异粒包膜控释肥料氮素释放特性的研究

Study on nitrogen characteristics of coated controlled-release fertilizer with different particle sizes

按照商品控释肥料的核芯肥料之粒级进行混配,利用底喷流化包膜技术制造出异粒包膜控释肥。通过静水培养试验,分别测得不同粒径控释肥料0、1、2、3、4、56、、71、4、21、28、56 d的氮素释放率,探讨粒径对氮素释放率、膜芯比等的影响。结果表明,随着粒径增加,氮素释放率明显降低,培养1 d,23~、34~、45~mm粒径控释肥料的氮素释放率依次为26.9%、4.45%、1.26% 23~mm粒径的控释肥料的控释期只有4 d,34~mm为28 d,45~mm的大于56 d。培养过程,即控释肥料氮素释放过程,前期释放的氮素主要来自〈3 mm粒径的控释肥料,后期则主要来自〉3 mm粒径的控释肥料。粒径大小对膜芯比有极显著的影响,膜芯比随着粒径的增加而增加。23~mm粒径控释肥料膜芯比比预设的降低15.58%,34~mm的降低了4.29% 而45~mm的膜芯比则比设计的增加了5.65%。因此要保证控释肥料产品的质量,核芯肥料的粒级是必须控制的重要因素之一。

At present,although controlled-release fertilizer（CRFs） has stepped on the industrial scale in China,the technology of controlled release is behind that of developed countries such as USA and Canada.Qualities of CRF of different products are different.One of the reasons for the quality difference might come from the difference of substrate of CRF,being kernel compounds of the CRF. Currently,most of researches on CRF pay great attention to the coating materials and coating technique rather than the substrate.The previous study of the authors has found that particle sizes and its distribution of the substrate affected greatly on the longevity,being a quality parameter of controlled release fertilizers.The CRFs used in this study were a resin coated Kemira Grow-How NPK（15-15-15） granule which is manufactured by Planta Controlled Release Company.The substrate was mixed based on the real proportion of particle size distribution of the commercial products.Amount of coating material is 7.7% of the substrate. Then the CRFs were divided into three groups of 23mm,34 mm and 45 mm,and incubated in distilled water with a ratio of fertilizer to water of 1∶20 for 0,1,2,3,4,5,6,7,14,21,28 and 56 days under constant temperature at 25℃±1℃,respectively.The ammonium and nitrate were determined at the given time to evaluate the effect of granule size on the nitrogen release rate（NRR）.Results showed that the NRR and initial solubility are decreased with the increase of the substrate particle sizes.However,the longevity of CRF is increased with the substrate particle size.The NRR after 24 h incubation was 26.9%,4.45% and 1.26% for CRF with a particle size of 2 to 3,3 to 4 and 4 to 5 mm,respectively.The longevity is 4 d,28 d and 56 d for CRF with a particle size of 2 to 3,3 to 4 and 4 to 5 mm separately.During the early stage of incubation,nitrogen released mainly from CRF which particle size is smaller than 3 mm,whereas the later stage is from CRF which particle size is bigger than 3 mm.The ratio of coating material to substrate is increased with increase of the particle size.The ratio of coating material to substrate of CRF with particle size of 2 to 3 mm is decreased by 15.58% and that of 3 to 4 mm decreased by 4.29%.Nevertheless,the ratio of coating material to substrate of CRF with particle size of 4 to 5 mm is increased by 5.65%. Therefore,the substrate evenly distributed in particle size is one of the most important factors affecting quality of CRFs.