Slow-released and Control-released fertilizers
May 20, 2016

Slow-released and Control-released fertilizers involve few proportion of the fertilizer market.

Different stages of plants growth needs uptake different nutrients. Their utility stems from the fact that fertilizers are subject to antagonistic processes. In addition to their providing the nutrition to plants, excess fertilizers can be poisonous to the same plant. Competitive with the uptake by plants is the degradation or loss of the fertilizer. Microbes in soil may degrade many fertilizers by immobilization or oxidation to prevent uptake of plants. Furthermore, fertilizers are lost by evaporation or leaching.

Most slow-released fertilizers are derivatives of urea, a straight fertilizer providing nitrogen.  Slow-released fertilizers convert in the soil to free urea slowly, which is rapidly uptake by plants.

Besides being more efficient in the utilization of the applied nutrients, slow-released fertilizers also reduce the impact on the environment and the contamination of the subsurface water.

Control-released fertilizers are traditional fertilizers encapsulated in a shell that degrades at a specified rate. Sulfur is a typical encapsulation material. Other coated products use thermoplastics (and sometimes ethylene-vinyl acetate and surfactants, etc.) to produce diffusion-controlled release of nitrogen or other element of fertilizers.