Soil carbon dynamics in a long-term corn-soybean rotation system with cover crops in succession

Abstract

The objective of this work was to evaluate changes in soil carbon contents and stocks in a ten-year long experiment under no-tillage, with the transition from corn to soybean, with cover crops and spontaneous vegetation in succession. The experimental design was a randomized complete block with three replicates, using ten different off-season covers: pigeon pea (Cajanus cajan), Brazilian jackbean (Canavalia brasiliensis), sunn hemp (Crotalaria juncea), black velvet bean (Mucuna aterrima), pearl millet (Pennisetum glaucum), radish (Raphanus sativus), sorghum (Sorghum bicolor), wheat (Triticum aestivum), ruzigrass (Urochloa ruziziensis), and spontaneous vegetation. Soil samples were collected in 2013, 2018, and 2024 at the depths of 0–10, 10–20, 20–30, 30–40, 40–60, 60–80, and 80–100 cm. Soil carbon stocks increased from 2013 to 2018, but declined between 2018 and 2024 after the introduction of soybean in 2021, except in treatments with sorghum and wheat. Between 2013 and 2024, soil carbon contents varied according to depth and type of cover crop. The corn-soybean rotation under no-tillage, with cover crops in succession, influences soil carbon dynamics. Sorghum shows the highest carbon accumulation between 2013 and 2024.