Synthesis of an Itaconic Acid‑Modified Cotton Stalk Biochar Fertilizer: Characterization, Slow-Release Properties, and Its Application in Cucumber Seedlings

Abstract

ABSTRACT Itaconic acid (IA), one of the top valuable biomass platform compounds, is promising in agriculture owing to its notable biodegradability and growth‑promoting properties. Nevertheless, the application of IA-modified cotton stalks biochar serving as a novel high-efficiency slow-release nitrogen fertilizer is not thoroughly evaluated. In this study, a new eco-friendly fertilizer of KH2PO4–poly(itaconic acid-co-urea)–poly(vinyl alcohol)–biochar (KPIUPVAB) was successfully formulated and characterized. Remarkably, KPIUPVAB exhibited good water-absorbing capacity (10.54 g g−1 at 90 min in distilled water), high water retention capability (29.26% at 30 d in soil), and a sustained slow-released property. The sustained-release rates of nitrogen (N) in distilled water at 15 d and in soil leaching at 21 d were 33.97% and 20.53%, respectively. It was observed that the release mechanism of KPIUPVAB in distilled water mainly occurred through gradual hydration and erosion of the outer Polyvinyl alcohol (PVA) layer. Nonetheless, it taken place in soil primarily via the diffusion of the biological carbon pores. Moreover, KPIUPVAB enhanced the growth of cucumber seedlings in terms of stem and leaf, as well as the accumulation of nutrient elements within leaves. Relative to the control, KPIUPVAB treatment increased stem length, leaf area, fresh weight of stem and leaf, total fresh biomass, and fresh-to-dry weight ratio by 42.17%, 112.72%, 64.71%, 49.32%, 33.58%, and 15.27%, respectively. Collectively, KPIUPVAB can be exploited as an innovative high-efficiency slow-release nitrogen fertilizer, and it has broad applications in new green fertilizers for agriculture.