The researchers studied how different levels of fertilizer and organic manure affect maize yield and soil fertility. They tested ten treatments on maize crops in Andhra Pradesh, India, and found that using 150% of the recommended fertilizer led to the highest grain yield. This treatment also increased soil organic carbon content and nutrient availability, resulting in higher nutrient uptake by the plants. Overall, combining fertilizers with organic manure can significantly improve maize yield and soil health.