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Reasonably utilize the recyclable waste cardboard (175 million tons every year) had attracted the increasing environmental concern. However, the poor hydrophobicity and the loose porous structure of the cardboard-derived coating materials caused the rapid release of nutrients, thereby limiting the development and application of the bio-derived synthetic polymer coated controlled-release fertilizers (BPCFs). In this work, the hydrophobic-densified double-modified waste-carton-derived controlled-release fertilizers (HDCFs) were developed with nontoxic modifying agent and the simple production technology. The controlled release abilities of HDCFs were significantly enhanced (< 2 h to 120.45 days) and the nutrient release prediction models were established. The enhanced performance was attributed to the improved hydrophobicity and the obviously compact coating structure characterized by the three-dimensional computerized tomography (5.76–1.08 %). Furthermore, the enhanced elasticity (5025.52–1325.68 MPa) of the HDCFs coatings also contributed to improve the controlled-release abilities. The controlled-release mechanism was also clarified: the atmosphere "stopper" in the "smaller and less" micropores in HDCFs coating only allows water vapor molecules (instead of liquid) slowly permeate into the internal urea core and significantly enhance the controlled-release longevities. The dramatically increased oilseed rape yield (71.75 %) showed the efficient application effect of the HDCFs. All the results indicate that HDCF with 90:10 of the proportion of the castor oil and liquefaction polyhydric alcohols from cardboard (LPAC) and 5 % of the siloxane of the total polyols exhibits the best performance effect. This work provides the efficient strategy to foster the end-user confidence in the low-cost and eco-friendly biowaste-derived controlled-release fertilizers. • The waste cardboard was utilized to produce controlled-release coating. • The enhanced performance was obtained with hydrophobic-densified double-modification. • The obviously reduced micropore porosities and improved hydrophobicity was observed. • The atmosphere "stopper" in micropore only allows H 2 O molecules enter internal core. • The improved nitrogen utilization efficiency showed the reliable application. [ABSTRACT FROM AUTHOR]

Bio-based controlled release fertilizers (BCRFs) are cost-effective and renewable thus gradually replacing petroleum-based controlled release fertilizers (CRFs). However, most of the study mainly focused on modifying BCRFs to improve controlled-release performance. It is necessary to further increase the functionality of BCRF for expanding the application. A multifunctional double layered bio-based CRF (DCRF) was prepared. Urea was used as the core of fertilizer, bio-based polyurethane was used as the inner coating, and sodium alginate and copper ions formed the hydrogel as the outer coating. In addition, mesoporous silica nanoparticles loaded with sodium selenate was used to modify the sodium alginate hydrogel (MSN@Se hydrogel). The results showed that the nitrogen longevity of the DCRF was much better than that of urea and BCRF. The selenium nutrient longevity of the DCRF was 40 h, much longer than that of sodium selenate. The DCRF improved the yield and nutritive value of cherry radish (Raphanus sativus L. var.radculus pers) with the elevated contents of selenium, an essential trace element. Moreover, the DCRF showed inhibitory effect on Fusarium oxysporum Schltdl. and could resist soil-borne fungal diseases continuously. Overall, this multifunctional fertilizer has great potential for expanding the use of BCRFs for sustainable development of agriculture. [Display omitted] [ABSTRACT FROM AUTHOR]

Bio-based coated controlled-release fertilizers (BCRFs) can significantly improve nutrient utilization and reduce pollution. However, challenges such as spray gun clogging, adhesion and tearing between fertilizers during the actual production of BCRFs pose a severe challenge to production chain development. In addition, the poor hydrophobicity and cross-linking properties of bio-based coatings severely affect the controlled release properties of BCRFs. Although some measures have been taken to ameliorate the above problems, the cumbersome and costly modification process is challenging to be applied on a large scale. Therefore, the primary goal of this work is to search for a more straightforward and efficient method of production and modification to address the aforementioned unresolved challenges in the field of CRFs. In this study, bio-based polyester polyol (BPP) was used as the base for polyurethane reaction, and low-viscosity castor oil (CO) was used as the modifier to reduce the viscosity of BPP. This led to the preparation of Inter-Modified Coated Controlled-Release Fertilizers (ICRFs) to prevent spray gun clogging. Building upon this, hydrophobic and dense wax-based coated fertilizer (WBCF) was prepared by modifying ICRF with Ceresin wax to alleviate the challenges associated with adhesion and tearing between fertilizer particles during the coating process. The WBCF exhibited remarkable controlled-release characteristics, with a nitrogen (N) release longevity of nearly 180 days, requiring only 3 % of the coating materials. This work provides a simple and efficient strategy for overcoming the key constraints in the development and production of CRFs and provides insights into developing green, low-cost fertilizers with excellent controlled-release properties. • Wax-based bio-based coated fertilizers (WBCFs) were fabricated. • The enhanced nutrient release longevities (21–180 days) were obtained. • Wax relies on permeability to plug pores, effectively slowing nutrient release. • The problem of uneven fertilizer coating in CRF production was solved. • The problem of spray-gun clogging in CRF production was solved. [ABSTRACT FROM AUTHOR]

Controlled-release fertilizer (CRF) was applied widely in China as an efficient utilization strategy for improving grain yield and reducing the nitrogen contamination. However, it was indeterminate to know the impacts of inevitably imported plastic into the soil on sustainable development. After ten-year fixed-site experiment, the visible residual coating microplastics were separated from the soil to measure their changes, then the long-term effects of CRF application (theoretical microplastic content 0.018–0.151 g kg−1 soil) on soil architecture and bacterial communities were evaluated. Based on soil organomineral complexes (OMC) distribution experiments and soil 16S rRNA sequence analysis, residual coating microplastics had no significant impact on soil architecture and limited effects on soil bacteria, but became the specific microbial habitat. The nitrogen rate and nitrogen release mode affected sand- and silt-grade OMC, and nitrogen rate impacted soil bacteria communities. The residual coating, small inert particles, is safe for soil OMC and bacterial communities in agricultural soil. Due to the effectiveness of CRF on reducing environmental pollution, CRF is considered as a favorable measure to the sustainable agricultural development in Shandong Province, China. [Display omitted] • After weathering, the additives were broken down and LDPE was left in CRF coating. • Microplastics brought by CRF would not impact soil architecture. • Soil bacteria was clustered based on nitrogen rate rather than microplastics. • Microplastics attracted decomposing bacteria and became specific microbial habitat. [ABSTRACT FROM AUTHOR]