AUTHOR=Zhou Jing , Yang Fugui , Zhao Xuechun , Gu Xinyao , Chen Chao , Chen Jihui 

TITLE=Influences of nitrogen input forms and levels on phosphorus availability in karst grassland soils

JOURNAL=Frontiers in Sustainable Food Systems

VOLUME=8

YEAR=2024

URL=https://www.frontiersin.org/journals/sustainable-food-systems/articles/10.3389/fsufs.2024.1343283

DOI=10.3389/fsufs.2024.1343283

ISSN=2571-581X

ABSTRACT=<p>The availability of soil phosphorus (P), a crucial nutrient influencing plant productivity and ecosystem function, is impacted by continuously increasing nitrogen (N) enrichment, which changes the soil P cycle. The effect of varying forms of N input on soil P dynamics in P-limited karst grassland ecosystems remains unclear. To address this knowledge gap, we conducted a greenhouse experiment to explore the effects of various forms of N addition [Ca(NO<sub>3</sub>)<sub>2</sub>, NH<sub>4</sub>Cl, NH<sub>4</sub>NO<sub>3</sub>, Urea] on soil P fractions in these ecosystems, applying two levels (N1: 50 mg N kg<sup>−1</sup>soil, N2: 100 mg N kg<sup>−1</sup>soil) of N input in two soils (yellow soil, limestone soil). Results indicated that P fractions in both soil types were significantly affected by N additions, with yellow soil demonstrating a higher sensitivity to these additions, and this effect was strongly modulated by the form and level of N added. High N addition, rather than low N, significantly affect the P fractions in both soil types. Specially, except for Ca(NO<sub><bold>3</bold></sub>)<sub><bold>2</bold></sub>, high N addition significantly increased the available P in both soils, following the order: Urea and NH<sub><bold>4</bold></sub>NO<sub><bold>3</bold></sub> &gt; NH<sub><bold>4</bold></sub>Cl &gt; Ca(NO<sub><bold>3</bold></sub>)<sub><bold>2</bold></sub>, and decreased NaHCO<sub><bold>3</bold></sub>-Pi in both soils. High N addition also significantly reduced NaOH-Po and C.HCl-Po fractions in yellow soil. Additionally, the response of root biomass and alkaline phosphatase activity in both soils to N input paralleled the trends observed in the available P fractions. Notably, changes in soil available P were strongly correlated with plant root biomass and soil alkaline phosphatase activity. Our study highlights that the N addition form significantly influences soil P availability, which is closely tied to plant root biomass and alkaline phosphatase activity. This finding underscores the importance of considering N input form to boost soil fertility and promote sustainable agriculture.</p>