Cover Crops and Biofuels Implications for Soil Characteristics
and Plant Development Deanna Boardman October 21, 2009 Slide 2
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
Slide 3 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) Slide 4 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 Slide 5
Slide 6 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. Slide 7
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 Slide 8 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.
Slide 9 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 Slide 10
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 Slide 11 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 Slide 12 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% Slide 13 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 Slide 14 Decrease bulk density Improves
soil structure Aggregated Low density High porosity Enhances
biological activity and transmittance of water, gases, and
nutrients Slide 15 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 Slide 16 Increases infiltration and soil
moisture content Reduces evaporation and run-off Intercept rainfall
Reduce wind velocity Prevent direct sunlight Reduces crusting Slide
17 Reduces soil temperature, up to 10 o 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 Slide 18
Pest cycles can be disrupted Chemical N reduces pH, cover crops do
not Suppress weeds Protect water quality Slide 19 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
