Location: Soil Drainage Research
Project Number: 5080-13210-002-041-I
Project Type: Interagency Reimbursable Agreement
Start Date: Apr 1, 2020
End Date: Sep 30, 2024
1. Estimate the relative contributions of recently applied and legacy P to edge-of-field (EOF) P loading using data analysis techniques and an extensive dataset from 46 agricultural fields located in the Western Lake Erie Basin (WLEB) and surrounding region. 2. Determine the effect of a P ‘hotspot’ on P concentration and loading at the field and watershed scale by building up soil test P levels within a small, select area of each. 3. Examine the fate of dissolved and particulate phosphorus in agricultural drainage ditches.
Objective 1: Use daily discharge and P load observations from the ARS edge of field (EOF) network to separate into “legacy” and “recently applied” timeframes based on the timing of P applications. Discharge and P load data from the legacy timeframe will be used to construct baseline relationships for each individually monitored outlet. These baseline discharge-P load relationships will then be applied to the recently applied timeframe data to predict expected baseline P loads from the observed discharge data. Subtraction of the expected P loads from the observed P loads will identify differences in P loads during the recently applied timeframe, which will be quantified as recently applied fertilizer P losses. The relative contributions of legacy P and recently applied fertilizer P to total P loading will then be calculated. Objective 2: The effect of P ‘hotspots’ on tile drainage P concentration and loading will be evaluated at the plot/field and watershed scale by creating a hotspot in each area. We aim to create hotspots that represent 1, 5, 10, and 20% of the field size. Analysis of data f will follow a before-after-control-impact design. Objective 3: At 6 sites, we will conduct reach-scale tracer experiments to quantify the fate of fine particulates and dissolved phosphorus (DP). We will measure nutrient uptake with short-term nutrient additions involving the injection of potassium phosphate to quantify soluble reactive phosphorus (SRP) uptake length, uptake velocity, and uptake rate. Surface water will be sampled at high frequency at the upstream and downstream ends of the reaches. We will conduct these experiments under a summer low-flow scenario, as well as spring high-flow scenario in a subset of sites.