# Soil Carbon and Organic Matter Fractions Under Nitrogen Management in a Maize–Soybean–Cover Crop System in the Cerrado

## TL;DR

This study shows how using cover crops and managing nitrogen can boost soil carbon storage in tropical farming systems.

## Contribution

The research reveals how specific crop sequences and nitrogen fertilization affect soil carbon fractions and stocks in tropical soils.

## Key findings

- Soil carbon stocks were higher during maize cultivation compared to soybean cultivation.
- Legume cover crops after maize increased carbon accumulation, especially with nitrogen fertilization.
- Raphanus sativus and Crotalaria juncea treatments showed the lowest soil carbon losses.

## Abstract

Using cover crops (CCs) following annual crops, together with sustainable nitrogen (N) management, significantly enhances soil carbon (C) storage. However, carbon accumulation in tropical soils is strongly influenced by the respective crop sequences. This study evaluated soil C stocks and fractions in a system incorporating maize–soybean rotation and successive CCs. A randomized block design with split plots was implemented, where main plots consisted of different CCs and the subplots of treatments with and without N fertilization of maize. Chemical fractions of soil organic matter (SOM) were analyzed at depths from 0 to 40 cm, and C stocks down to 100 cm. The SOM fractions responded to N topdressing of maize, varying with soil depth. Soil C stocks during the maize phase were significantly higher than during soybean cultivation (p < 0.05), likely reflecting greater residue inputs from species with elevated C:N ratios. Legume crops following maize intensified C accumulation, emphasizing the importance of N inputs for soil C dynamics. Soil C losses were lowest in the treatments with Raphanus sativus without and Crotalaria juncea with N fertilization. These findings highlight the relevance of combining CCs and N management to optimize C sequestration in tropical agroecosystems.