Research Article

The Relationship Between Soil Organic Carbon and Nitrogen Budgets and Climate Change in a Soybean Plantation Under Long-term Phosphorus Dose Applications

Burak Mert Cetin*, Furkan Kemal, Mehmet Elaldi and Ibrahim Ortas

Department of Soil Science and Plant Nutrition, Faculty of Agriculture, Cukurova University, Adana-Türkiye *Corresponding author e-mail: bcetin227@gmail.com

(Received: 04/09/2025; Revised: 25/11/2025; Accepted: 30/11/2025; Published: 20/12/2025)

ABSTRACT

This study evaluated the effects of long-term phosphorus (P) fertilization on soil physicochemical properties and mycorrhizal dynamics in a soybean-growing area. The experiment was established in 1998 as a long-term field trial in the Arık soil series at Cukurova University, Adana, Türkiye, and the current evaluation was initiated in 2023. Four different phosphorus doses were applied using a triple superphosphate fertilizer source (Control (0), 50, 100 and 200 kg P₂O₅ ha⁻¹). After harvest, soils were sampled from two depths (0–15 and 15–30 cm) and from both the rhizosphere and non-rhizosphere. These soils were analyzed for physical, chemical, and biological properties, including total carbon, organic soil carbon (SOC), lime analysis, total nitrogen, available phosphorus, mycorrhizal spore density and bulk density. Soil density and especially available P content in rhizosphere soils increased with higher P applications. In contrast, mycorrhizal spore density decreased, particularly in the 0-15 cm rhizosphere layer, suggesting suppression of mycorrhizal presence under high P availability. While soil organic carbon (SOC) and total nitrogen showed an increasing trend, most of the differences were not statistically significant. Overall, long-term phosphorus fertilization negatively affected soil biological indicators; these results once again demonstrate that balanced, sustainable phosphorus management strategies should be adopted to protect soil health and climate resilience.

Keywords: Mycorrhiza spores, soybean plant, phosphorus fertilization, organic carbon, Long-term experiment