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Peter J. Stoffella

Sweet Spanish onion (Allium cepa L. cv. Granex 33) was transplanted in two, three, or four rows per bed at 7.6, 15.2, or 22.9 cm in-row spacings resulting in plant populations ranging from 41,000 to 246,000 plants/ha during Winter 1991. Interactions between number of rows per bed and in-row spacings were nonsignificant for onion yield and bulb size traits. As number of rows per bed increased or in-row spacings decreased, marketable onion yield linearly increased and mean bulb size (g/bulb) decreased. Percentage of small, medium, and large bulbs was unaffected by number of rows per bed, but percentage of small and medium-sized bulbs increased and percentage of large bulbs decreased as in-row spacing decreased. Onion yields linearly increased, but at the expense of smaller-sized bulbs, whether plant populations were increased by more rows per bed or narrower in-row spacings.

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Peter J. Stoffella and Mike F. Fleming

Cabbage [Brassica oleracea L. (Capitata Group) cv. Bravo] transplants were grown on raised beds at Fort Pierce, Fla., during Fall 1987 and 1988. Plants were spaced at 8, 15, 23, 30, and 38 cm within rows or populations equivalent to 123,000, 61,500, 41,000, 30,800, and 24,600 plants/ha. Individual root weights, total plant weights, and core length increased linearly as within-row spacing (WRS) increased in both experiments. Untrimmed head weights, trimmed head weights, head height, head width, and core width increased quadratically as WRS increased in both experiments. Head shape and core index did not differ among WRS in either experiment, except for a quadratic increase in the head height: bead width ratio (head shape) as WRS increased in the 1988 experiment. Coefficients of variability (cv) for most measured variables decreased as WRS increased, indicating a reduction in plant-to-plant variation. Optimum marketable cabbage head size (>1 kg) and lower plant-to-plant variation (cv < 20%) were obtained at WRS of 23 cm or wider. However, trimmed cabbage yields decreased linearly as WRS increased in both experiments. In this study, a lower plant population (WRS > 23 cm) was more conducive to a once-over cabbage harvest since plant-to-plant variation in head size and other yield and quality characteristics was reduced.

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Nancy E. Roe and Peter J. Stoffella

Composts may improve crop growth in sandy soils. A biosolids-yard trimming compost (C) was incorporated into sandy soil at 134 t·ha–1 (49.7% moisture) before applying polyethylene mulch. Fertilizer (F) was applied at 0%, 50%, and 100% of the grower's rate (71N–39P–44K t·ha–1 broadcast and 283N–278K t·ha–1 banded in bed centers). `Elisa' pepper transplants were planted 20 Jan. 1994. Marketable fruit weights were 20, 31, and 32 t·ha–1 without C and 30, 35, and 32 t·ha–1 with C for 0%, 50%, and 100% F, respectively. Pepper fruit weights increased with increasing F rates and were higher in plots with C than without C. Without removing mulch, `Thunder' cucumbers were seeded on 26 Sept. 1994. Marketable fruit weights were similar at the three F levels, but were 23 and 27 t·ha–1 without and with C, respectively. One application of C significantly increased bell pepper yields and a subsequent cucumber crop.

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Milton E. Tignor and Peter J. Stoffella

Florida citrus has had an average annual on-tree-value of ≈1 billion dollars during the past decade in Florida. Nearly all of the 845,260 acres of citrus in Florida is produced on grafted trees consisting of a commercial scion cultivar and a rootstock selected specifically for local soil, environment, and pest pressures. With vastly different root-zone environments, ranging from deep sands to drained and cleared pine Flatwoods, a large number of different rootstocks are utilized. These rootstocks are started from seed at more than 100 commercial nurseries statewide, which currently produce an estimated 6 million trees a year. Although the optimum germination conditions, basic physiological performance, and adaptability of many rootstocks are known, there has been minimal investigation on early root development in seedling trays at the nursery. Four hundred seedlings of `Swingle' citrumelo (Citrus paradisi Macf. `Dunacn' × Poncirus trifoliata), `Smooth Flat Seville', `Volkamer' lemon (Citrus volkameriana), and `Sun Chu Sha' mandarin were seeded in a randomized block experimental design and grown at a commercial nursery. Seedling root systems (100/rootstock) were analyzed for a number of variables using the Rhizo (Regent Instruments, Inc.) software package and a dual light source scanner. Using the SAS general linear model procedure, hypothesis testing revealed rootstock selection had a significant effect on total root length, total root surface area, total root volume, number of root tips, number of root forks, root dry weight, and stem diameter. For most characteristics, rootstock genotype accounted for a greater portion of variability than samples (plant to plant variability).

