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- Author or Editor: Robert J. Dufault x
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The objectives of this study were 1) to identify high-quality broccoli cultivars for field production in spring, summer, and fall seasons; and 2) to illustrate dynamic changes in head quality of promising cultivars for a particular growing season compared to head quality over all seasons evaluated. Twenty-four hybrid cultivars were grown in spring, summer, and fall growing seasons 1993 to 1995 included `Arcadia', `Baccus', `Bonanza', `Citation', `Claudia', `Early Dawn', `Embassy', `Emerald City', `Everest', `Exselsior', `Galaxy', `Galleon', `Goliath', `Green Comet', `Green Duke', `Leprechaun', `Packman', `Paragon', `Skiff', `Southern Comet', `Sprinter', `Sultan', `Symphony', and `Viking'. Head density, color, leafiness, and shape, bead size, and consumer use were documented. `Symphony' performed best in Spring 1993 and 1994, and only `Paragon' tolerated heat in Summer 1993 and 1994. Fall climate in coastal South Carolina is most conducive to high-quality production versus spring and summer seasons, with the following cultivars producing superior heads in both years: `Symphony', `Embassy', `Galleon', `Galaxy', `Sultan', and `Emerald City'. Quality defects for each cultivar in each inappropriate growing season will be illustrated.
Pretransplant nutritional conditioning (PNC) of transplants during greenhouse production may improve recovery from transplanting stress and enhance earliness and yield of watermelon [Citrullus lanatus (Thumb.) Matsum. & Nakai]. Two greenhouse experiments (Expts. 1 and 2) and field experiments in South Carolina and North Carolina (Expt. 3) were conducted to evaluate N and P PNC effects on watermelon seedling growth and their effects on fruit yield and quality. `Queen of Hearts' triploid and `Crimson Sweet' diploid watermelon seedlings were fertilized with N from calcium nitrate at 25, 75, or 225 mg·liter–1 and P from calcium phosphate at 5, 15, or 45 mg·liter–1. In the greenhouse, most variation in the shoot fresh and dry weights, leaf count, leaf area, transplant height, and root dry weight in `Queen of Hearts' and `Crimson Sweet' was attributed to N. Cultivar interacted with N, affecting all seedling growth variables, but not leaf area in Expt. 2. To a lesser extent, in Expt. 1, but not in Expt. 2, P interacted with cultivar, N, or cultivar × N and affected shoot fresh and dry weights, leaf count and leaf area. In the field, transplant shock increased linearly with N, regardless of cultivar or field location. The effect of PNC on plant growth diminished as the growing season progressed. For both cultivars at both locations, N and P PNC did not affect time to first staminate flower, fruit set, fruit width or length, soluble solids concentration, or yield. Vining at Charleston for both cultivars was 2 days earlier when N was at 75 rather than 25 mg·liter–1, without further change with the high N rate. At Clinton, the first pistillate flower was delayed linearly the higher the N rate for `Crimson Sweet'. At Charleston, hollow heart in the `Queen of Hearts' increased nearly 3 times when N PNC rate was tripled (from 75 or 225 mg·liter–1), while N had no effect on hollow heart in `Crimson Sweet'. In contrast, at Clinton, hollow heart in either cultivar was affected by P PNC, not N. PNC with 25N–5P (in mg·liter–1) can be used to reduce seedling growth and produce a more compact plant for easier handling, yet not reduce fruit quality or yield.
To reduce transplant shock of bell peppers (Capsicum annuum L.), we tested the effectiveness of pretransplant nutritional conditioning (PNC) as a promoter of earliness and yield. In Expt. 1, `Gatorbelle' bell pepper seedlings were fertilized with N from Ca(NO3)2 at 25, 75, or 225 mg·liter-1 and P from Ca(H2PO4)2 at 5, 15, or 45 mg·liter-1. Nitrogen interacted with P, affecting shoot fresh and dry weight, leaf area, root dry weight, seedling height, and leaf count. In Expt. 2, transplants conditioned with N from 50, 100, and 200 mg·liter-1 and P at 15, 30, and 60 mg·liter-1 were field-planted in Charleston, S.C., and Clinton, N.C. Nitrogen- and P-PNC did not greatly affect recovery from transplant shock. Although N- and P-PNC affected seedling growth in the greenhouse, earliness, total yield, and quality were similar in field studies among all PNC treatments at both locations. PNC with 50 mg N and 15 mg P/liter can be used with this variety and not have any long-term detrimental effects on yield and quality.
