Tóm tắt: Đánh giá sự thay đổi hình thái phẫu diện, tính chất hóa học đất và khả năng cung cấp dưỡng chất NPK cho lúa trên đất phèn Đồng bằng sông Cửu Long

Đánh giá sự thay đổi hình thái phẫu diện, tính chất hóa học đất và khả năng cung cấp dưỡng chất NPK cho lúa trên đất phèn Đồng bằng sông Cửu Long.Đánh giá sự thay đổi hình thái phẫu diện, tính chất hóa học đất và khả năng cung cấp dưỡng chất NPK cho lúa trên đất phèn Đồng bằng sông Cửu Long.Đánh giá sự thay đổi hình thái phẫu diện, tính chất hóa học đất và khả năng cung cấp dưỡng chất NPK cho lúa trên đất phèn Đồng bằng sông Cửu Long.Đánh giá sự thay đổi hình thái phẫu diện, tính chất hóa học đất và khả năng cung cấp dưỡng chất NPK cho lúa trên đất phèn Đồng bằng sông Cửu Long.Đánh giá sự thay đổi hình thái phẫu diện, tính chất hóa học đất và khả năng cung cấp dưỡng chất NPK cho lúa trên đất phèn Đồng bằng sông Cửu Long.Đánh giá sự thay đổi hình thái phẫu diện, tính chất hóa học đất và khả năng cung cấp dưỡng chất NPK cho lúa trên đất phèn Đồng bằng sông Cửu Long.

THE MINISTRY OF EDUCATION AND

TRAINING CAN THO UNIVERSITY

SUMMARY OF THE DISSERTATION

Major: Soil Science Major Code: 62 62 01 03 TRAN VAN HUNG

EVALUATING CHANGES IN SOIL PROFILES, SOIL CHEMICAL PROPERTIES AND ABILITY

TO SUPPLY NPK NUTRIENTS FOR RICE PLANTED ON ACID SULFATE SOIL IN

MEKONG DELTA

Can Tho, 2022

THIS DISSERTATION HAS BEEN COMPLETED AT

CAN THO UNIVERSITY

Supervisor:1 Prof Dr Ngo Ngoc Hung

2 Assos Prof Dr Tran Van Dung

The doctoral dissertation was evaluated by the Committees at the basic level.

Meeting at:

At:

Reviewer1:

Reviewer2:

The thesis could be found in:

Learning Resource Center of Can Tho University

National Library of Vietnam

THE LIST OF PUBLISHED ARTICLES

1 Tran Van Hung, Le Van Dang,Ngo Ngoc Hung, 2017 Effect of

Phosphorus (P) blended with Dicarboxylated Acid Polymer (DCAP) onsoil available P, rice yield and P uptake in acid sulfate soil VietnamJournalofAgriculturalSciences,Vol15.N04:ISSN1859-0004.P(371- 379)

2 Tran Van Hung, Le Phuoc Toan, Tran Van Dung,Ngo Ngoc Hung,

2017 Morphological and physicochemical properties of acid sulfatesoils in Dong Thap Muoi Can Tho University Journal of Science,number of topics: Environment and Climate Change (2017) (2) ISSN1859-2333 P(1-10)

3 Tran Van Hung, Nguyen Quoc Khuong, Tran Ngoc Huu, Le Phuoc

Toàan, Nguyen Van Nghia,Ngo Ngoc Hung, 2018 Studying of

mineralnutrientsuptake(N,P,K)inricefromdryseasonandN,P,K,

Ca,MgsupplyingcapabilitiesfromacidsulfatesoilinMekongDelta Vietnamjournal of agriculture and Rural development 3+4/2018 ISSN 1859-

4581 P(62-71)

4 Tran Van Hung, Le Phuoc Toan, Tran Van Dung,Ngo Ngoc Hung,

2018.Studyingthemorphologicalandphysico-chemicalpropertiesof

acidsulfatesoilsinCuuLongdeltaafter20yearscultivation.Vietnam journal ofagriculture and Rural development number of topics: Development ofsustainable agriculture under the impact of climatechange:challengesandopportunitiesaugust–2018.ISSN1859-4581 P (125-136)

