# Increased organic fertilizer significantly increases leaf nitrogen and phosphorus but not carbon content in a tropical tea plantation

## TL;DR

Using organic fertilizer in tropical tea plantations boosts leaf nitrogen and phosphorus but does not affect carbon levels.

## Contribution

This study reveals how organic fertilizer affects leaf nutrient content and stoichiometry in two tea plant species.

## Key findings

- Organic fertilizer significantly increased leaf nitrogen and phosphorus content.
- Leaf carbon content remained unchanged despite fertilizer application.
- Soil nutrient correlations with leaf stoichiometry shifted from nitrate to ammonium under fertilization.

## Abstract

Carbon (C), nitrogen (N), and phosphorus (P) are essential elements for plant growth and metabolism, with their stoichiometry playing a pivotal role in ecosystem functioning. In tea plantations, fertilization strongly influences the balance of these elements. However, the effects of organic fertilizers on the leaf C, N, and P contents and their stoichiometry in tropical tea plants remain poorly understood. In this study, we examined the impact of organic fertilizer on the leaf C, N, and P contents and their ratios of Camellia sinensis var. assamica (CSA) and Camellia sinensis var. sinensis (CSS) in Hainan, China. Our findings indicated that organic fertilizer significantly increased leaf N and P contents but had no effect on leaf C content. Additionally, organic fertilizer significantly decreased leaf C: N ratio of CSA and CSS, as well as leaf C: P ratio of CSA, but significantly increased leaf N: P ratio of CSS. Soil organic carbon (SOC), total N, and total P also increased, while their stoichiometric ratios decreased in CSA but not CSS. In the unfertilized tea plantation, leaf C, N, and P contents and their stoichiometry of CSA and CSS were significantly correlated with soil NO3−-N, whereas they were significantly correlated with soil NH4+-N in the fertilized tea plantation. Our results suggest that the differential responses of leaf C, N, and P contents of CSA and CSS to organic fertilizer might be attributed to the distinct leaf physiological characteristics of these two tea plant species.

The online version contains supplementary material available at 10.1038/s41598-025-11057-z.