Browsing by Author "Mary Peet, Committee Member"

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Grafting for Open-field and High Tunnel Tomato Production.
(2010-06-04) Rivard, Cary Lee; Frank Louws, Committee Chair; Howard Shew, Committee Chair; Eric Davis, Committee Member; Mary Peet, Committee Member; Heike Inge Sederoff, Committee Member; Loren Fisher, Committee Member
Grafting Tomato to Manage Soilborne Diseases and Improve Yield in Organic Production Systems
(2007-04-30) Rivard, Cary Lee; Paola Veronese, Committee Member; Frank J. Louws, Committee Chair; Michael Benson, Committee Member; Mary Peet, Committee Member
The use of grafted tomato for commercial production has been implemented worldwide, where soilborne disease pressure is high. Grafting has been used to manage Fusarium, Verticillium, Root-knot nematodes, and bacterial wilt in several Asian, Mediterranean, and northern European countries. However, this technique is relatively unknown in the United States. With the increased direct-marketing avenues available to small, sustainable farmers, demand for vine-ripened organic heirloom varieties has also increased. These cultivars are open-pollinated, and are typically very susceptible to an array of soilborne and foliar diseases. A research program was initiated to investigate the potential of grafting as a major component in an integrated approach to reduce soilborne disease and increase crop productivity in organic heirloom tomato production. Because this research relies heavily on well-developed international techniques and practices, an extension objective was declared to better disseminate information regarding grafting benefits and technique, and to facilitate local adoption of this technology. During 2005 and 2006, field trials were implemented to determine the capability of grafting to reduce soilborne disease incidence in heirloom tomato. Bacterial wilt (caused by Ralstonia solanacearum) is a devastating soilborne disease in eastern North Carolina. CRA 66 and Hawaii 7996 genotypes were highly effective at reducing bacterial wilt in naturally-infested soils when utilized as a resistant rootstock. No evidence of wilt was seen among resistant rootstock treatments when terminal disease incidence among non-grafted treatments was 75%, and 79% in 2005 and 2006, respectively. Rootstock-specific cultivar, 'Maxifort', showed no symptomatic plants for fusarium wilt (caused by Fusarium oxysporum f.sp. lycopersici) in organic production, and non- and self-grafted controls had 45-50% disease incidence. Verticillium wilt is a severe endemic problem in the mountain growing regions of North Carolina due to the lack of genetic resistance against race 2. Grafting with 'Maxifort' showed high potential as a management tool for this disease based upon increased vigor under continuous and rotational treatments. Several field trials in 2005 and 2006 investigated the ability of rootstock-specific hybrids to increase crop productivity under organic management practices in a growing environment with little soilborne disease. Grafting with 'Maxifort' and 'Robusta' did not enhance yields when implemented into a typical on-farm organic production setting. Evaluation of alternative training systems indicated the importance of added vigor by 'Maxifort' through enhanced yields under ?twin-headed? management in 2005. In 2006, yields were not increased under alternative training methods as compared to standard training system, but grafting with 'Maxifort' rootstock showed enhanced crop productivity (P=0.005). Grafting could be a vital component in commercial organic production of heirloom tomato. The unification of heirloom scion with rootstock that confers disease resistance, tolerance to abiotic stressors, and enhanced vigor may be a valuable tool for organic and conventional growers in the United States.
The Use of Marine Derived Products and Soybean Meal as Fertilizers in Organic Vegetable Production
(2004-04-05) Brown, Melissa Ann; Greg Hoyt, Committee Member; Jeanine Davis, Committee Chair; Mary Peet, Committee Member
Seaweed extract, fish emulsion, and soybean meal (SBM) are United States Department of Agriculture (USDA) National Organic Program (NOP) allowed substances used by organic vegetable growers as fertilizers. Soil applied SBM and foliar applied seaweed, fish, fish/seaweed, 20-20-20, and a water control were tested on field-grown sweet peppers, broccoli, and lettuce to determine their effects on plant nutrition and crop yield. The SBM was applied at three rates: 0, 2466, and 4932 kg.ha-1 (0, 2200, and 4400 lb.acre-1). To test the duration of the SBM as a soil fertilizer, peppers, broccoli, and lettuce were grown in succession on the same beds after the initial SBM application. The foliar fertilizers were also tested on peppers on a certified organic farm for comparison to the research station study. In 2002, transplanting one day after SBM application caused fertilizer burn to the pepper roots. In 2003, peppers were planted one week after SBM application without harm to plant roots. SBM positively increased the nutrient level and yield of broccoli in 2002 and peppers in 2003. Lettuce yield was not affected by the SBM treatments because the previous pepper and broccoli crops had likely exhausted the SBM fertilizer. The foliar sprays did not affect plant nutrient levels or yields in any crop at either location. Greenhouse studies were conducted to investigate the effect of SBM on germination and growth of eight common vegetables. Treatments included five rates of SBM: 0, 1093, 2186, 3279, and 4372 kg.ha-1 (0, 975, 1950, 2925, and 3900 lb.acre-1) and two application methods: surface applied (SA) and incorporated (IN) into the media. For all vegetables combined, at applications of 1093 and 2186 kg.ha-1 IN SBM, shoot weight increased by 20% and 10%, respectively, compared to the unfertilized control. At the same rate of SA SBM, shoot weight was reduced by 6% and 18% respectively. At all rates of SA SMB, shoot weight was more reduced in small seeded vegetables (spinach, lettuce, carrot, and radish) than in large seeded vegetables (squash, cucumber, bean, and pea). At 3279 and 4372 kg.ha-1 of IN SBM, shoot weight of small seeded vegetables was reduced by 8% and 46%, respectively. The EC and pH of the media increased with increased rates of SBM and were greater with SA SBM than with IN SBM. Levels above pH 6.5 and EC 1.0 dS.m-1 were measured on day 7 for media at all SBM rates. These levels could be inhibitory to germinating seeds. Because SBM reduced growth of small seeded vegetables, it is not recommended that small seeded vegetables be surface fertilized with SBM or that they be sown directly into soil where SBM has been recently incorporated. SBM incorporated at low rates (<2186 kg.ha-1) could prove to be a useful fertilizer for large seeded crops without concerns of inhibition by SBM. Field studies were conducted to investigate the optimal rate and timing of SBM fertilization in plasticulture sweet pepper production. SBM was applied at three rates: 0, 2421, and 4842 kg.ha-1 (0, 2165 and 4330 lb.acre-1). Sweet peppers were then transplanted at four intervals following SBM incorporation and black plastic application: one day, three days, seven days, and fourteen days. Growth was initially inhibited in peppers planted into the high rate of SBM less than one week after incorporation. By the end of the season, these peppers had recovered and had a biomass greater than the unfertilized control. Peppers fertilized with the low rate of SBM did not suffer an initial inhibition and had the highest yield of marketable peppers at all planting times. This study suggests a moderate rate of SBM should be applied at least two weeks before the intended planting date.