Chapter 1: INTRODUCTION 1.1 The necessity of thestudy

The Mekong Delta has a relatively large area of acid sulfate soil(ASS), accounting about 1.6 million hectares Most of the acid sulfate soilsare grown in rice, with low pH, high iron and aluminum toxicity whichphosphorus fixation lead to difficult absorption for plants to limit factor inrice yield (Afzal et al., 2010; Paul et al., 2010; Qurban et al., 2015).Recently, a number of studies on NPK nutrients supplying to ricebasedonsitespecificnutrientmanagement(SSNM)intheMekongDelta that havebeen carried out to provide recommendations on fertilizers (Pham Sy Tan, 2005;Trinh Quang Khuong, 2005; Trinh Quang Khuong et al., 2010) At the same time,some other studies used the additive Avail@ polymer or the active ingredient(Dicarboxylic Acid Polymer- DCAP) cover on the DAP phosphate fertilizer toprotect the phosphate particle to limit by toxic iron and aluminum in low pH, calciumand magnesium at high pH soil conditions The results show that Avail phosphatefertilizer application has increasing the efficiency ofphosphorusandsomecropsyield(DunnandStevens,2008;Moosoetal., 2012).Therefore, the assessment of the change in morphology, the variabilityin the quality

of the acid sulfate soil and the ability to provide nutrients to rice on the acid sulfatesoil to beconsidered

1.2 The objective of thestudy

1.2.1 General objective

Thestudyaimedtoevaluatethechangeinsoilprofilemorphology, the properties

of acid sulfate soil and to determine NPK nutrient requirements for rice on acidsulfate soil in the MekongDelta

1.2.2 Specificobjectives

To evaluate the change in morphological profile and chemicalproperties of acid sulfate soil in the Mekong Delta after 20 years ofcultivation

TodeterminetheabilitytosupplyNPKnutrientsonriceoftypical acid sulfatesoils in the MekongDelta

To determine the efficiency of using phosphate fertilizer in the DAPmixed with Avail on rice of acid sulfate soil in the Mekong Delta

1.3 The activities of thestudy

Content 1:Determining the change in morphology and chemical

properties of acid sulfate soil in the Mekong Delta after 20 years forcultivation

Content2:DeterminingtheabilitytosupplyNPKnutrientstorice on typical

acid sulfate soils in the MekongDelta

Content 3:Determining the efficiency of phosphate fertilizer in the

DAP mixed with Avail for rice on acid sulfate soil in the Mekong Delta

1.4 The scientific and actual meaning of thethesis

1.4.1 The scientific of thethesis

The results on the thesis have provided information about the change

in morphology and soil chemistry after more than 20 years for cultivationApplyingfertilizermethodaccordingtovacantlottodeterminethe ability forsupplying nutrients N, P, K from soil and ability of rice yield by nutrients N, P and

K in each experimental site on acid sulfatesoil

Experimenting results for applying P fertilizer of DAP mixed withAvail to determine the efficiency of phosphate fertilizer on acid sulfate soil

on the Avail polymer active ingredient

This is a valuable resource for research, study and teaching

1.4.2 The actual meaning of thethesis

The results have determined the change in morphology and chemicalcharacteristics on five acid sulfate soil profiles after 20 yearscultivation.However,soilclassificationbasedondiagnostichorizonsand diagnosticproperties of FAO-WRB soil name did notchange

TheabilitytosupplynutrientsN,PandKfromthesoilforsummer- springricecropsat04experimentalsitesrepresenting 04 ecological regions of acidsulphate soil in the MekongDelta

autumnandwinter-The results of applying phosphate fertilizer on DAP mixed withAvailonlyeffectiveforricein01siteofheavilyactiveacidsulphatesoil

1.5 Subjects and scope ofresearch

1.5.1 Researchsubjects

The morphological and chemical properties of 05 typical acid sulfatesoils in the Mekong Delta include (Hong Dan - Bac Lieu; Phung

Hiep - Hau Giang; Tan Thanh - Long An; Thanh Hoa - Long An; Tan Phuoc - Tien Giang).

Efficiency of using NPK fertilizer for rice on acid sulphate soil.Efficiency of using phosphate fertilizer in the form of DAP mixed with Avail polymer active ingredient for rice on acid sulfate soil

OM 5451 is a high yielding rice variety with a relatively short

growing time (88 - 95 days), has high tolerance to alum

1.5.2 Researchscope

+ In terms of space

Research on acid sulfate soil morphology and characteristics in

the Mekong Delta

The study has organized in parallel of four experiments in the ricefield for the ability of supply nutrients N, P, K and evaluation theeffectiveness of Avail for rice representing on four ecological regions ofacid sulfate soil in the Mekong Delta

+ In terms of time

Evaluating the changes in morphological profile and chemical

properties of acid sulfate soil in the Mekong Delta on two time periods (2015 comparing to 1992)

