Wayne J. McLaurin
Wayne J. McLaurin
The standard mix used by most nurseries consist of a 9 pine bark: 1 sand. With the ever-increasing cost of bark, nurseries are looking for an alternative. Sawmill residue may hold potential utility as part of a potting mix. Although sawmill residue is highly variable, it can serve as soil bulk as well as an organic medium. The purpose of this study was to determine if old sawmill residue not treated by pathogen-free requirement procedures could be used “as is” as part of a nursery soil mix. For this study, a sample, a typical conglomerate of undetermined wood chips, bark, and soil particles, was obtained from an “old pile” (just how old is not known) of sawmill residue. To determine how this sample would function in a nursery bark/sand mix, tests were run on its physical properties of pore space and water-holding capacity. The sawmill residue had the following characteristics: a mean 44.2% porosity capacity, 23.4% air space, and 20.8% water holding capacity. A standard fertilizer and lime amendment package was added to the sawmill residue in the same rates as a regular nursery mix. The sawmill residue and the standard nursery mix were then blended according to the treatment percentages. The treatments were sawmill residue/standard nursery mix 0/100, 10/90, 30/70, 60/40, and 100/0. The Ilex crenata `Compacta' liners were planted into standard 1-gallon nursery pots filling to just below the rim. The pots were randomly placed on a well-drained rock surface in full sun. No additional fertilizer was used and watering was done as needed. Plants were grown for 1 year. Visual assessments were made throughout the growing period and at harvest. There was no visible difference in any of the treatments as far as overall growth was discerned. The plants were of uniform height and width showing consistent, even growth and good leaf color. Root system growth and development were evaluated visually and over all treatments were uniformly good. No root problems were noted. There was not any plant loss in any treatment over the entire study. Each plant was cut at the soil line and dried for 24 hours at 1150 °C. Dry weights were taken after the plant material had cooled for 4 hours. Results were based on four plants per treatment times four replications for a total of 16 plants per treatment. There was not any measurable growth difference in dry weight among treatments 1, 2, 3, and 4 [sawmill residue/standard nursery mix 0/100 (41.03 g dry weight), 10/90 (39.83 g dry weight), 30/70 (38.98 g dry weight), 60/40 (37.42 g dry weight)]. However, treatment 5 [100/0 (31.03 g dry weight)] was significantly lower when compared to the remaining four treatments. The lower dry weight may be attributed to the 100% sawmill residue being too heavy and not well-drained enough. However, the roots did not show any damage from being too wet. Further work is being done with the sawmill residue.
J. Kays and Wayne J. McLaurin
Flavor is a primary trait in the selection of foods. The role of flavor in acceptance of the sweetpotato, flavors status as a selection trait in existing breeding programs, and our current understanding of the flavor chemistry of the sweetpotato was reviewed. The sweetpotato, unlike most staple crops, has a very distinct and dominant flavor. In typical breeding programs, however, flavor is generally one of the last traits screened. A tremendous diversity and range of flavors has been reported within the sweetpotato germplasm (e.g., acidic, bland, baked potato, boiled potato. carrot, chalky, chemical, citrus, earthy, Ipomoeo/terpene, lemon, musty, pumpkin, salty, squash (titer type), starchy, sweet, sweetpotato (traditional), terpene, and turnip. These results indicate that the genetic diversity for flavor present in sweetpotato germplasm will allow making substantial changes in the flavor of new cultivars, thus potentially opening previously unexploited or under-exploited markets. Implementation involves solving two primary problems: 1) identification of desirable flavor ideotypes; and development of procedures that allow maximizing the selection of specific flavor types.
Wayne J. McLaurin and Stanley J. Kays
Jerusalem artichokes are one of a small number of crops that store carbon predominately in the form of inulin, a straight chain fructosan. There has been a tremendous increase in interest in inulin due to its dietary health benefits for humans and calorie replacement potential in processed foods. We measured the allocation of dry matter within the crop (cv. Sunckoke) during an entire growth cycle by harvesting plants over a 40-week period (2-week intervals) from initial planting through field storage. Plant characters assessed were: no. of basal stems, leaves, branches, flowers, and tubers; the dry weight of leaves, branches, flowers, tubers, and fibrous roots; and date of flowering. Total dry weight of above-ground plant parts increased until 18 weeks after planting (22 Aug.) and then progressively decreased thereafter. Tuber dry weight began to increase rapidly ≈4 weeks (19 Sept.) after the peak in above-ground dry weight, suggesting that dry matter within the aerial portion of the plant was being recycled into the storage organs. Tuber dry weight continued to increase during the latter part of the growing season, even after the first frost. Final tuber yield was 13.6 MT of dry matter/ha.
