The researchers conducted a field experiment to see how different levels of phosphorus, zinc, and iron affect the growth and yield of maize. They found that the treatment with phosphorus 60 kg/ha + zinc 25 kg/ha + iron 25 kg/ha resulted in the best plant height, number of leaves, dry weight, cob characteristics, grain yield, and economic returns. Another treatment with slightly lower iron levels showed the highest crop growth rate and root growth rate. Overall, the study suggests that specific combinations of these nutrients can significantly improve maize growth and yield.