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Brian A. Kahn

A 2-year study was conducted at Bixby, OK, to examine shoot characteristics of several eggplant (Solanum melongena) cultivars, including the vertical distribution patterns of fruit production, and to examine possible relationships of these traits to aspects of fruit quality. Plants of 11 cultivars of purple-fruited eggplant were field-grown following local production practices. Fourteen harvests of fruit that had reached horticultural maturity were made from 99 plants in each year over a period of ≈45 days per year. On each harvest date, every fruit that was harvested from an individual plant was charted. Before a fruit was severed from the plant, heights were measured from the soil surface to the pedicel attachment and to the blossom end. Each fruit was then weighed and categorized for marketability. On the day after the final harvest, each data plant was measured for height and diameter of the main stem and then severed at soil level for subsequent measurement of shoot dry weight. ‘Classic’, ‘Dusky’, ‘Megal’, and ‘Santana’ were the only cultivars that produced more than 50% marketable fruit in both years. There were no consistent relationships between plant height, stem diameter, or shoot dry weight and fruit quality. For a given cultivar, the fruiting plane was defined as the vertical space in which fruit were found over the course of the harvest period. This was delimited at the top by the mean height above the soil of the point of pedicel attachment and at the bottom by the mean height above the soil of the blossom end. The cultivars differed in fruiting planes, but height of fruit set was relatively unimportant as a determinant of overall fruit quality. Cull fruit usually had blossom ends that were higher off the ground than marketable fruit. The primary reason for cull fruit production was determined for two cultivars: ‘Black Beauty’ had poor fruit color and ‘Black Bell’ was relatively susceptible to fruit rot (primarily caused by Phomopsis vexans). Fruit scarring was found to be a major contributor to cull fruit production. Cultivars differed in fruit scarring in 1 of 2 years, and there was evidence that scarred fruit occurred higher in the crop canopy than marketable fruit.

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Brian A. Kahn

Growers of turnip `greens [Brassica rapa L. (Rapifera Group)] are accustomed to planting 5.6 to 10 kg of seed per hectare. A study was conducted in 1985 to determine whether reduced plant populations could be used without reducing yield or quality for `Alltop', a hybrid cultivar with relatively expensive seed. A trial planted on 4 Apr. showed that populations could be reduced from 64 to 33 plants/m of row without reducing yield or quality. A second trial, planted on 30 Aug., used populations of 36, 26, and 16 plants/m of row. Again, there were no statistically significant reductions in yield or quality as populations decreased. However, yields from the 36 and 16 plants/m treatments differed by almost 7 t·ha-1, indicating substantial variability. A conservative approach would be to use a population of 33 to 36 plants/m of row (≈ 725,400 plants/ha) to provide a balance between seed costs and yield. This can be achieved by seeding rates of 2.2 to 2.8 kg·ha-1.

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Brian A. Kahn

Paprika pepper (Capsicum annuum L.) plants were subjected to a single destructive harvest in either October, November, or December to determine an optimal month for once-over harvest. Studies were conducted at two locations in Oklahoma each year for two years. Total and marketable fruit yields were highest with October harvest dates in three of the four experiments. Marketable fruit red color intensity decreased between the November and December harvest dates at both locations in the second year. It appears that paprika harvest should be completed during October in this region.

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Brian A. Kahn

Paprika pepper (Capsicum annuum L.) plants were subjected to a single, destructive harvest in either October, November, or December to determine an optimal month for once-over harvest. Studies were conducted at two locations in Oklahoma each year for 2 years. Total and marketable fruit yields were highest with October harvest dates in three of the four experiments. Marketable fruit red pigment intensity decreased between the November and December harvest dates at both locations in the second year. When the crop is established by transplanting, paprika harvest should be completed during October in the southwestern United States.

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Brian A. Kahn

This review summarizes studies involving intercropping for field production of peppers [Capsicum spp. (typically Capsicum annuum)]. Intercropping is particularly important in developing countries and where arable land is limited. Fruit crops, vegetables, forages, and other crops representing over 12 botanical families have been intercropped with peppers. System recommendations may be affected by whether one is attempting to grow another species as an intercrop in a pepper field or whether peppers are being used as an intercrop in a different primary crop. Other factors such as the timing of the intercrop planting, climatic conditions, and local economics all contribute to the potential success or failure of intercropping with peppers. Although broad recommendations cannot be made, the reviewed studies offer several examples of successful combinations of peppers with other crops.

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Clydette Alsup and Brian A. Kahn

Cowpea [Vigna unguiculata L. (Walp.)] cover crops were grown in a rotation with broccoli (Brassica oleracea L. var. italica Plenck.), spinach (Spinacia oleracea L.), and turnip greens [Brassica rape L. var. (DC.) Metzg. utilis] to evaluate the legume's ability to remove excess P from soils when poultry litter was used as a fertilizer. Fertilizer treatments were litter to meet each crop's recommended preplant N requirements (1X), litter at twice the recommended rate, and urea at the IX rate as the control. Following the vegetable crops, cowpeas were planted on half of each replication, while the other half was fallowed. The cowpeas were harvested for green-shell seeds and then underwent a simulated haying operation. Soil samples were taken at 0-to 15-cm and 15- to 30-cm depths at the onset of the study and after each crop to monitor plant nutrient levels. The cowpeas effectively lowered soil N levels but not soil P levels. However, there was no consistent evidence of an increase in soil P or K levels with litter applications. All three vegetable crops were successfully grown using poultry litter, although the 1X rate appeared inadequate for maximum production of broccoli and turnip greens.

