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Tracy A. Ohler and Cary A. Mitchell

Photoperiod and harvest scenario of cowpea (Vigna unguiculata L. Walp) canopies were manipulated to optimize productivity for use in future controlled ecological life-support systems. Productivity was measured by edible yield rate (EYR: g·m-2·day-1), shoot harvest index (SHI: g edible biomass·[g total shoot dry weight]), and yield-efficiency rate (YER: g edible biomass·m-2·day-1per [g nonedible shoot dry weight]). Breeding lines `IT84S-2246' (S-2246) and `IT82D-889' (D-889) were grown in a greenhouse under 8-, 12-, or 24-h photoperiods. S-2246 was short-day and D-889 was day-neutral for flowering. Under each photoperiod, cowpeas were harvested either for leaves only, seeds only, or leaves plus seeds (mixed harvest). Photoperiod did not affect EYR of either breeding line for any harvest scenario tested. Averaged over both breeding lines, seed harvest gave the highest EYR at 6.7 g·m-2·day-1. The highest SHI (65%) and YER (94 mg·m-2·day-1·g-1) were achieved for leaf-only harvest of D-889 under an 8-h photoperiod. For leaf-only harvest of S-2246, both SHI and YER increased with increasing photoperiod, but declined for seed-only and mixed harvests. However, photoperiod had no effect on SHI or YER for D-889 for any harvest scenario. A second experiment utilized the short-day cowpea breeding line `IT89KD-288' (D-288) and the day-neutral breeding line `IT87D-941-1' (D-941) to compare yield parameters using photoperiod extension under differing lamp types. This experiment confirmed the photoperiod responses of D-889 and S-2246 to a mixed-harvest scenario and indicated that daylength extension with higher irradiance from high pressure sodium lamps further suppressed EYR, SHI, and YER of the short-day breeding line D-288.

Free access

Tracy A. Ohler, S. Suzanne Nielsen, and Cary A. Mitchell

Plant density and harvest time were manipulated to optimize vegetative (foliar) productivity of cowpea [Vigna unguiculata (L.) Walp.] canopies for future dietary use in controlled ecological life-support systems as vegetables or salad greens. Productivity was measured as total shoot and edible dry weights (DW), edible yield rate [(EYR) grams DW per square meter per day], shoot harvest index [(SHI) grams DW per edible gram DW total shoot], and yield-efficiency rate [(YER) grams DW edible per square meter per day per grams DW nonedible]. Cowpeas were grown in a greenhouse for leaf-only harvest at 14, 28, 42, 56, 84, or 99 plants/m2 and were harvested 20, 30, 40, or 50 days after planting (DAP). Shoot and edible dry weights increased as plant density and time to harvest increased. A maximum of 1189 g shoot DW/m2 and 594 g edible DW/m2 were achieved at an estimated plant density of 85 plants/m2 and harvest 50 DAP. EYR also increased as plant density and time to harvest increased. An EYR of 11 g·m–2·day–1 was predicted to occur at 86 plants/m2 and harvest 50 DAP. SHI and YER were not affected by plant density. However, the highest values of SHI (64%) and YER (1.3 g·m–2·day–1·g–1) were attained when cowpeas were harvested 20 DAP. The average fat and ash contents [dry-weight basis (dwb)] of harvested leaves remained constant regardless of harvest time. Average protein content increased from 25% DW at 30 DAP to 45% DW at 50 DAP. Carbohydrate content declined from 50% DW at 30 DAP to 45% DW at 50 DAP. Total dietary fiber content (dwb) of the leaves increased from 19% to 26% as time to harvest increased from 20 to 50 days.

Free access

Elsa S. Sánchez, Ermita Hernández, Mark L. Gleason, Jean C. Batzer, Mark A. Williams, Timothy Coolong, and Ricardo Bessin

