Research Article Multimicronutrient Slow-Release Fertilizer of...

Research ArticleMultimicronutrient Slow-Release Fertilizer ofZinc Iron Manganese and Copper

Siladitya Bandyopadhyay Kunal Ghosh and Chandrika Varadachari

Raman Centre for Applied and Interdisciplinary Sciences 16A Jheel Road Calcutta 700 075 India

Correspondence should be addressed to Chandrika Varadachari cvrcaisresin

Received 9 February 2014 Revised 5 June 2014 Accepted 12 June 2014 Published 1 July 2014

Academic Editor Janez Levec

Copyright copy 2014 Siladitya Bandyopadhyay et al This is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

Theprocess for the production of a slow-releasemicronutrient fertilizer is describedThe compound contains zinc ironmanganeseand copper as micronutrients and is produced by polymerizing a system containing phosphoric acid zinc oxide hematitepyrolusite copper sulfate andmagnesium oxide followed by neutralization of the polyphosphate chain with ammoniumhydroxideChanges in temperature density and viscosity of the reaction system during polymerization were studied Reaction kinetics wasstudied at three different temperatures Rate curves revealed a multistage process with essentially linear rates at each stage Thuseach stage displayed zero order kinetics The product was crystalline and revealed ordering of P-O-P chains It had low solubilityin water but high solubility in 033M citric acid and 0005M DTPAThree different field trials showed significant yield incrementsusing the slow-release micronutrient fertilizer compared to the conventional micronutrients Yield increments in rice were in therange of 10ndash55 over control (with no micronutrient) and up to 17 over the conventional micronutrient fertilizers There weresignificant increases in total uptake of zinc iron andmanganese in the grain Slow-release fertilizers also produced significant yieldincreases in potato as well as significant increase in vitamin C content of the tuber

1 Introduction

Micronutrients are essential components of proteins andenzymes and are vital for increasing crop yields as wellas improving the nutritional quality of food The bulk ofmicronutrients used all over theworld today arewater solublesalts that include mainly the sulfates or their chelated forms(EDTA DTPA etc) Water solubility of these materialsresults in leaching and run-off nutrient fixation by soilhigh dosage requirements and nonattractive cost economicsSlow-release fertilizers (which have low water solubility) aretherefore considered as the solution to the problem Thefocus of research on slow-release fertilizers has been on themacronutrients (NPK) Here slow-release functionality hasbeen achieved by encapsulation of water soluble materialswithin a membrane or conversion to polymers of the ureaaldehydes [1 2] For micronutrients the insoluble oxides andphosphate glasses are also used [3 4] A glassy phosphate pro-duced by fusing oxides of micronutrients in phosphoric acidat 800∘C has been described in a patent [5] Volfkovich [6]

studied long chain highly condensed potassium metaphos-phates containing small amounts of trace elements Linearmetaphosphates produced from ammonium and potassiumdihydrogen phosphates urea and salts of micronutrient ionswere described in a US patent [7]These slow-release compo-sitions are characterized by nutrient release mechanism thatis based on either (i) diffusion through a membranecoatingor (ii) slowhydrolysisMetaphosphates and glassy phosphatesdissolve by slow hydrolysis to release nutrient into the soilNutrient release by diffusion or hydrolysis is dependenton soil parameters like water content pH ionic contenttemperature and so forth Therefore the drawback of suchreleasemechanisms is the possiblemismatch between the rateat which the nutrient is released into the soil and the rate atwhich it is required by the crop Insoluble compounds can beeffective fertilizers only if rates of release of nutrient ions canmatch plant requirements throughout the growth period [8]

The slow-release fertilizer in this study has been devel-oped with a different mechanism of nutrient release Hereplant roots are able to ldquodigestrdquo certain insoluble compounds

Hindawi Publishing CorporationInternational Journal of Chemical EngineeringVolume 2014 Article ID 327153 7 pageshttpdxdoiorg1011552014327153

2 International Journal of Chemical Engineering

by ion-exchange with the root hairs or by extracellularorganic acid secretions that extract nutrients by chelationThese compounds have low water solubility and high sol-ubility in citrate and diethylene triamine penta acetic acid(DTPA) [8ndash12]

Whereas the earlier work mainly focused on individ-ual cationic slow-release compounds [10ndash12] the presentresearch was undertaken to develop a combined cationicmicronutrient fertilizer that would incorporate all the majorcationic micronutrients namely zinc iron manganese andcopper into a single compound The advantage of such aproduct would be that a single fertilizer would provide all thecationic micronutrients and would thus prove beneficial toboth the crop and the farmer

Here we report the process for production of slow-releasemultimicronutrient fertilizer of Zn Fe Mn and Cu Studieson polymerization kinetics process parameters changes inphysical properties and product characterization were doneThe process was optimized on a small pilot plant Finallyfield trials were conducted with three different crops Resultsindicate that the compound is a very promising fertilizer

2 Materials and Methods

21 Synthesis and Process Studies Based on the average levelsof Zn Fe Mn and Cu in plants [3] the weight ratio ofZn Fe Mn Cu was chosen as 3 1 05 025 From prelim-inary trials the proportions of P andMg were also optimizedso that the optimal weight ratio in the reaction system was3 1 05 025 0125 8 for Zn Fe Mn Cu Mg P

Synthesis was done with commercial grade chemicalsnamely hematite pyrolusite zinc ash copper sulfate roastedmagnesite and phosphoric acid All raw materials wereanalyzed prior to synthesis using analytical grade reagentsIron in hematite was determined spectrophotometrically asthe o-phenanthroline complex [13] Manganese in pyrolusitewas determined as the permanganate color after oxidationwith KIO

3[13] Zinc ash copper sulfate and magnesite

were analyzed for their Zn2+Cu2+Mg2+ contents by AASCommercial H

3PO4was analyzed for P content as the blue

phosphomolybdate [14] after fusion of polyphosphate withNaOH [10]Hematite contained 4628 Fe pyrolusite 4931Mn zinc ash 7670Zn copper sulfate 2224Cumagnesite4172 Mg and phosphoric acid 2556 P

