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- Author or Editor: Robert J. Dufault x
The objective of this study was to determine the best combination of planting dates (PDs) and cultivars on yield and quality for long-term production of romaine lettuce. `Green Forest' (GF), `Apache' (AP), `Darkland' (DK), `Green Tower' (GT), `Ideal Cos' (IC), and `Tall Guzmaine' (TG) were successfully grown to harvest maturity on 19 PDs from September 1998 to April 2001. Lettuce planted in September and April PDs (pooled over cultivars and year), required as little as 47 and 49 days, respectively, to reach harvest (all cultivars harvested on the same day). Lettuce planted in October, November, February, and March PDs (pooled over cultivars and year), required on average 64, 66, 75, and 67 days to reach harvest, respectively, but in the coldest PDs of December and January, 90 and 98 days, respectively, were needed to reach maturity. Of the eight PDs evaluated, marketable numbers/plot (pooled over cultivars and years) were greatest in the September PD, followed by April (–8% decrease from September PD) > March (–13%) > October (–17%) > November (–21%) > December = January = February (about –30%) and heads weighed the most in September > January = February (–7% decrease from September PD) > March = April (–14%) > October (–21%) > December (–25%) > November (–31%). Cull heads/plot (pooled over cultivars and years) were greatest in April > December (–5% decrease from April PD) > January = February (–16%) > November (–27%) > October (–34%) > March (–44%) > September (–49%). Two out of three November PDs were lost to freezing damage and this PD should be avoided. Significant bolting occurred primarily in the September and October PDs (in 1 of 3 years) with negligible bolting in the November, December, and January PDs, but bolting recurred again in the February, March and April PDs. Marketable numbers/plot (pooled over all PDs and years) were greatest for GF > GT (–7% decrease from GF) > AP (–8%) > IC (–9%) > DK (–11%) > TG (–21%). The interaction effect of cultivar × PD indicated that GF yielded the most marketable heads in 6 out of 8 PDs. The best performing cultivars by PD (pooled over years) were September and February = GF and IC; October = TG; November = AP; December, January, March, and April = GF.
Gerbera seedlings (Gerbera jamesonii H. Bolus Ex. Hook F.) `Florist Strain Yellow' were planted on drip-irrigated, plastic-mulched beds at 24,000, 36,000 or 72,000 plants/ha. Nitrogen and potassium fertilizers at 55, 110, or 220 kg·ha-1 were factorially combined with populations. In the 1st year of a 2-year study, the number of marketable flowers increased as N and K increased to 110 kg·ha-1, but as N and K were increased to 220 kg·ha-1, cull production increased. In the 2nd year, marketable and cull yields increased with N rate to 220 kg·ha-1; K did not affect yield. As populations increased from 24,000 to 72,000 plants/ha, marketable and cull flower production increased in both years. Flower size and quality were unaffected by plant populations. Nitrogen and potassium fertility did not affect flower size, quality, or vase life in either year.
Early spring sweet corn (Zea mays var. rugosa) is usually planted in cold soils at sub-optimal temperatures for seed germination. It is important for growers to understand the relationships among temperature, germination, and vigor of sweet corn in order to plan the earliest planting dates that will not significantly reduce plant stand. The objectives of this research were 1) to determine the minimum temperatures to germinate to 75%, (the minimum germination percent for interstate commerce) for 27 new sweet corn su (sugary), se (sugar enhancer), and sh2 (shrunken-2) cultivars; 2) to determine vigor differences among the phenotypes; and 3) to select the most promising se, su, and sh2 cultivars for cold tolerance and vigor for early spring planting. Seeds of each cultivar were placed along a temperature gradient on a thermogradient table, Type 5001 (Seed Processing Holland, Enkhuizen, The Netherlands), and allowed to germinate over a 7-day period. The gradient treatments were [±2 °F (1.1 °C)] 52, 56, 60, 64, 68, 72, 76, 80, 84, and 86 °F (11.1, 13.3, 15.6, 17.8, 20.0, 22.2, 24.4, 26.7, 28.9, and 30.0 °C). Germination data from thermogradient testing were used to determine the minimum temperatures and time required for su, se, and sh2 cultivars to germinate at ≥75%, defined as minimum acceptable germination percent (MAGP); and the minimum temperature to reach the maximum germination rate (MGR) for a cultivar, defined as the ability to germinate to MAGP at the same rate equally at low and high temperatures. Generally, su phenotypes germinated to MAGP within 4 days, with sh2 requiring 6 days, but with se requiring 5 days. We found that within each phenotype, however, cultivars reacted uniquely to temperature. The most vigorous and cold tolerant su cultivars were `NK 199' and `Merit' which germinated to MAGP at 52 °F with `NK 199' more vigorous than `Merit'. The su cultivar `Sweet G-90' was vigorous at warm temperatures, but the least cold tolerant and desirable for planting under cold conditions. Within the se cultivars, `Precious Gem', `July Gold', and `Imaculata' germinated to MAGP at 52 °F with `Precious Gem' requiring 6 days and `July Gold' and `Imaculata' requiring 7 days. `Accord' was the least cold tolerant se cultivar, requiring at least 60 °F for MAGP with a slow MGR, even at warm temperatures. None of the sh2 cultivars reached MAGP within 7 d at 52 °F, as was also observed for certain su and se cultivars.
