Elevated nitrogen (N) deposition can alter the composition and availability of soil phosphorus (P) and thus affect long-term plant growth. However, it remains elusive whether this effect differs between legume and non-legume forest ecosystems, which have distinct ability in using N and P. So far, direct tests for this question have never been found.

Researchers in the Institute of Subtropical Agriculture(ISA) of the Chinese Academy of Sciences measured soil P fractions in a legume (Acacia auriculiformis) and a non-legume (Eucalyptus urophylla) plantation in subtropical China after four-year of N addition.

The team found that the concentrations of soil total P, total Po, and NaOHPi (Po and Pi are organic and inorganic P, respectively) were significantly higher, but soil NaHCO₃-Po was significantly lower, in the legume plantation compared to the non-legume plantation.

Nitrogen addition significantly decreased soil labile P fractions (i.e. NaHCO₃-Pi and NaHCO₃-Po) in the legume plantation, but they did not change in the non-legume plantation.
In contrast, intermediate P fractions (i.e. NaOH-Pi and NaOH-Po) significantly increased with N addition in the legume plantation, but only NaOH-Po experienced a small increase in the non-legume plantation.

The recalcitrant P fractions were not significantly influenced by N addition in either plantation. “Due to more labile P decreased in the legume plantation than in the non-legume plantation, our results suggest that N deposition may cause more serious P limitation in the legume plantation than in the non-legume planation,” said CHEN Hao, a doctoral researcher at ISA.

Researchers’ study has useful implication for the plantation management in the tropics, where the studied plantations (Acacia and Eucalyptus) are widely planted and N deposition and fertilization is expected to increase more in the future.

The work was funded by the National Natural Science Foundation of China (41731176, 31500405; 31370011) and the Chinese Academy of Sciences through its “Light of West China” Program to Hao Chen, Natural Science Foundation of Guangxi Province of China (2017GXNSFAA198038).

The study entitled “Responses of soil phosphorus availability to nitrogen addition in a legume and a non-legume plantation” has been published in July 2018 in Geoderma. This article is available for download at https://linkinghub.elsevier.com/retrieve/pii/S0016706117310133.

Contact: CHEN Hao

E-mail: chenhao10902@scib.ac.cn

Institute of Subtropical Agriculture, Chinese Academy of Sciences
 
Responses of soil phosphorus fractions to nitrogen addition in a legume and a non-legume plantation (Image by Chen Hao)