Microplot design and plant and soil sample preparation for15nitrogen analysis

Jared A. Spackman, Fabian G. Fernandez

Research output: Contribution to journalArticlepeer-review


Many nitrogen fertilizer studies evaluate the overall effect of a treatment on end-of-season measurements such as grain yield or cumulative N losses. A stable isotope approach is necessary to follow and quantify the fate of fertilizer derived N (FDN) through the soil-crop system. The purpose of this paper is to describe a small-plot research design utilizing non-confined15N enriched microplots for multiple soil and plant sampling events over two growing seasons and provide sample collection, handling, and processing protocols for total15N analysis. The methods were demonstrated using a replicated study from south-central Minnesota planted to corn (Zea mays L.). Each treatment consisted of six corn rows (76 cm row-spacing) 15.2 m long with a microplot (2.4 m by 3.8 m) embedded at one end. Fertilizer-grade urea was applied at 135 kg N∙ha-1 at planting, while the microplot received urea enriched to 5 atom %15N. Soil and plant samples were taken several times throughout the growing season, taking care to minimize cross-contamination by using separate tools and physically separating unenriched and enriched samples during all procedures. Soil and plant samples were dried, ground to pass through a 2 mm screen, and then ground to a flourlike consistency using a roller jar mill. Tracer studies require additional planning, sample processing time and manual labor, and incur higher costs for15N enriched materials and sample analysis than traditional N studies. However, using the mass balance approach, tracer studies with multiple in-season sampling events allow the researcher to estimate FDN distribution through the soil-crop system and estimate unaccounted-for FDN from the system.

Original languageEnglish (US)
Article numbere61191
JournalJournal of Visualized Experiments
Issue number159
StatePublished - May 2020

Bibliographical note

Funding Information:
The authors acknowledge the support of the Minnesota Corn Research & Promotion Council, the Hueg-Harrison Fellowship, and the Minnesota's Discovery, Research and InnoVation Economy (MnDRIVE) Fellowship.

Publisher Copyright:
© 2020 Journal of Visualized Experiments.


  • Environmental Sciences
  • Fertilizer derived nitrogen
  • Fertilizer nitrogen use efficiency
  • Isotope sample preparation
  • Issue 159
  • Labeled N
  • Microplot
  • N enriched urea
  • N isotope
  • Soil derived nitrogen


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