Soil health indicators reveal that past dairy manure applications create a legacy effect

Understanding the long-term effects of manure applications on the soil microbial component in semiarid climates will be key to sustain essential processes that affect their productivity and soil health. In this paper, soil health indicators encompassed both selected chemical and biological indicators. From 2004 to 2009, solid dairy manure treatments were applied to plots at cumulative rates of 0, 134, and 237 dry Mg ha⁻¹ (34–56 dry Mg ha⁻¹ year⁻¹) in a randomized complete block with three replicates. Soil samples were taken from each manure rate in the spring of 2020 at 0–15 and 15–30 cm. Eleven years after manure applications ceased, many of the soil chemical and biological indicators were different between the manure and control treatments. In general, soil organic carbon and biological indicators were significantly greater in the 134 and 237 Mg ha⁻¹ treatments as compared to the 0 Mg ha⁻¹ treatment.