The importance of potassium for hay fields Posted in: News Potassium is all too often the most overlooked element in producing hay here in East Texas. For years producers have just thought about nitrogen. Soil potassium levels/fertility does not affect crude protein and digestibility (TDN, ADF) of forages. Deficient or low potassium fertility levels will most assuredly reduce forage growth.PLEASE LOG IN FOR PREMIUM CONTENT. Our website requires visitors to log in to view the best local news. Not yet a subscriber? Subscribe today!