The study looked at how adding nitrogen to soil affects its acidity and the levels of certain nutrients. They used pots in a greenhouse and added different amounts of nitrogen to see the effects. They found that as nitrogen levels increased, the soil became more acidic and had higher levels of harmful substances. The amount of important nutrients in the soil decreased with higher nitrogen levels. Low nitrogen levels helped some nutrients increase, but high levels made them decrease. This happened because the nitrogen made the soil more acidic, causing the nutrients to wash away.