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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.

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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 S30, single rows 0.95 m apart, plants within rows 30 cm apart; D30, 1.9 m between centers of double-row beds, double rows 30 cm apart on beds, plants within rows 30 cm apart; S37.5, single rows 0.76 m apart, plants within rows 37.5 cm apart; and D37.5, 1.52 m between centers of double-row beds, double rows 24 cm apart on beds, plants within rows 37.5 cm apart. Only the S30 and D30 arrangements were used in 2003 after 2002 results showed almost no differences between S30 and S37.5 or between D30 and D37.5. Choice of cultivar was more critical in Texas, where `X3R Wizard' consistently outperformed `King Arthur', than in Oklahoma. Single rows resulted in more full-season total marketable fruit weight than double rows in three experiments out of four, primarily as a result of an increased weight of U.S. No. 1 fruit with single rows. Average weight per marketable fruit was consistently unaffected by plant arrangement. Single rows also resulted in a greater full-season weight of sunburned fruit than double rows in two experiments out of four. Cultivar × plant arrangement interactions were not evident in Oklahoma and never involved full-season marketable fruit weights at either location in either year. Given the tested population, a single-row arrangement is likely to result in increased full-season production of U.S. No. 1 bell pepper fruit compared with a double-row arrangement, despite an increased potential for sunburned fruit with single rows.

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Wendy A. Nelson, Brian A. Kahn and B. Warren Roberts

Several prospective cover crops were sown into 1-m2 monoculture plots on 9 Mar. 1987 and 10 Mar. 1988 at Bixby, Okla., and on 14 Mar. 1988 at Lane, Okla., after sites were plowed and fitted. Densities and dry weights of cover crops and weeds were determined in late April or early May of both years. Plots also were evaluated for degree of kill by glyphosate in 1988. Fourteen cover crops were screened at Bixby in 1987. Kentucky bluegrass (Poa pratensis L.) and three fescues (Festuca rubra L., Festuca rubra L. var. commutata Gaud.-Beaup., and Festuca elatior L.) were eliminated from further consideration due to inadequate cover density and inability to suppress weeds. Screenings of the 10 remaining covers were conducted at both locations in 1988. Annual ryegrass (Lolium multiflorum L.) and three small grains [rye (Secale cereale L.), barley (Hordeum vulgare L.), and wheat (Triticum aestivum L.)] were the most promising cover crops with respect to cover density, competitiveness against weeds, and degree of kill by glyphosate. Crimson clover (Trifolium incarnatum L.) and hairy vetch (Vicia villosa Roth) were the most promising legumes, but they generally were less satisfactory than the grassy covers in all tested aspects. A single application of glyphosate was ineffective in killing hairy vetch at both locations. Chemical name used: N-(phosphonomethyl)glycine (glyphosate).

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Brian A. Kahn, Raymond Joe Schatzer and Wendy A. Nelson

The herbicides trifluralin, metolachlor, and paraquat were compared for efficacy of weed control in cowpea with and without cultivation as a supplemental strategy for two years. Herbicides also were compared against a no-herbicide control (with and without cultivation). Cultivation had no significant effect on seed yield, biological yield, or harvest index of cowpea. Paraquat, used in a “stale seedbed” system, was ineffective for weed control and did not change cowpea yield from that of the no-herbicide control. Trifluralin and metolachlor more then tripled cowpea seed yield compared to that of the no-herbicide control in 1988, when potential weed pressure was 886 g m-2 (dry wt.). Trifluralin and metolachlor did not significantly increase cowpea seed yield compared to that of the no-herbicide control in 1989, when potential weed pressure was 319 g m-2 (dry wt.). However, in 1989, these two herbicides each still increased net farm income by $206 per hectare compared to the income obtained without an herbicide.

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James R. Cooksey, Brian A. Kahn and James E. Motes

While ethephon [(2-chloroethyl) phosphonic acid] has increased yields of red fruits, its use as a pepper (Capsicum annuum L.) fruit ripening agent has been limited by premature fruit abscission and defoliation. We tested ethephon solutions of 0, 1500, 3000, 4500, and 6000 μl·liter-1 with or without 0.1M Ca(OH)2 as a one-time foliar application to field-grown paprika pepper in southwestern Oklahoma. There was a linear increase in fruit abscission with increasing ethephon rates in two out of three years, with or without added calcium. Ethephon at 6000 μl·liter-1 improved the percent of total fruit weight due lo marketable fruits in two out of three years, primarily by decreasing the weight of harvested green fruits. However, ethephon never significantly increased the dry weight of harvested marketable fruits over that obtained from the control. There also was no effect of ethephon on the intensity of red pigment extracted from dehydrated marketable fruits. The only significant effect of Ca(OH)2 was an undesirable increase in the retention of green fruits on the plants. Ethephon had little value as a fruit ripening agent for paprika under the conditions of our studies, and Ca(OH)2 was not useful as an additive to ethephon sprays.

