Soil hydro-physical properties affected by biomass-derived biochar and organic manure: a low-cost technology for managing acidic mountain sandy soils of north eastern region of India

Biochar, organic manure, and their combination are promising organic amendment for improving hydro-physical properties of sandy soils. It has been investigated the effect of organic manures and biochar on some selective soil physical properties after 6 years of maize-black gram cropping system in a sandy loam acidic mountain soil of India. Soil water content was highest in T-16: vermicompost 5 t ha(-1) + biochar 5 t ha(-1) (25.57%) and lowest in T-7: poultry manure 5 t ha(-1) + biochar 5 t ha(-1) (24.69%) than control (19.20%). Soil water content increased significantly with increase in biochar application rate. The volumetric water content was highest in vermicompost and lowest in poultry manure treatment. Among the manures with biochar treatment, the water holding capacity was highest in T-16: vermicompost 5 t ha(-1) + biochar 5 t ha(-1) (59.87%) and lowest in T-7: poultry manure 5 t ha(-1) + biochar 5 t ha(-1) (58.99%) than control (40.13%). Porosity was highest in vermicompost and lowest in poultry manure treatment. The porosity increased significantly with increase in biochar application rate. The T-16: vermicompost 5 t ha(-1) + biochar 5 t ha(-1) is best among all the treatment for decreasing the soil bulk density. Similar trend was also observed in 15-30 cm soil depth for bulk density study but with higher value. Among the manures with biochar treatment, the hydraulic conductivity was highest in T-7: poultry manure 5 t ha(-1) + biochar 5 t ha(-1) (0.30 cm s(-1)) and lowest in T-16: vermicompost 5 t ha(-1) + biochar 5 t ha(-1) (0.23 cm s(-1)) than control (0.43 cm s(-1)). Thus, the hydraulic conductivity decreased significantly with increase in biochar application rate. Soil porosity, aggregate stability, mean weight diameter, water holding capacity, and soil moisture content increased with increase in different types of biochar application rate irrespective of biochar type. But interestingly, soil bulk density and hydraulic conductivity decreased with increase in different types of biochar application rate. The average soil temperature for both maize and black gram significantly increased with application of biochar and manure combination than control. Hence, biochar and organic manure may be a potential organic amendment that could protect hard-setting soil from rapid degradation in long term, thus increasing the value of acidic soil's agronomy and engineering.