Slow Release Fertilizer Summary.ppt

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1、Slow Release and Controlled Release Fertilizers Why Use Slow Release/Controlled Release Fertilizers?More uniform growth responseNo growth surgeLonger growth responseLess chance of burnLess leaching of nitrateLabor savingSlow Release Fertilizer(SRF)vs Controlled Release Fertilizer(CRF)According to th

2、e Association of American Plant Food and Control Officials(AAPFCO),there is no official differentiation between SRF and CRFIn practice,the main difference is:SRF:the nutrient release pattern is fully dependent on soil and climatic conditions and it cannot be predictedCRF:the release pattern,quantity

3、 and time can be predicted within certain limitsThe biologically and microbially decomposed N products,such as UF,are commonly referred to in the industry as SRF;coated or encapsulated products are referred to as CRFHow do SRFs/CRFs Work?Delay of initial availability of nutrient(s)and/or extending t

4、he time of nutrient availabilityOccur by different mechanismscontrolled water solubility of the material by semi-permeable coatingsslow hydrolysis of water-soluble low molecular weight compoundsInhibition mechanismInhibition MechanismsStabilized nitrogen fertilizer:A fertilizer to which a nitrogen s

5、tabilizer has been addedThe nitrogen stabilizer extends the time nitrogen remains in the soil in the form of urea-N or ammoniacal-NNitrification inhibitor:A substance that inhibits the biological oxidation of ammoniacal-N to nitrate-NUrease inhibitor:A substance that inhibits hydrolytic action on ur

6、ea by the enzyme ureaseTypes of SRF/CRFOrganic-N low-solubility compoundsurea-formaldehyde(UF)chemically decomposing compounds,such as isobutylidene-diurea(IBDU)Fertilizers in which a physical barrier controls the releasetablets or granules coated by hydrophobic polymers or inorganic materials such

7、as sulfur matrices in which the soluble active material is dispersed in a continuum that restricts the dissolution of the fertilizer,e.g.,polyolefins,rubberInorganic low-solubility compoundsmetal ammonium phosphates(e.g.MgNH4PO4)Partially acidulated phosphate rock(PAPR)Urea-Aldehyde Type SRFsU-FMeth

8、ylene urea(MU)Urea-isobutyraldehyde/isobutylidene diurea(IBDU)Urea-alcetaldehyde/cyclo diurea(CDU)IBDU 32%NCondensation product of the reaction between isobutyraldehyde and ureaIn contrast to the condensation of urea with formaldehyde,which results in a number of different polymer chain lengths,the

9、reaction of urea with isobutyraldehyde results in a single oligomerThe theoretical nitrogen content is 32.18%Release Mechanism:Gradual hydrolysis of the sparingly soluble IBDU to urea,which is transformed by soil bacteria initially to ammonium ions and then to nitrateIBDU Releases N Based on Solubil

10、ityUreaNH4H2OUreaseRootRelease Depends on Granule Size-Small Granules Release FasterCDU 32.5%NFirst patented as a slow-release fertilizer in 1959The Chisso Corporation developed an economic,continuous industrial process to produce CDU from acetaldehyde and urea in 1962The molecule is formed by the a

11、cid-catalyzed reaction of urea and acetaldehydeCDU decomposes by both hydrolysis and microbial processes in the soil and temperatureCoated/Encapsulated SRF and CRFConventional soluble fertilizer materials,which are given a protective,water-insoluble coating after granulation,prilling or crystallizat

12、ionCoating controls water penetration and,therefore,the dissolution rate,nutrient release and duration of releaseThere are three main groups of coated/encapsulated fertilizers,based on the following coating materials:sulfursulfur plus polymers,including waxpolymeric materialsPolymer Coated Urea(PCU)

13、-Polymer Coating Remains IntactWaterDissolved UreaSolidUreaDissolvedUreaWaterDissolved UreaCompleteReleaseSulfur Coated Urea(SCU)-Sulfur Coating Breaks DownSolidUreaH2OH2OSolidUreaSolidUreaSulfurCoatingH2ODissolvedUreaH2OH2O+SU F Fertilizers Typical CharacteristicsIn general,UF fertilizers show a si

14、gnificant slow release of nitrogen with a good compatibility with most cropsBecause of their low solubility,they will not scorch vegetation or impair germinationBecause they are more effective at higher temperatures,they are widely used in warmer climates(in the Mediterranean region in Europe and in

15、 the southern and southwestern regions of the United States)Materials mainly used for coatingSulfurPolymers-e.g.,PVDC based copolymers,polyolefin,EVA,Urea Formaldehyde resin,alkyd-type resins,polyurethane-like resins,etc.Fatty acid salts-e.g.,calcium stearateLatex,rubber,guar gum,petroleum derived anti-caking agents,wax