The researchers studied how different levels of phosphorus and sulphur affected the growth and yield of black gram plants. They tested 12 combinations of phosphorus and sulphur levels in a field experiment. The plants treated with 60 kg/ha of phosphorus and 30 kg/ha of sulphur showed the best growth and yield, with taller plants, more branches and leaves, more root nodules, and higher grain and stover yields. This combination outperformed all other treatments, showing that using these specific levels of phosphorus and sulphur can significantly improve black gram crop production.