Testing soils and cornstalks to evaluate nitrogen management on the watershed scale

Area of Science:

• Agricultural Science
• Environmental Science
• Soil Science

Background:

• High nitrate concentrations in rivers are a concern in agricultural regions.
• Previous research linked nitrate levels to row crop production but not specific management practices.

Purpose of the Study:

• To experimentally link specific agricultural management practices to nitrate levels in rivers.
• To demonstrate the utility of soil and cornstalk nitrate testing for evaluating nitrogen management.

Main Methods:

• Collected over 3200 soil and cornstalk samples from cornfields over 12 years.
• Analyzed samples to measure nitrogen sufficiency levels and evaluate farmer-applied nitrogen management practices.
• Examined the relationship between in-field nitrogen levels and river nitrate concentrations.

Main Results:

• Early-season rainfall significantly impacted soil and cornstalk nitrogen concentrations due to nitrogen losses.
• An inverse relationship was observed between soil and river nitrate concentrations, suggesting field-to-river nitrogen movement.
• Applying nitrogen fertilizer later in the season was linked to more efficient crop nitrogen uptake.

Conclusions:

• Aggregate analysis of soil and cornstalk samples can identify key factors influencing nitrogen management outcomes.
• Specific nitrogen application timing is crucial for efficient fertilizer and manure use and minimizing environmental losses.
• This approach can inform best management practices to improve nitrogen use efficiency and reduce river nitrate pollution within watersheds.