Stanley J. Kays, Yan Wang and Wayne J. McLaurin
Sweetness, which is known to vary significantly among clones, is the dominant sensory attribute characterizing the flavor of sweetpotatoes [Ipomoea batatas (L.) Lam.]. The relative sweetness of baked roots, expressed as sucrose equivalents, was determined for 272 clones from the U.S. Department of Agriculture National Plant Germplasm System collection. The clones were from 34 countries that collectively produced 93% of the world's sweetpotato production in 2002. Individual clones were separated into five categories based upon the concentration and relative sweetness of individual sugars, expressed numerically as sucrose equivalents per 100 g dry mass: very high ≥38; high 29-37; moderate 21-28; low 12-20; and nonsweet ≤12. Based upon the mean sucrose equivalents of the clones for each country, only 9% of the countries, which accounted for only 2.1% of the total annual production of the countries surveyed, had sweetpotatoes that were classified as very high. While the majority (62%) of the countries surveyed had clones that were categorized as high, they represented only 4.4% of the total production of sweetpotatoes. None of the countries had mean sucrose equivalent values that were categorized as low or nonsweet, although a few individual clones were ranked as low and one as nonsweet. Countries that account for the majority (87%) of the sweetpotatoes grown worldwide had a mean sucrose equivalent ranking of moderate. Sweetness is derived from the composite of endogenous sugars (sucrose, glucose, fructose) and maltose formed via starch hydrolysis during baking. Maltose accounted for only 42% of the average contribution to the total sucrose equivalents. The range in the concentration of individual sugars among clones was substantial as was their contribution to sucrose equivalents. Sucrose equivalents due to maltose in individual clones ranged from 0.6 to 21.9 while endogenous sugars ranged from 6.4 to 46.9. The results indicate that essentially all of the sweetpotato clones tested from around the world were classified as equal to or greater than moderate in sucrose equivalents, and that there is substantial genetic diversity within the genepool such that the potential exists for tailoring the flavor of new cultivars, via significantly increasing or decreasing sugar content, to meet specific consumer preferences and/or product uses.
Robert J. Dufault, K. Dean Batal, Dennis Decoteau, J. Thomas Garrett, Darbie Granberry, Wayne McLaurin, Russell Nagata, Katharine B. Perry and Douglas Sanders
The experiment screened two spring and two fall planting dates in six regions within North Carolina, South Carolina, and Georgia. The objective was to extend the production over the southeastern United States rather than at a single location. Spring harvests lasted from mid-April to early July. Summer-to-winter harvests lasted from mid-August to late January. Collards were not harvested in any of the locations from late January to mid-April or from early July to mid-August. More extensive planting dates may further increase the longevity of production.
Laurie Hodges, Douglas C. Sanders, Katharine B. Perry, Kent M. Eskridge, K.M. `Dean' Batal, Darbie M. Granberry, Wayne J. McLaurin, Dennis Decoteau, Robert J. Dufault, J. Thomas Garrett and Russell Nagata
Four bell pepper (Capsicum annuum L.) cultivars were evaluated for yield (total weight of marketable fruit) performance over 41 environments as combinations of 3 years, three planting dates, and seven locations across North Carolina, South Carolina, and Georgia. Cultural practices, including trickle irrigation and double rows planted on black-plastic-covered beds, were uniform across all environments, except for fertilization, which was adjusted at each location based on soil tests. Comparing production over 3 years between the mountain location and the Coastal Plain location in North Carolina, yields were lower on the Coastal Plain. Spring plantings provided higher yields than summer plantings at both locations. Yield increases were obtained from hybrid cultivars over that of the open-pollinated (OP) standard [`Keystone Resistant Giant #3' (KRG#3)] in the summer planting in the mountains compared to the Tidewater Coastal Plain. Across the three-state region, hybrid cultivar yields were higher than those of the OP cultivar for the second spring planting date in 1986 and 1987. Although the hybrid yields were higher than that of the OP standard, the hybrid `Skipper' yielded less than the other hybrids (`Gator Belle' and `Hybelle'). `Gator Belle' generally out-yielded `Hybelle' at all locations, except in Fletcher, N.C. This difference may be related to the relative sensitivity of these two cultivars to temperature extremes, rather than soil or geographic factors, because there was a tendency for `Hybelle' yields to exceed `Gator Belle' in the earliest planting date. Based on the reliability index, the chance of outperforming KRG#3 (the standard) was 85% for `Hybelle', 80% for `Gator Belle', but only 67% for `Skipper'.