Curt R. Rom
As part of the NC-140 rootstock evaluation trials, `Starkspur Supreme Delicious' on 18 rootstocks planted in 1984 were evaluated for growth and pruning requirement. After 9 seasons, trees on the P.22 produced the smallest trees, 1.1 m width and 1.7 m height. The stocks P.16, P.2 and Bud.9 produced trees 2.0-2.2 m wide and 2.1-2.6 m tall. Trees on MAC.39, C.6, MAC 1, M.26 EMLA P.1, BUD.490, M.7 EMLA, CG.24, and domestic seedling were 2.9-3.4 m wide and 3.7-4.3 m tall. The largest trees were on P.18 and M.4; 3.6 m wide and 4.2 m tall. Dormant pruning time in two seasons significantly increased at an exponential rate with increasing tree width and height. An asymptote for maximum pruning time had an x-axis intersection at approximately 2.7 m tree height. Pruning time per tree significantly increased in a linear manner with increasing trunk cross section. When pruning time was calculated on a per hectare basis, trees planted at 1460 to 2000 trees/ha required less pruning time than when planted at ≤ 750 tr/ha or ≥ 4000 tr/ha. Trees on P.16, P.2, Bud.9 and C.6 required the least pruning per unit of fruit production.
Curt R. Rom
To enhance the opportunities for students to access information and the instructors of a large, general plant science class, “Virtual Classroom” concepts using computers resources were implemented. The Virtual Classroom uses three computer resources: 1) a closed subscription LISTSERV for the extramural class discussions, 2) electronic mail for homework assignment and submission, and 3) a World Wide Web Internet homepage for the course. In a large, introductory-level class, student–teacher interaction can be limited. The size of the class and the content may inhibit questioning and discussion among the class participants. The LISTSERV allowed for questions to be posed by students at their leisure and facilitated discussion among students and the instructor outside of the confines of the class meeting. The LISTSERV also allowed instructors to to respond to the students by referring questions to “experts” on a particular subject. Using e-mail for homework assignment and submission was useful for tracking when student read assignments and submitted completed assignments. Electronic assignment grading and returning was paperless and easy for instructors to maintain. The homepage provided students with a permanent syllabus, lecture outlines, homework assignment descriptions, and study aids. Additionally, from the homepage students were able to send e-mail to instructors and search library databases and other electronic databases. Experiences from the instructors using these computer resources will be presented and discussed.
Curt R. Rom
Current practices of fertilizer management, potential problems, and paths for fertilizer management research were discussed. Apple nutrition management in the humid southern regions of the U.S. is typically challenged by several factors such as inherently low soil pH, variable soil chemistry, and irregular precipitation. Some literature and personal experiences with orchard replant conditions and fumigation, fertigation, fertilizer delivery system, and time of fertilizer application were reviewed. On replant sites, fumigation and liming significantly improved tree survival and growth in the first 5 years. Fertigation with ammonium nitrate significantly lowered soil pH in the root zone compared to top dress applications. Using calcium nitrate resulted in less pH reduction. Results of studies of autumn application of N fertilizers have been mixed, with reports of no, decreased, or increased effects on fruit set, yield, and growth. Studies with size-controlling rootstocks indicate additional need to study the uptake of Mn and related Mn toxicity. Precocious rootstocks with high early yields have resulted in foliar K levels approaching deficiency within the first 10 years of production. Indications are that high-density orchards may have additional requirements for K fertilizers.
Curt R. Rom
Shoot growth `Starkspur Supreme Delirious' on 10 different rootstock was measured on 3-, 4- and 6-year-old trees at weekly intervals from budbreak until terminal bud formation. Spur density, spur development, and extension shoot leaf area development were measured in September. Growth rate was analyzed by regression against chronological time and accumulated growing degree days using linear and nonlinear statistics.
Rootstock affected shoot length, leaf number, leaf area, leaf size, leaf dry weight/leaf area and internode length. Trees on M.4, M.7 EMLA, P-1 and seedling had the longest shoots and highest shoot growth rate. Trees on P16 had least leaves and leaf area per shoot and smallest shoot leaves. Leaf dry wt./area were negatively correlated to leaf size. Typically, trees with shortest shoot length and smallest internode length had greatest spur density. Rootstock affected both rate and duration of shoot growth. Shoots on trees with P22 and P2 rootstocks grew for the shortest duration while trees on M.4 and M.7 EMLA grew for the longest period.
Curt R. Rom*
In a required introductory horticulture course during a 5-year period, students received early progress grades 1/3rd of the way through the course reflecting 20% of the possible points to be awarded in the class. It was thought that student knowledge of their grade performance may result in changes in behavior and class performance. The early progress and final grades both had a bell-shaped distribution with 45% and 48% of students receiving grades better than “C” for early progress and final grades, respectively. There was a significant although low correlation between early progress grades and final grades for the course (r 2 = 0.58). About 50% of the students received a final grade equal to the early progress grades, and 27% received grades higher than the early progress grades. The greatest change in performance were students who received a “D” early progress grade; 60% of those students improved their final grade. Nearly 25% of the students received final grades lower than the early progress grades. Of students receiving failing early progress grades (12%), nearly 60% withdrew from the course and only 10% received passing final grades.
Ken Kupperman and Curt R. Rom
The effect of soil preplant strategies winter solarization and methyl bromide fumigation were compared to a non-treated control on apple tree growth. Treatments were applied in the fall after removal of an existing orchard with spring planting of 'Jonee' and 'Smoothee Golden Delicious' on M.26 EMLA rootstock. Soil fumigation significantly increased shoot length in first year, trunk cross-sectional area increase during two seasons, and bloom and set in second year. The control and winter solarization treatments were similar in all responses. Foliar Mn concentrations were significantly lower with fumigated trees in second years compared to other two treatments, which were similar.
Curt R. Rom and Bruce Barritt
The role of spur leaves in bud and fruit development on two spur-type `Delicious' apple strains (Malus domestica Borkh.) and factors affecting spur development were studied. Reducing spur leaf area on vegetative spurs in August reduced the number of spurs that flowered the following year but did not affect flower size. On spurs that did flower, leaf area reduction the previous year did not influence leaf number or area, but the bourse shoot leaf area was reduced. Spur bud diameter, leaf area, size, specific leaf weight (SLW), and leaf dry weight were larger on 2-year-old vegetative spurs than on 1- or 3-year-old spurs. Within each age section of a limb, spur leaf number, area, size, SLW, and bud diameter decreased from the apical to basal positions on the limb. Flower number did not vary within a limb section, but fruit set was lower on the most apical and basal spurs compared to midshoot spurs. Fruit size was largest at the apical end of each limb section and was smallest at basal positions. These relationships were not affected by strain, tree age, or orchard location. Summer pruning at 30 days after bloom tended to increase leaf number, area, size, and spur length compared to unpruned trees or pruning later in the season but did not influence spur bud diameter.
Bryan Blackburn and Curt R. Rom
The effects of six freestanding training systems (Open Center, Untrained, 2-Scaffold V, 4-Scaffold V, Leaning V, and Central Leader at tree densities of 161, 161, 245, 375, 375, and 300 trees/acre, respectively) on yield and tree growth of `Redhaven' on Lovell rootstock were evaluated. Open-center and untrained trees were largest and had greatest yields per tree. The 2-scaffold V had the greatest production in kilograms per acre. Early productivity was related to tree density and pruning severity, not tree size. Training systems had no effect on fruit size.