The study looked at how different farming methods affect the recovery of nitrogen fertilizer in crops like maize and wheat. They used labeled urea to track the nitrogen and found that the permanent raised beds with residue burning had the highest recovery rates. The conventionally tilled beds had the lowest recovery rates after two cropping cycles. They also found that a significant amount of the labeled nitrogen ended up in the soil, showing the importance of long-term monitoring to avoid overusing mineral nitrogen fertilizer.