Transcript Cover Crops and Biofuels Implications for Soil Characteristics and Plant Development Deanna Boardman October 21, 2009

Cover Crops and Biofuels
Implications for Soil Characteristics
and Plant Development
Deanna Boardman October 21, 2009
 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
 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)
 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
 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.
 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
 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.
 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
 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

 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
 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%
 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
 Decrease
bulk density
 Improves soil structure
• Aggregated
• Low density
• High porosity
• Enhances biological activity and transmittance
of water, gases, and nutrients
 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
 Increases
infiltration and soil moisture
content
• Reduces evaporation and run-off
• Intercept rainfall
• Reduce wind velocity
• Prevent direct sunlight
 Reduces
crusting
 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
 Pest
cycles can be disrupted
 Chemical N reduces pH, cover crops do
not
 Suppress weeds
 Protect water quality
 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