Different responses of priming effects in long-term nitrogen- and phosphorus-fertilized soils to exogenous carbon inputs

Long-term nitrogen (N) and phosphorus (P) fertilization could immensely alter plant-soil-microbial properties, thereby impacting the priming effect (PE). However, previous studies mostly simulated PE responses to fertilization by adding nutrient in the laboratory, which could not represent PE changes under long-term fertilization-induced ecosystem alteration. Our aim is to clarify the PE alteration in soils with long-term fertilization history in an alpine meadow.

Soil samples (0–10 cm) were collected from a 9-year field fertilization experiment (including four treatments: control, + N with urea, + P with triple superphosphate, + NP with both fertilizers), and incubated for 30 days with ¹³C-labeled glucose amendment (2% SOC). Plant-soil-microbial properties were measured before/after incubation.

Glucose addition induced a positive PE in all soils with a range from 0.56 to 1.37 mg C g⁻¹ soil. N fertilization did not affect PE intensity due to the microbial adaptation and fast utilization of the added glucose for metabolic needs. P fertilization caused P accumulation in soils, and decreased available N and pH. Such changes inhibited microbes, and glucose activated microbial activities, causing higher PE intensity.

Long-term N fertilization did not significantly affect PE, while P fertilization stimulated PE intensity. Overall, we highlight that P fertilization may induce higher risk of CO₂ release, which deserves more attention when applying P fertilizers in this alpine meadow.