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The increasing concern over soil degradation and environmental impacts associated with excessive use of chemical fertilizers has led to growing interest in biologically driven nutrient management approaches. In this context, a field experiment was conducted during the Kharif season at the Agriculture Research Farm, Salema, Dhalai, Tripura, to evaluate the role of microbiome-assisted crop production in paddy cultivation. The study was carried out using a Randomized Block Design with ten treatments involving different combinations of recommended fertilizer doses and microbial inoculants, including Azotobacter , phosphate-solubilizing bacteria (PSB), and arbuscular mycorrhizal fungi (AMF). The results revealed that the integration of microbial consortia with reduced fertilizer levels significantly improved soil organic carbon, available nitrogen, phosphorus, and potassium compared to control treatments. The treatment receiving 75% recommended fertilizer dose along with microbial consortium recorded the highest grain yield (5.3 t ha⁻¹), while 50% fertilizer combined with consortium produced comparable yield (5.1 t ha⁻¹), indicating substantial scope for reducing chemical fertilizer inputs. Enhanced microbial biomass carbon, dehydrogenase activity, and soil respiration further confirmed improved soil biological activity and nutrient cycling. The findings suggest that microbiome-assisted nutrient management can effectively sustain crop productivity while reducing fertilizer dependency and improving soil health. This approach offers a promising pathway for sustainable and environmentally sound agricultural practices, particularly in regions with fragile soil ecosystems.
Keywords: Microbiome-assisted agriculture; Biofertilizers; Nutrient cycling; Paddy (Oryza sativa); Soil health; Fertilizer reduction; Sustainable agriculture; Microbiome-assistedagriculture; Biofertilizers; Nutrientcycling; Paddy(Oryzasativa); Soilhealth; Fertilizerreduction; Sustainableagriculture
Fertilizerreduction;Sustainableagriculture. Highlights semoyeetal.,2009;Benderetal.,2016).
• Microbialconsortiumsignificantlyimprovedsoil The importance of microbial processes in nutrient organiccarbonandnutrientavailabilityinpaddy cycling is well established. Biological nitrogen fixa- fields.
tion can significantly supplement plant nitrogen re- • Integrationofbiofertilizerswithreducedfertil- quirements, reducing dependence on synthetic fer- izerlevelsmaintainedorenhancedcropyield. tilizers(Gallowayetal.,2008). Likewise,phosphate- • Upto50%reductioninchemicalfertilizerwas solubilizingnutrientlossesandenhancingsustainabil- possiblewithoutsignificantyieldloss. ityinagriculturalsystems(Lal,2015).Additionally,mi- • Enhancedmicrobialactivityindicatedimproved crobialactivitycontributestosoilorganiccarbonaccu- soilhealthandnutrientcyclingunderfieldcon- mulationandstructuralstability,whichareessential ditions.
forlong-termsoilproductivity(Banerjeeetal.,2019). Despitetheseadvantages,thefield-levelperformance 1.Introduction ofmicrobialinoculantsoftenvariesdependingonsoil Agriculturalintensificationoverthepastfewdecades type,climaticconditions,andcropmanagementprac- haslargelydependedontheextensiveuseofchemi- tices. Therefore, region-specific studies are neces- calfertilizerstoachievehighercropproductivity. Al- sarytoevaluatetheireffectivenessunderlocalagro- thoughthisapproachhascontributedsignificantlyto ecologicalconditions.Thisisparticularlyrelevantfor global food security, it has also led to several unin- northeasternIndia,wherehighrainfallandacidicsoils tendedconsequences,includingsoildegradation,nu- influencenutrientdynamicsandmicrobialactivity. trientimbalance,declineinsoilbiologicalactivity,and Inthiscontext,thepresentstudywasundertakento environmental pollution (Tilman et al., 2011; Savci, assesstheeffectofmicrobiome-assistednutrientman- 2012).Theseissuesareofparticularconcerninregions agementonsoilproperties,cropgrowth,andyieldof with fragile ecosystems, where continuous fertilizer paddyunderfieldconditions.Thestudyalsoaimedto usewithoutadequatebiologicalinputscanaccelerate evaluatetheextenttowhichchemicalfertilizerinputs thedeteriorationofsoilhealth.
