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 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

 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