Biochar and Compost as Sustainable Amendments for Soil Health and Water Functions in Semi-Arid Agroecosystems

Organic amendments, including biochar and compost, are widely recognized for their potential to improve soil health, but their linkage to soil water functions (e.g., storage, infiltration, plant availability) is not clear. Over two years (2024–2025), we investigated soil water infiltration and associated soil health properties in response to soil amendment application under no-tillage conditions in semi-arid agroecosystems of the southwestern USA. Soil water infiltration was measured in biochar, compost, biochar and compost, and control plots using the SATURO dual-head infiltrometer. Soil physical and chemical properties, including bulk density (BD), soil moisture content (SMC), water-filled pore space (WFPS), residue cover, mean weight diameter (MWD) of dry aggregates, water-stable aggregates (WSA), pH, soil organic carbon (SOC), and total nitrogen (TN), were assessed at 0–15 cm soil depth. The results show a 31.5% higher infiltration rate along with, a small but statistically significant (3.7% lower) bulk density, and 119% greater wet aggregate stability in the biochar-amended plots than in the control plots. Compost with biochar also improved soil health, but infiltration responses were variable. Infiltration was positively correlated with residue cover and soil pH, whereas it was negatively correlated or not correlated with other soil properties. This study demonstrates that biochar under no-tillage conditions can enhance soil health and resilience of semi-arid agroecosystems by improving soil water functions.