Electron-irradiated superabsorbent polymer and zeolite amendments enhance soil properties, microbial activity, and tomato yield in greenhouse sandy loam

This study examines the synergistic effects of an electron-irradiated hybrid superabsorbent polymer (SAP), commercial Aquasorb SAP, and clinoptilolite-rich zeolite on soil properties, microbial populations, and tomato yield in greenhouse sandy loam soil. Twenty-three treatments varying SAP and zeolite types and doses (0.25–2.5 g kg -1 soil) were tested in a randomized pot experiment under controlled greenhouse conditions (25 ± 2 °C day and 18 ± 2 °C night, 60–70% relative humidity, 16:8 h day: night photoperiod). SAP amendments significantly improved soil porosity (from 44.8 % to 50.4 %) and reduced bulk density (from 1.49 to 1.29 g cm - ³). Water retention nearly tripled, with saturated and available water content increasing significantly ( p < 0.05). Zeolite enhanced water-stable aggregates by 25 %, increasing from 41 % to 52 %. Total organic carbon increased by 42 % under Aquasorb SAP treatment. Plant growth was stimulated, with leaf counts rising from 19 to 44 and branch number doubling. Fruit yield increased more than fivefold, reaching 501 g per plant with Aquasorb SAP, while zeolite alone boosted yield to 402 g per plant. Combined SAP and zeolite treatments showed additive benefits but did not exceed the highest SAP-only yields. Microbial populations of fungi and bacteria increased by 79 % and 59 %, respectively, indicating enhanced soil biological activity. The electron-irradiated SAP demonstrated similar effectiveness to commercial SAP, confirming the value of electron beam modification. Overall, combining irradiated SAPs with zeolite offers a promising approach to sustainably improve water retention, soil structure, microbial activity, and tomato productivity in greenhouse cultivation.