William C. Olien
William C. Olien
The population of flower buds in a peach orchard do not all bloom at the same time, but instead expand to bloom stage over time as a cumulative normal curve. This relationship is similar to seed germination and other processes restricted between 0% and 100% of response. Frequent sampling of bloom development over all treatments to be compared is frequently not possible. Treatment means may be compared on a given day for differences in % bloom, but the opposite question of whether differences exist in time of 50% bloom cannot be answered. Transforming the % response axis to Probits allows comparisons of bloom time and duration. Probit transformation linearizes the cumulative normal distribution curve by converting the % response axis to units of standard deviation. Best fit of a line to data is optimized by the method of maximum likelihood (least squares regression is not appropriate). In an example study on peach, % of total flower buds at or past bloom (pistil exposed) was counted daily on tagged shoots in control trees. Percent bloom on trees treated with different chemical bloom thinning treatments were counted only when control trees reached 10%, 50%, and 90% bloom. Bloom data were converted to Probits and response lines for each treatment were graphed. On this basis, quantitative comparisons among treatments could be made along the time axis for a) time of 50% bloom and b) duration of bloom.
William C. Olien
Dormant application of soybean oil formulations (SBO) effectively thin peach flower buds and delay bloom. Alternatively, thinners applied at bloom, such as ammonium thiosulfate (ATS), must be applied before pollination is complete. Consistent thinning with ATS is complicated by bloom duration and weather at bloom. Overall, 1995 peach bloom in South Carolina was delayed and progressed rapidly from 20% to 90% bloom in 2 days. Under these conditions, we compared thinning response of control (untreated), ATS (2%) applied at 70% bloom, SBO concentrations (2.5%, 5%, 7.5%, or 10%) applied 3 weeks before bloom (WBB), and application time of 5% SBO (1, 2, or 3 WBB). SBO was not available for applications earlier than 3 WBB. Treatments were applied by hand gun to six replications of single-tree plots of Redhaven. ATS had no effect on fruit set, yield, or fruit size, contrary to normal bloom years. Flower bud death increased linearly from 8% to 28% with increasing rate of SBO. Delay in SBO application decreased bud death. SBO at 5%-10% rates caused minor delay of 50% bloom, did not effect bloom duration, and increased mean fruit weight over control. Maximum effect was achieved with 10% SBO, reducing fruit number/ha and firmness by 72% and 18% and increasing fruit weight and soluble solids by 67% and 5% from control, respectively. Results show the advantage of bud thinning with SBO during the dormant season in a short bloom duration year.
William C. Olien
Benefits of nimblewill (Ms = Muhlenbergia schreberi), a warm-season, perennial grass, as an orchard ground cover are: 1) it is not competitive with tree growth and 2) it reduces ring nematode (Cx = Criconemella xenoplax) soil population, even in the presence of a tree fruit host. Ms is difficult to establish in orchards in warm fruit-growing regions. In field studies, we found that Ms establishment was decreased by chemical mowing relative to seeding only. Successive years of reseeding at 22 kg seed/ha per year, mechanical mowing, and control of winter annuals gave best establishment of Ms in peach orchards. An orchard microplot study was established to evaluate effects of five Ms densities and two Ms sources on Cx population and on growth of `Redhaven'–Lovell trees (10 replications). Cx numbers were reduced hyperbolically in response to Ms density. Ms cover of 5 g dw/m2 (planted at 9 kg seed/ha) reduced Cx from 200 (control) to the accepted threshold of 50 Cx/100 cc soil. Maximum Cx reduction to 26 Cx/100 cc was obtained at 34 g dw/m2 Ms (planted at 40 kg seed/ha). Cx response to Ms density was not affected by Ms source.
William C. Olien and C. Patrick Hegwood
William C. Olien, C.P. Hegwood Jr and James M. Spiers
Muscadine (Vitis rotundifolia Michx.) vineyards can be difficult to establish due to poor vine growth or survival during the first year after planting. Effects of the planting hole (five types), root manipulation (three levels), and peat amendment (0% and 50%) on first-year growth were studied at two sites with different soil types: a sandy loam (well-drained) and a silty loam (moderately well-drained). The planting hole had the major effect at both sites; large holes (25 liters) shoveled with straight or angled sides resulted in more shoot and root dry weight and greater total root length than auger holes (21 liters) or small shovel holes (10 liters). Vine response to planting in a subsoil slot 0.5 m deep × 6 m long was similar to that in large holes in sandy soil and small holes in heavier soil. Root manipulation treatments had little effect on vine establishment. Root pruning at planting, with or without root separation, did not increase vine dry weight relative to an undisturbed root ball in either soil type, but total root length was increased by root pruning in the heavier silty loam soil. Peat amendment increased total root length in the sandy soil but not in the silty loam soil.
William C. Olien, Barbara J. Smith and C. Patrick Hegwood Jr.
William C. Olien, David C. Ferree and Bert L. Bishop
Nine apple rootstocks grafted with `Starkspur Supreme Delicious' were evaluated in 19 states over 9 to 10 years by the NC 140 Regional Project as a randomized complete block with 10 replications in each site. Effects on trunk cross-sectional area (TA), cumulative yield per tree (Yc), and cumulative yield efficiency (YEc=Yc/TA) were evaluated. Rootstock differences in mean potential (mean performance at the mean site) and environmental stability (slope across sites) were compared by analysis of rootstock performance within a site linearly regressed on mean performance of all rootstock in that site. MAC 24 had the highest mean potential of Yc and TA with lowest stability, giving this rootstock the highest Yc and TA in best sites, and lowest in poor sites. M.27 EMLA was the opposite, having low potential and high stability in Yc and TA. In YEc, M.27 EMLA and MAC9 had high potential and low stability, while OAR1, M.7 EMLA, and especially MAC 24 were the opposite. YEc of Ott.3 and M.26 were average in both respects. M.9 had high potential YEc with average stability. M.9 EMLA was unique in having both high potential and high stability of YEc.
William C. Olien, Joe G. Harper and Katherine Ashe
A Teaching Fruit-Garden Project was developed as a joint project between two classes in Horticulture and Agricultural Education to develop a teaching resource for college classes, area kindergarten to 12th grade (K–12) schools, and members of the community who were interested in fruit and edible landscaping. Our teaching goal was to develop a sense of involvement in course subject matter among students. The project was based on coordination of team activity, writing across the curriculum, and hands-on learning. Final product in the horticulture course was a proposal consistent with low maintenance; sustainable production principles, including choice of fruit species and cultivars; management plan; and a preliminary site plan. Final products in agriculture education were self-contained teaching modules for K–12 school teachers, including sample lesson plans, projects, and teaching materials. Students liked combining efforts between the two classes. They also liked the idea that their efforts contributed to an on-going service to the community.