Quantifying the response of Goldrush potato to nitrogen on sandy soil
Data files
May 05, 2026 version files 18.11 KB
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Nrate_rawdata.csv
11.90 KB
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README.md
6.21 KB
Abstract
Optimizing nitrogen (N) application rate is essential for effective N management and requires an understanding of crop growth dynamics, nutrient partitioning, cultivar traits, and soil characteristics. This dataset contains plot-level measurements from a three-year nitrogen (N) rate experiment with the potato cultivar ‘Goldrush’ grown on irrigated sandy soils at the Hancock Agricultural Research Station in central Wisconsin, USA (2015–2017). Seven in-season N fertilizer rates, ranging from 37 to 391 kg N ha -1 including starter N, were applied in a randomized complete block design with four replications each year. The dataset is structured at the plot × year level and includes repeated measurements at early- and late-growth stages as well as final harvest. For each plot, the dataset provides aboveground biomass and tuber dry matter, tissue N concentration, and calculated N uptake in aboveground and tuber fractions at approximately 45 and 75 days after emergence and in total crop biomass. Final harvest data includes total and marketable tuber yield, tuber number and tuber mean weight derived from graded size classes, specific gravity, and the incidence of internal defects and relative total and marketable yield. These data are suitable for regression analyses of crop response to N, evaluation and comparison of quadratic, linear-plateau, and quadratic-plateau models, development of cultivar- and site-specific N recommendations, and calibration or validation of empirical and process-based potato models on coarse-textured soils. The dataset does not contain personal or sensitive information, and there are no known legal or ethical restrictions on reuse beyond citation of the associated article and dataset.
Dataset DOI: 10.5061/dryad.r4xgxd2sz
Description of the data and file structure
Files and variables
File: Nrate_rawdata.csv
Description: This dataset contains raw agronomic data collected from field experiments evaluating nitrogen (N) fertilizer rates and their effects on dry matter partitioning, nitrogen uptake, and yield components in potato cv. Goldrush. Field trials were conducted during the 2015 - 2017 growing seasons at the Hancock Agricultural Research Station in Wisconsin, USA.
Variables
- TotalNapplied: Nitrogen (N) fertilizer application rate in kg-N/ha. 37 kg-N/ha was applied as a starter at planting; all remaining rates received 68 kg-N/ha at emergence. Rates then varied across the final two applications: at tuber emergence and two weeks later.
- block: The study was design in a randomized complete block with four replicates (blocks) per treatment in each year.
- year: Field experiments were conducted at the Hancock Agricultural Research Station, during the potato growing seasons of 2015, 2016, and 2017.
- 45 DAE: 5 plants collected between 43-45 days after emergence, presented as dry matter (DM) (kg-DM/ha), scaled up based on seeding rate of 34,400 seeds ha–1
- 75 DAE: 5 plants collected between 75-77 days after emergence, presented as dry matter (DM) (kg-DM/ha), scaled up based on seeding rate of 34,400 seeds ha–1
- AGBDM45: Aboveground dry matter (mg/ha), collected between 43–45 days after emergence.
- TuberDM45: Tuber dry matter (mg/ha), collected between 43-45 days after emergence.
- TotalDM45: Total dry matter (mg/ha): sum of aboveground and tuber biomass, collected between 43-45 days after emergence.
- AGBNC45: Aboveground nitrogen concentration (g/kg), measured between 43–45 days after emergence.
- TuberNC45: Tuber nitrogen concentration (g/kg), measured between 43–45 days after emergence.
- AGBNU45: Aboveground nitrogen uptake (kg/ha) measured between 43-45 days after emergence.
- TuberNU45: Tuber nitrogen uptake (kg/ha) measured between 43-45 days after emergence.
- TotalNU45: Total nitrogen uptake (kg/ha) measured between 43-45 days after emergence.
- AGBDM75: Total nitrogen uptake (kg/ha) measured between 43-45 days after emergence.
- TuberDM75: Tuber dry matter (mg/ha), collected between 75-77 days after emergence.
- TotalDM75: Total dry matter (mg/ha): sum of aboveground and tuber biomass, collected between 75-77 days after emergence.
- AGBNC75: Aboveground nitrogen concentration (g/kg), measured between 75-77 days after emergence.
- TuberNC75: Tuber nitrogen concentration (g/kg), measured between 75-77 days after emergence.
- AGBNU75: Aboveground nitrogen uptake (kg/ha) mesasured between 75-77 days after emergence.
- TuberNU75: Tuber nitrogen uptake (kg/ha) mesasured between 75-77 days after emergence.
- TotalNU75: Total nitrogen uptake (kg/ha) mesasured between 75-77 days after emergence.