Fertilizer production was done in a pilot plant whichwas a 20 L acid-proof brick lined reactor vessel 10 kg ofphosphoric acid was taken in the vessel and 125 kg zincash was added to it This was followed by 069 kg 0324 kg0357 kg and 0096 kg respectively of hematite pyrolusitecopper sulfate and magnesite The mole ratios of the cationsadded with respect to moles of phosphorus are thus ZnP =018 FeP = 007 MnP = 003 CuP = 001 andMgP = 002 The mole ratio of all cations added to molesof phosphorus is 032 1 The reactants were heated withagitation at 200∘C for 230min The liquid was poured intoa mixer and cooled to room temperature After cooling theliquid formed viscous liquid and not a glass since fusiontemperatures were not attained during polymerization Thisliquid was then neutralized with 95 L of ammonia to pH

56 Due to exothermicity of the reaction temperature duringneutralization was around 90∘C Finally the neutralizedsuspension was dried in an oven at 70ndash80∘C ground andsieved through 80meshThis product obtained from the pilotplant was used for chemical and field studies

Changes in temperature density and viscosity in thecourse of polymerization reaction were recorded Tempera-ture was recorded in situ Density was recorded in a densitybottle Viscosity was recorded by Redwood viscometer with ahigh temperature bath set at the temperature of the reactionliquid

22 Reaction Kinetics Since the reaction for formation ofpolyphosphates is a polycondensation reaction kinetics ismost conveniently studied by recording weight loss (waterloss) of the system [15] Weight loss kinetics was studied inglass beakers using 110th of the reactants mentioned in thesynthesis experiment The process here was similar to thatdescribed in Section 1 except that it was done in borosilicatebeakers using accurately weighed reactants Initial weight ofbeaker was recorded and weights were also recorded afteraddition of acid Subsequently the process described abovewas followed except that heating was done in amuffle furnacewith temperature controls of 01∘C At specific time intervalsweight of the beaker was recorded and weight loss wasestimated Weight loss was recorded at 175∘ 200∘ and 225∘Cat periodic intervals up to 240min

23 Characterization and Testing Chemical analysis of thefertilizer for P was done by fusion of 01 g with 15 g ofNaOH beads and extraction in 02NHCl P was determinedspectrophotometrically as described above Cations weredetermined after digestion with concentrated H

2SO4-H2O2

and the solution analyzed for Zn Fe Mn Cu and Mg asdescribed earlier NH

4

+-content was determined by Kjeldahlmethod [14]

Solubility of the fertilizer in water was determined byadding 50mL water to 01 g fertilizer agitating for 60minfollowed by filtration The solution was analyzed for Zn FeMn Cu and P Solubility in 033M citric acid and 0005MDTPA was determined by a similar procedure except thatwater was replaced by 033M citric acid and 0005M DTPA

Infrared (IR) spectra of the powdered sample wererecorded on a Perkin Elmer Fourier transform infrared(FTIR) RX1 instrument with the scan range of 4500ndash450 cmminus1 (resolution plusmn 5 cmminus1) using KBr pellets X-ray dif-fraction (XRD) was recorded on a Philips PW 1140 X-raydiffractometer usingNi-filtered CuK

120572radiation at a scanning

speed of 2∘ 2120579minField tests were conducted with three crops at two

different locations These were at (i) Baruipur (South-24Parganas) West Bengal India (fine mixed hyperthermicaeric endoaquept new alluvium) pH573 EC

119890290 dSmand

organic carbon 905 gkg and (ii) Nalikul (Hooghly) WestBengal India (fine mixed hyperthermic typic haplusteptold alluvium) pH 617 EC

119890149 dSm and organic carbon

691 gkg Randomized block design (RBD) with 6 replicateswas used for the field trials with 9m2 area per microplotThe

International Journal of Chemical Engineering 3

Table 1 Solubility IR and XRD characteristics of the slow-release fertilizer

Chemicalcomponent

of total solubilized in IR absorption in wavenumber (cmminus1) XRD peaks

Water 033M citricacid

0005MDTPA

Wavenumber(cmminus1) Absorbance

Basal spacing 119889001

( A)Intensity (I)

Zn ND 937 839 44775443107311280614507165602375132384

4240364038414135

629533467441376308266262238234224160

16561515501001610138826

Fe ND 932 918Mn ND 909 801Cu 18 968 913P 84

treatments include (i) a control (where only NPK fertilizersbut no micronutrients were added) (ii) three different levelsof slow-release micronutrient fertilizer and (iii) the samethree levels of micronutrients as micronutrient sulfates Allplots received equal applications of N P K and Mg by calcu-lated additions of urea diammonium phosphate (DAP) KCland MgSO

4 Test crops were rice (JayaNiranjan varieties)

and potato (Jyoti variety) Micronutrient contents of ricegrain straw and potato tuber were analyzed for all treatmentsand replicates Grainstubers were oven dried powdered ina grinder digested in triacid mixture [14] and analyzed formicronutrients by AAS Potato tuber was also analyzed forvitamin C by extracting fresh sliced tuber with 4 oxalic acidand triturating the extract with 26-dichloro indophenol dye[16] All results were statistically analyzed

3 Results and Discussion

31 Process Parameters Temperature optimization studiesshowed that the reaction was 303 faster at 200∘C than at185∘C and 196 faster at 225∘C than at 200∘C Temperaturein the range of 175ndash185∘C required very long periods for com-pleting polymerization Again higher temperature (225∘C)consumed more energy and was not much faster comparedto 200∘C Thus temperature of 200∘C appeared to be theoptimum

Changes in temperature density and viscosity in courseof polymerization of Zn-Fe-Mn-Cu-Mg polyphosphate sys-tems are shown in Figures 1ndash3 Liquid temperature increasedwith time due to increase in boiling point of the phosphatewith polymerization Temperature increment followed a firstorder rate (Figure 1) Rate of temperature rise increases withtime as structural water reduces and fewer P-OH groups areavailable for polymerization

