In this study, controlled-release fertilizers (CRFs) with five different nitrogen release periods were prepared by coating large urea particles with polyethylene (PE) membranes under various experimental conditions. The preliminary and differential solubility rates, release periods, and membrane pore sizes of the obtained CRFs were measured using water immersion, scanning electron microscopy, and mercury porosimetry. For all CRF samples, the median pore diameters of the membranes were equal to 4.5–5.3 nm and pores with sizes smaller than 10 nm accounted for 86–96% of the total pore surface area. The obtained pore diameter distributions differed for the five studied types of CRF, having release periods of 1, 2, 4, 6, and 8 months. Thus, for the CRFs with a 1-month release period, the maximum pore diameter reached a magnitude of 4000 nm, while this value did not exceed 30 nm for the CRFs with a release period of 8 months. Hence, we have established a relationship between the release period of CRFs and their effective maximum pore sizes.

在这项研究中，通过在各种实验条件下用聚乙烯（PE）膜覆盖大尿素颗粒，制备了具有五个不同氮释放期的控释肥料（CRF）。使用水浸，扫描电子显微镜和水银孔隙率法测量获得的CRF的初步溶解度和差异溶解度，释放时间和膜孔径。对于所有CRF样品，膜的中值孔径等于4.5-5.3 nm，尺寸小于10 nm的孔占总孔表面积的86-96％。对于五个研究类型的CRF，获得的孔径分布不同，释放时间分别为1、2、4、6和8个月。因此，对于释放期为1个月的CRF，最大孔径达到了4000 nm，而对于CRF，释放时间为8个月，该值不超过30 nm。因此，我们建立了CRFs的释放期与其有效最大孔径之间的关系。