Comparison of CEC and SOM in 2004 and 2007
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
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).
- 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.
- 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 (p=0.05).
- 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.
- 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.
- Bosch, C.L., N.B. Decker and K.T. Merrick. 2003. Soil organic matter accumulation at the George Jones Farm: A comparison of organic treatments with natural processes and conventional management. ENVS 316.
- Chapin F.S., Matson P.A., Moony H.A. 2002. Principles of Terrestrial Ecosystem Ecology. Springer Science and Business Media, New York.
- Fliessbach A., Oberholzer H.R., Gunst L., Maeder, P. 2007. Soil organic matter and biological soil quality indicators after 21 years of organic and conventional farming. Agriculture, Ecosystems and Environement. 118: 273-284.
- Follett R.F., Stewart J.W.B., Cole C.V., Power J.F. 1987. Soil Fertility and Organic Matter as Critical Components of Production Systems. American Society of Agronomy, Inc.: Madison.
- Lindauer, O., S. Morris, R. Stenger. 2004. Comparison of soil properties in raised bed greenhouse and adjacent fallow fields: effects of 3 years of intense organic management at the Jones Farm Oberlin, Ohio. ENVS 316.
- Nelson, D.W. and L.E. Sommers. 1996. Total Carbon, Organic Carbon, and Organic Matter. Methods of Soil Analysis, Part 3: Chemical Methods. Soil Science Society of America, Inc. Madison, WI.
- Masi, B. and A. Englander. Personal communication. 26 November 2007.
- Sumner, M.E. and W.P. Miller. 1996. Cation exchange capacity and exchange coefficients. Methods of Soil Analysis, Part 3: Chemical Methods. Soil Science Society of America, Inc. Madison, WI.
- Thomas, G.W. 1996. Soil pH and soil acidity. Methods of Soil Analysis, Part 3: Chemical Methods. Soil Science Society of America, Inc. Madison.