Density increases almost linearly with temperaturereaching 213 gcc after 280minutes of heating (Figure 2)Formation of longer polymer chains and cross-linking of theP-O-P chains would account for such density incrementsViscosity changes showed an initial small reduction whichmay be attributed to the effect of increasing temperature

75

85

95

105

115

125

135

0 50 100 150 200 250 300Time (min)

Tem

pera

ture

(∘C)

Figure 1 Temperature change during the polymerization reaction

185

19

195

2

205

21

215

30 80 130 180 230

Den

sity

(gc

c)

Time (min)

Figure 2 Density change during the polymerization reaction

(Figure 3) Viscosity remained nearly constant till about120∘C and then increased very rapidly Increased viscositycorresponds to the beginning of polymerization Viscosity ofthe system was 101 centipoise at 134∘C

32 Reaction Kinetics Kinetics of condensation of Zn-Fe-Mn-Cu polyphosphates is shown in Figure 4 The rate curves


Table2Fieldtrialu

singslo

w-release

fertilizerson

ricea

ndpo

tatoesyieldsnu

trient

uptakeand

vitamin

C

Treatm

ents

Rice

atBa

ruipur

(new

alluvium

)[Va

riety119869119886119910119886]

Rice

atNalikul

(old

alluvium

)[Va

riety119873119894119903119886119899119895119886119899]

Potato

atNalikul

(oldalluvium

)[Va

riety119869119910119900119905119894]

Yield

(kgha)

Totaluptake(gha)

Yield

(kgha)

Totaluptake(gha)

Yield

(kgha)

Totaluptake(gha)

Vitamin

C(m

g100g

)Zn

FeMn

CuZn

FeMn

CuZn

FeMn

CuC

3242

706

246

140

213698

76492

206

419900

217

764

6991

621

S 13076

706

350

158

223724

80499

216

4210700

239

948

107

97453

S 23596

756

303

162

263961

78593

236

479500

216

915

9397

533

S 33748

857

341

179

233831

87577

229

44110

00277

756

85103

594

P 146

47bd

1051b

d472a

c236b

d33

4056

117bd

597

332b

d70

14075a

432a

c1966

a151a

163

844

ad

P 24998

bd

1208b

d615b

d288b

d33

4397

bc

122b

d876b

c351b

d76

12550

396

1756

140

148

631

P 34383

b110

6bc

492a

229b

3444

62bd

114bc

693

291b

c48

16025b

d560b

d2569

bd

225b

d198a

c811

c

CD(5)

7583

224

215

559

3732

208

2416

596

34600

839

4795

333

331

207

CD(1)

10212

298

2865

744

5026

281

3253

802

46875

113

6456

449

446

281

CCon

trolS 1

ndashS3sulfateso

fZn

FeM

nandCu

P1ndashP

3slo

w-rele

asem

icronu

trientsS 1

andP 11kghaZn

+033

kghaFe

+0165k

gha

Mn+0083k

gha

CuS

2andP 22

kghaZn

+066

kghaFe

+033

kgha

Mn+0165k

gha

CuS

3andP 34

kghaZ

n+13

3kgha

Fe+066

kghaM

n+033

kghaC

ua Significantw

ithrespecttocontrolat5levelb Significantw

ithrespecttocontrolat1levelc Significantw

ithrespect

tothec

orrespon

ding

water-solub

letre

atmentat5leveld Significantw

ithrespecttothec

orrespon

ding

water-solub

letre

atmentat1level


10

30

50

70

90

110

70 80 90 100 110 120 130 140 150

Visc

osity

(cen

tipoi

se)

Temperature (∘C)

Figure 3 Viscosity change during the polymerization reaction

did not fit into a first second or third order kinetic equationAs with polyphosphates studied earlier [10ndash12] polymeriza-tion exhibited several stages with each stage being nearlylinear Initial rapid rates have been attributed to the removalof one mole of H

2O from every two molecules of dihydrogen

phosphate with the formation of polyphosphates of varyingchain length [15] With the reduction in concentration of P-OH groups available for polymerization the reaction sloweddownThe absence of a plateau indicates that polymerizationwas incomplete at the temperatures and time periods studiedThus long chain metaphosphates would not have beenformed

At the start of reaction metal oxides would react withphosphoric acid to produce the respective dihydrogen phos-phates Subsequent (partial) polymerization to the polyphos-phates may be represented as

119899Zn(H2PO4)

2

997888rarr Zn119899H(2119899+2)

P2119899O(7119899+1)+ (119899 minus 1)H

2O

119899Fe(H2PO4)

3

997888rarr Fe119899H(4119899+2)

P3119899O(11119899+1)+ (119899 minus 1)H

2O

119899Mn(H2PO4)

4

997888rarr Mn119899H(6119899+2)

P4119899O(15119899+1)+ (119899 minus 1)H

2O

119899Cu(H2PO4)

2

997888rarr Cu119899H(2119899+2)

P2119899O(7119899+1)+ (119899 minus 1)H

2O

119899Mg(H2PO4)

2

997888rarr Mg119899

H(2119899+2)

P2119899O(7119899+1)+ (119899 minus 1)H

2O(1)

Cations includingMg2+ could form part of the chain and alsocross-link different chains and thereby stabilize the structure

33 Characterization and Testing The compound is a zinciron manganese copper magnesium ammonium polyphos-phate with a composition of 985 ZnO 370 Fe

2O3 203

MnO2 073 CuO 049 MgO 135 NH

4

+ 4711 P2O5

and 310 H2O The mole ratio of the cations to phosphorus

is thus ZnP = 019 FeP = 007 MnP = 003 CuP = 001and MgP = 002 A minor deviation from the added moleratios is possibly due to losses during pilot production suchas spillage and the fact that weighing at this level has loweraccuracy than lab scale weighing The final product is a free-flowing pinkish powder The extract with water showed that18 of total Cu and 84 of total P were soluble but other

