控释肥料养分释放动力学及其机理研究 第3报 土壤水分对包膜型控释肥料养分释放的影响(续完)

研究包膜型控释肥料在不同温度和不同土壤水分含量(从田间持水量到较低的风干土壤水平)条件下的养分释放。并将土壤含水量换算成水蒸气压,再将土壤中控释肥料包膜内外的水蒸气压差换算成纯水蒸气压条件下的温度,代入ArataKobayashi改进模型,比较释放率的预测值与实测值,分析了土壤水分与释放速率的关系。结果表明,当土壤水分含量30%(田间持水量的100%),0.42MPa的土壤水势包膜型控释肥料的养分释放速率的实测值与预测值一致,低于这一水分含量的土壤,释放速率下降。土壤含水量2.3%(相当田间持水量的7.7%),土壤水势在100MPa以上时,包膜型控释肥料的养分完全不能释放。在低水分含量下的土壤渗透势对包膜型控释肥料养分释放的影响较小,影响养分释放的主要因子是基质势。     

聚合物包膜肥料养分控释研究进展

聚合物包膜肥料的养分控释机理研究对包膜肥料的开发与应用起着重要作用,国内外研究学者在Fick扩散定理的基础上建立了包膜肥料控释理论和多种数学模型,探索了影响养分释放的因素。聚合物包膜肥料按扩散机制释放养分。养分释放速度的控制因素主要有两种不同看法,一种是养分扩散速率控制,另一种是水蒸气渗透速率控制。肥料包膜层厚度、包膜材料吸水性、温度、水蒸汽压、土壤含水量等均影响养分释放。     

淹水稻田土壤条件下包膜控释肥料养分释放的动力学与数学模拟

采用室内培养方法,对包膜控释肥料在不同温度淹水土壤条件下的养分释放动态变化开展试验,建立了养分释放数学模型。应用该数学模型对包膜控释肥料N释放率的动态变化进行模拟和验证计算。结果表明,模拟值与实测值基本一致,证明数学模型具有实用性。     

控释肥料养分释放动力学及其机理研究 第1报 温度对包膜型控释肥料养分释放的影响

研究 4种包膜型控释肥料养分释放及温度对释放过程的影响。供试 4种肥料具有指数线形和 S线形释放特征曲线。指数线型控释肥料与 SU GIHARA方程和 S线型控释肥料与 ISHIBASHI改进方程有良好的拟合性。4种包膜型控释肥料的养分释放曲线符合初始诱导期校正参数 tau的一级反应模型。具有指数释放特征曲线包膜型控释肥料的 tau可给出零。为了养分的开始释放 ,需要一定量的水分透入包膜肥料内 ,HCRF S70需要透入的水比HCRF E5 0的多。养分释放呈指数曲线形的 HCRF E5 0和养分释放呈 S曲线形的 HCRF S70在释放机理上没有差异。与指数曲线形的 HCRF E5 0相比较 ,S曲线形的 HCRF S70养分释放推迟是由于养分开始释放时所需水分量较大。因此 ,养分释放呈 S曲线形的控释肥料的诱导期依存于温度。     

几种缓控释肥料的养分释放特性研究

采用水浸提法对国内外6种缓控释肥料的养分释放特性进行了系统的比较研究,并探讨了土壤含水量对在水浸提试验中养分释放速率差异较大的两种肥料养分释放特性的影响。研究结果表明:通过一系列的数学变换,可以从理论上对缓控释机理不同的肥料进行新的分类;土壤含水量不但与缓控释肥料的养分释放率显著相关,还影响到普通缓溶肥料养分释放曲线拟合方程的相关系数和高分子聚合物包膜肥料的滞后期。     

控释肥料养分释放动力学及其机理研究第2报水蒸气压对包膜型控释肥料养分释放的影响

研究了水蒸气压差与包膜型控释肥料养分释放速率的关系。在 2 5℃不同水蒸气压差条件下进行了包膜型控释肥料的养分释放试验。在模拟预测值的过程中 ,采用了饱和溶液中的水蒸气压差换算成水中温度的方法。结果表明 ,包膜型控释肥料的养分释放率与膜内水蒸气压差成正比。在盐类饱和溶液中 ,包膜型控释肥料中养分释放受盐类饱和溶液渗透压的影响 ,最大释放率达不到 10 0 %。通过用水蒸气压差换算成温度条件后 ,释放率的预测值与实测值一致     

