The researchers studied how different levels of nitrogen and phosphorus affect the growth and yield of calendula plants. They tested various combinations of nitrogen and phosphorus levels in a controlled experiment. The results showed that using 100 kg of nitrogen and 50 kg of phosphorus per hectare led to the best stem diameter, plant spread, and flower production. This combination also resulted in the shortest time for the first flower bud to appear and the highest flower yield per hectare. The interaction between nitrogen and phosphorus levels had a significant impact on the number of flowers per plant and overall flower yield. The best treatment combination was found to be 100 kg of nitrogen and 50 kg of phosphorus per hectare.