0

004

008

012

016

0 50 100 150 200 250Time (min)

175∘C

200∘C

225∘C

Wei

ght l

oss (

gg

H3PO

4)

Figure 4 Kinetics of polymerization at 175 200 and 225∘C

4495

3406

4000 3500 3000 2500 2000 1500 1000 500

Wavenumber (cmminus1)

37538

32384

23751

16560

14507

12806

10731

5443

4477

Figure 5 IR spectra of zinc-iron-manganese-copper fertilizer

cations were not detectable Solubility in 033M citric acidwas gt90 for all micronutrients and solubilities in 0005MDTPA were slightly lower namely 80ndash90 (Table 1)

Infrared (IR) spectrum of the compound (Figure 5Table 1) showed absorption characteristic of polyphosphatesStrong absorption around 1100ndash1050 cmminus1 is due to P-O ionicstretching [17] and that between 550ndash540 cmminus1 is due to P-O stretching in the deformation mode Strong absorptionat around 3200ndash3100 cmminus1 is attributed to O-H stretching[17] An increase in length of the P-O-P chain results ina shift of the P-O ionic stretching at around 1000 cmminus1 tolonger wavenumbers [17] Absorption bands of the samplein the region of 1073 cmminus1 therefore suggest the presenceof medium chain polyphosphates Moderately strong absorp-tion at 1450 cmminus1 could be due to the presence of NH

4

+ ionin the compounds [17]

X-ray diffraction (XRD) characteristics of Zn-Fe-Mn-Cu-Mg polyphosphate are shown in Figure 6 and Table 1 Sharp


1200

1000

800

600

400

200

0

20 30 40 50 60

629

595

533

519

467

45441

401

391

376

308

364

345

336 323319

314

279

272

266

262

25

238

234

224 203

201

195

177

17

168

165

16

16

157

Cou

nts (

s)

2120579 (∘)

Figure 6 XRD of zinc-iron-manganese-copper fertilizer

bands indicate awell-crystallized structureThe strongest lineat around 308 A may be attributed to the polyphosphatebackbone since it has been persistently observed in otherpolyphosphates of similar nature [10ndash12 18] Strong lineswere also found at around 533 A due to the presence ofammonium phosphates and at around 376 A attributable toammonium phosphates and ammonium-iron pyrophosphate[19] Reflections have also been found at around 262 A and224 A indicating the presence of Mn

2P2O7[19]

Results of field trials showed that yield of rice grainsincreased by 35ndash55 in slow-release fertilizer treated plotsover the control in the experiment at Baruipur (new allu-vium) Yieldswere also higher compared to themicronutrientsulfate treated plots by 511 389 and 17 for treatments P

1

P2 and P

3 respectively over the corresponding micronu-

trient sulfate treatments S1 S2

and S3 Total uptake of

Zn Fe and Mn in the polyphosphate treated plots wassignificantly higher than control and micronutrient sulfatetreatments at 1 level (Table 2) Uptake of Cu increasedin all polyphosphate treatments but was not significant at5 level Significant yield increments with rice were alsoobserved from the trials at Nalikul (old alluvium) Yield ofgrain increased by 10ndash21 in the slow-release treatmentsover the control and by 9ndash16 over the correspondingmicronutrient sulfate treatments Total uptake of Zn Fe andMn in the slow-release fertilizer treated plotswas significantlyhigher than control and micronutrient sulfate treatmentsalthough increments of Cu did not appear as statisticallysignificant (Table 2) Slow-release fertilizer also producedyield increments in potato at levels P

1and P

2 Interestingly

Vitamin C contents in potato tubers treated with the slow-release fertilizer increased significantly by over 30 over thecontrol Micronutrient sulfates did not produce any increasein vitamin C levels Total uptake of micronutrients Zn FeMn and Cu in the tubers also increased significantly in slow-release fertilizer treatments (Table 2) It may be inferred fromthe field trials that the slow-release fertilizer is an effectivesource of micronutrients and superior to the conventionalmicronutrient sulfates that are generally in use

In conclusion the slow-release micronutrient fertilizerreported here is a crystalline polyphosphate of Zn-Fe-Mn-Cu-Mg-NH

4 It had low water solubility but was almost

completely soluble in organic acids namely 033M cit-ric acid and 0005M DTPA which suggests good plantavailability Reaction kinetics showed complex pattern withseveral stages each being nearly linear Features suggesteda condensation reaction of P-OH groups with zero orderrates that changed with degree of polymerization P-O-Plinkages were evidenced by IR spectra XRD showed longrange order of polyphosphate groups All three field testsresulted in significantly higher yields in the slow-releasefertilizer plots over the control plots as well as over theconventional micronutrients Plant uptake of micronutrientswas also higher with the slow-release fertilizer Potato tubershad significantly increased levels of vitamin C

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors thank Professor P Ray Department of ChemicalEngineering Calcutta University for his suggestions Theyalso thank NBSS amp LUP ICAR Nagpur for XRD scansand Professor A Patra Department of Chemistry CalcuttaUniversity for the IR analysis

References

[1] A Shaviv ldquoAdvances in controlled-release fertilizersrdquo Advancesin Agronomy vol 71 pp 1ndash49 2001

[2] F N Wilson Slow Release-True or False A Case of Control TheFertilizer Society of London London UK 1988

[3] J J Mortvedt F R Cox L M Shuman and R M WelchMicronutrients in Agriculture Soil Science Society of AmericaMadison Wis USA 1991

[4] G J Roberts ldquoFeO-K2

O-P2

O5

glasses as source of micronutri-ent in soilrdquoAmerican Ceramic Society Bulletin vol 54 pp 1069ndash1071 1975

[5] Krems-Chemie ldquoComplete fertilizers containing trace ele-mentsrdquo Austrian Patent 326160 1975

[6] S I Volfkovich ldquoPolymeric fertilizersrdquo Journal of AppliedChemistry of the USSR vol 45 pp 2479ndash2487 1972

