Vertical Stratification of Soil Phosphorus as a Concern for Dissolved Phosphorus Runoff in the Lake Erie Basin. Issue 6 (1st November 2017)

• Record Type: Journal Article
• Authors: Baker, David B.; Johnson, Laura T.; Confesor, Remegio B.; Crumrine, John P.
• Is Part Of: Journal of Environmental Quality. Volume 46:Issue 6(2017)
• Page Start: 1287
• Page End: 1295
• Publication Date: 2017-11-01
• Subjects: Agricultural ecology -- Periodicals; Environmental engineering -- Periodicals; Pollution -- Periodicals; 630
• DOI: 10.2134/jeq2016.09.0337
• Languages: English
• ISSNs: 0047-2425

Abstract

Abstract : During the re‐eutrophication of Lake Erie, dissolved reactive phosphorus (DRP) loading and concentrations to the lake have nearly doubled, while particulate phosphorus (PP) has remained relatively constant. One potential cause of increased DRP concentrations is P stratification, or the buildup of soil‐test P (STP) in the upper soil layer (<5 cm). Stratification often accompanies no‐till and mulch‐till practices that reduce erosion and PP loading, practices that have been widely implemented throughout the Lake Erie Basin. To evaluate the extent of P stratification in the Sandusky Watershed, certified crop advisors were enlisted to collect stratified soil samples (0–5 or 0–2.5 cm) alongside their normal agronomic samples (0–20 cm) ( n = 1758 fields). The mean STP level in the upper 2.5 cm was 55% higher than the mean of agronomic samples used for fertilizer recommendations. The amounts of stratification were highly variable and did not correlate with agronomic STPs (Spearman's r = 0.039, p = 0.178). Agronomic STP in 70% of the fields was within the buildup or maintenance ranges for corn ( Zea mays L.) and soybeans [ Glycine max (L.) Merr.] (0–46 mg kg −1 Mehlich‐3 P). The cumulative risks for DRP runoff from the large number of fields in the buildup and maintenance ranges exceeded the risks from fields above those ranges. Reducing stratification by a one‐time soil inversion has the potential for larger and quicker reductions in DRP runoff risk than practices related to drawing down agronomic STP levels. Periodic soil inversion and mixing, targeted by stratified STP data, should be considered a viable practice to reduce DRP loading to Lake Erie. Core Ideas: P stratification increases surficial soil‐test levels by 55% over agronomic cores. Agronomic soil‐test levels are not good indicators of surficial soil‐test levels. Soils in maintenance range account for the largest proportion of DRP runoff risks. Targeted stratification reduction could reduce DRP runoff more than drawdown. Stratification reduction could reduce DRP runoff more quickly than drawdown.