The researchers studied the best time to plant ratoon rice in South Henan's rice-growing areas. They compared how rice grows and yields under different planting dates. They found that planting ratoon rice in mid-March gives the best results, with the highest yield. Planting too early or too late can affect the growth of the rice plants and reduce the amount of rice produced. So, mid-March is the ideal time to plant ratoon rice in this region.