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  • Author or Editor: John C. Bouwkamp x
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Previous observations have shown that the diffusivity of water vapors is much larger than the value that is predicted theoretically from the magnitude of the diffusion coefficient of CO2, C2H4, or both. This has been ascribed to the ability of water to diffuse through the cuticle and to the transport of water via the capillaries of cellulase micorfibrels to the surface of the lenticels, where it evaporates. We measured the diffusivity of CO2 in `Gala' and `Granny Smith' apples. The former are more permeable to CO2 than the latter cultivar, in particular after prolonged storage at 2°C. The diffusivity of H2O was 10- to 20-fold larger than that of CO2. Furthermore, the ratio of D(H2O)/D(CO2) was similar for both cultivars. Infiltration of dyes and gas flow through apples submerged in water show that in `Gala' apples, the number of open lenticels is larger than in `Granny Smith'. Thus, the data indicate that lenticels are the main avenue of gas exchange in apples.

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Abstract

Four cultivars of sweet potatoes (Ipomoea batatas Lam.) were sampled bi-weekly during the period of storage root development Although the root weight increased nearly 8-fold during the sampling period there was only a 35% increase in the number of roots. Alcohol insoluble solids (AIS) and % dry matter generally showed a slight increase throughout the season and specific gravity a slight decrease. Total sugars and reducing sugars failed to show a trend. In contrast, the processed roots tended to become softer as the season progressed. Firmness was related to chronological age of roots rather than harvest date. The later the planting the higher were total and reducing sugars but planting date had no consistent effect on other raw product attributes.

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Production of `Top White', `Peterstar Pink', `Lilo Red', and `Red Success' poinsettias were evaluated in a treatment combinations that included 10 compost blends, three compost levels, and two commercial soilless substrates of Sunshine Mix 1 and Pro Gro 300S as controls. The compost feedstocks included PSG polymer dewatered biosolids (PSG), lime dewatered biosolids (CP), yard trimmings (YT), poultry litter (PL), and municipal solid waste (MSW Bedmininster). The PSG, PL, YT, and MSW were co-blended with CP on a 2:1 ratio (v/v), all other composts were co-blended on a 1:1 ratio (v/v). The compost levels of 33%, 50%, and 67% were mixed with peat:perlite (1:1, v/v). There were five replicates per treatment. Plants were fertilized once weekly with 200 mg·L–1 N from 21N–2.2P–16.6K. Sunshine mix produced control plants that had greater canopy diameter and plant grade than Pro Gro mix. Plant height was reduced as compost level increased from 33% to 67%. Blends of PSG:PL at the 33% and 50% levels and PSG:YT at the 33% level produced premium-quality plants. Good-quality plants, similar to those grown in Sunshine Mix, were produced with the PSG or PL compost blended with immature MSW at the 33% level; PSG:PL blend at a 67% level; PSG:YT blend at the 50% and 67% levels; and PL:YT blend at the 33% level.

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Blending compost from various feedstocks may increase the beneficial effects of compost as potting substrate. A factorial treatment combinations included 10 compost combinations, Sunshine Mix and Pro Gro 300S as controls, three compost levels, and three chrysanthemum cultivars. The compost combinations were Compro (CP), poultry litter (PL), PSG polymer dewatered biosolids (PSG), yard trimmings (YT), CP:PL, CP:PSG, CP:YT, PL:PSG, PL:YT, and PSG:YT; all blends were on a 1:1 ratio (v/v). The compost levels were 50%, 75%, 100%; and chrysanthemum cultivars included `Boaldi', `Cherry Davis', and `Yellow Favor'. All treatments were replicated six times. Plants were fertilized with 100 mg/L N from 20N–8.8P–16.6K twice weekly. All compost substrates, except PSG blends produced plants that were shorter than the controls. All compost blends produced similar or greater number of flower than the controls. Plants grown in substrates containing PSG and/or CP produced dark green or green foliages, and other substrates produced plants with pale green leaves. The PSG:PL and PSG: YT blends produced premium-quality plants. All other compost blends produced good-quality plants that were similar to the controls.

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Growth performance of potted `Peterstar Pink', `Top White', `Red Sails', and `Red Success' were evaluated in eight substrates and three fertilization rates. The substrates included Sunshine Mix 1 and Pro Gro 300S as control, and compost blends at 33%, 50%, and 67% of final substrate volumes mixed with peat and perlite (1:1). The blends included 2:1, 1:1, or 1:2 ratio of polymer dewatered biosolids (PDB):poultry litter (PL) and PDB: yard wastes (YW). Fertilization was applied twice weekly at 75, 100, and 150 mg/L N from 19N--2.2P-16.6K. Plants grown in Sunshine Mix 1 performed better than those grown in Pro Gro 300S. The growth parameters measured improved as the N rates increased for both controls. Plant diameter, grade, and dry weight of plants grown in 150 mg/L N treatment were usually similar to those in 100 mg/L N and were not 11% more than those at the lowest N treatment. The 1 PDB: 1 PL blend at the high N treatment produced premium-quality plants, and all remaining PDB:PL treatments produced good quality plants. The PDB:YW blends that received 100 and 150 mg/L N produced premium quality plants. The PDB:YW blends at the low N treatment produced slightly better quality plants than those grown in PDB:PL at the 75 mg/L N and were similar in quality as those grown in Sunshine Mix 1 at the 150 mg/L N treatment.

