Conversion of biomass into low-cost biochar along with organic manure improved soil hydro-physical environment through technological intervention for sandy soil restoration

We studied the influence of organic manures and biochar on structural stability of various soil aggregates and associated carbon contents after 6 years of maize-black gram cropping system in a sandy loam soil of India. The tensile strength was highest in poultry manure (1.02-1.12 kPa) and lowest in farm yard manure-FYM (0.77-0.87 kPa) treatment at 0-15 cm soil depth, and it decreased significantly with an increase in biochar application rate. Similarly, the aggregate density decreased significantly with an increase in biochar application rate also. Vermicompost with biochar resulted maximum aggregate (5-8 mm) moisture content (20.92-24.42%) and lowest in poultry manure (20.04-23.54%) with biochar treatment at field capacity (0-15 cm soil depth). The aggregate (2-5 mm) moisture increased significantly with an increase in biochar application rate at both the soil depth. The pig manure 5 t ha(-1) + biochar 5 t ha(-1) was best among all the treatment for increasing the normalized stability index (0.60 and 0.65 in both soil depth). Similarly, vermicompost 5 t ha(-1) + biochar 5 t ha(-1) was best for increasing the capillary rise mean weight diameter (4.43 and 4.79 in both soil depth). The dry mean weight diameter decreased significantly with an increase in biochar application rate. Wet mean weight diameter varies from 2.79- 3.05 than control (1.63) at 0-15 soil depth and from 2.49-2.75 than control (1.33) at 15-30 cm soil depth. Among the manures with biochar treatment, the macroaggregate (%) was highest in vermicompost 5 t ha(-1) + biochar 5 t ha(-1) (91.52) followed by FYM @ 10 t ha(-1) + biochar 5 t ha(-1) (86.98), poultry manure 5 t ha(-1) + biochar 5 t ha(-1) (85.13), goat manure 5 t ha(-1) + biochar 5 t ha(-1) (83.08) and pig manure 5 t ha(-1) + biochar 5 t ha(-1) (81.80) than control (47.18). All the aggregate-associated carbon at 0-15 cm increased significantly either with manures addition or biochar with manures addition or increases the rate of biochar application. Hence, it is recommended that maize stalk-derived biochar application at 5.0 t ha(-1) was beneficial irrespective of the type of organic manures whose effects on soil physical properties were variable. These results strongly suggested positive improvement of various soil hydro-physical properties following addition of organic manure and biochar amendment in acidic soil of Sikkim state of India.