- TuberNumber: Tuber number (1000 tubers/ha) measured based on graded potato categories (all size grades excluding culls).
- TMW: Tuber mean weight (g) measured based on graded potato categories (all size grades excluding culls).
- TuberYield: Total tuber yield (Mg/ha) sum of all grading sizes excluding culls.
- TYRY: Tuber relative yield (%), expressed as a percentage of the maximum total tuber yield observed.
- MarketYield: marketable tuber yield (Mg/ha) sum of grading categories above 57 g.
- MYRY: Market relative yield (%), expressed as a percentage of the maximum marketable yield observed.
- SpecGrav: Specific gravity of tubers, determined by the weight-in-air vs weight-in-water method.
- Brown Center (BC): Brown center
- Hollow Heart (HH): Hollow heart
- Internal Brn Spot (IBS): Internal brown spot
- Vascular Discoloration (VD): Vascular discoloration
- Stem End Discoloration (SED): Stem end discoloration
- Green: Green tubers
A period (.) indicates missing data.
Code/software
The following R packages were used and should be installed prior to running the script:
- tidyverse (including dplyr, ggplot2, readr and related packages) for data import, cleaning, and manipulation
- RColorBrewer, viridis, ggsci, ggpubr, and patchwork for data visualization and figure layout
- lme4, nlme, car, agricolae, and emmeans for linear models, mixed models, ANOVA, multiple comparisons, and estimation of marginal means
- easynls and minpack.lm for fitting non-linear response models (e.g., quadratic and plateau-type curves) using nlsfit and related functions
- Metrics for calculating goodness-of-fit metrics such as RMSE
- readxl for importing any Excel-based supporting files
Workflow:
- The script sets the working directory and reads the main data file (Nrate_rawdata.csv) using read.csv, with missing values coded as ".".
- Nitrogen rate, block, and year are converted to factors to define the experimental structure (randomized complete block design with four replicates per N rate and three years).
- Data are optionally subset by year (2015, 2016, 2017) for year-specific analyses.
- For each response variable (including aboveground, tuber, and total dry matter; nitrogen concentration and uptake at 45 and 75 days after emergence; total and marketable yield; relative total and marketable tuber yield; tuber number; and tuber mean weight), ANOVA models were fitted with nitrogen rate as the main explanatory factor, with year and block included when appropriate to account for the experimental design. These models were implemented using
aovand associated functions in R - Non-linear N response models (e.g., linear, quadratic, linear-plateau, quadratic-plateau) are fitted using nlsfit from easynls and/or functions from minpack.lm and nlme. Model performance is evaluated using diagnostics and RMSE from the Metrics package.
- Publication-quality figures of N rate versus response variables are created with ggplot2 (scatter plots with fitted model curves) and arranged using patchwork and ggpubr.
Running the provided R script reproduces the main statistical analyses and figures associated with the dataset.
Field experiments were conducted at the Hancock Agricultural Research Station (central Wisconsin, USA) during the 2015, 2016, and 2017 potato growing seasons. Each year, the trial was established in a different adjacent field on Plainfield loamy sand (Typic Udipsamment), under a regional rotation with soybean in the previous year and winter rye as a cover crop. The experimental design was a randomized complete block with four blocks per treatment and seven N fertilizer rates, resulting in 28 plots per year. Plots were approximately 7.3 m wide and 6.1 m long and were irrigated with well water according to standard station management.
The potato cultivar ‘Goldrush’ was planted at a target population of ~34,000 plants ha -1. All plots received a common starter fertilizer at planting that supplied N, P, K, S, micronutrients, and a systemic insecticide. In-season N was applied in one to three split applications at emergence (hilling), hook stage (early tuber initiation), and two weeks after hook stage, using ammonium sulfate at emergence and urea or ammonium nitrate for later applications. The seven total N rates (including starter N) ranged from 37 to 391 kg N ha -1 and are documented in the dataset along with application timing and source.
Whole-plant samples (aboveground biomass and tubers) were collected at approximately 45 and 75 days after emergence. Plant material was oven-dried at 65 °C to constant weight to determine dry matter, ground, and analyzed for total N concentration by dry combustion. Nitrogen uptake was calculated as the product of dry matter and N concentration for each plant component and summed to obtain total crop N uptake. At final harvest, tubers were mechanically harvested from the central rows of each plot, graded by size, and weighed to derive total and marketable yield, tuber number, and mean tuber weight. Specific gravity was measured on a subsample of tubers, which were also inspected for internal defects.
Statistical analyses reported in the associated article were performed using linear mixed-effects models and non-linear regression (quadratic, linear-plateau, and quadratic-plateau) to estimate yield responses and critical N rates. The dataset provided here includes the raw plot-level observations used in those analyses; no personal, human-subject, or sensitive species data are included.