Predicting Agricultural Management Influence on Long‐Term Soil Organic Carbon Dynamics: Implications for Biofuel Production

TLDR

Long‑term field experiments are ideal for predicting how agricultural management affects soil organic carbon dynamics and for evaluating biofuel crop residue removal policies. The study aims to simulate SOC dynamics across diverse climates, crop rotations, fertilization regimes, and residue managements with the CQESTR model, and to assess whether no‑tillage can sustain SOC stocks while harvesting crop residue. The authors used five long‑term field sites with documented management histories, varying from monoculture to multi‑year rotations, manure or no fertilizer, and residue returned, burned, or harvested. Measured and modeled SOC stocks were highly correlated (r² = 0.94), and simulations showed that sustainable residue harvest depends on initial SOC, rotation intensity, tillage, yield, and climate, with manure or cover crops under no‑tillage mitigating residue‑removal impacts while fertilizer alone is insufficient.

Abstract

Long‐term field experiments (LTE) are ideal for predicting the influence of agricultural management on soil organic carbon (SOC) dynamics and examining biofuel crop residue removal policy questions. Our objectives were (i) to simulate SOC dynamics in LTE soils under various climates, crop rotations, fertilizer or organic amendments, and crop residue managements using the CQESTR model and (ii) to predict the potential of no‐tillage (NT) management to maintain SOC stocks while removing crop residue. Classical LTEs at Champaign, IL (1876), Columbia, MO (1888), Lethbridge, AB (1911), Breton, AB (1930), and Pendleton, OR (1931) were selected for their documented history of management practice and periodic soil organic matter (SOM) measurements. Management practices ranged from monoculture to 2‐ or 3‐yr crop rotations, manure, no fertilizer or fertilizer additions, and crop residue returned, burned, or harvested. Measured and CQESTR predicted SOC stocks under diverse agronomic practices, mean annual temperature (2.1–19°C), precipitation (402–973 mm), and SOC (5.89−33.58 g SOC kg −1 ) at the LTE sites were significantly related ( r 2 = 0.94, n = 186, P < 0.0001) with a slope not significantly different than 1. The simulation results indicated that the quantities of crop residue that can be sustainably harvested without jeopardizing SOC stocks were influenced by initial SOC stocks, crop rotation intensity, tillage practices, crop yield, and climate. Manure or a cover crop/intensified crop rotation under NT are options to mitigate loss of crop residue C, as using fertilizer alone is insufficient to overcome residue removal impact on SOC stocks.