The process of nitrogen cycle that enrich the soil with ammonia are A. Ammonification                   B. Nitrification C. Nitrogen assimilation        D. Biological Nitrogen fixation

In ammonification there is release of ammonia from organic nitrogenous compounds of plant and animal bodies or their excreta by the action of ammonifying bacteria like Bacillus species. In Biological nitrogen fixation, molecular nitrogen is converted to ammonia. In Nitrogen assimilation inorganic nitrogen is converted to organic nitrogen by plants. In Nitrification, ammonia is converted to Nitrites and Nitrates.