The study looked at how using organic manure like decayed pig manure and rapeseed cake affects soil nitrogen levels and soil quality for growing crops. They found that applying organic manure before planting crops increased nitrate nitrogen in the soil early on, but applying it for the current crop led to higher levels later. The soil quality improved with organic manure, except for decayed pig manure. Overall, using organic manure before planting improved the soil environment for growing tobacco plants.