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Cover Crops and Biofuels Implications for Soil Characteristics and Plant Development Deanna Boardman October 21, 2009. Outline . Introduction Overview of residue removal for biofuels Effect on Soil Characteristics Effect on plant development

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Cover Crops and Biofuels

Implications for Soil Characteristics and Plant Development

Deanna Boardman October 21, 2009

outline
Outline
  • Introduction
  • Overview of residue removal for biofuels
  • Effect on Soil Characteristics
  • Effect on plant development
  • What cover crops can add to an agricultural system with residue removed
  • Conclusion
introduction
Introduction
  • Current pace of nonrenewable fuel consumption
  • Renewable energy sources
  • Plant biomass
  • Agricultural biomasses
    • Traditional principle crops vs. energy crops
    • Grain vs. residues
  • Corn residue is the single largest source of cellulosic agricultural biomass in America (Reddy & Yang, 2005)
introduction1
Introduction
  • Residue removal affects soil characteristics and subsequent crop development
  • Degree of change is dependent on the incorporation of other agricultural practices
    • primary crop rotation
    • residue removal rate
    • incorporation of cover crop
    • nitrogen rates applied to principle crop
soil characteristics affected by residue removal
Soil Characteristics Affected by Residue Removal
  • Residue management influences soil quality and crop productivity
  • Stages of decomposition
  • Cycle interruption
  • 32 year study by Bianca et al. (2008) focused on residue management and tillage, drew two major conclusions:
    • Tillage results in more dramatic changes to soil properties than harvesting of residues
    • Stover harvest is feasible under a no-till practice.
erosion
Erosion
  • Provides protective barrier
    • Prevent direct sunlight, affects temperature and moisture
    • Reduce wind velocity near surface
    • Intercept impact of rainfall
    • Reduces transport of water and soil from field, increasing infiltration
    • Runoff results in loss of nutrients
soil moisture
Soil Moisture

Most important factor essential to plant growth is water

Evaporation and runoff primary mechanisms of water loss

Ponding will result in further infiltration

Bianca et al. (2008) showed in a long term no till study, soils with complete residue removal had 8% less available water content than residue remaining.

soil crusting
Soil Crusting

Crusting results from the impact of raindrops

Rearrangement of particles into open soil spaces

Low porosity for water to infiltrate

Restricted seedling emergence and plant growth

organic matter
Organic Matter
  • Important for:
    • soil structure
    • water permeability
    • microbial activity
    • Nutrient source – traditionally recycled and utilized
  • Approximated two-thirds corn residue can be removed without causing harmful results on organic matter content
  • 32 year study of soils with 100% residue removal had only 8% less organic matter
bulk density
Bulk Density

Mass per unit volume for the soil

Residue naturally degrades and incorporates into the soil

Soil gradually increases in bulk density with residue removal

A study found complete removal resulted in 6-13% greater density

Denser soils create challenges to root expansion and reduces pore space

effects on plant development
Effects on Plant Development
  • How does soil changes affect principle crop development?
    • Emergence and other growth phases
    • Chlorophyll
    • Stalk stability
    • Chemical composition
  • 100% residue removal resulted in a 23% residue biomass reduction
  • Grain yield decreased by 21%
cover crops
Cover Crops
  • Biomass compensation for residue removed
  • Can help to minimize the soil changes associated with corn residue removal
  • Legumes vs. non-legumes
    • N fixation vs. catch
  • Adds mulch for soil coverage
cover crops organic matter
Cover Crops - Organic Matter
  • Decrease bulk density
  • Improves soil structure
    • Aggregated
    • Low density
    • High porosity
    • Enhances biological activity and transmittance of water, gases, and nutrients
cover crops nutrient source
Cover Crops – Nutrient Source
  • Organic nutrients mineralize relatively quickly
  • Replaces N fertilizer needed
    • As much as 2/3 N needed in corn
  • Release depends on C:N ratio
  • Redistribute nutrients to surface to become plant available
cover crops soil coverage
Cover Crops – Soil Coverage
  • Increases infiltration and soil moisture content
    • Reduces evaporation and run-off
    • Intercept rainfall
    • Reduce wind velocity
    • Prevent direct sunlight
  • Reduces crusting
cover crops soil coverage1
Cover Crops – Soil Coverage
  • Reduces soil temperature, up to 10o C
    • Depends on reflectivity and mass
    • Beneficial during heat stress
    • Unfavorable during cool spring, can result in irregular/delayed emergence and lower populations
    • Poor coverage of soil and seed-soil contact
cover crops misc benefits
Cover Crops – Misc. Benefits

Pest cycles can be disrupted

Chemical N reduces pH, cover crops do not

Suppress weeds

Protect water quality

conclusion
Conclusion

Residue removal influences soil characteristics and plant development

Important to evaluate management practices to minimize the effects of removal

Transformations due to revolutionizing agricultural practices are inevitable