The study tested different ways to grow late rice after watermelon, focusing on the number of seedlings and nitrogen fertilizer. Having enough seedlings per area is crucial for high yield. Adding more nitrogen fertilizer can help if there aren't enough seedlings, but too much can actually reduce yield. The best results were seen with 5kg of nitrogen fertilizer per 666.7m^2 and 16×10^4 seedlings per 666.7m^2, leading to high yield and cost savings.