Abstract:
To study the feasibility to obtain slow release 8-24-24 chemical fertilizer coating with soy protein isolate as an essential raw material. The coating material is mainly composed of soy protein isolate (SPI), distilled water, plasticizer, formaldehyde as cross-linking agent and color with an optimum composition of 7%, 82.5%, 7%, 3% and 0.5% by weight, respectively. It is found that the characteristic of coating film such as thickness of film and structure of the coating film are important factors affecting the release ability. The increase in thickness of film and the denseness of structure with small pores, resulting in extended period of releasing time. The main factor to increase a thickness of film is by coating fertilizer for several times. The factors to more dense the structure of coating film with small pores are using high concentration of soy protein isolate, using the mineral oil, a non-soluble material, as plasticizer and increasing cross-linking of protein bonds by activated coating film with formaldehyde solution that can change the structure of coating film from amorphous to crystall. From this work can conclude that the activated coated fertilizer have a long period of time for releasing nitrogen (N) compared with the non-activated coated fertilizer and uncoated fertilizer. The period of releasing time of these fertilizer are 9 days, 6 days and 3 days, respectively