聚己内酯薄膜中肥料氮、磷养分透过研究

试验测定了尿素-磷酸二氢钠-氯化钾复合肥水溶液中氮、磷养分透过可生物降解聚合物聚己内酯薄膜的渗透率数据,然后利用这些渗透率数据并结合Shaviv的包膜肥料颗粒中养分释放速率数学模型计算不同包膜肥料颗粒尺寸与聚己内酯包膜厚度下的包膜肥料氮养分和磷养分的释放。结果表明:聚己内酯薄膜中的氮养分累积渗透量随时间的变化与线性关系有一定的偏差;聚己内酯包膜肥料氮养分释放呈现明显的S形曲线且可以通过改变肥料颗粒半径和包膜厚度进行调节,为创制针对不同农作物的专用控释肥料提供了坚实的基础。     

控释肥料土壤中实际释放期快速预测方法

包膜控释肥料在土壤中实际释放期大多数在4～6个月甚至更长,为了快速预测控释肥料土壤中实际释放期,对3种不同包膜缓/控释肥料进行土壤中的养分释放特性测定,应用100℃快速浸提法测定的结果与之拟合,并对拟合结果进行评价和检验。结果表明,3种不同包膜的控释肥料在100℃的快速浸提结果与土壤中释放结果的拟合方程的拟合度均达到极显著水平,在土壤中释放期为4个月的包膜控释肥料在100℃下快速浸提只需6.2 h就可测出养分释放期。     

应用电导率评价包膜控释钾肥的养分释放特性

以山东农业大学“控释肥料中试车间”制作的包膜控释钾肥为材料,用静水浸泡法评价其在不同温度下的养分释放特性,分别采用电导率法和火焰光度法测定其养分释放速率。结果表明,硫酸钾溶液浓度与电导率呈极显著的正相关;温度是影响包膜控释钾肥养分释放速率的主要因素,供试肥料40℃处理比25℃处理的释放速率快2.5~3倍,且包膜仍保持热稳定性,能有效控制养分的释放。因此,在40℃蒸馏水中用电导率法测定包膜控释肥料的释放率,评价其养分释放特性,快捷准确。     

控释肥料释放期测定方法研究

小麦专用控释拌种复合肥以改性废弃油脂为包膜材料,可以与小麦种子混播,能够有效提高肥料利用率。聚合物包膜控释肥施入土壤后,温度是其养分释放的主要影响因素,相同的控释肥在不同温度地方的养分释放速率不同。主要研究了不同温度与小麦专用控释拌种复合肥释放期之间的关系,建立了三种小麦专用控释拌种肥在不同温度下释放期快速预测模型,快速测定控释肥在不同温度下的释放期,为其生产和施用提供理论依据。     

肥料和农药缓释/控释技术研究

缓释/控释技术作为一项新兴技术越来越受到重视,它可以有效地解决活性制剂释放速度快、有效时间短等问题。针对目前肥料和农药利用效率低、环境污染严重等现实问题,主要从加工工艺和缓释材料两方面,简要介绍了缓释技术的基本原理、类型和途径,综述了它在肥料和农药方面的应用进展,并且讨论了其发展特点及趋势。     

几种缓释尿基复合肥氮素释放的动力学研究

采用 2种恒温 (2 5℃ ,37℃ )培养试验研究了 4种化学物质 (B1 、B2 、HQ和 DCD)对尿素氮释放的缓效作用和用该化学物质研制 5种缓释尿基复合肥氮释放的动力学效应及其对土壤无机氮的影响。结果表明 ,中、高浓度B1 、B2 对土壤脲酶的抑制作用优于 HQ ,可作为高效无残毒的理想脲酶抑制剂 ;2 5℃下培养 14天 ,3种化学物质 (B1 、B2 、HQ)均明显降低尿素中氮的释放总量、释放速率和平均释放速率。施用缓释尿基复合肥对土壤无机氮含量的影响大 ,含 DCD的缓释复合肥 NH4 + N释放总量高 ,而 NO3- N数量低 ;含硼的 3种缓释尿基复合肥铵释放的动力学与环境温度关系密切 ,在 37℃下 ,铵释放速率大且峰值出现时间早 ;2 5℃时铵释放速率高峰期大大延迟 ,释放绝对量低 ;两种温度下表征铵释放的数学方程 y=a+blogt和 y=a+bt1 /2的 b值 (铵释放速率常数 )可作为衡量 5种缓释尿基复合肥养分释放性能的指标。缓释尿基复合肥对土壤无机氮释放过程的动力学效应能用一级反应动力学方程 Nt=No(1- ekt)极好地描述 ,在 4 2天内 ,土壤 NH4 + N和无机氮释放潜力 (No值 )均以 4种含硼缓释复合肥为低 ,仅为CK的 5 3.5 %～ 6 3.8%     

