Fraser fir [Abies fraseri (Pursh) Poir.] and Norway spruce [Picea abies (L.) Karst.] were grown in seven vegetation management programs ranging from 100% cover of grass-dominated vegetation to bare soil on opposing north and south aspects. Concentrations of 13 nutrients were determined at three growth stages during 2 years: active terminal growth, cessation of terminal expansion, and dormancy. Aspect did not affect nutrient concentrations. Vegetation management programs bad a significant impact on nutrient concentration for both species. Nitrogen, Ca, B, Fe, and Mn concentrations during dormancy were negatively correlated with herbaceous biomass. In contrast, N during active growth and P and Mg concentrations during all stages were positively correlated with herbaceous biomass. Vegetation management only affected the seasonal trend of Mo. Seasonal trends varied by nutrient in both species.
Stuart L. Warren, C. Ray Campbell and Walter A. Skroch
F.S. Davies, M.W. Fidelibus and C.A. Campbell
An experiment was conducted to determine if gibberellic acid (GA; ProGibb, Abbott Labs) can be mixed with Aliette or Agri-Mek and oil to reduce application costs, without reducing GA efficacy, and if Silwet and Kinetic adjuvants enhance GA efficacy. Five tank mixes were tested along with a nonsprayed control. The tank mixes included: 1) GA, 2) GA + Silwet, 3) GA + Kinetic, 4) GA + Silwet + Aliette, and 5) GA + Silwet + Agri-Mek + oil. All compounds were applied at recommended concentrations. In September, ≈24 L of each tank mix was applied with a hand sprayer to mature `Hamlin' orange trees [Citrus sinensis (L.) Osb.] on sour orange (Citrus aurantium L.) rootstock. Peel puncture resistance (PPR), peel color, and juice yield (percent juice weight) were evaluated monthly between Dec. 1997 and Mar. 1998. On most sampling dates the fruit of treated trees had higher PPR and were less yellow in color than fruit from control trees. However, in Jan., fruit treated with GA + Silwet and GA + Kinetic had greater PPR than other treatments. In Feb., fruit treated with GA + Silwet + Agri-Mek + oil had the lowest PPR. The effect of the different tank mixes on juice yield was usually similar to the effect of the tank mixes on PPR and peel color. On 8 Jan. 1998, fruit from trees treated with GA alone yielded significantly more juice than fruit from control trees. On 24 Feb. 1998, fruit from trees treated with GA alone yielded more juice than fruit from the other treatments. Thus, GA efficacy is generally not reduced by these tank mixes, nor improved by adjuvants.
F.S. Davies, M.W. Fidelibusa and C.A. Campbell
Gibberellic acid (GA) applied in late summer or fall delays subsequent loss of peel puncture resistance (PPR) and development of yellow peel color in many citrus cultivars. Our objective was to determine the optimal time to apply GA for increasing juice yield of `Hamlin' sweet orange [Citrus sinensis (L.) Osb.]. Mature trees on sour orange (Citrus aurantium L.) rootstock were sprayed with ≈24 L of a solution of GA (45 g a.i./ha) and organo-silicone surfactant (Silwet, 0.05%). Trees were sprayed on 26 Aug., 9 Sept., 2 Oct. (colorbreak), or 13 Oct. 1997, or nonsprayed (control). Peel puncture resistance, peel color, and juice yield were evaluated monthly between Dec. 1997 and Mar. 1998. Fruit from trees sprayed with GA had peels with higher PPR and less yellow color than fruit of control trees for most of the harvest season. The effect of GA on PPR and peel color lasted about 5 months. Juice yield was usually numerically greater for GA-treated fruit than for nontreated fruit. Fruit treated with GA at color break had significantly greater juice yield when harvested in late February than fruit from control trees. Thus, GA applied at color break appears to be the most effective time for enhancing peel quality and juice yield of `Hamlin' oranges.
M.A. McKellar, D.W. Buchanan, Dewayne L. Ingram and C.W. Campbell
Freezing tolerance and the lethal freezing temperature were determined for detached leaves of avocado (Persea americana Mill.) by either electrolyte leakage or visual appearance of browning. Leaves from field-grown trees of `Gainesville', `Booth8', and `Winter Mexican' in both Gainesville and Homestead, Fla., were evaluated. All cultivars in both locations survived ice formation in their tissue. Leaf tissue had a temperature limit (lethal freeze temperature) at and below which the tissue died. The lethal freezing temperature varied from -5.1 to -9.3C, depending on time of year and location. The lethal freeze temperature for a cultivar decreased over the fall and winter as temperatures decreased. Leaves of `Booth-8' and Winter Mexican' decreased 2.5 and 1.5C, respectively, in Homestead from 13 Nov. 1982 to 5 Feb. 1983. The plants growing at the lower temperature location (Gainesville) had lower lethal freeze temperatures. Leaves of `Gainesville' had a lethal freeze temperature of - 9.3C from trees at Gainesville and - 7.8C from trees at Homestead.
