Evaluation of Three Commercially-Available Composts for Use in Strawberry Production on Plastic

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Title: Evaluation of Three Commercially-Available Composts for Use in Strawberry Production on Plastic
Author: Ferguson, Mary Helen
Advisors: Frank J. Louws, Committee Member
Carl R. Crozier, Committee Member
Gina E. Fernandez, Committee Chair
Abstract: Intent to farm organically and restrictions on the use of methyl bromide (MeBr) are two reasons why some growers have sought alternatives to the MeBr and chloropicrin fumigant mixture traditionally used in annual strawberry (Fragaria x ananassa Duch.) production on plastic mulch. This study investigated the effects of three commercially available composts in a strawberry production system using organic practices. The composts included one made from a 50:50 mixture of pine bark and peanut hulls ("PBPH"); one based on a blend of food waste, animal manure, and egg shells ("egg shell"); and a certified organic compost containing only poultry litter ("organic"). Cultivars Bish, Sweet Charlie, Camarosa, and Chandler were tested in Year 1, and the latter two cultivars were used in Year 2. No effect on marketable yield was found, but cull incidence was lower in the egg shell compost treatment than others in the second season, possibly due to the combined effect of high calcium in that compost, resulting in firmer and more rot-resistant berries, and high tissue N early in the spring, resulting in larger berries. Differences were found in average berry weight in both seasons, but the differences were not consistent. Low nitrogen conditions prevailed in both harvest seasons, likely lowering yields. The three composts differed with respect to nutrient levels, soluble salts, and carbon to nitrogen (C:N) ratio. One or more composts increased pH and CEC, decreased soil bulk density, or increased soil organic matter, but not all were equally effective in these respects. The PBPH compost had the highest C:N ratio and the lowest soluble salt, pH, and dry matter levels. It had the least effect on soil nutrient levels but was effective in increasing levels of soil organic matter. The egg shell compost contained high levels of calcium and iron, while the organic compost contained the highest levels of most nutrients and had the greatest effect on soil and tissue nutrients levels. The organic compost also had the highest soluble salts and pH, the lowest C:N ratio, and was the only compost found to decrease bulk density. It was under-matured in Year 1, highlighting the need for quality control. Both egg shell and organic composts increased soil calcium, pH, CEC, and soil organic matter. The organic compost treatment sometimes had more root rot than other treatments, possibly due to the high level of soluble salts in the compost. There was evidence of plant stunting in the organic compost treatment in Year 1, but differences did not persist throughout the season. Plants in the egg shell compost treatment were stunted early in Year 2, compared to the other two compost treatments, likely because of a lower rate of available nitrogen in that treatment than in others. There were some instances of superior plant growth in the PBPH treatment in the second year, for 'Camarosa'. 'Camarosa' plants typically had more root rot than 'Chandler' plants, but marketable yields were not significantly different or were greater in 'Camarosa'. The ability of compost to alter soil properties—including nutrient levels, pH, CEC, and percent organic matter—was demonstrated, although disease suppression was not observed. Growers can benefit from using compost analyses to determine what compost to use, when to apply it, and how to fertilize in conjunction with compost application.
Date: 2006-12-06
Degree: MS
Discipline: Horticultural Science
URI: http://www.lib.ncsu.edu/resolver/1840.16/2303

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