Applying excessive nitrogen at one time can result in nitrate runoff that will likely contaminate local bays and estuaries. It is better to apply smaller amounts of nitrogen over a long period of time or use a slow-release fertilizer. Phosphorus is necessary for young plant and seedling growth. Other symptoms may include reduced branching and increased color intensity. Although phosphorus is mobile in the plant, it does not leach from soil readily, especially in heavy clay soils like is found in much Nueces County and the inland areas of the Coastal Bend.
High phosphorus interferes with micronutrient absorption and nitrogen absorption.
That is why it is extremely important not to over fertilize with phosphorus in heavy clay soils. Phosphorus does leach from soils high in organic matter such as bark or peat. That is why potted flowering plants and vegetables with an organic based soil mixture need to be fertilized regularly with fertilizers high in phosphorus. Phosphorus is also important to be added in sandy soils as in the Flour Bluff, Padre Island and Rockport areas. Phosphorus is not tied up by either the sand or compost that is added to the soil.