As broccoli populations increased from 24,000 to 72,000 plants/ha at N rates of 112, 168, or 224 kg/ha, head weight decreased linearly. Increasing the N rate from 56 to 224 kg/ha at any population linearly increased broccoli head weight and marketable yields, and decreased cull yields. Broccoli yields were highest at 72,000 plants/ha and 224 kg N/ha. No marketable cauliflower curds were produced at 56 kg N/ha at any population evaluated. As populations increased from 24,000 to 72,000 plants/ha with N rates held constant at either 112 or 224 kg/ha, marketable curd weight decreased linearly and cull production increased linearly. Increasing the N rate from 112 to 224 kg/ha did not increase marketable curd weight or yields at any population. Increasing the N rate to 112 kg/ha or higher reduced cull production at 24,000 plants/ha, but not at populations of 36,000 or higher. Cauliflower yields were optimized at 24,000 plants/ha and 112 kg N/ha based on reduced cull production, satisfactory curd weights, and transplant economy.
Broccoli (Brassica oleracea L. var italica) and cauliflower (Brassica oleracea L. var botrytis) were seeded and grown for 4 weeks in containers ranging from 3.8 to 30.5 cm3 in volume, 2.0 to 4.3 cm wide, 3.2 to 7.2 cm deep, and at densities of 540 to 2500 plants/m2. The objective of the study was to determine the effect of container size on growth of 4-week-old plants and on their subsequent yield. The number of leaves/plant, leaf dry weight/plant, plant height, and leaf area/plant of 4-week-old broccoli and cauliflower plants generally increased with increasing container width, volume, and decreasing plant density. Container depth did not affect these variables, except to increase plant height as depth increased. Container volume, width, and depth and density did not affect marketable yields of broccoli and cauliflower. Earliness, length of harvest season, and cull yields of broccoli and cauliflower generally were unaffected by container size. Small containers (2.0 cm wide, 3.2 to 4.5 cm deep, 3.8 to 5.9 cm3 in volume, and 2500 plants/m2) are economical and appropriate depending on seedbed conditions.
Seed of asparagus (Asparagus officinalis L.) germinated normally after 2 months of constant freezing (-10°C) or chilling (4°) under water-saturated conditions in laboratory germination studies. However, temperatures cycling weekly from chilling to freezing for 2 months reduced germination to less than 50%, and temperatures cycling weekly from warm (21°/16°, day/night) to chilling to freezing for 2 months reduced germination to 0. The stands of asparagus, field-seeded in November and December, were reduced 85% by winterkill in comparison to spring seeding in March and April. Seeding densities from 10 to 40 seed/m did not compensate for stand loss. The greatest contributor to winterkill apparently was seed rot. March seeding increased plant height, but not crown quality or the number of shoots initiated in comparison to conventional April seeding. High seeding densities did not reduce plant growth or crown yields in the spring plantings. Stand establishment was not different between the spring planting dates. Early March seeding at high densities is recommended.