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Brian A. Kahn, James R. Cooksey and James E. Motes

Raw seed, primed seed, and transplants were compared for effects on stand establishment, plant morphology, and yield of paprika pepper (Capsicum annuum L.) Raw seed seemed satisfactory for stand establishment, although primed seed had the potential to provide better initial stands. When populations were equalized, there were few differences in plant growth, plant morphology, or fruit yield attributed to seed treatment. Morphology of plants established by direct seeding generally was favorable for mechanical harvest. Use of transplants did not result in higher marketable fruit yields than direct seeding in two out of three years. When compared to plants established by direct seeding, three trends were consistent across all three years for plants established by transplanting: a) they were more massive: b) they had larger vertical fruiting planes: and c) they had more branches. These traits would increase the difficulty of mechanical harvest and would create the potential for more trash in the harvested product. Thus, transplanting is not recommended for stand establishment of paprika intended for mechanical harvest.

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James R. Cooksey, Brian A. Kahn and James E. Motes

Nontreated seed, primed seed, and transplants were compared for effects on stand establishment, plant morphology, and yield of paprika pepper (Capsicum annuum L.). Nontreated seed was satisfactory for stand establishment, although primed seed had the potential to provide greater initial stands. When populations were made equal by thinning, there were few differences in stem and leaf dry weight, fruit yield, or plant morphology attributed to seed treatment. Generally, morphology of plants established by direct seeding was favorable for mechanical harvest. Using transplants did not result in higher marketable fruit yields than direct seeding in 2 of 3 years. When compared to plants established by direct seeding, three trends were consistent across all 3 years for plants established by transplanting: 1) they were more massive, 2) they had larger vertical fruiting planes, and 3) they had more branches. These traits increase the difficulty of mechanical harvest and create the potential for more leaves and stems (trash) in the harvested product. Thus, transplanting is not recommended for stand establishment of paprika pepper intended for mechanical harvest.

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Yaying Wu, Brian A. Kahn and John B. Solie

We are developing a mechanical harvest system for okra [Abelmoschus esculentus (L.) Moench]. Our objective was to identify a high-density (HD) plant arrangement and a harvest timing that would maximize marketable fruit yield per hectare with a destructive harvest. We compared destructively harvested plants grown at spacings of (in cm) 15 × 15, 23 × 23, and 30 × 30 with hand-harvested plants grown at 90 × 23 cm. Within HD treatments, marketable fruit weight increased inconsistently as plant density increased. The 30 × 30-cm spacing was not dense enough. Branching decreased and the position of the first marketable fruit attachment moved up as plant density increased. Delaying destructive harvest until many over-mature fruit were present often did not increase marketable fruit yield and always reduced the proportion of total harvested fruit weight due to marketable fruit. Overall, percentages of marketable yield obtained by destructive harvests of HD plants were low compared to the cumulative marketable yield from control plants. However, the labor-saving potential was high. A prototype machine for harvest of HD okra has been developed, and further testing is planned.

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James R. Cooksey, James E. Motes and Brian A. Kahn

Ethephon has increased yields of red fruit, but its use as a pepper (Capsicum annuum L.) fruit ripening agent has been limited by premature fruit abscission and defoliation. We tested ethephon solutions of 0,1500,3000,4500, and 6000 μl·liter-1 with or without 0.1 m Ca(OH)2 as a onetime foliar application to field-grown paprika pepper in southwestern Oklahoma. There was a linear increase in fruit abscission with increasing ethephon rates in 2 of 3 years, with or without added Ca. Marketable fruit as a percentage of total harvested fruit weight was improved by ethephon at 6000 μl·liter-1 in 2 of 3 years, primarily due to a decrease in weight of harvested green fruit. However, ethephon never significantly increased the dry weight of harvested marketable fruit over that obtained from the control. There also was no effect of ethephon on the intensity of red pigment extracted from dehydrated marketable fruit. The only consistently significant effect of Ca(OH)2 was an undesirable increase in the retention of green fruit on the plants. Ethephon had little value as a fruit-ripening agent for paprika pepper under the conditions of our studies, and Ca(OH)2 was not useful as an additive to ethephon sprays. Chemical name used: (2-chloroethyl) phosphoric acid (ethephon).

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Michael D. McCullough, James E. Motes and Brian A. Kahn

Two problems associated with machine harvesting of peppers (Capsicum annuum L.) are plant lodging during growth and uprooting. Factorial combinations of four bedding treatments and two N rates were compared for effects on lodging, uprooting, and fruit yield of chile and paprika-type peppers in Fort Cobb and Bixby, Okla. Bedding treatments were 1) no bed (T1); 2) no bed with 5 cm of soil hilled to the plant bases (T2); 3) bedded preplant, but bed not sustained (i.e., allowed to erode) during the growing season (T3); and 4) bedded preplant and bed sustained during the growing season (T4). All plots received preplant N at 45 kg·ha–1. In 1992, one-half of the plots were sidedressed with 45 kg N/ha. In 1993, one-half of the plots were sidedressed with N at 45 and 90 kg·ha–1 for paprika and chile, respectively. The higher N rates consistently produced larger and higher-yielding chile plants and generally increased yield and stem and leaf weights of paprika plants. The force required to uproot plants was not significantly affected by N rates. Plant lodging was significantly worse at the higher N rates in only one of five studies. Bedding treatments did not have a consistent influence on fruit yield. The force required to uproot plants was greater with T2 and 4 compared to T1 and 3 in three of four studies. Plant lodging was not influenced by the bedding treatments.