What effect do surface residues have on surface soil warming in the spring?

Surface residues play a significant role in influencing surface soil temperatures during the spring. When residues, such as crop remains or cover crops, are present on the surface, they create a physical barrier that affects how sunlight reaches the soil. This barrier can significantly reduce the amount of direct solar radiation that warms the soil during the cooler spring months.

The presence of these residues slows down the warming of the soil by blocking the sunlight from directly hitting the soil surface and absorbing heat. Additionally, as the surface residues decompose, they can retain moisture, which further contributes to cooler temperatures in the soil beneath them. The insulation effect of the residues acts to maintain a cooler soil environment compared to bare soil, where sunlight can directly warm the surface.

By creating this insulating layer, surface residues effectively retard the warming process, making it slower for the soil to reach optimal temperatures for planting and seed germination. Hence, the impact of residues on surface soil warming in the spring is that they retain and slow down the heating of the soil.