Effects of different amount of biochar application on soil property and bacterial community structure in acidified tea garden

Objectives  Biochar is considered as an efficient, green and multifunctional soil conditioner. The long-term effect of biochar application on the properties of acidified tea garden soils was researched, in order to provide scientific references for reasonable application of biochar in acidified soil improvement.

Methods  A field experiment was carried out in Anxi County, Fujian Province, where the tea garden was planted for more than 7 years and the soil was yellow earth. Six biochar application levels of 0, 2.5, 5, 10, 20 and 40 t/hm² were setup, and all the biochar were once added into soils. The soil pH, EC and bacterial community structure were analyzed five years later.

Results  After the biochar was applied for five years, the pH of tea garden soil increased by 0.16 to 1.11 units, the dissolved organic carbon contents (DOC) increased by 52.6% to 92.3%, and the EC values decreased by 1.85% to 47.77%. The pH of 10–40 t/hm² biochar treatments was significantly higher than that of 0–5 t/hm² biochar treatments. The indexes of Chao and ACE increased with the increase of biochar rate, the Shannon index firstly increased and then decreased. The relative abundance of bacteria suitable for neutral, acid or weakly alkaline environment, such as Arthrobacter, Nitrospira and Xanthomonas, increased due to biochar application, and the relative abundance of Acidobacteria decreased. The correlation analysis between bacterial community structure and environmental factors showed that the bacterial communities of 0–10 t/hm² of biochar treatments was greatly affected by pH and EC. The bacterial communities of 20–40 t/hm² of biochar treatments were greatly affected by DOC. The relative abundances of Nitrospira, Alphaproteobacteria, Acidobacteriaceae, Conexibacter had significant correlation with soil pH and EC.

Conclusions  Biochar has relatively long soil remediation effect. After applying biochar for five years, the pH, DOC and bacterial diversity indexes of tea garden soils are significantly increased, the abundance of bacteria suitable for weakly acid to weakly alkaline environments increased, and the abundance of acidophilic bacteria decreased. Under biochar application amount of 0–10 t/hm², the pH and EC are the environmental factors that significantly affect the bacterial community structure, and under biochar application rate of 20–40 t/hm², DOC is the main environmental factor.