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- Author or Editor: Robert J. Dufault x
Abstract
‘Southern Comet’ broccoli (Brassica oleracea L. Group Italica) was grown in a NP deficient soilless medium in 15-liter pots for 45 days in a greenhouse averaging 21°C during the growth period. Fertilizer treatments were split-applied and consisted of factorial combinations of 1.9, 3.7, 5.6 g N (total) per pot from urea and 0.07, 0.14, and 0.21 g P (total) per pot from monocalcium phosphate. Potassium from KCl was split-applied at a constant rate of 1.6 g K (total) per pot. Increasing N rate increased head fresh weight, stem diameter, floret total chlorophyll, root and top dry weight (stem, petiole, leaf, and head), plant height, and head quality, and decreased days to heading and to harvest. Increasing P rates increased floret total chlorophyll, height, and root dry weight to a lesser degree than N. For quality broccoli production in the greenhouse, 5.6 g N, 0.21 g P, and 1.6 g K per 15 liter pot were required.
The first objective of this paper is to review and characterize the published research in refereed journals pertaining to the nutritional practices used to grow vegetable transplants. The second objective is to note those studies that indicated a direct relationship between transplant nutritional practices and field performance. The third objective is to suggest some approaches that are needed in future vegetable transplant nutrition research. Even after review of the plethora of available information in journals, it is not possible to summarize the one best way to grow any vegetable transplant simply because of many interacting and confounding factors that moderate the effects of nutritional treatments. It is, however, important to recognize that all these confounding factors must be considered when developing guidelines for producing transplants. After thorough review of this information, it is concluded that transplant nutrition generally has a long term effect on influencing yield potential. Therefore, derivation of a nutritional regime to grow transplants needs to be carefully planned. It is hoped that the information that follows can be used to help guide this process.
Short productive lifespan is a major problem with asparagus (Asparagus officinalis L.), whether harvested in the spring or forced in late summer in coastal South Carolina. A modification of the Taiwanese system of mother stalk (MS) culture might enhance asparagus longevity and yield. The objective of this research was to determine if modified MS culture improved plant survival and yields in spring or summer-forced harvests compared with conventional spring clear-cut (CC) harvesting or with nonconventional summer-forced CC harvesting. `Jersey Giant' asparagus was harvested for 3 years (1994-96) using the following harvest systems: 1) spring CC (normal emergence in February in this location); 2) spring MS followed by summer MS (mow fern down on 1 Aug. and establish new mothers); 3) spring MS only; 4) summer CC only (mow fern on 1 Aug. and harvest); and 5) summer MS only. All systems were harvested for ≈7 weeks. All MS plots produced 40 mother stalks per 12-m row length each year before harvesting began. All mother stalks were trellised and tied to prevent lodging. Three-year total yields (kg·ha-1) and stand reduction (%) for nonharvested controls, spring CC harvesting, spring MS culture, spring MS combined with summer MS, summer CC, and summer MS were: 0 and 54%, 1621 and 96%, 779 and 99%, 1949 and 86%, 4001 and 58%, 3945 and 58%, respectively. All spring harvesting systems failed because by midsummer, aged fern, harvest pressures, and, apparently, higher rates of crown respiration reduced crown carbohydrate reserves. Yearly repetition of these stresses ultimately killed the spring-harvested plants. The MS culture did not ameliorate stand loss by significantly increasing carbohydrate reserves. Yields of summer-forced asparagus were consistently acceptable because aged ferns were removed at about the time they apparently became inefficient photosynthetically. After termination of the summer harvest season and with recovery in the following spring, ample carbohydrates were produced well before summer forcing began again in August the following year. Therefore, plant longevity was better sustained by summer forcing than by traditional spring harvesting.
Abstract
‘Utah 52-70R’ celery (Apium graveolens L.) seedlings were grown in a N- and P-deficient soilless medium amended with N and P slow-release fertilizers (Osmocote) in greenhouses maintained at either 21° to 32°C (warm house) or 14° to 24° (cool house). Generally, as N rate increased from 1.25 to 10 g N/kg of medium, plant stands, chlorophyll, shoot number, plant height, leaf area, and shoot and root dry weights increased; but, from 10 to 20 g N/kg of medium, these variables decreased. As P rates increased from 2.5 to 10.0 g·kg−1 of medium, only chlorophyll content decreased linearly. Temperatures in the warm house generally reduced celery growth compared to the cool house. At the experiment's termination, it was determined that as N and P rates increased, media conductivity, nitrate-N, and phosphorus levels increased, but pH decreased. A N rate of 1.25 and 2.5 g P/kg of medium was adequate to produce quality celery transplants in a cool house.
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
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
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.
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.