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Brian A. Kahn, John P. Damicone, Kenneth E. Jackson, James E. Motes and Mark E. Payton

Nine nematicide treatments were evaluated from 1993 through 1995 in field experiments on paprika pepper (Capsicum annuum L.). Materials tested included a chitinurea soil amendment and six chemicals: fosthiazate, carbofuran, aldicarb, oxamyl, fenamiphos, and 1,3-dichloropropene (1,3-D). Stands at harvest were increased relative to the control by chitin-urea, fosthiazate, and 1,3-D, but only fosthiazate increased marketable fruit yield relative to the control. Aldicarb reduced preharvest nematode populations relative to the control, but aldicarb did not result in a significant fruit yield increase. Chitin-urea was the only treatment to produce a net increase in nematode counts from preplant to preharvest in all three years. Although fosthiazate was promising, nematicide treatments were of limited benefit under the conditions of these studies. Chemical names used: (RS)-S-sec-butyl O-ethyl 2-oxo-1,3-thiazolidin-3-ylphosphonothioate (fosthiazate); 2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate (carbofuran); 2-methyl-2-(methylthio)propionaldehyde O-(methylcarbamoyl)oxime (aldicarb); methyl N′N′ -dimethyl-N-[(methylcarbamoyl)oxy]-1-thiooxamimidate (oxamyl); ethyl 3-methyl-4-(methylthio)phenyl(1-methylethyl) phosphoramidate (fenamiphos).

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Brian A. Kahn, Phillip G. Shilling, Gerald H. Brusewitz and Ronald W. McNew

Broccoli [Brassica oleracea L. (Italica Group)] crops may be rejected by wholesale buyers due to unacceptably tough stalks. Four experiments were conducted to examine the effects of various N levels and two within-row spacings (15 and 30 cm) on force to shear the stalk, stalk diameter, and yield of transplanted `Premium Crop' broccoli. Shear was not affected by within-row spacing, and average stalk diameter was decreased only 3 mm by reducing spacing from 30 to 15 cm. Although the 15-cm spacing sometimes produced the greatest total number of marketable, heads, this spacing resulted in higher cull head production, lower average marketable head weight, delayed maturity, and a lower percentage of field-planted transplants producing marketable heads than the 30-cm spacing. Increasing N fertilization decreased force to shear the stalk in only one experiment, when plants were exposed to water deficits and high temperatures. Nitrogen affected stalk diameter only when very low rates (37 and 74 kg·ha-1) were included. Yield of marketable-quality heads often showed no significant response to rates of applied N >112 kg·ha-1, particularly at the 30-cm spacing. Hollow stem was negligible in all experiments.

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Brian A. Kahn, Niels O. Maness, Donna R. Chrz and Lynda K. Carrier

Six experiments were conducted on ‘Genovese’ basil (Ocimum basilicum L.) in Oklahoma to study the feasibility of establishing basil in the field by direct seeding. Variables examined included use of raw seed or pelleted seed, seeding depth, seeding rate, and comparison with transplanting. Direct seeding was done using a hand-pushed planter (first four experiments), a tractor-drawn planter (fifth experiment), or both types of planter (sixth experiment). Plants were destructively harvested by machine. Stands were established successfully using transplants or using raw or pelleted seed with a hand-pushed planter. Planting at a depth of ≈10 mm resulted in lower yields than planting at a depth where seeds barely were covered with soil (≈5 mm). Seeding rates of ≈80 seeds/m led to higher final stands and higher yields than those obtained with seeding rates of ≈30 seeds/m. These studies were not designed to test effects of plant population on basil yield, but data suggest that final stands above the common recommendation of one plant per 30.5 cm in rows spaced 90 cm apart may result in yield increases. Plots direct-seeded with the tractor-drawn planter failed to establish in the fifth experiment. Plants established using pelleted seed with the hand-pushed planter did not differ from plants established by transplanting in cumulative yields in the sixth experiment, even though the transplanting treatment allowed one additional harvest. The lowest cumulative yields in the sixth experiment came from plants established using pelleted seed with the tractor-drawn planter. Thus, direct seeding of basil was successful only with a hand-pushed planter. While direct seeding is a potentially viable alternative to transplanting for basil stand establishment, there is a need to identify a tractor-drawn seeder that can plant basil at the required shallow depth. In the interim, large-scale producers of basil should continue to use transplants to obtain reliable stand establishment.

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Yaying Wu, Brian A. Kahn, Niels O. Maness, John B. Solie, Richard W. Whitney and Kenneth E. Conway

Okra [Abelmoschus esculentus (L.) Moench] was grown at various highly dense (HD) plant populations for destructive harvest, and compared with control plants grown at spacings of 90 × 23 cm and harvested repeatedly by hand. Our objectives were to identify a HD plant arrangement and an optimum harvest timing to maximize marketable fruit yield per hectare with a single destructive harvest, and to evaluate the potential for regrowth of cut plants followed by one or more subsequent harvests. Within HD treatments, marketable fruit weight per hectare tended to increase as the plant population density increased. Spacings of 30 × 30 cm and wider were not dense enough for the destructive harvest system due to a low marketable yield potential. Wide spacings did favor regrowth of cut plants in two experiments, but total marketable yields were still highest with the highest plant populations tested. Delaying destructive harvest until many overmature fruit were present did not consistently affect marketable fruit yield, but always decreased the proportion (by weight) of marketable fruit to total harvested fruit. Overall, percentages of marketable yield obtained by destructive harvests of plots with HD plant populations were low relative to the cumulative marketable yield from control plots. The lack of concentrated fruit set in okra remains a limiting factor for destructive harvest. However, the labor-saving potential of this system should stimulate further research.

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Yaying Wu, Brian A. Kahn, Niels O. Maness, John B. Solie, Richard W. Whitney and Kenneth E. Conway

Research was conducted to develop a cultural system that would permit a destructive mechanical okra [Abelmoschus esculentus (L.) Moench] harvest. This paper reports on studies to determine the responses of okra plant architecture to various highly dense (HD) plant populations, and to consider the implications of those responses for destructive mechanical harvest. Growing okra in plant arrangements more densely planted than the control (which was spaced at 90 × 23 cm) did not affect overall plant heights. The position of the first bloom or fruit attachment and of the first marketable fruit attachment tended to become higher on the stem as plant population density increased, especially when comparing plants from the 15 × 15 cm spacing to control plants. The number of marketable fruit per plant was usually unaffected by plant population. Branch number and defruited dry weight per plant decreased as plant population density increased. Plant architecture did not affect the ability of an experimental mechanical harvester to recover marketable fruit from three different okra cultivars grown in a HD arrangement. The lack of concentrated marketable fruit set, rather than plant architecture, was the main limiting factor to the success of densely planted okra for destructive harvest.