Recovery and Reuse of Nutrients from Hydroponic Effluent in the Context of Circular Agriculture

This research evaluated the recovery and reuse of dolomitic calcareous amendment saturated with nutrients adsorbed from hydroponic effluent as a soil improver and its impact on the agronomic performance of Phaseolus vulgaris. Initially, the dolomitic calcareous amendment (DCA) was saturated with nutrients from the hydroponic effluent through adsorption tests. The characterization of the DCA was conducted before and after nutrient saturation to verify its composition. Soil analysis was carried out prior to the trial, and a completely randomized experimental design was applied with four treatments and five replications, totaling 20 experimental units for each soil type (sandy and clayey): T1 (control), T2 (raw dolomitic calcareous amendment—DCA), T3 (saturated dolomitic calcareous amendment—DCAS), and T4 (granulated dolomitic calcareous amendment—DCAG). Agronomic performance parameters of Phaseolus vulgaris were assessed to determine nutrient availability to the plant: number of pods, pod length (cm), number of seeds per pod, and weight of 100 seeds (g). Data normality was verified using the Shapiro–Wilk test, and results were analyzed using ANOVA and mean comparisons through Tukey’s test (p < 0.05) using InfoStat software 2020I. Additionally, plant tissue was analyzed to determine nutrient absorption in the seeds, and both soil types were analyzed after harvest. Adsorption results indicated that the DCA retained phosphorus, manganese, calcium, and zinc. According to the characterization, DCA primarily consisted of calcium and magnesium carbonates; following the saturation process, an increase in carbonate groups was observed due to calcium adsorption from the hydroponic effluent. Results in both soil types showed no significant differences in pod number, pod length, or seeds per pod, except for the weight of 100 seeds in sandy soil, where T1, T2, and T3 differed significantly from T4. Based on references, the phosphorus content in the harvested seeds from T3 in sandy soil is classified as sufficient. The findings demonstrate the potential of recovering and reusing nutrients from hydroponic effluent using DCA and transforming it into a value-added agricultural input for soil improvement, presenting a promising alternative for more sustainable and efficient agriculture.