Biochar application improves soil bulk density, aggregation and microbial biomass carbon

Nitrogen (N) is an essential nutrient element for crop production, nevertheless too much or too little N is harmful for soil, environment and crops. Over the last century the reactive N (Nr) in the environment has become doubled from industrial and agricultural activities. Such Nr may impact soil physical, chemical and biological characteristics especially at farm level due to improper fertilizer management. Therefore, an experiment was conducted at the farmer’s field of Tokenagar village of Kapasia upazila under Gazipur district to evaluate the effects of various N management practices including biochar application on bio-physicochemical properties of soils in the Boro-T. Aman rice pattern. The experiment consisted of five treatments: T1-, control (zero nitrogen), T2 - farmer’s practice (FP) of N as prilled urea (PU), T3- recommended dose of N (RDN) as PU, T4 - biochar (2 t ha-1) + RDN (BRDN), and T5 - deep placement of urea super granule (USG). Soil samples were collected after each crop harvest s and analyzed for different physical and chemical parameters. Results indicated that biochar + RDN (T4 ) treatment positively contributed to decreased soil bulk density and increased water-holding capacity. The same treatment increased soil pH by 4.9% and the USG treatment (T5 ) did increase by 2.8% compared to the initial level. Compared to the control, water stable soil aggregates markedly increased in biochar (148-157%) and USG (54-111%) treatments. Smaller size soil particles (0.25 mm) were found more stable than larger sized particles (0.50 mm) size particles. Improvement of soil fertility is also evidenced, however, increment of 18% carbon for the biochar treatment is notable in terms of carbon-negative economy. Furthermore, the highest microbial biomass C and N due to biochar treatment confirms its effectiveness for sustained soil quality and environment.