Effects of Superabsorbent Polymer and Agroperlite on Soil Water Retention Under Controlled Evaporation Conditions

Soil moisture conservation is critical in arid and semi-arid agroecosystems, but open-top laboratory mass-loss tests quantify evaporation dynamics rather than field water-holding capacity. This study evaluated three laboratory experiments with dark chestnut soil (Haplic Kastanozem) and Ordinary Chernozem (Haplic Chernozem) represented by local light-, medium-, and heavy-loam classes. Experiment 1 compared an untreated control, SAP-P (100 mesh powder; 0.20% of dry-soil mass), agroperlite (5.0%), and their composite over a standardized 7-day interval. A randomized-block analysis across six soil-texture combinations detected a significant treatment effect (F3,15 = 12.90, p < 0.001). Fisher’s LSD separated the control from all amended treatments, while the three amendments did not differ from one another. Experiment 2 evaluated five SAP doses over a common 12-day interval. Dose responses were non-monotonic and were not significant for SAP-P, SAP-B, or SAP-G in the primary ANOVA (p = 0.155, 0.983, and 0.471, respectively); therefore, no statistically supported optimum dose was inferred. Experiment 3 found no significant particle-form effect in either light loam (p = 0.148) or heavy loam (p = 0.536). The results support a general reduction in short-term evaporation loss by the amendments in Experiment 1, but they do not identify a superior amendment, optimum SAP dose, or superior SAP particle form. Field validation is required before agricultural recommendations are made.