[7] J W Lyons G A Rauh Jr and S A Vandersall ldquoMixed cationpolyphosphatesrdquo US Patent no 3574591 1971

[8] S Bandyopadhyay I Bhattacharya K Ghosh and CVaradachari ldquoNew slow-releasing molybdenum fertilizerrdquoJournal of Agricultural and Food Chemistry vol 56 no 4 pp1343ndash1349 2008

[9] C Varadachari ldquoProcess for the manufacture of bio-releasefertilizers of zinc-iron-manganese iron-manganese-copper andzinc-iron-manganese-copperrdquo US Patent 8216337 2012

[10] S K Ray C Varadachari and K Ghosh ldquoNovel slow-releasingmicronutrient fertilizers 1 Zinc compoundsrdquo Industrial andEngineering Chemistry Research vol 32 no 6 pp 1218ndash12271993


[11] S K Ray C Varadachari and K Ghosh ldquoNovel slow-releasingmicronutrient fertilizers 2 Copper compoundsrdquo Journal ofAgricultural amp Food Chemistry vol 45 no 4 pp 1447ndash14531997

[12] P K Chandra C Varadachari and K Ghosh ldquoA new slow-releasing iron fertilizerrdquo Chemical Engineering Journal vol 155no 1-2 pp 451ndash456 2009

[13] J A Maxwell Rock and Mineral Analysis Interscience NewYork NY USA 1968

[14] M L Jackson Soil Chemical Analysis Prentice Hall NewDelhiIndia 1973

[15] C Varadachari ldquoAn investigation on the reaction of phosphoricacid with mica at elevated temperaturesrdquo Industrial amp Engineer-ing Chemistry Research vol 31 no 1 pp 357ndash364 1992

[16] M B Davies J Austin and D A Partridge Vitamin CIts Chemistry and Biochemistry Royal Society of ChemistryLondon UK 1991

[17] D E C Corbridge E J Lowe and D E C Corbridge ldquoInfraredspectra of some inorganic phosphorus Compoundsrdquo Journal ofChemical Society pp 493ndash502 1954

[18] I Bhattacharya S Bandyopadhyay C Varadachari and KGhosh ldquoDevelopment of a novel slow-releasing iron-manga-nese fertilizer compoundrdquo Industrial amp Engineering ChemistryResearch vol 46 no 9 pp 2870ndash2876 2007

[19] JCPDS Power Diffraction File International Centre for Diffrac-tion Data Pennsylvania Pa USA 1984

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by ion-exchange with the root hairs or by extracellularorganic acid secretions that extract nutrients by chelationThese compounds have low water solubility and high sol-ubility in citrate and diethylene triamine penta acetic acid(DTPA) [8ndash12]

Whereas the earlier work mainly focused on individ-ual cationic slow-release compounds [10ndash12] the presentresearch was undertaken to develop a combined cationicmicronutrient fertilizer that would incorporate all the majorcationic micronutrients namely zinc iron manganese andcopper into a single compound The advantage of such aproduct would be that a single fertilizer would provide all thecationic micronutrients and would thus prove beneficial toboth the crop and the farmer

Here we report the process for production of slow-releasemultimicronutrient fertilizer of Zn Fe Mn and Cu Studieson polymerization kinetics process parameters changes inphysical properties and product characterization were doneThe process was optimized on a small pilot plant Finallyfield trials were conducted with three different crops Resultsindicate that the compound is a very promising fertilizer

2 Materials and Methods

21 Synthesis and Process Studies Based on the average levelsof Zn Fe Mn and Cu in plants [3] the weight ratio ofZn Fe Mn Cu was chosen as 3 1 05 025 From prelim-inary trials the proportions of P andMg were also optimizedso that the optimal weight ratio in the reaction system was3 1 05 025 0125 8 for Zn Fe Mn Cu Mg P

Synthesis was done with commercial grade chemicalsnamely hematite pyrolusite zinc ash copper sulfate roastedmagnesite and phosphoric acid All raw materials wereanalyzed prior to synthesis using analytical grade reagentsIron in hematite was determined spectrophotometrically asthe o-phenanthroline complex [13] Manganese in pyrolusitewas determined as the permanganate color after oxidationwith KIO

3[13] Zinc ash copper sulfate and magnesite

were analyzed for their Zn2+Cu2+Mg2+ contents by AASCommercial H

3PO4was analyzed for P content as the blue

phosphomolybdate [14] after fusion of polyphosphate withNaOH [10]Hematite contained 4628 Fe pyrolusite 4931Mn zinc ash 7670Zn copper sulfate 2224Cumagnesite4172 Mg and phosphoric acid 2556 P

Fertilizer production was done in a pilot plant whichwas a 20 L acid-proof brick lined reactor vessel 10 kg ofphosphoric acid was taken in the vessel and 125 kg zincash was added to it This was followed by 069 kg 0324 kg0357 kg and 0096 kg respectively of hematite pyrolusitecopper sulfate and magnesite The mole ratios of the cationsadded with respect to moles of phosphorus are thus ZnP =018 FeP = 007 MnP = 003 CuP = 001 andMgP = 002 The mole ratio of all cations added to molesof phosphorus is 032 1 The reactants were heated withagitation at 200∘C for 230min The liquid was poured intoa mixer and cooled to room temperature After cooling theliquid formed viscous liquid and not a glass since fusiontemperatures were not attained during polymerization Thisliquid was then neutralized with 95 L of ammonia to pH

56 Due to exothermicity of the reaction temperature duringneutralization was around 90∘C Finally the neutralizedsuspension was dried in an oven at 70ndash80∘C ground andsieved through 80meshThis product obtained from the pilotplant was used for chemical and field studies

Changes in temperature density and viscosity in thecourse of polymerization reaction were recorded Tempera-ture was recorded in situ Density was recorded in a densitybottle Viscosity was recorded by Redwood viscometer with ahigh temperature bath set at the temperature of the reactionliquid

