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Kent E. Cushman and Thomas E. Horgan

Mississippi growers produce southernpea for the fresh market on raised beds using 20 to 30 lb/acre nitrogen. This study compared conventional production practices to alternative approaches in a 3 × 2 × 2 factorial arrangement in a randomized complete-block design with four replications. Three cultivars of southernpea, `Quickpick' (QP), `Texas Pinkeye' (T × PE), and `Mississippi Pinkeye' (MsPE), were planted into either raised or flat beds using either 30 lb/acre ammonium nitrate without seed inoculation or no ammonium nitrate with Rhizobium seed inoculation. QP and T × PE were harvested with a one-row Pixall harvester and MsPE was hand harvested. All plots were harvested at the mature-green stage. Yields were reduced due to drought conditions during pod fill. MsPE was hand harvested only once due to dry conditions and less-than-ideal yields. QP produced significantly greater yield (1208 lb/acre) than T × PE (962 lb/acre) or MsPE (981 lb/acre). The two nitrogen treatments were not significantly different. QP and T × PE were not affected by bed architecture, but MsPE on raised beds yielded significantly more than on flat beds. As with a similar study in 1998, also under nonirrigated conditions, MsPE had a significantly greater shellout than QP or T × PE. There were no significant interactions for yield or percent shellout.

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William B. Evans, Christine E. Coker, Kent E. Cushman, Thomas E. Horgan, and Keri L. Paridon

Three years of trials in Mississippi have led to the naming of a Mississippi Medallion vegetable award winner for 2007, the fourth vegetable winner in the program's history. The Medallion program looks for garden crops that will perform throughout the state of Mississippi and help improve sales of plant materials to gardeners at retail. The Medallion selection process illustrates how growers and marketers, not just gardeners, can select specialty vegetables and cultivars for production and sale. Between 2003 and 2005, the Mississippi Medallion trials evaluated 11 sweet peppers with no green fruit stage for ornamental and yield value. Each site had three or four replications of all cultivars under evaluation annually with four plants per plot set out on raised beds with drip irrigation. Objective evaluation included total yield, marketable yield, fruit size, and days to harvest. Subjective evaluation included crop uniformity, pest tolerance, and appearance of the fruit based on color, uniformity, and shape. After nine trials, four cultivars were among the highest-yielding group in most trials: Mavras, Tequilla, Blushing Beauty, and Gypsy. The Medallion winner, to be announced in Fall 2006, was selected in part because it was within or near the top-yielding group, by least significant difference, in most trials. The perceived attractiveness of the mature fruit to the evaluating team and the perceived potential marketability of the cultivar moved it above the others under consideration. The reasons for not selecting other cultivars as the winner are as important as the reasons for selecting the winning cultivar. In the Medallion pepper case, these were mostly marketability concerns with the other cultivars, not yield issues, relative to that of the winner.

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Kent E. Cushman, Thomas E. Horgan, David H. Nagel, and Patrick D. Gerard

Pumpkins (Cucurbita pepo, C. moshata) were grown in northern Mississippi during 2000 and 2001 for the purpose of more narrowly defining plant population recommendations for commercial production in the humid southeastern United States. Four plant populations were examined for `Aspen': 908, 1361, 2045, and 3068 plants/acre (2244, 3363, 5053, and 7581 plants/ha, respectively) and for `Howden Biggie': 605, 908, 1361, and 2045 plants/acre (1495, 2244, 3363, 5053 plants/ha, respectively). Plant populations were adjusted by varying in-row spacing while holding between-row spacing constant at 8 ft (2.4 m). Plant population significantly affected yield of `Aspen' and `Howden Biggie'. Linear and quadratic terms were significant for `Aspen', with maximum yield (ton/acre and fruit/acre) for the quadratic relationship occurring at about 2045 plants/acre. In contrast, yield of `Howden Biggie' decreased significantly (ton/acre) and nonsignificantly (fruit/acre) in a linear relationship as plant population increased from 605 to 2045 plants/acre. Plant population significantly affected fruit weight and size. As plant population increased, weight and size decreased slightly but significantly in a linear relationship for `Aspen' (lb/fruit and inch3/fruit) and `Howden Biggie' (lb/fruit). The quadratic relationship for `Howden Biggie' (inch3/fruit) was significant and the minimum value occurred at about 1361 plants/acre. Plant population significantly affected pumpkin yield components associated with plant productivity. As plant population increased, number and weight of fruit per plant decreased sharply in a quadratic relationship for `Aspen' (lb/ plant and fruit/plant) and `Howden Biggie' (lb/plant). The linear relationship for `Howden Biggie' (fruit/ plant) also decreased significantly. At the highest plant populations for `Howden Biggie', 40% of the plants did not produce marketable pumpkins. In conclusion, recommendations of optimum plant populations for a semi-vining cultivar such as `Aspen' should be centered on about 2045 plants/acre. Published recommendations from Kentucky appear sound, advocating plant populations within the range of 1360 to 2720 plants/acre (3361 to 6721 plants/ha). For a vining cultivar such as `Howden Biggie', recommendations can be as low as 605 plants/acre. Published recommendations from Kentucky and Georgia, along with those published in the Vegetable Crop Guidelines for the Southeastern U.S., advocate plant populations for vining cultivars of approximately 725 to 1465 plants/acre (1790–3620 plants/ha). Our results with `Howden Biggie', a cultivar that produces larger pumpkins than most other vining cultivars grown for the wholesale market, indicate that producers of vining cultivars should use plant populations from the lowest values of these recommendations or use even lower values. Our results also indicate that growers can control size and weight of pumpkins by varying plant population, with increasing populations resulting in a slight decrease of size and weight.

