Effects of Different Planting Years of Hazelnut on Soil Organic Carbon and Humic Acid Structural Characteristics

Abstract

ABSTRACT Different planting ages of forests will have a certain impact on the physical and chemical properties of the soil. This study investigated whether different growth years of hazelnut have an influence on soil organic carbon (SOC) content and humic acid (HA) structure. To do this, four treatments were implemented: no hazelnut planting (CK), hazelnut planting 2 years (A2), hazelnut planting 4 years (A4), hazelnut planting 5 years (A5), hazelnut planting 8 years (A8) were considered. With the extension of the hazelnut cultivation years, the SOC content of 0～20 cm and 20～40 cm gradually decreased, reaching 18.84 and 24.53 g kg−1 in the fifth year, but increased by 10.36 and 3.50 g kg−1 in the eighth year. The H/C ratio in the HA structure of 0～20 cm and 20～40 cm soil of A8 increased by 0.010 and 0.057. The Fourier transform infrared spectroscopy (FTIR) spectra and thermogravimetric analysis (TG) results revealed that at 2, 4, and 5 years after planting hazelnut, the structural condensation of HA increased and the degree of aliphatic group decreased. In 8 years after planting, the HA structure had the weakest degree of condensation and more aliphatic structure, while the HA structure was younger and unstable. In conclusion, this study is helpful for hazelnut cultivation and effective management of sustainable utilization of garden soil .