UVM Theses and Dissertations
Format:
Print
Author:
Hills, Karen M.
Dept./Program:
Plant and Soil Science
Year:
2007
Degree:
MS
Abstract:
Soilborne diseases such as root rot and damping-off affect a wide variety of ornamental and crop plants and cause significant economic losses for commercial growers. Some organic amendments, often used to improve soil quality, can suppress soilborne disease. However, the effect of initial soil health on the development of suppression is not well understood. This study investigated the ability of raw dairy manure, composted dairy manure, oat (Avena sativa) green manure and the commercial biocontrol product, RootShield® soil drench (Trichoderma harzianum), to suppress damping-off in two Vermont soils with differing management histories and evaluated the usefulness of four biological soil quality indicators (microbial activity, active carbon, quantity and quality of free particulate organic matter) as predictors of suppressiveness.
The second objective of this study was to assess the response of these four soil quality indicators to the addition of organic amendments in soils with differing management histories. Suppression did not occur in either soil until 80 days after amendment and was no longer significant by 160 days after amendment. In the organically managed soil, manure and composted manure both resulted in significantly lower disease severity on day 80. In the conventionally managed soil, only the oat green manure treatment resulted in significant suppression. RootShield® soil drench did not suppress disease on any sampling date in either soil. Free particulate organic matter quantity and microbial activity were correlated with disease severity on days 80 and 160, respectively. Active carbon and fPOM quality were not correlated with disease severity on any of the sampling dates.
Of the four biological soil quality indicators examined, active carbon was the least responsive to recent amendment. In general the indicators were more strongly correlated to each other and to other soil measurements (C, N, C to N ratio) in the conventionally managed soil. These results have possible implications for the choice of indicators to predict disease suppressiveness and to monitor soil quality and warrant further study involving a wider range of soils and field conditions.
The second objective of this study was to assess the response of these four soil quality indicators to the addition of organic amendments in soils with differing management histories. Suppression did not occur in either soil until 80 days after amendment and was no longer significant by 160 days after amendment. In the organically managed soil, manure and composted manure both resulted in significantly lower disease severity on day 80. In the conventionally managed soil, only the oat green manure treatment resulted in significant suppression. RootShield® soil drench did not suppress disease on any sampling date in either soil. Free particulate organic matter quantity and microbial activity were correlated with disease severity on days 80 and 160, respectively. Active carbon and fPOM quality were not correlated with disease severity on any of the sampling dates.
Of the four biological soil quality indicators examined, active carbon was the least responsive to recent amendment. In general the indicators were more strongly correlated to each other and to other soil measurements (C, N, C to N ratio) in the conventionally managed soil. These results have possible implications for the choice of indicators to predict disease suppressiveness and to monitor soil quality and warrant further study involving a wider range of soils and field conditions.