canbereducedthroughtheuseofmicrobialconsortia Soilisnotmerelyaphysicalmediumforplantgrowth withoutcompromisingcropproductivity. butadynamiclivingsysteminhabitedbydiversemicro- bialcommunities.Thesemicroorganismsplayacen- 2.MaterialsandMethods tralroleinregulatingkeybiogeochemicalprocesses suchasnitrogenfixation,phosphorussolubilization, 2.1 StudyLocationandSiteDescription andorganicmatterdecomposition(Bergetal.,2017). ThefieldexperimentwascarriedoutduringtheKharif Beneficialmicrobes,includingAzotobacter,Rhizobium, seasonattheAgricultureResearchFarm,Salema,lo- andphosphate-solubilizingbacteria,areknowntoen- catedinDhalaidistrictofTripura,India.Theareafalls hancenutrientavailabilitythroughnaturalbiological underahumidsubtropicalclimatewithhighrainfall, processes,therebyimprovingnutrientuseefficiency mostofwhichisreceivedduringthemonsoonmonths incrops(Vessey,2003;RichardsonandSimpson,2011). (JunetoSeptember).Duringthecroppingperiod,the Similarly,arbuscularmycorrhizalfungi(AMF)establish temperaturegenerallyrangedbetween24°Cand32°C, symbioticassociationswithplantrootsandfacilitate whichisfavourableforpaddycultivation. Thesoilof theuptakeofrelativelyimmobilenutrients, particu- theexperimentalfieldwassandyloamintexturewitha larlyphosphorus(SmithandRead,2008).
moderatelyacidicreaction.Beforeinitiatingtheexper- iment,compositesoilsampleswerecollectedandan- Inrecentyears,therehasbeenincreasinginterestin alyzedtodeterminebaselinefertilitystatusfollowing utilizingsoilmicrobiomesasasustainablealternative standardlaboratoryprocedures(Jackson,1973).The toconventionalfertilizer-basedsystems.Theconcept soilwasfoundtobemediuminavailablenutrients. ofmicrobiome-assistedcropproductioninvolvesthe application ofbeneficialmicrobialconsortia tosup- portplantgrowth,improvesoilfertility,andenhance 2.2 ExperimentalDesignandTreatmentDetails nutrientcycling(Singhetal.,2020).Suchapproaches TheexperimentwaslaidoutinaRandomizedBlockDe- notonlyreducerelianceonsyntheticinputsbutalso sign(RBD)withtentreatmentsandthreereplications. contributetomaintainingecologicalbalance.Previous Eachexperimentalplotmeasured4m×5m,andsuffi- studieshaveindicatedthatintegratingbiofertilizers cientspacewasmaintainedbetweenplotstoavoidlat- withreducedchemicalfertilizerdosescansustaincrop eralmovementofnutrientsandmicrobialinoculants. yieldswhileimprovingsoilbiologicalproperties(Ade- Thetreatmentsconsistedofdifferentcombinationsof recommendedfertilizerdose(RDF)andmicrobialinoc- • SoilpHwasdeterminedusingaglasselectrode ulants,includingAzotobacter,phosphate-solubilizing pHmeter(Jackson,1973) bacteria(PSB),andarbuscularmycorrhizalfungi(AMF). • OrganiccarboncontentwasestimatedbyWalk- Thetreatmentstructurewasdesignedtoevaluateboth leyandBlack’smethod(WalkleyandBlack,1934) individualandcombinedeffectsofmicrobialinputs • Availablenitrogenwasdeterminedbyalkaline underreducedfertilizerlevels,alongwithappropriate permanganatemethod(SubbiahandAsija,1956) controltreatments.
• Available phosphorus was estimated using Olsen’sextractionmethod(Olsenetal.,1954) Thetreatmentswereasfollows: • Available potassium was determined using a • T1:100%RecommendedDoseofFertilizer(RDF) flamephotometer(Jackson,1973) (Control) • T2:75%RDF+Azotobacter 2.5 PlantGrowthandYieldObservations • T3:75%RDF+Phosphate-SolubilizingBacteria Observationsonplantgrowthandyieldparameters (PSB) wererecordedfromrandomlyselectedplantswithin • T4:75%RDF+AMF(Glomusspp.)
