Global technological development is linked to the needs of society and, given the exponential increase in population, agrarian expansion has gained prominence due to the use of large-scale fertilizers. The design of materials with effective properties that aid agricultural development has gained prominence in recent decades, mainly inputs for the quantified and prolonged release of nutrients used in different cultures in Brazil. This project studies the formation of composite films between K-carrageenan and alginate, attractive polysaccharides due to environmentally favorable properties and low cost to obtaining, with an increment of nutrient ammonium dihydrogen phosphate (ADP) and reinforced with cellulose nanofibers (CNF) at different concentrations, in order to act as a support and release of nutrients in a programmed way. Init.ially, a study was developed about the best proportion among the Kc / Alg constituents using the casting technique, obtaining the 40/60 polymer fraction as a response. To this composition, CNF (1, 2, and 4%) and ADP (12%) fractions in relation to the dry mass of the materials were added to this composition (Figure 1). Satisfactory results were obtained through swelling and thermal analysis for composition 40Kc/60Alg/4%CNF/ADP (Figure 2), observing films with good thermal stability and best properties for swelling. Thus, the study of new materials with high added value, coming from sustainable, renewable, and abundant sources, is strategic not only from a technological/economic point of view but also environmental, due to the reduction of damages caused by the use excessive amount of fertilizers in Brazilian crops.