Goals:

1
Intensive management increases soil organic
matter and cation exchange capacity An analysis
of differently managed sites at the George Jones
Farm
Emma B. Bishop, Callen Miracle, Christy
Rollinson ENVS 316, Systems Ecology Oberlin
College, Oberlin OH
Background
Effects of Treatments and Time

• Soil Organic Matter
• All treated sites had significantly higher SOM
  than the unmanaged field, indicating all of the
  studied soil amendments have increased SOM.
• The high SOM observed in the greenhouse is
  explained by large applications of organic
  material. Also, eroding factors, such as wind
  and water applications, are highly controlled in
  the greenhouse, so organic matter is not lost
  through erosion.

The George Jones Memorial Farm in Oberlin, OH was
conventionally managed in a corn-soybean rotation
until 2001. As a result of this management
history, organic matter in the topsoil was
severely depleted at the time that the farm was
converted to organic management (Masi
2000). Soil organic matter (SOM) contains
essential plant nutrients and is related to
cation exchange capacity (CEC) and other
properties important to crop productivity. CEC
measures the ability of soils to retain and
exchange positively charged ions, many of which
are critical for plant growth. (Follett et al.
1987). Understanding the effects of soil
management on SOM and CEC is crucial to
successful farm management. Many studies have
analyzed the effects of farming practices on soil
properties (Fliebach et al. 2007). Previous
studies at the Jones Farm assessed the effects of
various organic management strategies on soil
quality after three years. Strategies include
cover-cropping and the addition of compost (Bosch
et al. 2003, Lindauer et al. 2004). The effects
of these practices on SOM and CEC after seven
years of organic management are not yet known.

• Cation Exchange Capacity
• SOM and CEC are highly correlated (R2.78), so
  the high CEC in the greenhouse can be explained
  by a relatively high SOM. The addition of lime
  to control acidity also contributed to the high
  CEC in the greenhouse (there is a greater
  capacity for ion exchange in less acidic soils).

• Goals
• Quantify the effects of existing management
  practices at the Jones Farm. Provide baseline
  data for assessing the efficacy of new management
  strategies.
• Determine change over time in soil properties
  resulting from continued management since 2004.
• Provide information about effective management
  practices that can be used by the Jones Farm and
  other organic farming operations.
• Hypotheses
• We expected greenhouses to have the highest
  levels of SOM, followed by the garden, chicken
  run and meadow. The quantity of organic matter
  added to the greenhouse was greatest among the
  treatments. The greenhouse and garden received
  significant additions of organic matter while the
  chicken run was more passively managed. The
  meadow is currently unmanaged.
• We expected an increase in SOM at all managed
  sites since 2004, due to continued additions of
  organic matter. We expected the meadow's SOM to
  increase due to biomass accumulation as the
  ecosystem develops.
• We expected CEC to follow the same trends as SOM
  as close correlations between the two properties
  have been found (Chapin 2002).

Bars labeled with the same letter are not
significantly different.
Note In 2004, the only sample sites used were
the meadow and greenhouse so these were the only
sites that could be assessed for change.
Treatments and Methods
Several soil management practices have been
employed at different locations, in combination
or alone (see table). We sampled along transects
in four differently managed locations at the
Jones Farm using a 2 cm diameter soil corer to
collect samples to a depth of 15 cm at multiple
points along each transect. Multiple transects
were used for all sites except the chicken run,
which had one transect. We used a GPS device to
record the exact location of every sampling
point. For meadow transects, we used the GPS to
return to the sampling sites used by Lindauer et
al. (2004). In the greenhouse, we used the
diagrams of Lindauer et al. (2004) to return to
their sampling points. We analyzed each soil
sample for SOM and percent moisture (Nelson and
Sommers 1996). We combined the samples for each
transect and analyzed CEC and pH of three
transects for each site (Sumner and Miller 1996,
Thomas 1996). For the chicken run, we analyzed
three replicates of the single transect.
Statistical analysis was done using single factor
ANOVA (p0.05).

• SOM in the greenhouse remained relatively high
  between 2004 and 2007 and did not increase
  significantly. It is possible that SOM content
  was close to a saturation point in 2004. The
  warmer temperature in the greenhouse may also
  limit accumulation of SOM higher temperatures
  lead to higher rates of soil respiration, which
  results in more decomposition of SOM.
• Decreased SOM in the meadow could be the result
  of increased decomposition of organic matter with
  system development, preventing net accumulation
  of SOM.

• CEC did not change significantly between 2004 and
  2007 in either the meadow or the greenhouse. For
  the greenhouse this could be explained by the
  lack of change in SOM. In the meadow, however,
  SOM decreased while CEC remained unchanged. For
  the meadow, however, the low SOM may have been
  unable to influence CEC. Other factors, such as
  a consistent pH, may have lead to the meadow's
  insignificant change in CEC.

Conclusions
Site Year Initiated Treatments CEC and pH Analysis
Garden Plot (a) 2003 Manure, composted leaf mulch, cover-cropping All three transects analyzed.
Chicken Run (b) 2006 6-10 chickens in an enclosure, periodically moved along a strip Three samples analyzed from the single transect.
Green-house (c) 2002 Beds made up of leaf mulch. Treated with manure, com-post (leaf mulch, food- and brew-waste), lime, chickens Three transects randomly selected for analysis.
Meadow (control) (d) 2001 Conventionally managed crop field mowed and planted with clover. Now un-managed, high biodiversity. Three transects randomly selected for analysis.

• The Jones Farm is currently using successful
  techniques to increase SOM and CEC.
• Quantity of organic matter added is more
  important than its origin.
• High levels of SOM and CEC can be achieved within
  a few years using the management regime applied
  in the greenhouse.
• SOM and CEC may have saturated by 2004. This
  could mean that less intense management at the
  Jones Farm might result in the loss of SOM and
  CEC because organic matter is currently being
  replaced at the rate it is being removed from the
  system.

a
b
References
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Soil organic matter accumulation at the George
Jones Farm A comparison of organic treatments
with natural processes and conventional
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years of organic and conventional farming.
Agriculture, Ecosystems and Environement. 118
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bed greenhouse and adjacent fallow fields
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Methods of Soil Analysis, Part 3 Chemical
Methods. Soil Science Society of America, Inc.
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communication. 26 November 2007. Sumner, M.E.
and W.P. Miller. 1996. Cation exchange capacity
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Analysis, Part 3 Chemical Methods. Soil Science
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G.W. 1996. Soil pH and soil acidity. Methods
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