Synthesis and Characterization of Okara-Poly(acrylic acid) Superabsorbent Hydrogels for Enhancing Vegetable Growth through Improving Water Holding and Retention Properties of Soils

Abstract

Okara (Ok), a byproduct of soybean milk and curd production, is a suitable candidate for developing biobased renewable materials. Herein, we report the synthesis and characterization of okara-poly(acrylic acid) (Ok-PAA) superabsorbent hydrogels by grafting and cross-linking PAA on fresh okara. The dried Ok-PAA hydrogel granules in different sizes were added into three types of soils, i.e., lawn sand, mixed soil, and potting mix, as a soil supplement. Overall, the hydrogel supplementation could improve the water holding and retention capacities much more significantly for sand and mixed soil than potting mix. Further, the hydrogels were evaluated for enhancing the growth of a green Asian leafy vegetable, the Brassica rapa subsp. chinensis var. parachinensis (choy sum) in the three soils. In mixed soil, the effect of the hydrogels for enhancing the vegetable growth and reducing the water leaching was particularly significant. Therefore, the Ok-PAA hydrogels are promising for agricultural and farming applications where the soil texture is similar to mixed soil.

Hydrogels improved parsley (Petroselinium crispum(Mill.) Nyman) growth and development under water deficit stress

“…It has been determined that hydrogel applications have a positive effect on the growth of Raphanus sativus and Phaseolus vulgaris vegetables in arid conditions and enable these plants to have longer life spans ( Durpekova et al, 2022 ). Hydrogel applications increased leaf area, as well as the yield of leafy vegetables by 35% to 60% and encouraged the development of Brassica rapa subsp chinensis var parachinensis ( Zhu et al, 2022a , 2022b ). In our experiment, the increase in leaf and root size, main stem length, and number of tillers in parsley were found to be higher than in Shankarappa et al (2020) , although the results were similar.…”