Abstract
Water scarcity and soil salinity jointly constrain irrigated crop production in the arid regions of Central Asia. This field study evaluated an experimental cotton-linter-based superabsorbent polymer (SAP) as a soil amendment for corn and cotton grown in salt-affected sierozem in Otyrar District, southern Kazakhstan, during 2025. The SAP was produced by grafting acrylic acid onto purified cotton linter, with sodium hydroxide as the neutralizing agent, ammonium persulfate as the initiator, and N,N′-methylenebisacrylamide as the crosslinker. Corn and cotton formed the main plots, and SAP rates of 0, 30, 40, and 50 kg ha⁻¹ formed the subplots in a split-plot randomized complete block design with four blocks. The polymer was incorporated into the seed zone at sowing. Seasonal rainfall was only 12.3 mm, while soil electrical conductivity increased from 3.2 dS m⁻¹ at 0–20 cm to 5.1 dS m⁻¹ at 80–100 cm. Across the tested rate range, crop establishment, yield components, marketable yield, and irrigation water productivity increased progressively with SAP application. Corn grain yield rose from 2.69 Mg ha⁻¹ in the control to 3.60, 5.40, and 6.30 Mg ha⁻¹ at 30, 40, and 50 kg ha⁻¹, respectively; corresponding irrigation water productivity increased from 0.60 to 1.40 kg m⁻³. Seed-cotton yield increased from 2.90 to 4.20, 4.99, and 5.46 Mg ha⁻¹, while irrigation water productivity increased from 0.29 to 0.55 kg m⁻³. Lint percentage remained nearly unchanged, indicating that higher lint yield primarily reflected improved stand establishment and boll production. Post-harvest soil bulk density varied little among SAP rates, with within-depth differences generally not exceeding 0.02 g cm⁻³. Thus, the short-term agronomic response was substantially greater than the measured structural response. Yield, yield-component, and irrigation-water-productivity responses to hydrogel rate were statistically significant (P < 0.05) based on split-plot analysis of variance across four field blocks. The findings provide field evidence that cotton-linter-based SAP can improve corn and cotton productivity under arid, saline–alkaline conditions; multi-season trials, soil-water monitoring, economic evaluation, and full polymer characterization are still required before an optimum rate or long-term environmental performance can be established.