Microbial residues in soil are important for storing carbon and maintaining soil health. A 31-year study looked at how different crops and fertilizers affect these residues. They found that a pure legume system increased fungal residues in soil, while manure combined with fertilizers increased overall microbial residues. However, the increase in microbial residues did not directly lead to more carbon storage in soil. Phosphorus fertilizer was especially important for increasing microbial residues in legume systems. Overall, legume crops are good for storing carbon in soil by increasing fungal residues.