Carbon Farm Planning

Minimize Soil Disturbance

In healthy soil, the soil particles are loosely arranged as soil aggregates, with tiny spaces or pores between and within aggregates that allow for root penetration, water infiltration, and provide habitat and space for microbial activity.

Soil disturbance often reduces soil pores, decreasing soil function. Soil disturbance can be categorized as :

Physical Disturbances- Tillage, soil compaction, animal trailing, and exposure to wind and water erosion serve as physical disturbances to soil. This section will focus primarily on tillage impacts.
Biological Disturbances

Mendocino, CA Soil Same soil different input and management histories (Fibershed)

Physical Disturbances through Tillage

What happens with you till soil?

Historically, producers implement conventional tillage practices as means of preparing the soil for planting, weed control, and as a method of mixing soil amendments and crop residue into the soil (8). However, by implementing reduced or no-till practices, producers can begin to see the following benefits:

Increased soil carbon and organic matter
Increased aggregate stability
Reduction in soil greenhouse gas emissions
Reduced soil compaction
Improved microbial habitat

The video below introduces No-Till and additional benefits of reducing tillage intensity.

Tillage Impact on Soil Carbon and Microbial Biomass:

Maintaining soil aggregation and stability is essential for maintaining soil carbon stocks. As soil organic carbon levels decrease, essential nutrients decrease along with it (9). Long term reduced soil disturbance like no-till systems can lead to an increase in the organic carbon content in soil. The figure below from Agricultural soils as a sink to mitigate CO2 emissions compares the soil carbon change between conventional and no till treatment over a 20 year period (10).

With increased soil organic carbon through reduced tillage intensity, there is more energy or fuel available for microbes, thus increasing microbial biomass. The figure below shows an increase in microbial biomass as a result of long-term no tillage (11).

Differences in soil carbon between paired no-till (NT) and conventional till (CT) treatments from several temperate zone long-term experiments. Values show percent relative differences vs duration of experiment. Filled in symbols are for heavy-textured soils, and open symbols are for all other soil types (6). The graph represents data from four field experiments comparing how no-till and conventional tillage impact the relative aggregate stability of two soil management systems. The data are expressed as a ratio of aggregate stability under NT vs CT. Generally, aggregate stability increases in the no-till systems over time (expressed as a higher aggregation ratio) compared to conventional tillage. (10)

Tillage & Aggregate Stability

Soil aggregate stability is dynamically influenced by soil organic matter content and will increase as organic matter increases (12). The first figure in the image carousel below demonstrates the relationship between aggregate stability and a no till management scenario. In reduced tillage or no-till systems, soil organic matter remains protected from decomposition within the pore space between soil aggregates and within soil aggregates themselves (13).

Depending on soil type, soil aggregates include particles that are bound together by older, stabilized soil organic matter and can be used as an indicator for soil health (12). The second figure in the carousel below provides a soil profile comparison of a no-till and a conventionally tilled system. The final video provides a close look at long-term no-till and a first year no-till soil comparison. Tillage disrupts aggregate structure, thus altering soil pore space critical for biological activity, root growth, and water infiltration (13). By reducing tillage intensity, additional benefits of tillage reduction in relation to aggregate stability are provided. These co-benefits include:

Protection of soil organic matter and organic carbon protection from decomposition
Improved water infiltration & available water holding capacity
Decreased susceptibility to erosion
Improved root penetration

The graph represents data from four field experiments comparing how no-till and conventional tillage impact the relative aggregate stability between soil systems. The data are expressed as an aggregation ration of NT vs CT. Generally, aggregation increases in the no-till systems over time (expressed as a higher aggregation ratio) compared to conventional tillage. (14)

Tillage & Greenhouse Gas Emissions

Preparing the soil for planting through conventional tillage typically involves overturning the soil, thus exposing soil carbon to oxygen and increasing the rate at which soil microbes are able to oxidize and respire that carbon. Carbon dioxide, as a bi-product of respiration, is then released to the atmosphere. While soil microbe respiration is necessary for metabolic processes and soil health, increased respiration rates from conventional tillage increase the rate at which carbon dioxide returns to the atmosphere. Decreasing tillage intensity reduces the exposure of microbes to oxygen, therefore reducing the amount of carbon dioxide returning to the atmosphere as a results of microbial respiration. As a tool for estimating greenhouse gas emissions related to conservation practice scenarios, COMET-Farm compares the emissions from a baseline scenario to a management change. The report below is the report for the Croplands Carbon Demo Project for the Allee Demonstration Farm in Newell, Iowa.

