缓释肥料 (SRF) 的开发引起了越来越多的关注,特别是在过去二十年,因为过度使用肥料导致了公认的环境问题。已经开发了不同类型的 SRF,包括化学或物理反应、装载到具有多孔和层状结构的支架、涂层和水凝胶保持等。在不同的发展阶段和从不同的角度对各种技术进行了回顾。同时,已经开发并使用了各种方法来评估不同种类的 SRF 的释放性能。然而,报告的结果与不同的评估方法有很大不同。在这项工作中,我们首先根据制造分类简要回顾了 SRF 的发展:(1)化学合成,(2) 装载,(3) 涂层,(4) 可生物降解聚合物的应用,和 5) 基于水凝胶的系统,然后重点审查不同的评估方法及其机制。还讨论了用于描述和预测释放行为的各种模型。评价方法一般有四种:(1)浸水法,(2)土淋法,(3)温室栽培法,(4)产量比较法。发现大多数传统合成产品和常规聚合物包膜肥料在水中相当稳定,因此浸水法是合适的。尽管如此,大多数水敏涂料或混合物基产品仍需要通过土壤浸出进行评估。温室和产量比较都是简单可靠的方法,已广泛用于最终评估和确认,但时间问题和不可预测的天气条件的弱点限制了它们在开发初期的应用。结果发现,尽管释放趋势相似,但不同方法之间没有直接关系,因为它们的释放机制不同。各种评估方法需要根据不同的产品进行修改,并根据实验室能力(测量技术)进行调整。还讨论了元素检测方法和环境问题。本文回顾了用于描述和预测释放行为的各种模型。本文还总结了不同国家的SRF标准。指出实际控释肥对植物的养分输送应与植物生长需求紧密匹配。以单一剂量(施肥)为整个作物生长持续供应养分可以节省劳动力和处理成本。此外,不同的植物在不同的土壤和条件下生长良好是可以理解的,因此肥料也应该在不同的环境和情况下进行评估。评价方法应紧密贴合植物生长要求,如水稻在水中,玉米在固土中。此外,不同的植物在不同的土壤和条件下生长良好是可以理解的,因此肥料也应该在不同的环境和情况下进行评估。评价方法应紧密贴合植物生长要求,如水稻在水中,玉米在固土中。此外,不同的植物在不同的土壤和条件下生长良好是可以理解的,因此肥料也应该在不同的环境和情况下进行评估。评价方法应紧密贴合植物生长要求,如水稻在水中,玉米在固土中。
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Fabrication, evaluation methodologies and models of slow-release fertilizers: A review
The development of slow-release fertilizers (SRFs) has attracted increasing attention, especially in the last two decades since the well-recognized environmental problem caused by overusing fertilizers. Different kinds of SRFs have been developed, including chemical or physical reactions, loading into the holders with porous and layer structures, coating, and holding by hydrogels, etc. Various techniques have been reviewed at different development stages and from different angles. Meanwhile, various methodologies have been developed and used to evaluate the release performances of different kinds of SRFs. However, the reported results are significantly different from the different evaluation methodologies. In this work, we have firstly briefly reviewed the development of SRFs according to the fabrication classification: (1) chemical synthesizing, (2) loading, (3) coating, (4) application of biodegradable polymers, and 5) hydrogel-based systems, then focused on reviewing different evaluation methodologies and their mechanisms. Various models used to describe and predicate release behaviors were also discussed. Generally, there are four kinds of evaluation methodologies: (1) immersing in water, (2) leaching by soil, (3) planting in greenhouse, and (4) yield comparison. It was found that most of the traditional synthesized products and coated fertilizers by conventional polymers are reasonably stable in water, so the method of immersing in water is suitable. Still, most of the water-sensitive coating or mixture-based products need to be evaluated through leaching by soil. Both greenhouse and yield comparison are simple and reliable methods and has been widely used for final evaluation and confirmation, but the weakness of time issue and unpredictable weather conditions limit their application during the initial developing step. It was found that there is no direct relationship between different methodologies since their releasing mechanisms are different even though the releasing trend is similar. Various evaluation methodologies need to be modified according to different products and adjusted according to laboratory capability (measurement techniques). The methods of element detection and environmental issues were also discussed. Various models used to describe and predicate releasing behaviors were reviewed in this paper. This paper also summarized the standards of SRFs from different countries. It was pointed out that the nutrient delivery to plants by actual controlled-release fertilizers should closely match the growing demand of the plants. A sustained supply of nutrients for the entire crop growth in a single dose (fertilizing) can save labor and handling costs. Furthermore, it is understandable that different plants grow favorably in different soil and conditions, so the fertilizers should also be evaluated in different environments and situations. The evaluation method should closely match plant growth requirements, such as rice in the water while corn is in solid soil.