Assessment of Application Efficacy for Agro-Forestry Absorbent Polymers and Their Environmental Risks
Since the performing of Seventh Five-Year(1986-1990)National Scientific and Technological Projects in China,when the national dryland farming research projects started,the super-absorbent polymers for agriculture and forestry(SAP-AF),as one of the technical products for drought-resistance and water-retention in agriculture and forestry,have been given concerned.A Chinese agricultural standard of Agro-forestry absorbent polymer(NY 886)was issued in 2004,and then revised three times in 2010,2016 and 2022,respectively.However,so far there is still no relevant standard or regulation on experiment and assessment for the SAP-AF application efficacy,thus greatly affecting its promotion and application.Based on the literature review on the relevant research and application status of the SAP-AF for more than 30 years(1990-2023),this paper focused on the research about the effects of the SAP-AF application on soil water retention,crop water use,and crop yield,as well as environmental impact.The results showed as follows.(1)The SAP-AF products could enhance the ability to soil water storage and retention(especially for sandy soils),and be beneficial to protecting crop seedlings against drought,water-saving,and yield-increasing,as well as water use efficiency(WUE)-improving in dry-farming areas.(2)The assessment indicators(mainly including soil water storage,crop water consumption,crop yield,and WUE)were proposed to be applicable to evaluate the experiments for the SAP-AF product application efficacy.(3)According to the phenomenon that the SAP-AF application for crops in some regions could not always show a significant effect on yield increase,or sometimes had a negative return,it was proposed that SAP-AF application should formulate corresponding technical regulations,and determine the appropriate product types,and their application methods and dosage for crops.(4)The environmental safety of the SAP-AF products(mainly in the form of polyacrylamide or polyacrylic acid(PAM or PAA)-based materials)mainly involved the biodegradability of the PAM or PAA-based materials and the biological toxicity induced by the residual monomers(acrylamide or acrylic acid(AM or AA))in the products.The residual AM or AA monomer content detected in the PAM or PAA-related products on the market were partly at the risk of exceeding the allowable limits(accounting for about 22%-100%of the total,referred to as the standard limits for some similar products).The review also indicated that some natural polymer materials such as such as starch grafted based polymer materials would be the replaycement of the SAP-AF in the future.The results of this study provided the reference for the formulation of evaluation standards or regulations for SAP-AF product application efficacy.It was suggested that relevant departments should strengthen the detection of residual monomer and its limit requirements for PAM or PAA-based SAP-AF products,and quantify the biodegradability index of products,in order to provide protection for the environmental safety of agricultural and forestry water protection agent products.It was suggested to strengthen the detection of residual AM or AA monomers,and research on the environmental safety threshold of residual monomers for such PAM or PAA-based SAP-AF products;but also need to further explore the relationship between the product biodegradability indicators in the soils and the safety of soil ecological environment,in order to ensure the product environmental safety.
agro-forestry absorbent polymersoil water contentcrop water consumptionwater use efficiencyenvironmental safety risk
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