Exploring management and environment effects on edge-of-field phosphorus losses with linear mixed models

Area of Science:

• Agricultural science
• Environmental science
• Water quality research

Background:

• Phosphorus (P) loss from agricultural watersheds is a major concern for water quality.
• Understanding the drivers of P loss is crucial for developing effective mitigation strategies.

Purpose of the Study:

• To evaluate the impact of weather, farm management, and soil conditions on total phosphorus (TP) and dissolved phosphorus (DP) loss.
• To identify key factors influencing P loss in agricultural runoff.

Main Methods:

• Analysis of 125 site-years of runoff data from Wisconsin and Minnesota Discovery Farms.
• Application of three linear mixed models (LMMs) to assess the influence of rainfall, manure application timing, tillage, surface condition, and soil test phosphorus (STP).
• Models included all runoff events, manured sites only, and precipitation events only.

Main Results:

• Manure application timing showed only a marginal association with P loads and concentrations.
• No-till practices were associated with greater DP loads and concentrations, especially under frozen soil conditions.
• Positive associations were found between DP load and DP flow-weighted mean concentration (FWMC) loss at the 0- to 15-cm depth.
• The precipitation event LMM yielded the highest R-squared value.

Conclusions:

• While LMM predictive capacity was limited, the study identified the relative importance of management and environmental variables on P loss.
• Tillage practices, particularly no-till, are significant factors influencing DP loss.
• Findings can guide future research on P loss mitigation in agricultural regions.