Effects of rice husk and its derived biochar on soil properties and stability of aggregates

  Objectives  Long-term planting of Lei bamboo (Phyllostachys praecox) can destroy the soil structure and lead to acidification. Here, we compared the effects of applying rice husk and its biochar at different rates on soil physicochemical properties and aggregate fractions to promote sustainable Lei bamboo production.

  Methods  A Lei bamboo pot experiment was conducted. The experimental soil samples were collected from a long-term cultivated Lei bamboo plantation with a pH of 5.3. This study had five treatments, including rice husk and its biochar at 10 t/hm² (10H, 10B) and 30 t/hm² (30H, 30B) and no rice husk and rice husk biochar as control (CK). Soil samples were collected 262 days after planting Lei bamboo to determine the basic physicochemical properties of soil. Soil aggregates were measured using the wet-sieving method, and the concentrations of organic carbon (OC) and total nitrogen (TN) in each aggregate fraction were also determined.

  Results  The 30H and 30B treatments reduced the content of <0.053 mm aggregates compared to the CK (P<0.05). Mean weight diameter (MWD), geometric mean diameter (GMD) and >0.25 mm aggregate increased in 30H and 30B (R_0.25). However, 10H and 10B did not affect the MWD and GMD of the water-stable soil aggregates and R_0.25 (P>0.05). 30B increased the concentration of OC in >2 mm, 0.25–2 mm, and 0.053–0.25 mm aggregates (P<0.05) , and the highest increase was recorded for soil aggregates >2 mm. 10H and 30H increased the concentration of OC in <0.053 mm aggregates, but had no effect on the concentration of OC in other aggregate fractions compared with the CK (P>0.05).

  Conclusions  Rice husk and its biochar applied at 30 t/hm² enhanced the stability of soil structure. Compared with rice husk application, rice husk biochar increased the OC concentration in macro-aggregates to increase the soil organic carbon (SOC) concentration. Therefore, applying 30 t/hm² of rice husk biochar instead of rice husk to Lei bamboo soil can improve the soil structure and increase soil carbon sequestration simultaneously.