DOI: 10.5061/dryad.hqbzkh1wm
title: Contribution of new and old phosphorus from organic and inorganic fertilizers in subsurface-drained fields using machine learning.

description: Phosphorus (P) is essential for crop growth but leaches through subsurface
 drainage discharge, impacting water quality. This study’s objectives are:
 (1) apply machine learning to quantify the contributions of incidental
 (new) and legacy (old) P in drainage discharge from Organic site and
 Inorganic site, and (2) evaluate the effect of manure application timing
 on P loss. We collected data from two on-farm sites in southeast Michigan,
 USA. We applied the Weighted Regression on Discharge and Seasons (WRDS)
 equation to analyze P load based on drainage discharge and fertilizer
 application timing. The data was divided into calibration and validation
 sets, and machine learning was employed for training. The results showed
 strong model prediction performance. Organic fertilizers contributed
 approximately twice the total phosphorus (TP) loss (7.54 kg ha⁻¹ vs. 3.73
 kg ha⁻¹) and nearly four times the dissolved reactive phosphorus (DRP)
 loss (4.90 kg ha⁻¹ vs. 1.05 kg ha⁻¹) compared to inorganic P loss. When
 applied during winter months (Dec-Jan), organic fertilizer contributed to
 greater new P loss, whereas early fall applications (Oct-Nov) resulted in
 lower new P loss, showing the importance of application timing. At the
 Organic site, legacy P was the dominant contributor to total phosphorus
 (TP) and dissolved reactive phosphorus (DRP) losses, accounting for 84%
 and 79% of losses, respectively. At the Inorganic site, Legacy P was
 responsible for 97% of TP loss and the entirety (100%) of DRP loss. In
 conclusion, legacy P was the dominant source of P loss through drainage
 discharge, and timing of organic fertilizer application significantly
 influenced new P loss.
description: ## Contribution of New and Legacy Phosphorus from Organic and Inorganic
 Fertilizers in Subsurface-Drained Fields Using Machine Learning **Access
 this dataset on Dryad** This dataset contains field-scale subsurface
 drainage, precipitation, and phosphorus load observations collected from
 subsurface-drained agricultural fields managed with organic and inorganic
 fertilizer systems. The data support analysis of total phosphorus (TP) and
 dissolved reactive phosphorus (DRP) transport dynamics, including
 differentiation between new and legacy phosphorus contributions, and are
 intended for use in statistical and machine learning–based modeling
 frameworks. --- ## Description of the Data and File Structure This dataset
 consists of a single Microsoft Excel workbook containing time-series
 observations of hydrologic and phosphorus transport variables measured at
 two experimental subsurface-drained field sites. The workbook is organized
 into separate worksheets to distinguish fertilizer management systems and
 to facilitate comparative analysis between organic and inorganic
 phosphorus sources. --- ## Files Included in This Dataset ###
 **Raw_Data(New_P_paper0).xlsx** This Excel file contains all observed
 hydrologic and phosphorus load data used in the associated analysis. ####
 Worksheet Structure * **Page 1: Organic Fertilizer Site**\ Contains data
 collected from a subsurface-drained field managed with organic fertilizer
 inputs. * **Page 2: Inorganic Fertilizer Site**\ Contains data collected
 from a subsurface-drained field managed with inorganic fertilizer inputs.
 The separation of worksheets was implemented to maintain clarity between
 management systems and to avoid ambiguity during analysis and model
 development. --- ## Variables and Definitions All variables are
 consistently defined across both worksheets. Units are provided to ensure
 reproducibility and proper interpretation. ### **date** * Description:
 Calendar date of observation * Format: MM-DD-YYY --- ### **precipitation**
 * Description: Daily precipitation depth measured at or near the field
 site (daily) * Units: centimeters per day (cm) --- ###
 **drainage_discharge** * Description: Daily subsurface drainage discharge
 from the field * Units: centimeters per day (cm day⁻¹) * Represents the
 volume of water exiting the subsurface drainage system --- ### **TP_load**
 * Description: Observed total phosphorus load exported via subsurface
 drainage * Units: kilograms per hectare (kg ha⁻¹) * Includes both
 particulate and dissolved phosphorus fractions --- ### **DRP_load** *
 Description: Observed dissolved reactive phosphorus load exported via
 subsurface drainage * Units: kilograms per hectare (kg ha⁻¹) * Represents
 the bioavailable fraction of phosphorus in drainage water --- ## Notes on
 Missing and Zero Values * Days with **zero drainage discharge** indicate
 no measurable subsurface flow; phosphorus load values on these days are
 recorded as null. * Days with measurable drainage discharge but **missing
 TP or DRP values** may result from: * Autosampler malfunction or data loss
 * Phosphorus concentrations, particularly DRP, falling below analytical
 detection limits Null values are left unfilled to preserve data integrity
 and avoid artificial inflation of nutrient loads. --- ## Definitions of
 Phosphorus Terms **Total Phosphorus (TP)**\ The sum of all phosphorus
 forms, including particulate-bound and dissolved fractions, transported in
 drainage water. **Dissolved Reactive Phosphorus (DRP)**\ The soluble,
 immediately bioavailable form of phosphorus that readily contributes to
 eutrophication in receiving waters. **New Phosphorus**\ Phosphorus derived
 from recent fertilizer applications. **Legacy Phosphorus**\ Phosphorus
 stored in the soil from historical fertilizer applications that continues
 to contribute to drainage losses over time. --- ## Sharing and Access
 Information This dataset is publicly available through the Dryad Digital
 Repository. * **Repository:** Dryad * **Dataset DOI:**
 10.5061/dryad.hqbzkh1wm --- ## Data Source Data were collected from an
 on-farm subsurface-drained agricultural field site located in **Lenawee
 County, southeastern Michigan, USA**. --- ## Code and Software No
 executable scripts are included in this submission. The dataset can be
 accessed and analyzed using: * Microsoft Excel * R * Python * MATLAB *
 Other statistical or scientific computing environments capable of reading
 Excel (.xlsx) files --- ## Dataset Readiness Statement All variables are
 explicitly defined with consistent units across fertilizer management
 systems. The dataset is fully documented to support transparency,
 reproducibility, and reuse in studies focused on phosphorus transport,
 subsurface drainage, nutrient management, and machine learning–based
 environmental modeling.