• T5:75%RDF+MicrobialConsortium(Azotobac- Theparametersincluded: ter+PSB+AMF) • T6:50%RDF+Azotobacter • Plantheightatmaturity • T7:50%RDF+PSB • Numberoftillersperhill • T8:50%RDF+AMF • Paniclelength • T9:50%RDF+MicrobialConsortium • Numberofgrainsperpanicle • T10:AbsoluteControl(nofertilizer,nomicrobial Atharvest,grainandstrawyieldswererecordedfrom inoculation) thenetplotareaandconvertedtoyieldperhectare. Carrier-basedAzotobacterandPSBwereeachapplied attherateof2.0kgha−1.Theseweremixedwithwell- 2.6 AssessmentofSoilMicrobialActivity decomposedfarmyardmanure(FYM)anduniformly Tounderstandthebiologicalchangesinthesoil,se- broadcastintherespectiveplotsbeforetransplanting. lectedparametersofmicrobialactivityweremeasured. TheAMFinoculum(Glomusspp.)wasappliedat10.0kg Soilmicrobialbiomasscarbon(MBC)wasdetermined ha−1 directlyintherootzoneatthetimeoftransplant- usingthefumigation-extractionmethod(Vanceetal., ing.Intreatmentsinvolvingmicrobialconsortium,all 1987). Dehydrogenaseactivity(DHA),whichreflects inoculantswereappliedtogetheratthesameindivid- overallmicrobialactivity,wasestimatedfollowingthe ualrates.Therecommendedfertilizerdoseforpaddy methoddescribedbyCasidaetal.(1964).Soilrespira- was applied as per regional recommendations. Fer- tionwasmeasuredbasedontheevolutionofCO2as tilizerswereappliedinsplitdosesfollowingstandard describedbyAnderson(1982).
Theseindicatorswereusedtoassessthefunctional activityofsoilmicroorganismsunderdifferenttreat- 2.3 CropEstablishmentandManagementPractices ments.
Thetestcropusedinthestudywaspaddy(Oryzasativa L.).Healthyseedlings,approximately25–30daysold, 2.7 StatisticalAnalysis weretransplantedinthefieldmaintainingaspacingof Theexperimentaldataweresubjectedtoanalysisof 20cm×15cm.Allinterculturaloperationssuchasirri- variance(ANOVA)appropriateforRandomizedBlock gation,weeding,andplantprotectionmeasureswere DesignasoutlinedbyGomezandGomez(1984).The carriedoutuniformlyacrosstreatmentstominimize significanceoftreatmenteffectswastestedatthe5% variability.Carewastakentoensurethatnoadditional levelofprobability. Whereversignificantdifferences inputsinterferedwiththetreatmenteffects. wereobserved,treatmentmeanswerecomparedusing theLeastSignificantDifference(LSD)test. 2.4 SoilSamplingandLaboratoryAnalysis Soilsampleswerecollectedfromadepthof0–15cmat 2.8 EthicalandQualityConsiderations twostages:beforetransplantingandaftercropharvest. The experiment was conducted following standard The samples were air-dried, processed, and passed agronomicpracticesandresearchprotocols.Allmicro- througha2mmsievepriortoanalysis.
bialinoculantsusedinthestudywerenon-pathogenic Thefollowingparameterswereanalyzedusingstan- and suitable for agricultural application. Care was dardprocedures: taken during data collection and analysis to ensure accuracyandconsistency.Thestudydoesnotinvolve microbial activity. The differences were statistically anyethicalissuesrelatedtohumanoranimalsubjects. significant,suggestingthatmicrobialinoculationen- hancedbiologicalprocessesinthesoil.
3.Results 4.Discussion 3.1 SoilChemicalProperties Theapplicationofmicrobialinoculantsshowednotice- Theresultsobtainedfromthepresentstudyindicate ablechangesinsoilpropertiesafterharvest. Ingen- that the use of microbial inoculants, particularly in eral,treatmentsreceivingmicrobialinputsperformed combination,hadaclearinfluenceonsoilproperties, betterthanthecontrol. Theimprovementwasmore cropgrowth,andyieldofpaddy. Theimprovements pronouncedwhenmicrobialconsortiumwasapplied observedwerenotlimitedtoasingleparameterbut alongwithreducedfertilizerlevels.
werereflectedacrosssoilfertility,plantperformance, andbiologicalactivity,suggestingabroadereffectof Observation:Amongthetreatments,T5(75%RDF+ microbiome-basedinterventions.
