The study looked at how adding potassium fertilizer affects the yield of rice and rapeseed crops in Jianghan plain. By using 187.5 kg of K2O per hectare, they found that both rice and rapeseed yields increased significantly. The crops absorbed more nutrients with this potassium application, leading to higher yields. Even though there was a potassium deficit in all treatments, it decreased as more potassium was added. On the other hand, nitrogen showed a surplus in the rice-rapeseed rotation system.