Part 1, Section 2: Soil Fertility Management
Soil Fertility Management
Blended fertilizers are made by physically mixing fertilizer materials to give a desired grade. The individual particles remain separate in the mixture, and segregation may occur. This problem can be reduced by using materials with the same particle size. The quality of the blended fertilizer, particularly the segregation of the individual fertilizer materials, should be an important factor in choosing a fertilizer. Poor quality blends may contain the guaranteed nutrients but if there is segregation these nutrients will not be supplied uniformly to the crop. If properly made so as to reduce segregation during transportation and application, blends generally are equal in agronomic effectiveness to granulated complete fertilizers. Blends have the added advantage of allowing a very wide range of fertilizer grades, thus making it possible to match a fertilizer exactly to a soil test recommendation.
When using a blend as a starter fertilizer, try to avoid urea and diammonium phosphate as ingredients. Both materials produce free ammonia, which can hurt seed germination and seedling growth.