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Brian A. Kahn and Wendy A. Nelson

Trellised plants of `Oregon Sugar Pod II' and `Snowflake' snow peas (Pisum sativum var. macrocarpon Ser.) were grown in single and double rows on l-m centers at a constant population of 20 plants/m2 in 1988 and 1990. Plants of `Oregon Sugar Pod II' produced a greater number and weight of fresh pods than plants of `Snowflake' in both years. Plants grown in double rows (10 cm within-row spacing) produced a greater number and weight of fresh pods than plants grown in single rows (5 cm within-row spacing) in 1988, but not in 1990. Vine dry weights were greater from plants grown in double rows than from plants grown in single rows in both years. Double rows seemed more promising for home gardeners than for commercial growers because of the increased branching and more widely scattered pod distribution on plants grown in double rows compared with plants grown in single rows.

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Brian A. Kahn and Niels O. Maness

Factorial combinations of two row arrangements on 1.8-m-wide beds (either four rows, each 30 cm apart, or eight rows, each 15 cm apart) and two in-row seeding rates (either 48 or 96 seeds per 30 cm of row) were compared on ‘Santo’ cilantro (Coriandrum sativum L.) in five experiments at Bixby, OK. Plots were harvested once per experiment by cutting at a height of ≈7 cm with a small-plot greens harvester, and fresh weight yields were taken. Treatments minimally affected canopy height at harvest. Eight rows resulted in higher yields than four rows in three of five experiments. Main effects of seeding rate or interactions of row number and seeding rate on yield were rare. Of the four combinations tested, the eight-row arrangement sown at 48 seeds per 30 cm would be recommended. This arrangement was used in three other experiments to test effects of a single preharvest spray application of gibberellic acid (GA). Treatments were a water control and GA at either 10 or 20 g·ha−1. Treatment with GA increased bolting in a 17 Apr. planting and increased canopy height at harvest in two of three experiments. However, GA treatments did not affect yield. Treatment with GA would not be recommended for a spring cilantro crop and may have limited impact on increasing machine recovery of raw product in a fall crop.

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Brian A. Kahn* and Daniel I. Leskovar

Single- and double-row arrangements of a fixed population (one plant every 0.285 m2) were compared in factorial combination with two (2002) or five (2003) cultivars for effects on yield and fruit quality of bell pepper (Capsicum annuum L.). Arrangements for 2002 were: (1) 1.9 m between centers of double-row beds, rows on beds 30 cm apart, plants within rows 30 cm apart; (2) single rows 0.95 m apart, plants within rows 30 cm apart; (3) 1.52 m between centers of double-row beds, rows on beds 24 cm apart, plants within rows 37.5 cm apart; and (4) single rows 0.76 m apart, plants within rows 37.5 cm apart. Only arrangements (1) and (2) were used in 2003. Row arrangement did not affect marketable fruit production in Oklahoma in 2002, but single rows resulted in a greater weight of fruit with blossom-end rot than double rows. Arrangement (2) resulted in both a greater weight of U.S. No. 1 fruit and a greater weight of sunburned fruit than arrangement (1) in Texas in 2002. `King Arthur' produced more marketable fruit than `X3R Wizard' in Oklahoma in 2002, but the opposite occurred in Texas. Arrangement (2) resulted in a greater weight of U.S. No. 1 fruit than arrangement (1) in both locations in 2003. Arrangement (2) also resulted in greater weights of sunburned (Oklahoma) or total cull (Texas) fruit than arrangement (1) in 2003. `Lafayette' and `X3R Wizard' produced a greater weight of marketable fruit than `Boynton Bell', `Karma', and `King Arthur' in Texas in 2003, but not in Oklahoma. Plant arrangement × cultivar interactions were not evident in Oklahoma and minimal in Texas. Given the tested population, a single row arrangement is likely to result in higher U.S. No. 1 fruit yields than a double-row arrangement, despite an increased potential for cull fruit production with single rows.

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Brian A. Kahn and William G. McGlynn

Snap bean (Phaseolus vulgaris L.) cultivars with pods representing a range of greenness were grown in Oklahoma field trials in 2001 and 2004. Objective color evaluations (L* value and hue angle) performed on raw and cooked pod samples from 10 (2001) or 12 (2004) of these cultivars indicated that color testing of raw snap bean pods may not be sufficient to determine the color after cooking. Although L* values may be expected to decrease after cooking, the magnitude of the changes may not be predictable. Changes in hue angle values after cooking appear to be even more variable among cultivars. Therefore, if the color of the cooked beans is expected to be a deciding factor in cultivar selection, we would recommend conducting color tests on cooked bean pods as well as the raw product. Twenty relatively straight, unblemished pods per cultivar were harvested on 20 June 2001 and on 30 June 2004 from plants of ‘Blue Lake 274’, ‘Brio’, ‘Charon’, ‘Jade’, and ‘Seville’. The five most uniform pods per cultivar (all sieve Size 4) were presented as raw samples that same day to an untrained panel consisting of seven males and 18 females (2001) or nine males and 18 females (2004). This was an affective test; panelists were asked to evaluate intensity of color and likeliness to buy using a 5-point semantic differential scale. Correlation coefficients for the two attributes were calculated. Sensory panelists were able to make subjective distinctions among the cultivars based on color. However, these differences did not necessarily correlate with either objective color measures or likelihood of purchase. Snap bean pod color is not an overriding selection criterion, but only one of many criteria considered by consumers.