农药控释技术研究进展

论述了缓释农药的发展概况及其相对于传统药剂的优越性。详细介绍了几种常见的缓控释剂型的特点，并列举了研究实例。对该技术的应用前景和发展方向作了分析和预测。     

剥离剂的选择及乳液型剥离剂的应用

本文介绍了剥离剂的选择要求，类型和乳液型剥离剂与溶剂型剥离剂在使用和性能上的差别以及乳液型剥离剂的使用范围等。     

乳液型隔离剂的合成与应用

介绍了有机硅乳液型隔离剂的合成 ,乳液型隔离剂用乳化剂的合成与配制 ,以及在使用和性能方面与溶剂型隔离剂的比较等。     

Measurement of release rates of gossyplure from controlled release formulations by mini-airflow method

The use of the mini-airflow apparatus for the measurement of gossyplure release rates is described. The method involves the passage of air over controlled-release dispensers containing radiolabeled pheromone, through a coarse frit, and entrapment of the gossyplure on glass beads. Desorption of the beads with solvent is followed by quantification by liquid scintillation counting. The results of release rate measurements from hollow fibers, red rubber septa, and red rubber wicks are discussed.     

我国控释肥料的研究进展

简述了近40年来我国研制控释肥料的背景和研究现状,包膜控释肥料的研究,控释肥料中氮、磷效应研究和养分释放的评价方法及我国控释肥料的发展前景。     

Parametric study of tumbling fluidized bed to evaluate nitrogen release characteristics of biopolymer-coated controlled release urea

To impede nitrogen loss due to leaching and NH₃ volatilization, pristine urea particles are coated with synthetic polymers such as poly(acrylic acid) and polyethylene for the controlled release of nitrogen. However, due to nonbiodegradability and environmental and economic issues, these synthetic polymers are replaced with cheap, biodegradable, and green coating materials. In this study, borax-modified starch biopolymer is used to produce controlled release urea (CRU) in a tumbling fluidized bed. Central composite rotatable design is used to study the interactive effect of process parameters on time and kinetics of nitrogen release. Nitrogen release in distilled water is monitored by the UV–Vis spectrophotometer and soil burial test is used to observe release in soil. The optimum values of process parameters and response objectives generated by the analysis of variance are validated by triplicates of confirmation runs and the % error is reported as a precision indicator. A mathematical model is used to determine the diffusion coefficient of nitrogen release. Biopolymer-coated urea results in much better release performance when compared with starch-based CRU reported in the literature. The most influential process parameter both for time and kinetics of nitrogen release appears to be the coating time. Release time increases linearly with coating time and the diffusion coefficient decreases with increase in coating time. The kinetic study reveals that some of the samples followed non-Fickian diffusion and others followed Case-II transport during the release of nitrogen.     

Nitrogen release from polyolefin-coated urea with attention to individual weights

Nitrogen release from individual granules of polyolefin-coated urea (POCU) was studied in order to evaluate a variation in N release. Individual granules were immersed in 10 ml water at 25°C for 7 and 20 d. Individual granules of POCU had different weights and N release rates. An increase in the individual weights of POCU led to a decrease in the N release for both incubation periods. This relationship between the N release and individual weights may be related to the coating thickness.     

Controlled drug release via minimization of burst release in pH-response kappa-carrageenan/polyvinyl alcohol hydrogels

Kappa-carrageenan/polyvinyl alcohol cross-linked hydrogels was formulated using genipin as a natural and non-toxic cross-linker to achieve a controlled drug release. β-Carotene was immobilized and the release study was evaluated under in vitro conditions. Monitoring β-carotene release was carried out by structure modification using cross-linker and minimization of burst release. It was found that using genipin can stop burst release in the hydrogels and control active material better than native films as a result of structural modification. This suggests that the burst release is depended highly on the degree of cross-linking and the mesh space available for drug diffusion. Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) are carried out to study the characteristics changes of native and cross-linked hydrogels. Also, field emission scanning electron microscope (FESEM) was performed to study microstructure of hydrogels. The transport mechanism seems to be determined by the strength of the gel network due to genipin concentration changes. Finally, diffusion coefficient is determined for native and cross-linked hydrogel.