CNF/p(AM-co-KAA) Semi-Interpenetrating Network Hydrogel Fertilizer Carriers for Enhanced Nutrient Use Efficiency, Water Retention, and Salt–Alkali Resistance

TL;DR

A new hydrogel fertilizer carrier improves nutrient efficiency, water retention, and salt-alkali resistance in soil, boosting crop growth.

Contribution

A semi-IPN hydrogel is developed to synchronize nutrient release, water retention, and soil amendment in a single material.

Findings

The CPAUH hydrogel showed high mechanical strength and water absorption capacity with structural stability over multiple cycles.

Nutrient release was sustained, with urea and humic acid eluting 66.91% and 92.45% over 15 days, respectively.

CPAUH improved wheat growth and reduced soil electrical conductivity by 39.16% under salt stress.

Abstract

Developing functional agricultural materials that synchronize nutrient release, water retention, and soil amendment is crucial to advancing resource-efficient, sustainable farming systems. However, integrating these multifunctional properties within a single material remains a significant challenge. In this work, we fabricated a multifunctional hydrogel (CPAUH) via a one-pot synthesis strategy, which was composed of carboxylated cellulose nanofibers as a rigid network combined with poly(AA-co-KAA), forming a semi-interpenetrating network (semi-IPN) for loading urea and humic acid. The structure and properties of hydrogels were characterized by FTIR, TGA, SEM, and XPS. The CPAUH exhibited outstanding mechanical strength (0.169 MPa), water absorption capacity (121.65 g g−1), and retained 118 g g−1 after three absorption–desorption cycles, demonstrating remarkable structural stability. Nutrient release kinetics revealed sustained-release behavior, with cumulative elution of only 66.91% for urea and 92.45% for humic acid over 15 days. Under salt stress, the 1.5% CPAUH amendment (P2) markedly enhanced wheat growth compared with the non-amended control (P0), as reflected by significant increases in plant height, chlorophyll content, fresh weight, dry weight, and nitrogen uptake. Concurrently, CPAUH application effectively improved soil conditions by reducing electrical conductivity by 39.16% (to 4.38 mS·cm−1). These collective findings of CPAUH hydrogel offer substantial potential as a multifunctional soil amendment for enhancing water-fertilizer efficiency, reclaiming saline–alkali soils, and improving crop productivity under resource-limited conditions.

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