Carbon Balance of Pulse Crops in Rotation with Spring Wheat

Carbon footprint and C balance are used to understand whether an agroecosystem is a C source or sink. Our objective was to evaluate C inputs and outputs for determining C balance for pulse crops in rotation with spring wheat (Triticum aestivum L.) from 2021 to 2022 to 2024–2025 in the US northern Great Plains. Pulse crops (chickpea [Cicer arietinum L], lentil [Lens culinaris Medik.], and pea [Pisum sativum L.]) were rotated with spring wheat to form four crop rotations (chickpea–spring wheat, lentil–spring wheat, pea–spring wheat, and spring wheat–spring wheat). Straw C was 26–74% lower for pulse crops than spring wheat, but 19–23% greater for pea–spring wheat than chickpea–spring wheat and lentil–spring wheat. Root biomass and rhizodeposit C were 24–31% greater for spring wheat–spring wheat than chickpea–spring wheat and pea–spring wheat. Grain C was 21% greater for pea than chickpea, but 64–97% lower for pulse crops than spring wheat. Cumulative CO2 flux from May to April was 14–17% greater for spring wheat–spring wheat than chickpea–spring wheat and lentil–spring wheat. Soil C sequestration rate was greater for pea and spring wheat than chickpea and lentil, or greater for pea–spring wheat and spring wheat–spring wheat than other crop rotations. Carbon balance was 5–16% lower for pulse crops than spring wheat, or 9–16% lower for pulse crop–spring wheat rotations than spring wheat–spring wheat. Because of greater C input and C sequestration rate, spring wheat can reduce C loss compared to pulse crops, or continuous spring wheat can reduce the loss compared to pulse crop–spring wheat rotations.