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Characterizing the fine-scale spatial distribution of soil phosphorus for efficient phosphorus management in an Illinois tile-drained field

  • 0Department of Natural Resources and Environmental Sciences, University of Illinois, Urbana, Illinois, USA.
Journal of Environmental Quality +

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May 13, 2025

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May 13, 2025

View abstract on PubMed

Summary

This summary is machine-generated.

Accurate soil phosphorus (P) mapping in agricultural fields, especially those with depressions, is crucial. Improved mapping reduces overfertilization and P loss to water, conserving resources and protecting water quality.

Area Of Science

  • Agricultural Soil Science
  • Nutrient Management
  • Water Quality Protection

Background

  • Closed depressions in post-glacial landscapes can accumulate phosphorus (P), becoming hotspots for nutrient loss, particularly when underlain by subsurface (tile) drainage.
  • Traditional soil P mapping using a 1-ha grid may miss these depressions, leading to underestimation of soil P levels, overfertilization, and subsequent nutrient loss.
  • Subsurface drainage systems can exacerbate P loss from these accumulated hotspots.

Purpose Of The Study

  • To enhance the characterization of soil P spatial distribution at a sub-field scale by specifically accounting for closed depressions.
  • To assess the impact of improved soil P mapping on fertilizer prescriptions and tile P loss.
  • To evaluate novel sampling and interpolation methods for more accurate soil P assessment.

Main Methods

  • Implemented stratified sampling that included closed depressions within a standard 1-ha grid.
  • Utilized nonstationary interpolation (external drift kriging) incorporating depression depth data to estimate soil P distribution (0-16 cm).
  • Applied the methods to a corn-soybean rotation field in Douglas County, IL.

Main Results

  • The novel approach generated an improved soil P map, identifying a 47% increase in land area not requiring P fertilizer (approx. 4 metric tons P reduction).
  • Soil P estimated from the improved map was a stronger predictor of dissolved reactive P concentration in tile drainage during the non-growing season compared to traditional methods.
  • This highlights the significant impact of depressions on P dynamics and loss.

Conclusions

  • Improved characterization of soil P spatial distribution using stratified sampling and interpolation with depression depth is essential for accurate nutrient management.
  • This approach optimizes fertilizer application, aligning P supply with crop requirements and reducing environmental losses.
  • The findings demonstrate a pathway to protect water quality and conserve finite phosphorus resources.