The goal of this study was to develop a systems-based strategy for organic muskmelon (Cucumis melo var. reticulatus) in Pennsylvania (PA), Iowa (IA), and Kentucky (KY) to manage bacterial wilt (Erwinia tracheiphila) and nutrients while safeguarding yield and enhancing early harvest. Spunbond polypropylene rowcovers deployed for different timings during the growing season were evaluated for suppressing bacterial wilt and locally available compost was applied based on two different estimated rates of mineralization of organic nitrogen (N) to manage nutrients. In KY only, the use of rowcovers suppressed bacterial wilt incidence compared with not using rowcovers. However, the timing of rowcover removal did not impact wilt incidence. Under lower cucumber beetle [striped cucumber beetle (Acalymma vittatum) and spotted cucumber beetle (Diabrotica undecimpunctata howardi)] pressure in PA and IA, rowcovers did not consistently suppress season-long incidence of bacterial wilt. In four of five site-years in PA and IA, more marketable fruit were produced when rowcovers were removed 10 days after an action threshold (the date the first flower opened in PA; the date when ≥50% of plants in a subplot had developed perfect flowers in IA and KY) than when no 10-day delay was made or when no rowcovers were used. In addition, the no-rowcover treatment consistently had lower weight per marketable fruit. In KY, the same action threshold without the 10-day delay, followed by insecticide applications, resulted in the largest number of marketable fruit, but did not affect marketable fruit weight. In PA, marketable yield was higher using compost compared with the organic fertilizer in 1 year. No yield differences were observed by nutrient treatments in 2 years. In IA, marketable yield was lower with the low amount of compost compared with the organic fertilizer and yields with the high amount of compost were not different from the low amount or the organic fertilizer in the year it was evaluated. In KY, marketable yield was unaffected by the nutrient treatments in the year it was evaluated. Given these results, muskmelon growers in PA, IA, and KY who use compost may choose the lower compost rate to minimize production costs. Overall, these findings suggest that rowcover-based strategies for organic management of bacterial wilt need to be optimized on a regional basis, and that fertilization with compost is compatible with these strategies.

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Brian P. Pellerin, Deborah Buszard, David Iron, Charles G. Embree, Richard P. Marini, Douglas S. Nichols, Gerald H. Neilsen, and Denise Neilsen

Tree fruit growers use chemical and mechanical thinning techniques in an attempt to maintain regular annual flower production and maximum repeatable yields of varieties susceptible to biennial bearing. If the percentage of floral buds an apple tree could produce without causing yield depression in subsequent years was known, it would be possible to better manage crop-thinning regimes. This study proposes that thinning is a partial transfer of potential flower buds from one year to the next year and estimates the maximum repeatable sequence of flower buds without biennial bearing. The conceptual framework is tested on a 50-year simulation with 0% to 100% transfer of thinned flower buds. Results indicate that the maximum repeatable sequence of flower buds rises sharply when the final years of the orchard approach and declines when the percent transfer of thinned buds is near 0%.

Free access

Shuyang Zhen and Marc W. van Iersel

, this information has seldom been used to examine how the supplemental light use efficiency changes with changing PPF and how supplemental lighting can be optimized for different species. van Iersel and Gianino (2017) reported that plants with

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Scott B. Lukas, Joseph DeFrank, and Orville C. Baldos

, emersion in boiling water and exposing seeds to low RH conditions ( Baskin et al., 2004 ). Baskin suggests that storage can be used as a dormancy-breaking treatment, but it can also play a fundamental role in optimizing seed longevity. To maximize the

Open access

Jaime Barros da Silva Filho, Paulo Cezar Rezende Fontes, Paulo Roberto Cecon, Jorge F.S. Ferreira, Milton E. McGiffen Jr., and Jonathan F. Montgomery

and mist cooling systems to optimize product application (insecticide, herbicide)—droplet size, spray angle, and avoiding wetting the floor, for example. When we chose antidrip misting nozzles, we thought that these benefits could improve the

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Susannah Amundson, Dennis E. Deyton, Dean A. Kopsell, Walt Hitch, Ann Moore, and Carl E. Sams

ways to increase yield. Greenhouse tomato production requires many environmental, cultural, and biological practices to optimize production and fruit quality. Plant density and pruning methods are two important cultural approaches to increase yield. It

Open access

Eliezer Louzada, Omar Vazquez, Sandy Chavez, Mamoudou Sétamou, and Madhurababu Kunta

; Zhang et al., 2015 ). Although vqPCR has been widely used, the method is not standardized and needs to be optimized for each specific situation ( Fittipaldi et al., 2012 ). Many parameters affect the reliability of vqPCR. Any factor affecting sample

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Ramón A. Arancibia, Cody D. Smith, Don R. LaBonte, Jeffrey L. Main, Tara P. Smith, and Arthur Q. Villordon

market for jumbo and canner grades is primarily the processing industry. Because of the differences in size and quality standards for the processing industry vs. the fresh market, diverse production strategies may be necessary to optimize returns. In the