22 Reaction Kinetics Since the reaction for formation ofpolyphosphates is a polycondensation reaction kinetics ismost conveniently studied by recording weight loss (waterloss) of the system [15] Weight loss kinetics was studied inglass beakers using 110th of the reactants mentioned in thesynthesis experiment The process here was similar to thatdescribed in Section 1 except that it was done in borosilicatebeakers using accurately weighed reactants Initial weight ofbeaker was recorded and weights were also recorded afteraddition of acid Subsequently the process described abovewas followed except that heating was done in amuffle furnacewith temperature controls of 01∘C At specific time intervalsweight of the beaker was recorded and weight loss wasestimated Weight loss was recorded at 175∘ 200∘ and 225∘Cat periodic intervals up to 240min

23 Characterization and Testing Chemical analysis of thefertilizer for P was done by fusion of 01 g with 15 g ofNaOH beads and extraction in 02NHCl P was determinedspectrophotometrically as described above Cations weredetermined after digestion with concentrated H

2SO4-H2O2

and the solution analyzed for Zn Fe Mn Cu and Mg asdescribed earlier NH

4

+-content was determined by Kjeldahlmethod [14]

Solubility of the fertilizer in water was determined byadding 50mL water to 01 g fertilizer agitating for 60minfollowed by filtration The solution was analyzed for Zn FeMn Cu and P Solubility in 033M citric acid and 0005MDTPA was determined by a similar procedure except thatwater was replaced by 033M citric acid and 0005M DTPA

Infrared (IR) spectra of the powdered sample wererecorded on a Perkin Elmer Fourier transform infrared(FTIR) RX1 instrument with the scan range of 4500ndash450 cmminus1 (resolution plusmn 5 cmminus1) using KBr pellets X-ray dif-fraction (XRD) was recorded on a Philips PW 1140 X-raydiffractometer usingNi-filtered CuK

120572radiation at a scanning

speed of 2∘ 2120579minField tests were conducted with three crops at two

different locations These were at (i) Baruipur (South-24Parganas) West Bengal India (fine mixed hyperthermicaeric endoaquept new alluvium) pH573 EC

119890290 dSmand

organic carbon 905 gkg and (ii) Nalikul (Hooghly) WestBengal India (fine mixed hyperthermic typic haplusteptold alluvium) pH 617 EC

119890149 dSm and organic carbon

691 gkg Randomized block design (RBD) with 6 replicateswas used for the field trials with 9m2 area per microplotThe



Chemicalcomponent



0005MDTPA



( A)Intensity (I)

Zn ND 937 839 44775443107311280614507165602375132384

4240364038414135

629533467441376308266262238234224160

16561515501001610138826

Fe ND 932 918Mn ND 909 801Cu 18 968 913P 84








75

85

95

105

115

125

135

0 50 100 150 200 250 300Time (min)

Tem

pera

ture

(∘C)


185

19

195

2

205

21

215

30 80 130 180 230

Den

sity

(gc

c)

Time (min)





Table2Fieldtrialu

singslo

w-release

fertilizerson

ricea

ndpo

tatoesyieldsnu

trient

uptakeand

vitamin

C

Treatm

ents

Rice

atBa

ruipur

(new

alluvium

)[Va

riety119869119886119910119886]

Rice

atNalikul

(old

alluvium

)[Va

riety119873119894119903119886119899119895119886119899]

Potato

atNalikul

(oldalluvium

)[Va

riety119869119910119900119905119894]

Yield

(kgha)

Totaluptake(gha)

Yield

(kgha)

Totaluptake(gha)

Yield

(kgha)

Totaluptake(gha)

Vitamin

C(m

g100g

)Zn

FeMn

CuZn

FeMn

CuZn

FeMn

CuC

3242

706

246

140

213698

76492

206

419900

217

764

6991

621

S 13076

706

350

158

223724

80499

216

4210700

239

948

107

97453

S 23596

756

303

162

263961

78593

236

479500

216

915

9397

533

S 33748

857

341

179

233831

87577

229

44110

00277

756

85103

594

P 146

47bd

1051b

d472a

c236b

d33

4056

117bd

597

332b

d70

14075a

432a

c1966

a151a

163

844

ad

P 24998

bd

1208b

d615b

d288b

d33

4397

bc

122b

d876b

c351b

d76

12550

396

1756

140

148

631

P 34383

b110

6bc

492a

229b

3444

62bd

114bc

693

291b

c48

16025b

d560b

d2569

bd

225b

d198a

c811

c

CD(5)

7583

224

215

559

3732

208

2416

596

34600

839

4795

333

331

207

CD(1)

10212

298

2865

744

5026

281

3253

802

46875

113

6456

449

446

281

CCon

trolS 1

ndashS3sulfateso

fZn

FeM

nandCu

P1ndashP

3slo

w-rele

asem

icronu

trientsS 1

andP 11kghaZn

+033

kghaFe

+0165k

gha

Mn+0083k

gha

CuS

2andP 22

kghaZn

+066

kghaFe

+033

kgha

Mn+0165k

gha

CuS

3andP 34

kghaZ

n+13

3kgha

Fe+066

kghaM

n+033

kghaC

ua Significantw



ithrespect

tothec

orrespon

ding

water-solub

letre


ithrespecttothec

orrespon

ding

water-solub

letre

atmentat1level


10

30

50

70

90

110

70 80 90 100 110 120 130 140 150

Visc

osity

(cen

tipoi

se)

Temperature (∘C)






119899Zn(H2PO4)

2

997888rarr Zn119899H(2119899+2)

P2119899O(7119899+1)+ (119899 minus 1)H

2O

119899Fe(H2PO4)

3

997888rarr Fe119899H(4119899+2)

P3119899O(11119899+1)+ (119899 minus 1)H

2O

119899Mn(H2PO4)

4

997888rarr Mn119899H(6119899+2)

P4119899O(15119899+1)+ (119899 minus 1)H

2O

119899Cu(H2PO4)

