Synthesis of controlled release hydrogels from dimethylacrylamide/maleic acid/starch and its application in lettuce cultivation

Over or under the application of fertilizers raises concerns about soil and environmental degradation, and the recently developed controlled application of fertilizers is the focus of addressing these concerns. In this study, we aimed to synthesize a new N,N-Dimethylacrylamide (DMAAm)-Maleic Acid (MA) - Starch (St)-based superabsorbent (p(DMAAm-co-MA-co-St) (DMSt(1))) and to evaluate the suitability of controlled release fertilizers in lettuce cultivation. HCl/NaOH were used to create negative and positive surface modifications of DMSt(1) and respectively, were named to be p(DMAAm-co-MA-co-Starch)/HCl (DMSt(2)) and p(DMAAm-co-MA-co-Starch)/NaOH (DMSt(3)). The finished product had a high-water absorbency and improved the soil's water retention capacity. Moreover, after the urea sorption and release studies of the synthesized superabsorbent were carried out in vitro, their effects on the development of the lettuce plant were also examined. During the application, the length, root diameter, number of leaves, chlorophyll amount and color characteristics of the lettuce were measured. It was also observed and photographed how the morphological and structural properties of lettuce were affected by applying drought stress. At the end of the drought stress, the color of the lettuce growing in pots with hydrogel was found to be greener and the chlorophyll content was higher compared to the control group. In addition, according to the results of the membrane damage index obtained from lettuce leaves, it was determined that water deficiency did not occur in the lettuce thanks to the hydrogels, and thus, no deterioration in the structure of the membranes occurred. In summary, it can be said that the newly synthesized superabsorbent has an alternative application potential in agricultural production.

Automated summary

This study synthesized a new superabsorbent material and evaluated its suitability as a controlled release fertilizer in lettuce cultivation. The results showed that the synthesized material had high water absorbency and improved soil water retention capacity. It also positively affected the growth and development of lettuce. Additionally, the material mitigated the negative effects of drought stress on lettuce and maintained the health of the leaves.