Impact of nitrogenous fertilizers on soil

Excessive nitrogenous fertilizers cause two main problems: increased soil acidity (statement 2 is correct) due to the decomposition of ammonium compounds, and leaching of nitrate into groundwater (statement 3 is correct), which is a major water pollution concern. Statement 1 is incorrect because excessive nitrogen actually suppresses nitrogen-fixing microorganisms since the soil already has abundant nitrogen. The proliferation of nitrogen-fixing bacteria occurs in nitrogen-poor soils. Nitrate leaching is well-documented as a primary cause of groundwater contamination in agricultural regions. > Excessive N-fertilizer → Soil acidification + Nitrate leaching, but suppresses N-fixers. Answer: (c).