2

997888rarr Cu119899H(2119899+2)

P2119899O(7119899+1)+ (119899 minus 1)H

2O

119899Mg(H2PO4)

2

997888rarr Mg119899

H(2119899+2)

P2119899O(7119899+1)+ (119899 minus 1)H

2O(1)



2O3 203


4

+ 4711 P2O5



0

004

008

012

016

0 50 100 150 200 250Time (min)

175∘C

200∘C

225∘C

Wei

ght l

oss (

gg

H3PO

4)


4495

3406

4000 3500 3000 2500 2000 1500 1000 500


37538

32384

23751

16560

14507

12806

10731

5443

4477




4




1200

1000

800

600

400

200

0

20 30 40 50 60

629

595

533

519

467

45441

401

391

376

308

364

345

336 323319

314

279

272

266

262

25

238

234

224 203

201

195

177

17

168

165

16

16

157

Cou

nts (

s)

2120579 (∘)



2P2O7[19]


1

P2 and P





1and P

2 Interestingly







Acknowledgments


References





O-P2

O5




















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











Chemicalcomponent



0005MDTPA



( A)Intensity (I)

Zn ND 937 839 44775443107311280614507165602375132384

4240364038414135

629533467441376308266262238234224160

16561515501001610138826

Fe ND 932 918Mn ND 909 801Cu 18 968 913P 84








75

85

95

105

115

125

135

0 50 100 150 200 250 300Time (min)

Tem

pera

ture

(∘C)


185

19

195

2

205

21

215

30 80 130 180 230

Den

sity

(gc

c)

Time (min)





Table2Fieldtrialu

singslo

w-release

fertilizerson

ricea

ndpo

tatoesyieldsnu

trient

uptakeand

vitamin

C

Treatm

ents

Rice

atBa

ruipur

(new

alluvium

)[Va

riety119869119886119910119886]

Rice

atNalikul

(old

alluvium

)[Va

riety119873119894119903119886119899119895119886119899]

Potato

atNalikul

(oldalluvium

)[Va

riety119869119910119900119905119894]

Yield

(kgha)

Totaluptake(gha)

Yield

(kgha)

Totaluptake(gha)

Yield

(kgha)

Totaluptake(gha)

Vitamin

C(m

g100g

)Zn

FeMn

CuZn

FeMn

CuZn

FeMn

CuC

3242

706

246

140

213698

76492

206

419900

217

764

6991

621

S 13076

706

350

158

223724

80499

216

4210700

239

948

107

97453

S 23596

756

303

162

263961

78593

236

479500

216

915

9397

533

S 33748

857

341

179

233831

87577

229

44110

00277

756

85103

594

P 146

47bd

1051b

d472a

c236b

d33

4056

117bd

597

332b

d70

14075a

432a

c1966

a151a

163

844

ad

P 24998

bd

1208b

d615b

d288b

d33

4397

bc

122b

d876b

c351b

d76

12550

396

1756

140

148

631

P 34383

b110

6bc

492a

229b

3444

62bd

114bc

693

291b

c48

16025b

d560b

d2569

bd

225b

d198a

c811

c

CD(5)

7583

224

215

559

3732

208

2416

596

34600

839

4795

333

331

207

CD(1)

10212

298

2865

744

5026

281

3253

802

46875

113

6456

449

446

281

CCon

trolS 1

ndashS3sulfateso

fZn

FeM

nandCu

P1ndashP

3slo

w-rele

asem

icronu

trientsS 1

andP 11kghaZn

+033

kghaFe

+0165k

gha

Mn+0083k

gha

CuS

2andP 22

kghaZn

+066

kghaFe

+033

kgha

Mn+0165k

gha

CuS

3andP 34

kghaZ

n+13

3kgha

Fe+066

kghaM

n+033

kghaC

ua Significantw



ithrespect

tothec

orrespon

ding

water-solub

letre


ithrespecttothec

orrespon

ding

water-solub

letre

atmentat1level


10

30

50

70

90

110

70 80 90 100 110 120 130 140 150

Visc

osity

(cen

tipoi

se)

Temperature (∘C)






119899Zn(H2PO4)

2

997888rarr Zn119899H(2119899+2)

P2119899O(7119899+1)+ (119899 minus 1)H

2O

119899Fe(H2PO4)

3

997888rarr Fe119899H(4119899+2)

P3119899O(11119899+1)+ (119899 minus 1)H

2O

119899Mn(H2PO4)

4

997888rarr Mn119899H(6119899+2)

P4119899O(15119899+1)+ (119899 minus 1)H

2O

119899Cu(H2PO4)

2

997888rarr Cu119899H(2119899+2)

P2119899O(7119899+1)+ (119899 minus 1)H

2O

119899Mg(H2PO4)

2

997888rarr Mg119899

H(2119899+2)

P2119899O(7119899+1)+ (119899 minus 1)H

2O(1)



2O3 203


4

+ 4711 P2O5



0

004

008

012

016

0 50 100 150 200 250Time (min)

175∘C

200∘C

225∘C

Wei

ght l

oss (

gg

H3PO

4)


4495

3406

4000 3500 3000 2500 2000 1500 1000 500


37538

32384

23751

16560

14507

12806

10731

5443

4477




4




1200

1000

800

600

400

200

0

20 30 40 50 60

629

595

533

519

467

45441

401

391

376

308

364

345

336 323319

314

279

272

266

262

25

238

234

224 203

201

195

177

17

168

165

16

16

157

Cou

nts (

s)

2120579 (∘)



2P2O7[19]


1

P2 and P





1and P

2 Interestingly







Acknowledgments


References





O-P2

O5




















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










Table2Fieldtrialu

singslo

w-release

fertilizerson

ricea

ndpo

tatoesyieldsnu

trient

uptakeand

vitamin

C

Treatm

ents

Rice

atBa

ruipur

(new

alluvium

)[Va

riety119869119886119910119886]