For the purposes of this demonstration project, we assumed the 60 acre parcel was in a grain corn-soybean rotation. Corn was intensively tilled with 160 lbs of nitrogen from anhydrous ammonia at the time of planting in the 1st week of May. No manure or compost was applied, there was no irrigation, liming or burning. Soybeans were planted using reduce-till with no fertilizer, irrigation, organic matter/compost additions, liming or burning.

Results are presented in metric tones of CO2 equivalent with negative values indicating emission reductions or carbon sequestration. Allee Farms saw a change in emissions by 38.5 metric tones of CO2 equivalent by converting to a no till system.

Management change: Both grain corn and soybeans were converted to no-tillage systems.

COMET-Farm calculates emissions resulting from management practices using peer-reviewed, USDA sanctioned entity-level inventory methods.

Check your knowledge!

Through implementing carbon farming practices to minimize soil disturbance, such as reducing tillage intensity, select the impact on the following soil health properties:

As soil carbon increases through reducing soil disturbance, aggregate stability [increases or decreases] , contributing to a(n) [increase or decrease] in greenhouse gas emissions and [increased or decreased] pore size allowing for [increased or decreased] water infiltration rates. Microbial biomass also [increases or decreases] as carbon increases in the soil.

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Role of Carbon in Soil Health and Agricultural Productivity

Discussion board: If you have any questions throughout Module 1, please use the discussion board below to post.

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Maximize Biodiversity

Citations

(1) Claassen, Roger, Maria Bowman, Jonathan McFadden, David Smith, Steven Wallander. Tillage Intensity and Conservation Cropping in the United States, EIB-197, U.S.Department of Agriculture, Economic Research Service, September 2018

(2) Soil Quality Indicators (USDA Natural Resource Conservation Service, 2008; https://www.nrcs.usda.gov/wps/PA_NRCSConsumption/download?cid=nrcs142p2_051276&ext=pdf).
(3) Paustian, K., Six, J., Elliott, E. et al. Management options for reducing CO2 emissions from agricultural soils. Biogeochemistry 48, 147–163 (2000). https://doi.org/10.1023/A:1006271331703
(4) R.T. Conant, M. Easter, K. Paustian, A. Swan, S. Williams Impacts of periodic tillage on soil C stocks: a synthesis Soil Till. Res., 95 (2007), pp. 1-10
(5) Lal, R., M. Griffin, J. Apt, L. Lave, et al. 2004. Managing Soil Carbon. Science, 304(5669):393.
(6) Paustian, K., Andrén, O., Janzen, H.H., Lal, R., Smith, P., Tian, G., Tiessen, H., Van Noordwijk, M. and Woomer, P.L. (1997), Agricultural soils as a sink to mitigate CO2 emissions. Soil Use and Management, 13: 230-244. doi:10.1111/j.1475-2743.1997.tb00594.x
(7) M.M. Al-Kaisi, A. Douelle, and D. Kwaw-Mensah. November 2014. Soil microaggregate and macroaggregate decay over time and soil carbon change as influenced by different tillage systems. Journal of Soil and Water Conservation. 69 (6) 574-580; DOI: https://doi.org/10.2489/jswc.69.6.574.
(8) Report published by USDA NRCS, Penn State University Extension, capital Resource Conservation & Development, and Clinton County Conservation District.
(9) Andrade DS, Colozzi-Filho A, Giller KE (2003) The soil microbial community and soil tillage. In: El Titi A (ed) Soil tillage in agro-ecosystems. CRC Press, Boca Raton, pp 51–81
(10) Duiker, S.W., Myers, J., Blazure, L. Soil Health: In field and forage crop production, Report published by USDA NRCS, Penn State University Extension, capital Resource Conservation & Development, and Clinton County Conservation District.

(11) Ogle, S.M., et al. 2014. Chapter 3: Quantifying Greenhouse Gas Sources and Sinks in Cropland and Grazing Land Systems. In Quantifying Greenhouse Gas Fluxes in Agriculture and Forestry: Methods for Entity‐Scale Inventory. Technical Bulletin Number 1939. Office of the Chief Economist, U.S. Department of Agriculture, Washington, DC. 606 pages. July 2014. Eve, M., D. Pape, M. Flugge, R. Steele, D. Man, M. Riley‐ Gilbert, and S. Biggar, Eds.
(12) Derner, J.D., T.W. Boutton, and D.D. Brisk. 2006. Grazing and ecosystem carbon storage in the North American Great Plains. Plant Soil, 280(77‐90).

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