Benjamin L. Campbell, Robert G. Nelson, Robert C. Ebel and William A. Dozier
For most grocery stores, external quality standards require that premium mandarins be orange, unblemished, and large. Thus, for consumers to differentiate among the premium mandarins on any dimension other than price, additional positioning attributes must be evaluated. This study considered consumer preferences for price ($2.18/kg, $4.39/kg, or $15.41/kg), packaging (1.36 kg of loose fruit, 1.36-kg bag, 2.27-kg box, or 0.23-kg clamshell with peeled fruit sections), type of mandarin (clementine, satsuma, tangerine), shelf life from the day of purchase (3, 14, or 31 days), and vitamin C content (with or without a label stating high in vitamin C). A conjoint survey was conducted in four grocery stores located in Birmingham and Montgomery, Ala. In total, 289 respondents used a 7-point intention-to-buy scale to rate photographs of 16 product profiles. Six market segments were identified, based on maximal similarity of preferences within each segment and maximal differences between segments. A simulation was conducted of the effect that an introduction of peeled-and-sectioned satsumas would have on the market share and gross revenue of other mandarins. This product showed great potential, but should be offered in a product mix that includes the loose form as well. Labeling for vitamin C was preferred by all segments, but did not contribute much to the intention-to-buy rating. Awareness and recognition of satsumas needs to be addressed in promotional campaigns. The longest shelf life was the first choice of almost half the respondents.
Robert G. Nelson, Benjamin L. Campbell, Robert C. Ebel and William A. Dozier Jr.
This article reviews the results of 5 years of marketing research on Alabama satsumas and makes recommendations for future progress. Although there are only 28 ha of satsuma orchards in production in Alabama at this time, there are a number of encouraging developments that suggest considerable potential for expanding the industry such as microsprinkler freeze protection, new early-maturing and cold-tolerant varieties, contract sales through the Farm-to-School Program, and rising demand for premium mandarins. Prospects for the industry marketing effort are considered from the perspectives of analyzing marketing opportunities, identifying market segments, selecting attractive target markets, designing marketing strategies, planning marketing programs, and managing the continuing marketing effort. A number of distinct consumer segments have been identified, including one that prefers fruit that is still slightly green and another that prefers a longer shelf life. A peeled-and-sectioned product also appears to have considerable market potential. Name recognition is still a problem as is insipid flavor from fruit that is marketed beyond its optimal ripeness. Needs for the future are detailed and include the needs of the commodity (freeze protection and expanded acreage), the needs of the market (consistency and quality), the needs of the product (quality standards and consumer awareness), the need for and the needs of a brand (recognition and equity potential), the needs of an organization (cooperation and leadership), and the needs of the industry (processes for building equity, forestalling competition, reducing supply shocks, and attracting investment).
G.S. Miner, E.B. Poling, D.E. Carroll, L.A. Nelson and C.R. Campbell
Annual-hill strawberry (Fragaria ×ananassa Duch.) production with black plastic mulch and drip irrigation is gaining popularity in North Carolina. Two experiments (E1 and E2) were conducted on a Wagram loamy sand (Arenic Kandiudult) in 1992 and on a Norfolk sandy loam (Typic Kandiudult) in 1993 to investigate the effects of fall-applied N and spring-applied N and K on `Chandler' strawberry yield and fruit quality. E1 treatments included factorial combinations of banded fall-applied N (0, 34, and 67 kg·ha-1) and drip spring-applied N (0, 0.19, 0.37, 0.56, and 0.75 kg·ha-1·d-1 and 0, 0.37, 0.75, and 1.12 kg·ha-1·d-1 in 1992 and 1993, respectively). E2 treatments included combinations of drip spring-applied N (0.56, 1.12, 1.68, and 2.24 kg·ha-1·d-1) and K (0.46, 1.39, and 2.32 kg·ha-1·d-1 and 0, 0.75, 1.49, and 2.24 kg·ha-1·d-1 in 1992 and 1993, respectively). There were no significant interactions among main effects for any of the measured variables. Market yield maximized with total N at ≈120 kg·ha-1 with one-half banded in the fall and the remainder drip-applied in the spring. Fruit firmness decreased with increasing N rate. Fruit pH and concentrations of total acids and soluble solids were not affected by N treatments, but soluble solids increased as the harvest season progressed. Plant crown number was not affected by N treatment but crown yield increased with N rate similar to market yield. There was no response to drip-applied K for any variable in either year. Based on soil test, fall-applied K (broadcast-soil incorporated) met the K requirements both years.
Benjamin L. Campbell, Robert G. Nelson, Robert C. Ebel, William A. Dozier, John L. Adrian and Brandon R. Hockema
Satsuma mandarins (Citrus unshiu) have been produced intermittently along the Gulf Coast for over a century. However, very little is known about the market potential for this citrus fruit in today's consumer markets. This study evaluated consumer preferences for seven external attributes over a range of levels: price ($1.07, $2.18, or $4.39/kg), color (green-yellow, yellow-orange, or orange), size (5.08, 6.35, or 7.62 cm in diameter), seediness (0, 3, or 7 seeds), blemishes (0, 1.91, or 3 cm in diameter), production region label (Alabama or U.S.A.), and organic production (yes or no). Consumers from grocery stores in nine cities in Alabama and Georgia were asked to evaluate 20 photographs of various combinations of these attribute levels using a seven-point intention-to-buy scale. 605 useable surveys were collected and a conjoint analysis was conducted to determine the strength of preference for the attribute levels and the relative importance for attributes. Three consumer segments were identified by cluster analysis of strengths of preferences: the no-blemish segment (37% of sample), the price-sensitive segment (23% of sample), and the no-seeds segment (41% of sample). A multinomial logit analysis identified several demographic, socioeconomic, and usage variables as significant determinants of segment membership.
