In the image above, the green healthy plants were grown in float water fertilized with a water soluble fertilizer made with mostly nitrate-nitrogen, while the stunted plants were fertilized with a water soluble fertilizer made with mostly urea-nitrogen. The float media initially lacks the appropriate balance of microbes to fully convert urea to the plant available nitrate from. The partial conversion lead to a build-up of nitrite-nitrogen which is toxic to the young seedlings at high levels. For more information on appropriate fertilizers for the float system, see AGR-163: Selecting the Right Fertilizer for Tobacco Transplant Production in Float Systems.