Controlled-release membrane was prepared based on the phase inversion method in which circulated urea particles were coated with polyethylene and olefin dispersed in tetrachloroethylene solution.The effect of atomizing on the membrane structure and nutrients release characteristics was investigated systematically.The results showed that as atomizing diameter changed from 43 μm to 120 μm

the average pore diameter of membrane increased from 25.1 nm to 149.2 nm

thus

the release duration of nitrogen coated-urea dropped from 360 d to 96 d consequently.Atomizing diameter played an important role in the structure and characteristics of the membrane and atomizing influenced the membrane formation during phase inversion

therefore

nitrogen release rate of controlled-release urea was manipulated by the mini-pore structure of membrane.Furthermore

in order to obtain satisfactory release

the atomizing diameter should be optimized around 40—120 μm

and the ideal average diameter of the membrane pores should be in the range of 50—150 nm.