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Potted `Boaldi', `Red Akron', and `Yellow Boaldi' growth performance were evaluated in eight substrates and four N rates. The substrates included Sunshine Mix 1, Pro Gro 300S, and six compost blends. The compost feedstocks were polymer dewatered biosolids (PDB) blended with poultry litter (PL) or yard wastes (YW) and peat:perlite at final ratios of 4:2:1:1, 3:3:1:1, and 2:4:1:1. Plants received N at 75, 100, 150, or 200 mg•L-1 from 21N-2.2P-16.6K twice a week. Number of flowers, height, diameter, and grade of plants that received N at 200 mg•L-1 treatment were significant better than those received the other N treatments. For all compost blends, premium-quality plants were produced with N at 200 mg•L-1 treatment and good-quality plants were obtained with the remaining N treatments. The control substrates produced good quality plants with N treatments at 150 and 200 mg•L-1, the remaining N treatments resulted in plants that were only salable at reduced price. `Red Akron' is a free-branching spray cultivar, had more flowers and branches than the other two cultivars.

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Use of wild species for in vitro sweetpotato improvement has been limited, in part, by the lack of suitable regeneration systems for these species. Shoot regeneration in 4 closely related species, I. batatas, I. cordatotriloba, I. trifida and I. triloba, were evaluated. Callus was initiated using methods described by Otani and Shimada (1988). Calli were transferred to regeneration media containing 17.75 uM BAP and 0, 1, 10 and 100 uM PCIB. Organogenesis was enhanced by the presence of PCIB. With I. cordatotriloba calli grown on media with 10 uM PCIB, a 2-fold increase in the percentage of calli exhibiting shoot regeneration was observed as compared to calli grown on media with BAP alone. A significant increase in the average number of shoots per callus was also observed. The other species examined appeared to be less sensitive than I. cordatotriloba to the PCIB treatments.

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Vegetable culture with Municipal Solid Waste Compost (MSWC) amended soils was evaluated with the emphasis on crop and soil responses. There were three treatments of 0, 20, and 40 t·ha–1 of MSWC applied in the fall of 1993 to a Matapeake Silt Loam on the Eastern Shore of Maryland. The following spring the soil was prepared for planting tomatoes and green beans. All crop management practices were in accordance with the standard procedures followed in Maryland for each crop, except for the addition of the MSWC. Both crop yields were significantly increased with the addition of the MSWC. Following the bean crop, broccoli transplants were established in the fall of 1994. Again, the yields obtained with the MSWC plots as compared to the control were significantly greater. Soil properties were also favorably affected by the addition of the compost. Analysis of soil samples indicated significant increases with MSWC, such as cation exchange capacity, soil pH, percent organic matter, and water-holding capacity.

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Municipal solid waste (MSW) may be a potential substitute for peat substrate in soilless medium. Adequate N and P are needed for a complete composting of MSW. MSW piles treated with diammonium phosphate (MSWP) or without P on Mar. 1994 were cured for 5 months. In Fall 1994, a factorial treatment combination of nine mixes and 3 fertigation treatments were evaluated in a completely randomized design on soft-pinched, single-stem `Red Sail' poinsettia. Mixes were MSW or MSWP ranging from 33% to 100% by volume in 1 peat: 1 perlite (v/v) and Sunshine mix was used as the control. Fertigation treatment began on the 1st, 2nd, or 3rd week after potting. Fertigation solution contained 266 mg·liter–1 N from 30N–4.4P–8.8K. The total fertigations ranged from eight to 10 for the 13-week study. With MSW mixes, shoot dry mass at the week 1 fertigation was 36% larger than at the week 3 fertigation. At the week 3 fertigation, shoot dry mass with 100% MSWP was ≈53% greater than with the 100% MSW. Shoot dry mass with 100% MSWP was similar to the control at the week 1 fertigation.

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Optimum conditions for composting encourage and maintain the growth of microorganisms. Aerobic conditions must be maintained along with a 30 C: 1 N ratio and appropriate moisture levels. Our research found that P along with C and N are primary nutrients required by the microorganisms involved in composting. Phosphorus is a very important component of ATP and ADP, which drive most biochemical processes and are therefore necessary to all energy-driven processes. Results of this experiment show that MSW treatments with a minimum of 120 C: 1 P result in significantly higher temperatures during the composting process; lower final C: N ratios; greater volume reduction; and more available N in the final product. Emphasis of ongoing research is to determine appropriate C: P levels.

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