Rice

atNalikul

(old

alluvium

)[Va

riety119873119894119903119886119899119895119886119899]

Potato

atNalikul

(oldalluvium

)[Va

riety119869119910119900119905119894]

Yield

(kgha)

Totaluptake(gha)

Yield

(kgha)

Totaluptake(gha)

Yield

(kgha)

Totaluptake(gha)

Vitamin

C(m

g100g

)Zn

FeMn

CuZn

FeMn

CuZn

FeMn

CuC

3242

706

246

140

213698

76492

206

419900

217

764

6991

621

S 13076

706

350

158

223724

80499

216

4210700

239

948

107

97453

S 23596

756

303

162

263961

78593

236

479500

216

915

9397

533

S 33748

857

341

179

233831

87577

229

44110

00277

756

85103

594

P 146

47bd

1051b

d472a

c236b

d33

4056

117bd

597

332b

d70

14075a

432a

c1966

a151a

163

844

ad

P 24998

bd

1208b

d615b

d288b

d33

4397

bc

122b

d876b

c351b

d76

12550

396

1756

140

148

631

P 34383

b110

6bc

492a

229b

3444

62bd

114bc

693

291b

c48

16025b

d560b

d2569

bd

225b

d198a

c811

c

CD(5)

7583

224

215

559

3732

208

2416

596

34600

839

4795

333

331

207

CD(1)

10212

298

2865

744

5026

281

3253

802

46875

113

6456

449

446

281

CCon

trolS 1

ndashS3sulfateso

fZn

FeM

nandCu

P1ndashP

3slo

w-rele

asem

icronu

trientsS 1

andP 11kghaZn

+033

kghaFe

+0165k

gha

Mn+0083k

gha

CuS

2andP 22

kghaZn

+066

kghaFe

+033

kgha

Mn+0165k

gha

CuS

3andP 34

kghaZ

n+13

3kgha

Fe+066

kghaM

n+033

kghaC

ua Significantw



ithrespect

tothec

orrespon

ding

water-solub

letre


ithrespecttothec

orrespon

ding

water-solub

letre

atmentat1level


10

30

50

70

90

110

70 80 90 100 110 120 130 140 150

Visc

osity

(cen

tipoi

se)

Temperature (∘C)






119899Zn(H2PO4)

2

997888rarr Zn119899H(2119899+2)

P2119899O(7119899+1)+ (119899 minus 1)H

2O

119899Fe(H2PO4)

3

997888rarr Fe119899H(4119899+2)

P3119899O(11119899+1)+ (119899 minus 1)H

2O

119899Mn(H2PO4)

4

997888rarr Mn119899H(6119899+2)

P4119899O(15119899+1)+ (119899 minus 1)H

2O

119899Cu(H2PO4)

2

997888rarr Cu119899H(2119899+2)

P2119899O(7119899+1)+ (119899 minus 1)H

2O

119899Mg(H2PO4)

2

997888rarr Mg119899

H(2119899+2)

P2119899O(7119899+1)+ (119899 minus 1)H

2O(1)



2O3 203


4

+ 4711 P2O5



0

004

008

012

016

0 50 100 150 200 250Time (min)

175∘C

200∘C

225∘C

Wei

ght l

oss (

gg

H3PO

4)


4495

3406

4000 3500 3000 2500 2000 1500 1000 500


37538

32384

23751

16560

14507

12806

10731

5443

4477




4




1200

1000

800

600

400

200

0

20 30 40 50 60

629

595

533

519

467

45441

401

391

376

308

364

345

336 323319

314

279

272

266

262

25

238

234

224 203

201

195

177

17

168

165

16

16

157

Cou

nts (

s)

2120579 (∘)



2P2O7[19]


1

P2 and P





1and P

2 Interestingly







Acknowledgments


References





O-P2

O5




















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










10

30

50

70

90

110

70 80 90 100 110 120 130 140 150

Visc

osity

(cen

tipoi

se)

Temperature (∘C)






119899Zn(H2PO4)

2

997888rarr Zn119899H(2119899+2)

P2119899O(7119899+1)+ (119899 minus 1)H

2O

119899Fe(H2PO4)

3

997888rarr Fe119899H(4119899+2)

P3119899O(11119899+1)+ (119899 minus 1)H

2O

119899Mn(H2PO4)

4

997888rarr Mn119899H(6119899+2)

P4119899O(15119899+1)+ (119899 minus 1)H

2O

119899Cu(H2PO4)

2

997888rarr Cu119899H(2119899+2)

P2119899O(7119899+1)+ (119899 minus 1)H

2O

119899Mg(H2PO4)

2

997888rarr Mg119899

H(2119899+2)

P2119899O(7119899+1)+ (119899 minus 1)H

2O(1)



2O3 203


4

+ 4711 P2O5



0

004

008

012

016

0 50 100 150 200 250Time (min)

175∘C

200∘C

225∘C

Wei

ght l

oss (

gg

H3PO

4)


4495

3406

4000 3500 3000 2500 2000 1500 1000 500


37538

32384

23751

16560

14507

12806

10731

5443

4477




4




1200

1000

800

600

400

200

0

20 30 40 50 60

629

595

533

519

467

45441

401

391

376

308

364

345

336 323319

314

279

272

266

262

25

238

234

224 203

201

195

177

17

168

165

16

16

157

Cou

nts (

s)

2120579 (∘)



2P2O7[19]


1

P2 and P





1and P

2 Interestingly







Acknowledgments


References





O-P2

O5




















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










1200

1000

800

600

400

200

0

20 30 40 50 60

629

595

533

519

467

45441

401

391

376

308

364

345

336 323319

314

279

272

266

262

25

238

234

224 203

201

195

177

17

168

165

16

16

157

Cou

nts (

s)

2120579 (∘)



2P2O7[19]


1

P2 and P





1and P

2 Interestingly







Acknowledgments


References





O-P2

O5




















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation





















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









Research Article Multimicronutrient Slow-Release Fertilizer of...

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