Biochar is a carbon-rich material obtained from thermochemical conversion (slow, intermediate, and fast pyrolysis or gasification) of biomass in an oxygen-limited environment. It can be produced from a range of feedstock, including forest and agriculture residues, such as straw, nut shells, rice hulls, wood chips/pellets, tree bark, and switch grass . Biochar has been described as a possible tool for soil fertility improvement, potential toxic element adsorption, and climate change mitigation. The beneficial effects of biochar on plant productivity and soil microbial population are related to the improvement of specific surface area, cation exchange capacity, bulk density, pH, water, and nutrients within the soil.biochar with organic or inorganic fertilizers could lead to enhanced soil physical, chemical, and biological properties, as well as plant growth matrix. the combination of biochar with compost has proved to be suitable, allowing the reduction of fertilizer inputs, stabilizing the soil structure, and improving its nutrient content and water retention capacity.

@ Abiola, addition of biochar during the composting process changes the compost properties, and quality and can lead to improved physico-chemical properties (organic carbon content (OC), pH, moisture content) and nutrient availability (nitrogen, phosphorous and other important nutrients) in the end product (Prost et al. 2013) that may be the reason for getting positive effect of total nitrogen in the treatment of biochar.

The problem may be the state of the soil after the amendments. Biochar improves soil structure, but how does cattle manure affect it? What was the pH and temperature of the soil after the addition of cattle manure? Were they compatible with Streptomyces' living conditions? The cattle manure needs microorganisms for its degradation. Perhaps there would have been competition between these microorganisms and Streptomyces?

Thank you all Prem Baboo Carine Temegne Nono J. C. Tarafdar , I am still searching further to understand the dynamics. Your given reasons will be considered.

Biochar contains K, Mg, Na, N and P and enriches the substrate via sorption due to large surface area, high pore volume and negative surface charge. Biochar supplies nutrients to microbes via sorption of nutrient cations and inorganic anions with its surface functional group such as carboxylate gp. However, nutrient conditions of biochar depend upon different aspects of its preparation including feed stock type, pyrolysis temp., ageing period and relationship between pH and CEC. As biochar has recalcitrant SOC pool, its application may favor the fungal growth compared to bacteria and the former being more efficient in decomposition of OM.

Biochar is typically alkaline and carbon rich. In order to be most valuable for use as a biofertilizer it must be activated/inoculated with microbes' rich material (compost, vermicompost, etc.). Activated biochar will be most effective in exchanging nutrients (mainly bases with hydrogen ions). A better knowledge of the biology/ecology of Streptomyces spp. could provide a plausible answer to your question.