microbialconsortium)recordedthehighestvaluesfor organiccarbonandavailablenutrients. Thiswasfol- Anincreaseinsoilorganiccarbonwasobservedintreat- lowedbyT9(50%RDF+consortium). Theabsolute mentsreceivingmicrobialinputs,especiallywherecon- control(T10)consistentlyshowedthelowestvalues. sortium was applied. This may be attributed to en- ThedifferencesbetweenT5andcontrolwerestatisti- hancedmicrobialactivityleadingtobetterdecomposi- callysignificantforallparameters,indicatingaclear tionoforganicmatterandstabilizationofcarboninsoil. improvementinsoilfertilityduetomicrobialapplica- SimilarobservationshavebeenreportedbyLal(2015), tion.
whoemphasizedtheroleofsoilmicroorganismsincar- bonsequestrationandmaintenanceofsoilstructure. 3.2 PlantGrowthParameters Under field conditions, such gradual improvements Growthattributesofpaddywereinfluencedbythedif- areimportantforsustainingproductivityovertime. ferenttreatments.Plantsinplotsreceivingmicrobial Theavailabilityofnitrogenwascomparativelyhigher inoculantsappearedmorevigorouscomparedtothose intreatedplots,whichcanbelinkedtotheactivityof undercontrolconditions.
nitrogen-fixingorganismssuchasAzotobacter.Biolog- Observation:Thetallestplantsandhighestnumberof icalnitrogenfixationcontributestothepoolofplant- tillerswererecordedinT5,followedcloselybyT9.The availablenitrogenandreducesdependenceonexter- controltreatment(T1)showedcomparativelylowerval- nalinputs.Earlierstudieshavealsopointedoutthat ues,whiletheabsolutecontrol(T10)recordedthemin- plantgrowth-promotingrhizobacteriacanimproveni- imum.Thedifferencesobservedwerestatisticallysig- trogenuptakeefficiencyandoverallcropperformance nificant,particularlyfortillernumberandplantheight. (Vessey,2003).Thetrendobservedinthepresentstudy supportsthisunderstanding.
3.3 YieldandYieldAttributes: Similarly,higherphosphorusavailabilityinPSBand Yieldperformanceofpaddyvariedacrosstreatments consortiumtreatmentsindicatestheroleofmicroor- dependingontheleveloffertilizerandmicrobialin- ganismsinmobilizingotherwiseunavailablenutrients. puts.
Thereleaseoforganicacidsbyphosphate-solubilizing Observation: Thehighestgrainyieldwasrecordedin bacteriaisknowntoconvertinsolublephosphorusinto T5(5.3t/ha),whichwassignificantlyhigherthanthe formsaccessibletoplants(Sharmaetal.,2013).Inaddi- control. TreatmentT9alsoperformedwellandpro- tion,thepresenceofarbuscularmycorrhizalfungilikely ducedyieldcomparabletoT5. Theabsolutecontrol contributedtoimprovednutrientuptakebyextending recordedthelowestyield.Theresultsindicatethatre- theeffectiverootsurfacearea(SmithandRead,2008). ducedfertilizerlevels,whencombinedwithmicrobial Thecombinedeffectofthesemicrobialgroupsappears inoculants,cansustainyieldeffectively. tohaveresultedinbetternutrientuseefficiency. Theimprovementinplantgrowthparameters,such 3.4 SoilMicrobialActivity asplantheightandtillernumber,maybeassociated Microbialactivityinsoilwasinfluencedconsiderably with better nutrient availability as well as the pro- bytheapplicationofbio-inoculants.
ductionofgrowth-promotingsubstancesbysoilmi- Observation: Highermicrobialbiomassandenzyme crobes.Microbialsynthesisofcompoundslikeauxins activitywereobservedintreatmentsreceivingmicro- andotherphytohormoneshasbeenreportedtostimu- bial inoculants. T5 recorded the highest values, fol- laterootgrowthandplantdevelopment(Adesemoye lowedbyT9.Theabsolutecontrolshowedthelowest et al., 2009). In the present study, the overall plant OrganicCarbon Available N Available P Available K Treatments (%) (kg/ha) (kg/ha) (kg/ha) T 0.58 235 21 185 T 0.62 245 24 190 T 0.63 242 26 188 T 0.64 240 25 187 T 0.70 265 30 198 T 0.60 230 22 182 T 0.61 228 24 180 T 0.62 226 23 179 T 0.68 255 28 195 T 0 0.50 200 18 170 SEm(±) 0.02 5.2 1.3 3.5 CD(p=0.05) 0.05 15.1 3.8 10.2 EffectofTreatmentsonGrowthParametersofPaddy e ule a V T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 Treatments PlantHeight(cm) Tillers/hill PanicleLength(cm)
naseactivity,andsoilrespirationobservedinthisstudy furtherindicatesthatmicrobialprocessesweremore activeintreatedsoils.Theseparametersareoftenused Yieldperformancefollowedasimilartrend,withthe asindicatorsofsoilbiologicalhealthandreflectthein- highestyieldrecordedinthetreatmentreceiving75% tensityofmicrobial-mediatedtransformations(Casida RDFalongwithmicrobialconsortium.Itisnoteworthy etal.,1964).Highervaluesinconsortiumtreatments thatevenat50%fertilizerlevel,whencombinedwith suggestamoreactiveandfunctionalsoilmicrobialsys- microbialinoculants,theyieldremainedcomparable tem.
