The Effects of Rootstock Selection and Carbon-based Fertility Amendments on Apple Orchard Productivity and Soil Community Ecology
| dc.contributor.author | Thompson, Ashley A. | en |
| dc.contributor.committeechair | Peck, Gregory M. | en |
| dc.contributor.committeemember | Williams, Mark A. | en |
| dc.contributor.committeemember | Maguire, Rory O. | en |
| dc.contributor.committeemember | Wolf, Anthony K. | en |
| dc.contributor.department | Horticulture | en |
| dc.date.accessioned | 2018-06-02T06:00:11Z | en |
| dc.date.available | 2018-06-02T06:00:11Z | en |
| dc.date.issued | 2016-12-08 | en |
| dc.description.abstract | In apple (Malus domestica Borkh.) orchards, rootstock genotype, and soil fertility management practices impact soil fertility, plant associated soil microbial communities, and orchard productivity. Apple growers select rootstocks to confer beneficial traits, including size control, precocity, and pest and disease resistance. Rootstock genotype may also influence microbial communities, resulting in changes that affect tree health and productivity. Many apple growers apply synthetic nitrogen fertilizers to improve fruit yield and quality. In excess of tree requirements, nitrogen fertilizers may reduce crop yield and quality, as well as contribute to water pollution. The addition of carbon-based amendments, such as yardwaste, chicken litter composts, and biochar, may potentially reduce nitrogen and water loss, while improving soil structure and mineral nutrient availability. Orchard and pot-in-pot experiments were designed to study the following objectives: 1) determine the effects of integrated carbon-based fertilizer amendments on tree growth, productivity, and orchard soil fertility, 2) assess the effects of biochar on tree growth, leaf mineral nutrition, soil physiochemistry, and microbial community structure and activity, and 3) understand how rootstocks and fertilizers alter soil microbial communities. Applications of composts, integrated compost-calcium nitrate fertilizers, and biochar increased soil carbon, organic matter, cation exchange capacity and microbial respiration. In the orchard study, nitrogen fertilizer application did not increase tree growth, fruit quality, or leaf nitrogen concentration. Biochar applied at high rates with nitrogen fertigation increased tree growth and leaf nitrogen concentration similar to nitrogen fertigation. In the pot-in-pot compost study, chicken litter compost increased tree growth, and integrated compost-calcium nitrate fertilizer applications increased leaf N concentration. Analysis of the microbial community structure of bulk soil samples from the biochar and compost pot-in-pot experiments determined that the community structure was similar for all treatments during the three-year study. Metagenomic sequencing of the rhizosphere bacterial community indicated that compost applications altered community diversity and evenness, and that compost treatments were more similar to each other than to the calcium nitrate treatment. Data from my dissertation research suggests that compost can be used to increase orchard soil fertility, tree growth, and leaf nutrition, and that compost applications increase soil microbial community diversity and activity. | en |
| dc.description.abstractgeneral | Rootstock genotype and soil fertility management practices in apple (<i>Malus × domestica</i> Borkh.) orchards impact soil health and nutrient status, plant associated soil microbial communities, and tree growth and fruit yield. Growers select specific apple rootstocks for use in their orchards to confer beneficial traits, including size control, earlier fruit production, increased fruit yield, and pest and disease resistance. Many apple growers also apply synthetic nitrogen fertilizers to improve fruit yield and quality. However, in excess of tree requirements, nitrogen fertilizers may reduce crop yield and quality, as well as contribute to environmental pollution. The addition of carbon-based amendments, such as compost and biochar, may reduce nitrogen and water loss, improve soil structure, and make certain mineral nutrients more available to plants and microorganisms. The use of integrated fertilizers, which are carbon-based amendments applied in conjunction with synthetic nitrogen fertilizers, may also enhance edaphic properties while providing plants with adequate nitrogen at times of greater demand. Orchard and pot studies were designed to: 1) determine the effects of carbon-based, and integrated carbon-based fertilizer amendments on tree growth, fruit yield and quality, and orchard soil fertility, 2) determine the effects of rootstocks and fertilizers on soil microbial community composition and activity, and 3) assess the effects of biochar on tree growth, leaf mineral nutrition, soil fertility, and microbial community structure and activity. In this study, applications of composts, integrated fertilizers, and biochar increased soil fertility measures, such as soil carbon, organic matter, cation exchange capacity and microbial respiration, in fine textured orchard soils. Applying nitrogen fertilizer did not increase tree growth, fruit quality, or leaf nitrogen concentration in the orchard study, however, in the pot study, chicken litter compost increased tree growth, and integrated compost-calcium nitrate fertilizer applications increased leaf N concentration. Biochar applied with synthetic nitrogen fertilizer increased tree growth and leaf nitrogen concentration similar to nitrogen fertilizer alone. Analysis of the microbial community structure of bulk soil samples from the biochar and compost pot experiments determined that the community structure was similar for all treatments during the three-year study. Metagenomic sequencing of the rhizosphere bacterial community indicated that compost applications altered community diversity and evenness, and that compost treatments were more similar to each other than to the synthetic nitrogen treatment. Data from my dissertation research suggests that compost can be used to increase orchard soil fertility, tree growth, and leaf nutrition, and that compost applications increase soil microbial community diversity and activity. | en |
| dc.description.degree | Ph. D. | en |
| dc.format.medium | ETD | en |
| dc.identifier.other | vt_gsexam:9161 | en |
| dc.identifier.uri | http://hdl.handle.net/10919/83441 | en |
| dc.publisher | Virginia Tech | en |
| dc.rights | In Copyright | en |
| dc.rights.uri | http://rightsstatements.org/vocab/InC/1.0/ | en |
| dc.subject | Apples | en |
| dc.subject | Compost | en |
| dc.subject | Fertilizer | en |
| dc.subject | Nitrogen | en |
| dc.subject | Biochar | en |
| dc.title | The Effects of Rootstock Selection and Carbon-based Fertility Amendments on Apple Orchard Productivity and Soil Community Ecology | en |
| dc.type | Dissertation | en |
| thesis.degree.discipline | Horticulture | en |
| thesis.degree.grantor | Virginia Polytechnic Institute and State University | en |
| thesis.degree.level | doctoral | en |
| thesis.degree.name | Ph. D. | en |
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