Three-year field study on grass growth and soil hydrological properties in biochar-amended soil

Abstract

Field monitoring was conducted to investigate and quantify the long-term effects of peanut shell biochar on soil-grass interaction over three years. Three 10 m × 5 m grassed plots were constructed in completely decomposed granitic soil. Two of them were amended, respectively, with 5% and 10% biochar contents (m3/m3) for grass growth, while the third was without biochar amendment. During the three-year monitoring, plant characteristics, saturated water permeability (ks) of grassed soil and soil suction were measured. The monitored results show that the grass leaf area index (LAI) and root length density (RLD) with biochar amendment were improved by 38% and 200%, respectively. In the grassed plot without biochar, a threshold RLD existed with a value of 1.7 cm/cm3, beyond which ks raised pronouncedly. The threshold RLD increased by 52% when biochar content increased from 0% to 10%. This implies that biochar may restrict the increase in ks of grassed soil due to the rise in the threshold RLD. The presence of biochar and grass can retain over 100% higher suction after heavy rainfalls, while 54% lower peak suction under evapotranspiration (ET) compared with the non-amended plot. Biochar can alleviate the negative effects on hydraulic properties caused by plant growth and reduce ET-induced excessive water loss. A 5% peanut shell biochar content is recommended for the long-term management of vegetated earthen infrastructures.