In plant growth media of low negative charge, potassium (K) is leached out easily with adverse consequences on its availability to plants and on the environment, since all K fertilizers are completely soluble. The objective of this study was to prepare films based on sodium carboxymethylcellulose (CMC), sodium alginate (SA) and a 1:1 (v/v) CMC:SA mixture to incorporate K and investigate its subsequent release. The film properties were evaluated considering miscibility, glass transition temperature, morphology and permeation of potassium. The absence of strong interactions, the small variation in the glass transition temperature and the roughness detected in the cross-section micrographs of the 1:1 CMC:SA mixtures, indicated a partial miscibility among the components. As a consequence of the above-mentioned characteristics, film release of potassium was highest for the 1:1 CMC:SA mixture and lowest for SA. The release mechanism of K from the 1:1 CMC:SA mixture was controlled by a diffusion process, however, associated effects due to swelling and erosion of the matrix films, were observed for the pure CMC and SA systems. Films of CMC, SA and their 1:1 mixture were able to delay the K release, which can bring considerable benefits in terms of plant growth when media with low negative charges are used.
carboxymethylcellulose; sodium alginate; potassium release; biodegradable polymers