Growth studies of field-seeded hybrid and open-pollinated asparagus (Asparagus officinalis L.) were conducted to determine the differences in shoot, bud, and crown growth during the first season after seeding and to determine growth relationships between shoot and crown variables that indicate critical periods of bud and crown production. F1 hybrid (UC 157) and UC800 open-pollinated (OP) asparagus seedlings emerged 4 to 6 weeks after seeding. A lag phase of shoot and root growth lasted 4 to 5 weeks after emergence in both cultivars. UC157 initiated more roots and accumulated more fern and crown fresh weight than UC800 early in the season, but by harvest crowns were not different in root and bud number, fresh weight, or fructose content (crown quality). Root/shoot ratios increased from a 2:1 ratio 6 weeks after emergence to 8:1 (UC157) and 6:1 (UC800) 23 weeks after emergence. Shoot/bud ratios stabilized from an approximate 2:1 ratio initially to an approximate 1:2 ratio 18 weeks after emergence. Bud production in the F1 and OP cultivars increased 6 and 10 weeks after emergence, respectively, and continued unabated up to crown harvest 23 weeks after emergence. Shoot number and fresh weight were not correlated highly with bud number. The number of roots vs. buds and the crown vs. fern fresh weights were correlated highly and were the best indicators of quality crown production. Vigorous fern development throughout the growing season increased the potential to produce higher-quality large crowns.
In 3 separate experiments, the effects of container types, transplant age, and growing media on asparagus (Asparagus officinalis L.) transplant quality were determined. These transplants then were field planted to determine the effects of propagation methods on plant growth after one growing season. Transplants grown for 10 weeks in deep peat pots (10 cm deep, 177 cm3, and 364 plants/m2) produced crowns and fern of higher fresh and dry weight than other containers (ranging in depth from 5.5 to 7.6 cm, in volume from 53 to 186 cm3, and plant density/m2 from 277 to 1624). Shoot and root growth of 7-, 8.5-, and 10-week-old transplants (grown in identical containers) were similar, but crown fresh and dry weight were reduced for 6-week-old transplants. Ten-week-old transplants originally broadcast-seeded in flats of 1 vermiculite: 1 peat medium (v:v) produced more roots, buds, shoots and fern and crowns of greater fresh and dry weight than those grown in 1 peat : 1 perlite or 1 perlite : 1 vermiculite media. At the end of the growing season, plants originally grown in deep peat pots were superior in number of shoots and fleshy roots, and crown and fern dry weight to those grown in other container types, to transplants of various ages, and to bareroot transplants.
Ten triploid and 25 diploid watermelon (Citrullus lanatus) selections were evaluated to determine the temperature range and length of test for which germination index (rate of germination over time) and germination percentages were maximum for expediting vigor and seed testing practices. Temperature interacted with watermelon selection indicating that certain selections germinated faster within specific, but differing temperature ranges. Within 2 days after starting the germination process, 90% of triploid selections and 96% of diploid selections germinated to their greatest level and prolonging germination data collection for one week did not change this relationship. Although optimal temperature ranges may differ among the selections, the one temperature within the range common for all selections evaluated that maximized germination was 85 to 90 °F (29.4 to 32.2 °C) for diploids and 85 °F for triploids.
Feverfew has aspirin-like properties and has been utilized for the treatment of pain, particularly migraine headache. Parthenolide is the sesquiterpene lactone believed to be responsible for the medicinal properties. The potential for utilizing existing tobacco production and handling systems for the production and postharvest handling of feverfew was investigated. In year one, 8 commercial tobacco growers each planted about one-half acre of feverfew (Tanacetum parthenium L. Schulz-Bip.). The yield of dry herb varied among farmers from about 122 to 772 (55 to 350 kg) pounds per half-acre. The parthenolide content of the dried herb from most producers was within the range desired by industry, but four factors precluded its salability: a) presence of foreign matter, primarily weeds; b) excessive ash content due to contamination from sandy soils; c) mold resulting from processing with excessive moisture content, and; d) insect infestation (tobacco beetles Lasioderma serricorne) during storage. All of these limitations resulted from the failure to implement good agricultural aractices (GAPs) and good manufacturing practices (GMPs) during production and handling of the product. A second planting of the feverfew was carried out with strict attention to GAPs and GMPs. In this trial, all of the dried feverfew met the requirements for sale. Here we report on the management of production and handling systems for feverfew that can enable growers to produce high quality herbs that meet the high standards for medicinal use.