R.C. Ebel, B.L. Campbell, M.L. Nesbitt, W.A. Dozier, J.K. Lindsey and B.S. Wilkins
Estimates of long-term freeze-risk aid decisions regarding crop, cultivar, and rootstock selection, cultural management practices that promote cold hardiness, and methods of freeze protection. Citrus cold hardiness is mostly a function of air temperature, but historical weather records typically contain only daily maximum (Tmax) and minimum (Tmin) air temperatures. A mathematical model was developed that used Tmax and Tmin to estimate air temperature every hour during the diurnal cycle; a cold-hardiness index (CHI500) was calculated by summing the hours ≤10°C for the 500 h before each day; and the CHI500 was regressed against critical temperatures (Tc) that cause injury. The CHI500 was calculated from a weather station located within 0.1 km of an experimental grove and in the middle of the satsuma mandarin (Citrus unshiu Marc.) industry in southern Alabama. Calculation of CHI500 was verified by regressing a predicted CHI500 using Tmax and Tmin, to a measured CHI500 calculated using air temperatures measured every hour for 4 winter seasons (1999-2003). Predicted CHI500 was linearly related to measured CHI500 (r 2 = 0.982). However, the slope was a little low such that trees with a CHI500 = 400, near the maximum cold-hardiness level achieved in this study, had predicted Tc that was 0.5 °C lower than measured Tc. Predicted and measured Tc were similar for nonhardened trees (CHI500 = 0). The ability of predicted Tc to estimate freeze injury was determined in 18 winter seasons where freeze injury was recorded. During injurious freeze events, predicted Tc was higher than Tmin except for a freeze on 8 Mar. 1996. In some freezes where the difference in Tc and Tmin was <0.5 °C there were no visible injury symptoms. Injury by the freeze on 8 Mar. 1996 was due, in part, to abnormally rapid deacclimation because of defoliation by an earlier freeze on 4-6 Feb. the same year. A freeze rating scale was developed that related the difference in Tc and Tmin to the extent of injury. Severe freezes were characterized by tree death (Tc - Tmin > 3.0 °C), moderate freezes by foliage kill and some stem dieback (1.0 °C ≤ Tc - Tmin ≤ 3.0 °C), and slight freezes by slight to no visible leaf injury (Tc - Tmin < 1.0 °C). The model was applied to Tmax and Tmin recorded daily from 1948 through 2004 to estimate long-term freeze-risk for economically damaging freezes (severe and moderate freeze ratings). Economically damaging freezes occurred 1 out of 4 years in the 56-year study, although 8 of the 14 freeze years occurred in two clusters, the first 5 years in the 1960s and 1980s. Potential modification of freeze-risk using within-tree microsprinkler irrigation and more cold-hardy cultivars was discussed.
R.J. Schnell, J.S. Brown, C.T. Olano, A.W. Meerow, R.J. Campbell and D.N. Kuhn
Mango (Mangifera indica L.) germplasm can be classified by origin with the primary groups being cultivars selected from the centers of diversity for the species, India and Southeast Asia, and those selected in Florida and other tropical and subtropical locations. Accessions have also been classified by horticultural type: cultivars that produce monoembryonic seed vs. cultivars that produce polyembryonic seed. In this study we used 25 microsatellite loci to estimate genetic diversity among 203 unique mangos (M. indica), two M. griffithii Hook. f., and three M. odorata Griff. accessions maintained at the National Germplasm Repository and by Fairchild Tropical Botanic Garden in Miami, Fla. The 25 microsatellite loci had an average of 6.96 alleles per locus and an average polymorphism information content (PIC) value of 0.552 for the M. indica population. The total propagation error in the collection (i.e., plants that had been incorrectly labeled or grafted) was estimated to be 6.13%. When compared by origin, the Florida cultivars were more closely related to Indian than to Southeast Asian cultivars. Unbiased gene diversity (Hnb) of 0.600 and 0.582 was found for Indian and Southeast Asian cultivars, respectively, and both were higher than Hnb among Florida cultivars (0.538). When compared by horticultural type, Hnb was higher among the polyembryonic types (0.596) than in the monoembryonic types (0.571). Parentage analysis of the Florida cultivars was accomplished using a multistage process based on introduction dates of cultivars into Florida and selection dates of Florida cultivars. In total, 64 Florida cultivars were evaluated over four generations. Microsatellite marker evidence suggests that as few as four Indian cultivars, and the land race known as `Turpentine', were involved in the early cultivar selections. Florida may not represent a secondary center of diversity; however, the Florida group is a unique set of cultivars selected under similar conditions offering production stability in a wide range of environments.