Tracing C and N during crop residue decomposition to optimize C sequestration and predict N transfer credit

Term: 4 years, ending December 2025
Status: Ongoing
Researcher(s): Bobbi Helgason, University of Saskatchewan; Reynald Lemke, Agriculture and Agri-Food Canada; Melissa Arcand, Richard Farrell and Diane Knight, University of Saskatchewan
SaskCanola Investment: $79,698
Total Project Cost: $210,008
Funding Partners: Sask Wheat, SaskBarley

Project Description

Crop residues supply critically needed carbon (C) and nutrients to the soil. These residue-derived resources support plant growth and the formation of soil organic matter, a cornerstone of soil health. Crop residues retain nutrients for potential recapture by subsequent crops, but these nutrients, especially nitrogen (N) can also be lost through gaseous emissions and other pathways including leaching and runoff. The C in root and shoot residues left behind after the crop is harvested each year is the major source of energy that drives soil microbial activity and ultimately, nutrient cycling. Through decomposition, microorganisms transform plant C to soil organic C, releasing some as CO and sequestering the remainder in soil with varying degrees of stability and permanence. Understanding the fate of residue C and N is needed to store additional C in the soil, reduce greenhouse gas emissions and efficiently recycle N for future crop growth.

Purpose

More information about the biochemical composition of common crop residues is needed to understand and predict the release of nutrients from residues during decomposition. Although our team has done work to quantify the uptake and retention of N in above- and belowground residue of select crops, quantity alone was not a good predictor of the availability to subsequent crops. There is little if any information available about the biochemical composition, beyond C:N ratios, of key Western Canadian field crops, particularly for roots. Through the combined use of C and N stable isotope tracing and microbial community profiling, we will develop a more comprehensive understanding of the drivers of nutrient release and turnover from crop residues in support of optimized residue management and more sustainable and profitable crop rotations.

Goal

We propose to quantify differences in chemical composition of root and shoot tissue of important field crops to better understand the impact of residue chemistry on decomposition. We will use this new knowledge of residue composition to better understand the plant (residue) factors—and residue x environment interactions—controlling decomposition, which in turn will provide for better assessments of the potential contribution of residue-N to the next crop. Moreover, a better understanding of crop residue decomposition is essential to improving our capacity to explain and predict C and N transformations in the soil and develop farmer-friendly strategies to optimize soil C sequestration, organic matter accumulation and mitigate against N losses.

Objectives

1. Characterize the chemical composition of crop root and shoot tissues (wheat, barley, canola, lentil, field pea, and soybean).

2. Determine the N credits transferred from residues of wheat, barley, canola, lentil, field pea and soybean to the subsequent crop.

3. Quantify residue- soil C transfer during decomposition of different residue types.

4. Relate the chemical composition of crop residues to carbon and nitrogen dynamics during decomposition.