The researchers studied how different levels of nitrogen fertilizer affect the yield of rice in various varieties. They found that using N150 or N100 resulted in the highest grain yield, while using no nitrogen led to the lowest yield. The variety Birupa had the highest 1000 grain weight, and MTU-1010 had the highest overall grain yield. N-22 had the lowest grain yield, and Nidhi had the lowest 1000 grain weight. Overall, using N50 instead of N100 had the least impact on grain yield in Birupa.