Tomato (L.ycopersicon esculentum Mill.) seedlings were nutritionally conditioned with solutions containing factorial combinations of N at 25, 75, and 225 mg·liter -1, P at 5, 15, and 45 mg·liter-1, and K at 25, 75, and 225 mg·liter -1 to determine the effect of nutritional regimes on tomato transplant growth and quality. As N increased from 25 to 225 mg·liter-1, fresh shoot weight, plant height, stem diameter, leaf number, leaf area, shoot and root dry weights, and total chlorophyll increased. Nitrogen accounted for the major source of variation. Phosphorus effects were significant only in 1988; Pat 45 mg·liter-1 increased fresh shoot weight, plant height, stem diameter, leaf number, and leaf area in comparison to 5 and 15 mg·liter -1. Potassium did not significantly influence any of the growth variables measured in the study. For quality transplant production, nutrient solutions should contain at least N at 225 mg·liter-1, P at 45 mg·liter-1, and K at 25 mg·liter-1.
Excessive cutting pressure (CP) early in the lifespan of an asparagus (Asparagus officinalis L.) plantation may weaken and reduce yields and quality. The objective of this research was to determine how increasing CP affects yield, quality, and survival of spring-harvested and summer-forced asparagus. `Jersey Gem' asparagus was harvested for 4 years (1999–2002) in spring or summer-forced on 1 Aug. using the following CP (weeks/year from 1st to 4th years, respectively): 2, 3, 4, 6 (low), 3, 4, 5, 7 (medium), and 4, 5, 8, 10 (high). In all harvest years, as CP increased, marketable number and weight increased. Yield in spring harvest seasons significantly increased with each increase in CP. In summer, yield significantly increased only when high CP was used with equivalent yields at low and medium CP. With summer forcing, there were 48% and 55% fewer large spears at medium and high CP, respectively, compared to the same CP used during spring harvest seasons. Stands tended to decrease with CP from 1997 to 2003, but these differences were not significant and not severe enough to kill the plants. Yearly root fructose concentrations (RFC) with all CP increased yearly from 1999 to 2001 and plateaued from 2002 to 2003. From 1999 to 2002, RFC increased 53%, 27%, 13%, and 13% in unharvested control, low, medium, and high CP, respectively, indicating that with a greater CP, RFC decreased. RFC in summer-forced asparagus was significantly less than spring-harvested in 83% of all sample months. RFC in spring-harvested asparagus was similar to unharvested asparagus in February, March, April, November, and December; however, in all other sample months, spring-harvested RFC was significantly lower than unharvested control plants. The highest CP scheme is appropriate for spring-harvested asparagus based on greatest marketable yields and acceptable cull losses. For summer-forced asparagus, the lowest CP scheme is more appropriate based on acceptable marketable yields and to avoid undue plant stress verified by unacceptably large cull losses mostly attributed to spindly spear size and lower RFC.
Abstract
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.
Abstract
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.
Abstract
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.
Our objectives were to determine 1) if shrimp sludge has any value as a soil amendment in broccoli production and 2) an appropriate rate of sludge for head production. Four levels of N–P–K per 15-L pot (in grams; 2.0 N–0.07 P–1.4 K; 4.0 N–0.14 P–2.8 K; or 6.0 N–0.21 P–4.2 K; and 0.0 N–P–K) were factorially combined and replicated 10 times with four volumes of shrimp sludge (0%, 10%, 20%, and 40% v/w in 15-L pots blended with 100%, 90%, 80%, and 60% Metro Mix 300, respectively). Four-week-old `Emerald City' broccoli transplants were planted into sludge + media–fertilizer mixtures on 12–14–95 and were grown to harvest maturity in a greenhouse. As sludge volume increased, the days to harvest, plant height, and root fresh weight: head fresh weight ratio decreased, but leaf number, fresh weight and area, head fresh weight, stem diameter, and shoot: root fresh weight ratio increased. As N–P–K rate increased, leaf number, area, and fresh weight, stem diameter, head fresh weight, and shoot: root fresh weight ratio increased, but root: head fresh weight ratio and plant height decreased. Using head fresh weight as the determinant, heaviest heads were optimized with 20% sludge and 4.0g N–0.14g P–2.8g K per 15-L pot. Sludge alone or N–P–K alone did not produce the heaviest broccoli heads as using combinations of sludge and N–P–K in a fertility program.
Abstract
Sweet peppers (Capsicum annuum L. cv. Midway) were grown in field plots with diffuse solar reflectors and/or white polyethylene mulches. Solar reflectors significantly increased photosynthetically-active radiation (PAR) levels over the season. The reflective flux in PAR of mulched ground surfaces was 3 times as large as the bare soil plots. Plants grown with a white mulch were shorter, fruited earlier, and produced higher overall yields than unmulched plants. Solar reflectors did not affect earliness to fruit and increased the overall yield of fruit to a lesser extent than mulched plants. Stem diameter and fresh and dry weights were unaffected by any treatment. Solar reflectors minimally affected plant growth and yield. The beneficial effect of reflective mulches could not be ascribed to solar enhancement, to soil moisture conservation, or to other microclimatic factors.