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  • Author or Editor: R.J. Dufault x
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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.

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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.

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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.

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Three broccoli (Brassica oleracea L. Italica group) cultivars (Baccus, Packman, and Southern Comet) were grown for 14, 24, or 34 days at 22/18C (day/night) in a greenhouse. Then plants were moved to growth chambers where temperatures were maintained at 26/22, 30/26, or 34/30C and were grown for 1, 2, or 3 weeks before returning them to the greenhouse. A1 varieties when exposed to high temperatures developed smaller heads Packman when exposed to high temperatures resulted in a reduction in uniformity. Other cultivars were not effected. Lack of openness, an important marketable characteristic was reduced by high temperatures. However, Baccus at 34 days old was not effected by the heat. We would expect this response since this is the head development stage and cultivar is heat tolerant. Plant exposed to high temperatures developed heads earlier when held for 3 weeks. When plants were held at 36/30C for 3 weeks, the largest reduction in plant growth was recorded. However, all plants showed a reduction in growth when exposed to high temperatures.

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Three broccoli (Brassica oleracea L. Italica group) cultivars (Baccus, Packman, and Southern Comet) were grown for 14, 24, or 34 days at 22/18C (day/night) in a greenhouse. Then plants were moved to growth chambers where temperatures were maintained at 26/22, 30/26, or 34/30C and were grown for 1, 2, or 3 weeks before returning them to the greenhouse. A1 varieties when exposed to high temperatures developed smaller heads Packman when exposed to high temperatures resulted in a reduction in uniformity. Other cultivars were not effected. Lack of openness, an important marketable characteristic was reduced by high temperatures. However, Baccus at 34 days old was not effected by the heat. We would expect this response since this is the head development stage and cultivar is heat tolerant. Plant exposed to high temperatures developed heads earlier when held for 3 weeks. When plants were held at 36/30C for 3 weeks, the largest reduction in plant growth was recorded. However, all plants showed a reduction in growth when exposed to high temperatures.

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Abstract

Increasing the P rates from 0 to 20 ppm increased shoot and crown fresh and dry weight, plant height, and fleshy root and bud production in 10-week-old asparagus (Asparagus officinalis L.) seedlings. Increasing K rates from 0 to 200 ppm decreased the production of fleshy roots relative to buds. Shoot production progressively increased as N rates increased from 100 to 200 ppm in conjunction with P rates increasing from 10 to 20 ppm. The partitioning of dry weight into crowns predominated over that partitioned into shoots in any combination of N rate from 0 to 200 ppm, and P rate from 0 to 20 ppm. With P rates held constant at 0 to 20 ppm, however, increasing the N rates from 0 to 200 ppm tended to reduce the partitioning rate into crowns and enhanced partitioning into the shoots. Nutrient solutions containing at least 20 ppm P and 100 ppm N and K are recommended in vermiculite-perlite-peat media natively low in NPK.

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Abstract

Single applications of ancymidol at 0.03, 0.12, 0.50, or 1.0 mg/plant were soil applied to asparagus seedlings (Asparagus officinalis L.) 3.5, 5.5, or 7.5 weeks after seeding. Increasing ancymidol rates from 0.03 to 1.0 mg/plant decreased bud number, fern dry weight, but not shoot number at all application times. When ancymidol was applied at 1.0 mg/plant at 3.5 weeks it reduced fleshy root production, but in plants treated at 5.5 to 7.5 weeks, it did not reduce fleshy root production. Increasing ancymidol rates from 0.03 to 1.0 mg/plant reduced the crown dry weight of plants 5.5 weeks and younger. Ancymidol from 0.03 to 1.0 mg/plant applied to 3.5-week-old plants increased the partitioning of dry matter into fern rather than crowns, but delaying application to 7.5 weeks after seeding reversed this relationship suggesting increased carbohydrate storage. Application of ancymidol from 0.03 to 1.0 mg/plant to plants 5.5-weeks-old or younger was considered detrimental to plant growth. Ancymidol at 0.50 mg/plant or less applied to 7.5-week-old plants enhanced the production of a stocky, compact transplant. Chemicals used. Ancymidol: α-cycloprophyl-α-(4-methoxyphenyl)-5-pyrimidinemethanol.

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`Jewel' sweetpotato was no-till planted into crimson clover, wheat, or winter fallow. Then N was applied at 0, 60, or 120 kg·ha–1 in three equal applications to a sandy loam soil. Each fall the cover crop and production crop residue were plowed into the soil, beds were formed, and cover crops were planted. Plant growth of sweetpotato and cover crops increased with N rate. For the first 2 years crimson clover did not provide enough N (90 kg·ha–1) to compensate for the need for inorganic N. By year 3, crimson clover did provide sufficient N to produce yields sufficient to compensate for crop production and organic matter decomposition. Soil samples were taken to a depth of 1 m at the time of planting of the cover crop and production crop. Cover crops retained the N and reduced N movement into the subsoil.

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A 5-year study using winter cover crops (wheat or rye, crimson clover, and fallow) in a tomato and bean rotation indicated several soil responses to the cover crops. Advantages of crimson clover winter cover crop to the soil in a tomato-bean rotation included adding organic matter to the soil, which resulted in an increase in the amount of inorganic nitrogen in the upper levels of the soil profile and an increase in the soil's water-holding capacity. An additional benefit of winter cover crops to the soil was the potential of reduced nitrogen leaching.

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Cucumber and potato crops were tested in a rotation with winter cover crops at different locations in Georgia, North Carolina, and South Carolina from 1991 to 1994. Biomass DM of vegetable crops was greatest when grown after crimson clover. Clover plantings resulted in a greater biomass than wheat when preceded spring cucumber crop. Vegetable biomass produced on clover plots or with N rates of 60 to 120 kg·ha–l was equivalent. Nitrogen recovery by cover and vegetable crops was enhanced by clover plantings. Clover biomass (tops only) provided an average of 138 kg N/ha for the cucumber crop, compared to an average of 64 kg N/ha provided by wheat. Nitrogen recovery by vegetable crops was also enhanced with 60–120 kg N/ha rates. Yields were highest when high N rates were used and when crops were produced on clover plots. Vegetable yield, cover crop biomass, and N recovery were positively correlated with vegetable biomass and applied N.

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