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Sandra B. Wilson and Peter J. Stoffella

Peat is used extensively in the nursery industry as a primary component in commercial “soilless” potting media. The increased use of peat as an organic amendment with superior water-holding capacity is challenged by economic and environmental pressures. Developing inexpensive and nutrient-rich organic media alternatives can potentially reduce fertilization rates, irrigation rates, and ultimately, nursery costs. In addition, controversy over the effects of peat mining has inspired a national search for peat substitutes. With our burgeoning population, it is logical to screen waste products as potential alternatives to peat. Growth of Pachystachys lutea Nees. (Golden Shrimp Plant) transplants was evaluated in media containing 0%, 25%, 50%, 75%, or 100% compost derived from biosolids and yard trimmings. Compost was amended with a commercial peat- or coir-based media. As compost composition in the peat or coir-based media increased from 0% to 100%, carbon/nitrogen (C/N) ratios decreased, and media stability, N mobilization, pH, and electrical conductivity (EC) increased. Bulk density, particle density, air-filled porosity, container capacity, and total porosity increased as more compost was added to either peat- or coir-based media. Plants grown in media with high volumes of compost (75 or 100%) had reduced leaf area and reduced shoot and root DW than the controls (no compost). Regardless of percentage of compost composition in either peat or coir-based media, all plants were considered marketable after 8 weeks.

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Daniel I. Leskovar and Peter J. Stoffella

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Brian A. Kahn and Peter J. Stoffella

Seeds of `Rutgers California Supreme' tomato (Lycopersicon esculentum Mill.) were exposed to outer space conditions aboard the long duration exposure facility (LDEF) satellite in the space exposed experiment developed for students (SEEDS) project of the National Aeronautics and Space Administration (NASA). Seeds aboard the LDEF were packed in dacron bags forming four layers per sealed canister. Some of these seeds were used in Oklahoma and Florida for studies of germination, emergence, and fruit yield. Among all measured variables in three experiments, there was only one significant main effect of canister 2 versus canister 7 (for mean time to germination) and only one main effect of layer (for seedling shoot dry weight). There also were only two inconsistent canister x layer interactions in the germination tests. The contrast of Earth-based control seed versus space-exposed seed was significant four times: in Oklahoma in 1991 the mean time to germination of space-exposed seeds and the days to 50% of final germination were 0.7 days less than for Earth-based seeds, and in Florida in 1992 seedling percent emergence and shoot dry weight were increased by space exposure. Fruit yield and marketability were unaffected in plants grown from space-exposed seeds. These results support student findings from the SEEDS project, and provide evidence that tomato seeds can survive in space for several years without adverse effects on germination, emergence, and fruit yield.

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Brian A. Kahn and Peter J. Stoffella

Field experiments were conducted in 1985 at Fort Pierce, Fla., and Bixby, Okla., to quantify and describe the distribution of nodules among root morphological components of cowpea [Vigna unguiculata (L.) Walp.]. Plants of `Knuckle Purplehull', `Mississippi Cream', and `White Acre' were sampled by cultivar on separate dates at three growth stages: pre-anthesis, seed initiation, and harvest, when most pods were dry. Root masses were partitioned into adventitious, basal, lateral, and taproot components. Nodules were removed from roots, grouped according to root morphological component of origin, and weighed. No linear correlation was found between the weight of a particular root morphological component and the nodule weight associated with that component. Total root weight and total nodule weight also were not strongly correlated. Nodule weights usually were lower at harvest than at earlier stages of ontogeny, especially for nodules from taproots. Although ≈70% of the root mass was in the taproot and its associated laterals at both locations, the taproot per se was not the primary locus of nodulation. Instead, most nodules generally were located on the basal and lateral roots. When percentage distribution of total nodule weight was examined, neither growth stage nor cultivar was found to affect nodulation of basal or lateral roots.

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Charles A. Powell and Peter J. Stoffella

Mature-green and mature-red tomato (Lycopersicon esculentum Mill.) fruit were harvested from spring- and fall-grown plants infested with sweet potato whitefly (SPWF; Bemisia tabaci Gennadins). The mature-green fruit were either ripened at 20 to 22C or cold-stored at 10 to 13C for 3 weeks and then were allowed to ripen at 20 to 22C. There was no significant difference in the appearance of either external or internal tomato irregular ripening (TIR) symptoms between the two storage–ripening regimes or in the appearance of internal TIR symptoms among the two storage regimes and vine-ripened tomatoes. Thus, removing the tomatoes from the SPWF during ripening does not reduce TIR symptoms. About half of the mature-green tomatoes, ripened with or without cold storage (10 to 13C), developed no external TIR symptoms, but about half of these tomatoes had internal TIR symptoms. About one-third of the tomatoes developed external symptoms during ripening, but these symptoms disappeared after ripening was complete. A high percentage (71%) of these tomatoes with external symptoms also had internal symptoms. The remaining tomatoes developed external TIR that did not disappear, and almost all of these tomatoes had internal symptoms. These data suggest that culling tomatoes that develop external TIR during ripening will reduce but not eliminate tomatoes with internal TIR from the fresh-fruit market.