Nanocapsules of urea in chitosan and polymethacrylic acid and their application to hydroponic culture of lettuce (Lactuca sativa L)

Urea was nanoencapsulated in nanospheres of chitosan (QS) and polymethacrylic acid (MPA), seeking for a reduction of urea during the hydroponic culture of lettuce. Nanocapsules with and without urea were characterized by FTIR, TEM and DLS, nanocapsules’ charge was determined by zeta potential. The results of TEM indicated that nanocapsules without urea had a size of 50 nm and with urea 80-100 nm. The hydrodynamic size obtained by DLS was 110 ± 10nm. The FTIR spectra exhibit a peak at 1539 cm^-1 in QS-APM nanocapsules, indicating the ionic interaction between the COO- groups and NH⁺ ₂. New peaks were observed in the nanocapsules containing urea at 1618 and 1458 cm^-1 by interaction with the polymers. The physical differences of lettuce crops, control (C1) and experimental (C2), were: foliage weight of C2 was lower compared to C1. The root weight of C2 was 0.5 times greater than C1. The percentage of nitrogen determined in the leaves was similar in both cases. However the amount of urea used as fertilizer in C2 nanocapsules was only 16% of the control.