.9 clonal rootstock is not as productive and as precocious as many other M.9 clonal stocks in this trial. After 10 years of evaluation, there appears to be no significant difference in cropping, cumulative yield, for `Gala' among the top eight rootstocks led by M.9 Pajam 2. M.9 NAKB 337 is not among the top eight rootstocks at this site. Pajam 2 is impressive from the view that while it is the top cropping stock, it is the rootstock in 2003 which also averaged the largest fruit. Among the M.9 clonal rootstocks, PJ 2 is also the most vigorous which for North American commercial apple orchards, has excellent commercial potential to withstand field and production stresses.

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Zhanao Deng, Brent K. Harbaugh and Natalia A. Peres

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Gregory A. Lang

Sweet cherries (Prunus avium L.) can be one of the most profitable tree fruits cultivated in temperate climates. While cherry trees grow naturally to relatively tall heights (≈35 ft [≥10 m]), new size-controlling cherry rootstocks similar to those used in high-density apple (Malus domestica Borkh.) orchards are now a reality. The Gisela (GI.) and Weiroot (W.) series from Germany, the Gran Manier (GM.) series from Belgium, the P-HL series from Czech Republic, `Tabel Edabriz' from France, and others of international origin are at various stages of scientific and field testing in North America, with some now being used for commercial fruit production. These stocks confer several advantageous traits besides vigor control, including precocious fruiting and high productivity. While these beneficial traits are exciting, serious problems also have been documented on occasion, such as small fruit size and tree decline. As many of these rootstocks are interspecific Prunus L. hybrids, might there be significant limitations for fruit quality and orchard longevity? What is known about their tolerance to various soil types and/or climatological stresses? What is known about their susceptibilities to pathogens and pests? Further, with the U.S. and worldwide orchard area planted to fresh-market sweet cherries already expanding to record levels throughout the 1990s and a time-honored agricultural tendency toward overproduction until grower profits are minimized (e.g., recent international apple markets), what might be the future impact of such precocious, productive rootstocks on sweet cherry profitability and sustainable production? This overview addresses these topics, providing some answers and some areas for future scientific investigation and industry discussion.

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Thomas H. Yeager

Multiple branched liners of llex vomitoria were greenhouse-grown in 3-liter containers with a common nursery medium and received either 2.5 g N surface-applied in 1 application as Osmocote (18N-2.6P-10K) or a total of 0, 0.5, 1,5 or 2.5 g N per container from a solution that contained N, P and K in a ratio of 6:1:3. The solution fertilizer was applied either 1, 2, 3 or 4 times per week with total N applied per container equally divided among individual applications, After 26 weeks, shoot dry weights were greatest for plants that received 2.5 g of N as either 2 soluble applications per week or as Osmocote applied once at the beginning of the experiment. Plants that received 1.5 g of N applied 4 times per week had similar shoot dry weights. Nitrogen uptake will be calculated to determine if 4 applications par week resulted in greater utilization than 2 applications par week or 1 application of Osmocote during the growing season.

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Miklos Faust and Howard J. Brooks

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Thomas Yeager, Claudia Larsen and Gisele Martins

Multiple branched liners of Ilex vomitoria Ait. `Nana' were greenhouse-grown in 3-L containers with a 2 pine bark: 1 Canadian peat: 1 sand substrate. Plants were fertilized weekly with a solution of 50 N, 10 P, and 30 K (mg·L–1) for either 5, 10, or 15 weeks. Then plants for each of the three fertilizer durations were fertilized weekly with a solution of either 50, 150 or 300 N, 10 P, and 30 K (mg·L 1) for an additional 15 weeks, at which time root and shoot dry weights were determined. A control group of plants was fertilized weekly with 300 N (mg·L–1) for 30 weeks. Shoot dry weight increased linearly as fertilizer rate or duration of fertilization increased. Root dry weights increased linearly as fertilizer duration increased while root dry weights were not different due to fertilizer rate. These data indicate that duration of fertilization is important in promoting root and shoot growth; however, the largest amount of root and shoot dry weight resulted from the highest N application rate (300 mg·L–1) for the longest duration (30 weeks).