Effects of nitrogen fertilization and bioenergy crop type on spatial distributions of extracellular hydrolases associated with nitrogen and phosphorus acquisition

Authors: LI, JIANWEI - Tennessee State University; WANG, XUEHAN - Tennessee State University; JIAN, SIYANAG - Tennessee State University; GAMAGE, LAHIRU - Tennessee State University; HUI, DAFENG - Tennessee State University; Fay, Philip

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/3/2025
Publication Date: 7/16/2025
Citation: Li, J., Wang, X., Jian, S., Gamage, L., Hui, D., Fay, P.A. 2025. Effects of nitrogen fertilization and bioenergy crop type on spatial distributions of extracellular hydrolases associated with nitrogen and phosphorus acquisition . Scientific Reports. https://doi.org/10.1038/s41598-025-10440-0.
DOI: https://doi.org/10.1038/s41598-025-10440-0

Interpretive Summary: This paper examines the effects of nitrogen fertilization on soil hydrolase activities in switchgrass and eastern gamagrass, two biomass feedstock crops. Switchgrass and eastern gamagrass were grown in a replicated experiment with unfertilized controls and a low (84 kg per hectare) and high (168 kg per hectare) fertilization applied for three years. Soils were extensively sampled to characterize the overall response to treatments and spatial variability in soil hydrolases involved in microbial acquisition of nitrogen and phosphorus: leucine aminopeptidase (LAP), ß-N-acetylglucosaminidase (NAG), and acid phosphatase. Fertilization with nitrogen increased LAP activity and spatial variation in hydrolase activity in soils from switchgrass and increased NAP+LAP activity in soils from gamagrass, where fertiliziation did not affect spatial variability in hydrolase activity. Together these results suggest that low fertilization rates reduce activities of enzymes involved in breakdown of slower decomposing soil organic carbon but also reduce spatial variation, which may low losses of carbon from switchgrass cropping systems, and to a lesser extent also from gamagrass systems. LAP may play a key role in facilitating soil C and N sequestration in fertilized switchgrass crops.

Technical Abstract: Extracellular hydrolases associated with nitrogen (N) and phosphorus (P) acquisitions are important for soil nutrient cycling. The spatiotemporal patterns of N- and P-hydrolases were rarely studied under N fertilization. It is also unclear whether the N fertilization effects likely vary in different crop species. This study employed a spatially explicit design and soil sampling strategy (288 samples at 0-15cm) in a fertilization experiment with zero, low and high N input (NN, LN and HN: 0, 84, and 168 kg N ha-1 yr-1 urea, respectively) in switchgrass (SG: Panicum virgatum L.) and gamagrass (GG: Tripsacum dactyloides L.) croplands in Middle Tennessee. N-acquisition hydrolases such as leucine aminopeptidase (LAP), ß-N-acetylglucosaminidase (NAG), their sum (Nacq), urease (UREA), and P-acquisition hydrolase acid phosphatase (AP) were quantified. Geostatistical analyses were applied to explore the effects of fertilization and plant type on spatiotemporal variations of N- and P-hydrolases. Results showed large plot-to-plot spatial variation and generally increased variation in soil hydrolyses with N fertilization in both croplands. NAG and Nacq were significantly higher by 15–32% in GG than in SG soils. Relative to NN, HN significantly increased LAP by 54% in SG soils. LAP appeared to be highly responsive to N fertilization. Future studies will examine whether a specific peptidase (i.e., LAP) may likely facilitate soil C and N sequestration under intensive fertilization in switchgrass soil.