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T. Casey Barickman, Thomas E. Horgan, Jennifer R. Wheeler, and Carl E. Sams

Lettuce is one of the major crops of the United States and can provide a large portion of income for small to medium size growers. Growing lettuce in adverse environmental conditions can have negative effects on quality. Elevated levels of potassium (K) have been shown to positively influence quality in various fruits and vegetables, such as tomato, pepper, and strawberry. However, research is lacking on the effects of elevated levels of K on leafy vegetables such as lettuce. Therefore, seeds of ‘Cimmaron’ lettuce were sown into a soilless medium and grown in greenhouse conditions at 25/20 °C (day/night). At 27 days after seeding, the plantlets were transferred to 3.8-L plastic nursery pots. Plants were grown under increasing K treatments of 98 (control), 185 (2×), 370 (3×), and 740 (8×) kg·ha−1. Plants were harvested 56 days after seeding. Application of elevated levels of K fertilizer treatments in red romaine lettuce had a positive quadratic effect on plant height increasing 7.0% from the control. Fresh weight (FW) increased 13.0% from the control and dry weight (DW) increased 15.5%. There was linear increase of 30.0% in sucrose concentrations in lettuce leaf tissue. In addition, the increase in K treatments caused an increase of 43.3% in K concentrations in the leaf tissue. In other nutrients, such as Calcium (Ca), Magnesium (Mg), and Sulfur (S), there was a decrease in the leaf tissue of 61%, 52%, and 46% when compared with the control treatment, respectively. The results of the current study suggest that increasing K fertilizer to 185 kg·ha−1 has the best results for plant height, FW and DW, and mineral nutrient concentrations. This study may initiate research that could examine the effects of increasing K fertilizer levels in lettuce or other leafy green vegetables on antioxidant levels and postharvest storability.

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Valtcho D. Zheljazkov, Thomas E. Horgan, Tess Astatkie, Dolores Fratesi, and Charles C. Mischke

The aquaculture industry generates significant nutrient-rich wastewater that is released into streams and rivers causing environmental concern. The objective of this controlled environment study was to evaluate the effect of waste shrimp water (SW), vermicompost (VC), at rates of 10%, 20%, 40%, and 80% by volume alone or in combination with SW, controlled-release fertilizer (CRF), and water-soluble fertilizer (WSF) on bell peppers (Capsicum annuum L.) cv. X3R Red Knight. Application of VC at 80% or SW alone increased yields relative to unfertilized control. Combined applications of VC and SW increased yields compared with VC alone. Overall, total yields were greatest in the chemical fertilizer treatments (CRF and WSF) and least in the unfertilized control. SW and VC increased growth medium pH relative to the unfertilized control or to the chemical fertilizer treatments. In pepper fruits, the greatest nitrogen (N) content was found in the CRF treatment, although it was not different from VC at high rates or WSF treatments. Phosphorus concentration in peppers was greatest in the CRF treatment, less in all VC or SW treatments, but not different from unfertilized control or WSF treatment. Iron, magnesium (Mg), and zinc concentrations in peppers were greatest in CRF treatment but not different from control or WSF treatments. Overall, N accumulation in peppers was negatively correlated to growth medium pH and calcium (Ca); phosphorus (P) in peppers was negatively correlated to growth medium pH, Ca, and sodium (Na), whereas potassium (K) in peppers was negatively correlated to growth medium P, Mg, and Na. Results indicated: 1) SW may not be a viable pepper nutrient source; (2) SW can provide a similar nutrient supply as VC; and (3) chemical fertilizers can provide higher pepper yields compared with SW or VC alone or in combination.