Trends in Agricultural Chemical Concentrations for Three Sites

with Corn Production

Ashlynn StillwellCE397: Statistics for Water Resources

April 30, 2009

Outline

• Background• Hypotheses• Data & Results• Current Conclusions• Future Work• Questions

Ashlynn StillwellCE397 | 4/30/2009

Background

• Policy mandates increase in biofuels• Major feedstock for ethanol is corn• Chemicals used to grow corn can pollute

water

Ashlynn StillwellCE397 | 4/30/2009

Hypotheses

1. Corn production has increased over time.2. Agricultural chemicals in water have

increased over time.3. There is a positive relationship between corn

production and chemical concentrations.

Ashlynn StillwellCE397 | 4/30/2009

Sites

1 2

3

Ashlynn StillwellCE397 | 4/30/2009

Corn Production

Ashlynn StillwellCE397 | 4/30/2009

Agricultural Chemicals

• Total nitrogen vs. time not statistically different from mean (R2 = 0.028)

• Similar for phosphorus and atrazine (R2 ≤ 0.3)

• Only one R2 > 0.047

Ashlynn StillwellCE397 | 4/30/2009

Corn-Chemical Relationship

Ashlynn StillwellCE397 | 4/30/2009

Corn-Chemical Regression

Nitrogen = 5.64 - 1.6E-05*Corn (2.85) (-1.17)

R2 = 0.15 Se = 1.71 F = 1.37

Phosphorus = 0.61 - 2.4E-06*Corn (5.66) (-3.21)

R2 = 0.56 Se = 0.09 F = 10.3

Atrazine = 7.95 - 4E-05*Corn(2.22) (-1.80)

R2 = 0.45 Se = 2.02 F = 3.24Ashlynn Stillwell

CE397 | 4/30/2009

Current Conclusions

1. Corn production has increased at each of the three sites.

2. No statistically significant increase in chemical concentrations at three sites.

3. Small negative relationship between corn and chemicals, though not always significant.

Ashlynn StillwellCE397 | 4/30/2009

Future Work

• Perform statistical tests on difference between means

• Consider transforming data for better regression fit

• Use SPARROW to estimate nitrogen at sites• Write report

Ashlynn StillwellCE397 | 4/30/2009

Questions

Ashlynn StillwellCE397 | 4/30/2009