This study aimed to mathematically define the water sorption and nutrient release of HPC/CMC/Alg agricultural hydrogels by determining the kinetic parameters for models under more realistic mechanisms such as (i) concentration-dependent diffusion coefficients and (ii) moving boundary. The Berens-Hopfenberg model was modified to account for the concentration-dependence of diffusion coefficients. The water sorption behavior resulted in a high correlation with a diffusion-fraction xF = 0.3086, diffusion coefficient at infinite dilution per squared radius D0’ = 0.00000981 min-1, and concentration coefficient β = 0.1632. The behavior of nutrient release resulted in a high correlation with xF = 0.2398, D0’ = 0.05976 min-1, and β = 0.9205. With low values of xF, both behaviors exhibited uptake that are more significant during relaxation than diffusion. To account for moving boundaries due to water sorption, a semi-empirical model was derived based on Fick’s Law. The water sorption behavior resulted in a high correlation with diffusion coefficient D = 0.0199 mm2/min, correction factor A = 1.291, and time coefficient K = 0.0342. The nutrient release achieved a high correlation with D = 0.272 mm2/min, A = 1.530, and K = 0.203. When applied to second-cycle water sorption data, the fitted models were found to be overestimated. This is due to the permanent changes in the structure of the polymer matrix during swelling-deswelling.