tohigherinputtreatments. Thissuggeststhatapart ofthechemicalfertilizerrequirementcanbesubsti- Fromanenvironmentalperspective,reducingfertilizer tutedbybiologicalinputswithoutadverselyaffecting inputwithoutyieldlossisanimportantoutcome.Ex- productivity. Similarfindingshavebeenreportedby cessivefertilizeruseisoftenassociatedwithnutrient Benderetal.(2016),whohighlightedtheimportance losses,watercontamination,andgreenhousegasemis- ofsoilmicrobialdiversityinmaintainingcropyields sions(Tilmanetal.,2011).Theresultsofthepresent underreducedinputconditions.
studyindicatethatmicrobiome-assistedapproaches PlantHeight PanicleLength Treatments (cm) Tillers/hill) (cm) T 102.5 10.2 24.1 T 105.8 11 25.3 T 106.2 11.3 25.8 T 107.0 11.5 26.0 T 112.4 12.8 27.5 T 100.5 9.8 23.8 T 101.2 10.0 24.0 T 102.0 10.3 24.2 T 110.2 12.0 26.8 T 0 95.6 8.5 22.0 SEm(±) 1.8 0.4 0.6 CD(p=0.05) 5.2 1.2 1.7
GrainYield StrawYield Treatments Grains/Panicle (t/ha) (t/ha) T 120 4.6 5.8 T 128 4.8 6.0 T 130 4.9 6.1 T 132 5.0 6.2 T 145 5.3 6.6 T 118 4.4 5.6 T 120 4.3 5.5 T 122 4.4 5.6 T 140 5.1 6.4 T 0 105 3.8 5.0 SEm(±) 4.5 0.12 0.15 CD(p=0.05) 13.0 0.35 0.44 cancontributetominimizingsuchriskswhilemaintain- 5.Conclusion ingproductivity.
Based on the results of the present investigation, it canbeconcludedthatmicrobiome-assistednutrient management has considerable potential in improv- Overall,thefindingssupporttheviewthatintegrating ingsoilhealthandsustainingpaddyproductivity.The microbialinoculantswithreducedfertilizerdosescan useofmicrobialconsortia,comprisingnitrogen-fixing, beaneffectivestrategyforimprovingsoilfertilityand phosphate-solubilizing, and mycorrhizal organisms, sustainingcropyieldunderfieldconditions.However, contributedtobetternutrientavailability,enhanced itmaybenotedthatresponsestomicrobialinoculants microbialactivity,andimprovedcropperformanceun- canvarydependingonlocalsoilandclimaticcondi- derfieldconditions.
tions, andtherefore, location-specificevaluationre- Amongthedifferenttreatments,thecombinationof mainsimportant.
75%recommendedfertilizerdosewithmicrobialcon- sortiumconsistentlyperformedbetterintermsofsoil MBC DHA SoilRespiration Treatments (µg/gsoil) (µgTPF/gsoil/day) (mgCO2/kg/day) T 280 32 45 T 310 36 50 T 315 38 52 T 320 39 53 T 360 45 60 T 275 30 43 T 270 29 42 T 278 31 44 T 345 42 58 T 0 250 25 38 SEm(±) 8.5 1.5 2.8 CD(p=0.05) 24.5 4.3 8.1 properties,growthparameters,andyield.Atthesame shipsthatcouldbeconstruedasapotentialconflictof time,thetreatmentwith50%fertilizercombinedwith interest.
microbialinoculantsproducedyieldlevelscompara- bletohigherfertilizerinputs,indicatingthatchemical