Various fertilizers have been widely used in agricultures and horticultures.More than 400 million tons fertilizers are used in the world every year.However

fertilizer cannot be resealed in dry soil

and could be flashed out with heaven rain or irrigation without controlling into river

which results in polluting water resources.Actually

fertilizers have already caused serious pollution for rivers and degeneration of land.Therefore

various controlled release fertilizers have been developed.This paper reviewed development of controlled release fertilizer based on both fundamental issues such as system designing and mechanisms

and materials used for coating as well as their fabrication.So far most of the materials used for coating are synthetic polymeric materials

such as PS

PE etc.

which are not biodegradable.Environmentally friendly biodegradable coatings have attracted increasingly attention

but still in development stage in laboratory.On the other hand

dry and desertification are big challenges for agriculture in China.Using superabsorbent polymers as coating materials could add the function of keeping moisture for the fertilizer

which is particularly important for dry area.It is expected that the superabsorbent polymer coatings could be favorable for crops through helping seed sprout; increasing sprouting ratio

reducing irrigation and enhancing fertilizer efficiency etc.