Browsing by Author "Greg Hoyt, Committee Member"

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Cover Crop Mulches for No-till Organically Managed Onion Production
(2008-12-04) Vollmer, Emily R.; Nancy Creamer, Committee Chair; Chris Reberg-Horton, Committee Member; Greg Hoyt, Committee Member
Combining the environmentally sound practices of reduced tillage and cover crop use with organic vegetable production systems requires management choices that are tailored to specific climate and crop combinations. In the southeastern U.S. summer cover crops can be grown through the fall until desiccation by frost. At this time a cash crop such as bulb onions (Allium cepa L.) can be grown using reduced tillage for over winter production. Field experiments were conducted on first year transitional (non-organic) land in 2006-07 and 2007-08. Cover crops of foxtail millet â€˜German Strain Râ€™ [Setaria italica (L.) Beauv.] and cowpea â€˜Iron & Clayâ€™ [Vigna unguiculata (L.) Walp.] were grown as monocrops (MIL, COW) and biculture mixtures and compared to a bare ground control (BG). Mixtures of cowpea and millet consisted of seeding rates aimed at producing 70%, 50%, and 30% millet per total biculture biomass (MIX-70, MIX-50, MIX-30). Cover crop residue treatments were evaluated for weed suppression and N contribution to no-till organic onion production. Supplemental N in the form of surface applied soybean meal [Glycine max (L.) Merrill] was applied to cover crop treatment subplots at three rates: 0, 105, and 210 kg Nâˆ™ha-1. Onion yields increased linearly from 0 to 210 kg Nâˆ™ha-1 rates of soybean meal. Cover crop treatments COW and BG had the greatest total marketable onion yield and were statistically equivalent both years. Losses in marketable yield were primarily due to mortality in MIL and MIX in 2006-07 and bolting across all cover crop treatments, which averaged 28% in 2006-07 and 72% in 2007-08. Onion mortality was over 50% in MIL and MIX treatments in 2006-07 and was attributed to physical properties of thick surface mulch. Onion mortality in 2007-08 was highest on MIL compared to all other cover crop treatments but remained below 20%. Weed interference during onion production was highest in COW and lowest in treatments with millet (MIL, MIX) in 2006-07. Nitrogen rates of 105 and 210 kg Nâˆ™ha-1 increased soil mineral N (NO3- and NH4+) on BG plots two weeks after surface application of soybean meal at the end of November each year but generally ceased to have an effect on soil mineral N by February or March. The 105 kg Nâˆ™ha-1 soybean meal rate appeared to be more than sufficient for use as a starter fertilizer. Split applications of soybean meal could be an important improvement in N management to avoid N leaching and better meet increased N uptake demand during bulb initiation and growth in the spring. Overall, this study shows that cowpea cover crops grown preceding an over-wintered no-till allium crop is feasible with appropriate management, and provides onion yield comparable to bare ground production.
Optimizing Substrates for Organic Tomato Transplant Production
(2005-11-25) Larrea, Elizabeth Sykes; Mary Peet, Committee Chair; Greg Hoyt, Committee Member; Nancy Creamer, Committee Member; Paul Nelson, Committee Member
Organically grown transplants required by the National Organic Program are rarely commercially available and are usually produced on-farm from locally available, inexpensive substrates. Six experiments were conducted to study the effect of potting mixes and their components on seed germination and seedling growth of tomato (Lycopersicon esculentum Mill cv. 'Celebrity') and to compare existing commercial organic and conventional substrates with a sample grower mix (GM20) (peat, perlite, vermicompost, feather meal, kelp meal). Variations on GM20 were added in some experiments including both higher and lower rates of vermicompost and feather meal in order to optimize seed germination and nitrogen nutrition. Although soluble organic fertilizers are often applied to conventional transplants after several weeks, no additional fertilizers were added in this study because allowable soluble organic fertilizers are generally cost prohibitive and are usually not locally available. Analysis of pH, salts, physical properties, nutrient content, and distribution of nitrogen between ammonium and nitrate forms was conducted on each potting mix and on the components of the grower mix. Tissue nutrient content was analyzed weekly from each treatment to determine plant nutrient status. Seed germination was consistently high in the original commercial organic and conventional media (73-89%). Germination in two additional commercial organic mixes was significantly lower (76-82%) in all but one case. Germination in the original grower mix was lower than the original commercial substrates, except in Experiment 4, where germination was higher overall compared to earlier experiments. It was not clear which components of the grower mix were responsible for reducing germination. Reducing vermicompost from 20% to 10% did not consistently improve germination. Increasing feather meal as a component by 50% reduced germination in one of two experiments while doubling its rate reduced germination in both experiments. Eliminating feather meal resulted in comparable germination (87-92%) to the original commercial mixes and higher germination than mixes containing feather meal in one of the two experiments. There was also no consistent relationship between media pH, salt levels, or physical properties and germination rates. Components of the organic mixes and the organic mixes themselves varied considerably between experiments in EC and pH except for the original commercial organic mix which was consistently low in EC and high in germination. In 3 of 4 experiments, transplants grown in GM20 had a significantly higher dry weight than those grown in the original commercial organic and conventional potting mixes. Nitrogen deficiencies were present by the final week of transplant production in all commercial and custom mixes during at least one experiment. Addition of higher rates of feather meal did not consistently eliminate nitrogen deficiencies. Over all experiments, only one phosphorus deficiency was found in a custom mix including vermicompost. The most consistent source of potassium was the conventional mix, with deficiencies showing up by week 4 in most of the organic treatments. Even in the conventional mix, transplants were at the critical level for deficiency in one experiment. Results of this study indicate that it is possible to add sufficient phosphorus into potting media for the period required for transplant production through the utilization of vermicompost, however, all media tested would require additions of soluble fertilizer in order to provide sufficient nitrogen and potassium. All media and components tested showed some variation with time and batch, but variation in the vermicompost was particularly striking. Thus, when utilizing grower mixed substrates it is important to have nutrient analyses performed on the substrate prior to use. Germination was sometimes reduced in media containing higher levels of nutrients, so care should be taken to optimize conditions during germination.
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.