Desenvolvimento de fertilizante a base de ureia, reforçado com nanofibrila de celulose para controle da liberação de nitrogênio

Abstract

In order to meet the current demand for food, the agricultural sector has used large amounts of fertilizers. Conventional urea is most used in nitrogen fertilization because it is cheaper. However, it presents several disadvantages, such as loss of nitrogen by leaching or volatilization, which decreases the fertilization’s efficiency and leads to environmental and economic issues. A solution to minimize nitrogen losses could be the use of slow released fertilizers. Therefore, the objective of this work is to develop a nitrogen fertilizer based on different cellulose nanofibrils (NFCs) concentrations and characterize their N release curves. The fertilizers are composed by urea, montmorillonite clay, macaúba cake, lignin and different percentages of NFCs (0, 10, 15 and 20%). Manual extrusion was used for the pellets’ preparation, then the pellets were dried in an oven at 50 °C and subsequently received a coating of lignin emulsion. Tests of mechanical strength were applied (% of fines content, durability, diametral and simple compression). Thermogravimetric analysis, FTIR, TEM, SEM and elemental analyzes, were used to characterized the materials. A controlled release test was done using 10 g of each fertilizer. The samples were filled into pots containing 200 ml of acclimatized distilled water at 30 °C and pots were stored in a release chamber with a constant temperature of 30 °C. Aliquots were collected at 24, 48, 72, 96 hours and then at every 168 hours for 2 months. The treatments with NFCs presented better results in all tests performed. Only in the test of fines content that all treatments were statistically similar. The increase of NFCs decreases the number of apparent pores and intensifies the mechanical resistance of the treatments. The NFCs filled the empt spaces of the surface imperfections present on the pellets, which reduced its porosity. Finally, in the N-release test the NFC-containing materials also presented better results than conventional urea and NFC-free treatment. In all tests, treatments 15 and 20% presented statistically similar results. With these results, we conclude that the NFCs are efficient in the delay of N release and they can improve the resistance of nitrogen fertilizer pellets.