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不同缓释肥料养分释放期有较大差异,一般为2~9个月或更长,因此建立一个快速测定和评价其养分释放期的方法和手段尤为重要。根据菲克定律和质量守恒定律结合数学与物理计算方法建立了快速预测包膜肥料缓释过程的数学模型,该模型也提供了一种解决扩散类机制过程的处理方法。同时,本研究还对3种不同包膜缓释肥料利用25℃浸提法进行测定,应用100℃快速浸提法测定的结果与之拟合,并对拟合方程进行评价和检验。在此基础上,还对100℃快速浸提液进行了电导率法的测定。结果表明:(1)该模型能有效地预测出在扩散机制下包膜缓释肥的养分释放情况,拟合相关系数R~2分别为0.9997、0.9978和0.9994。(2)3种不同包膜的缓释肥料在100℃的快速浸提结果与25℃浸提结果的拟合回归方程的拟合度均达到极显著水平,在25℃释放期为2~6个月的包膜缓释肥在100℃下快速浸提只需8~48 h就可初步测定出养分释放期;在25℃释放期为2个月的缓释肥料,100℃快速测定的养分释放期最大误差为3 d(1.12%);缓释期为6个月的最大误差为8 d(4.44%)。(3)100℃电导率法能在较短时间内准确预测出缓释肥料的养分释放率,其对释放期为6个月的包膜肥料预测值最大误差为10 d(5.60%)。
Different slow-release fertilizer nutrient release period are quite different, usually 2 to 9 months or longer, so to establish a rapid determination and evaluation of the method of releasing nutrients and means is particularly important. According to Fick’s law and the law of conservation of mass, a mathematic model is established to rapidly predict the process of sustained release of coated fertilizers by combining mathematical and physical calculation methods. The model also provides a solution to the process of diffusion mechanism. In the meantime, three kinds of coated slow release fertilizers were also tested by 25 ℃ extraction method. The results of 100 ℃ rapid extraction method were fitted and the fitting equation was evaluated and tested. On this basis, the method of conductivity measurement was also performed on the 100 ℃ fast extract. The results show that: (1) The model can effectively predict the nutrient release of coated slow-release fertilizer under the diffusion mechanism. The fitting correlation coefficients R ~ 2 are 0.9997, 0.9978 and 0.9994, respectively. (2) The fitting results of the fast regression results of the three kinds of coated slow-release fertilizers at 100 ℃ and the fitting results at 25 ℃ reached the extremely significant level, and the release rates at 25 ℃ were 2 ~ 6 The slow-release fertilizers coated with slow-release fertilizer at 100 ℃ for 8 months can be used to measure the release period of nutrients at a fast rate of 100 ℃ for 2 months. The maximum error of release was 3 days (1.12%). The maximum error of 6 months was 8 days (4.44%). (3) The 100 ℃ conductivity method can accurately predict the nutrient release rate of slow-release fertilizer in a short period of time. The maximum error of the forecast value of coated fertilizer with 6-month release period is 10 days (5.60%).