Surveying on the ability to supply nutrients N, P, K and theeffectivenessofDAPfertilizermixedwithactiveingredientAvailforrice crops inSummer-Autumn 2014 and Winter-Spring (2014 -2015)

1.6 New contributions of the thesis

Determining the morphological change levels on acid sulfate soil inthe Mekong Delta after more than 20 years for rice cultivation

Evaluating the change in chemical properties on five typical acidsulfate soil profiles in the Mekong Delta after more than 20 years ofcultivation

Determining the ability to provide nutrients N, P, K from the soil andthe ability of rice yield on nutrients N, P and K in the experimental sites onfour ecological regions of acid sulfate soil in the Mekong Delta

Evaluatingtheeffectivenessofphosphatefertilizersonacidsulfate soil mixedwith active ingredient Avail polymer

Chapter 2: MATERIALS AND METHODS 2.1 Researchmaterials

Table 2.1: Location, Coordinates of soil profiles in 2015

Profil Symbol Profiles location (UTM-WGS.84)Coordinates

1 HD-BL Hong Dan district (now belongs to PhuocLong), Bac Lieu Province 0532992 1029322

2 PH-HG Phung Hiep district, Hau Giang Province 0567882 1080733

3 TT-LA Tan Thanh district, Long An Province 0613046 1175920

4 TH-LA Thanh Hoa district, Long An Province 0630916 1176116

5 TP-TG Tan Phuoc district, Tien Giang Province 0641482 1158609

Study area:ability to provide NPK nutrients and determine the

effectiveness of using DAP phosphate fertilizer mixed Avail for rice ontypical alum soil in the Mekong Delta (Table 2.2)

Table 2.1: Time of sowing and harvesting of rice in SA and WS at 04 experimental sites on acid sulfate soil in the Mekong Delta

Notes: LXQ-Long Xuyen Quadrangle; HAD-Depressed Areas of The Hau River;

CMP-Ca Mau Peninsula; PR-Plain of Reeds; (SA) Summer-Autumn; (WS) Winter-Spring

2.3 Hydrometeorology, farming system and seasonal calendar of

alum land survey area(As presented in thethesis)

2.4 Laboratory soil characteristics(As presented in thethesis)

2.5 Researchmethods

The relationship between the research contents on the alum land of the

Mekong Delta(As presented in the thesis)

2.5.1 Content 1: Methods of surveying Soil

Survey of natural elements and farming methods

Interviewing the households where the site of digging for samples onthe place, the history of land cultivation, solutions to renovate alum land.Survey of geomorphology, climate, water level/aquatic level, wild plants

Method of digging and describing morphology of profiles

Use2mtroughdrillingtore-explorethesoiltochoosethelocation representingthe digger/soil profiles The size of the soil profiles is 1.5 mlong,1.0mwideand1.5mdeep.Descriptionofthesoilontheplains,the

descriptionispreparedasthe2ndand4thFAO'sprinteddescription"Soil ProfilesDescription Guidelines" (1998; 2006) Identify and re-describe the morphology of soilprofile in 2015 and the research site in the periodof1992.UseaGPStolocatethelongitudeandlatitudeofthestudypoint

Method of collecting samples and analyzing of soil physico- chemical

Collect soil samples according to the soil layer, bring it to theprocessing laboratory to serve for analysis Based on the Handbook ofanalysis of soil, water, fertilizers, crops (Institute of Agriculturalization

of Turkey, 1998) to collect soil samples for early analysis(method ofanalysis of physical and chemical targets of soil which was described

in detail in the thesis).

Soil Classification method

UsetheFAO-WRBsoilclassificationsystem(2006)toclassifyand rename the soil foreach soilprofile

Assess the change of some characteristics of acid sulfate soil

Compare the morphological description results between two differenttimes (2015 and 1992), find similarities and differences in targets of soilmorphology Combine comparing soil characteristics to chart and evaluatethe direction of change according to the soil layers

2.5.2 Content2:MethodofdeterminingNPKdemandforriceonacid

sulfatesoil

Arrange NPK omission lot experiments

The experiment was carried out on 3 different on-farm researchhouseholdsateachtestsite(Table3.6),with3repetitionsonalotareaof 25 m2 Theformula for fertilizing 4 test sites in the NPK SA case is (80- 60-30), the

WS case is (100-60-30) Use OM 5451 for the experiment Fertilizer isfertilized at 3 times, 10, 20 and 45 days after sowing (DAS), in specificquantity (Table2.3)

Table 2.3: The amount of N, P and K applied at three times of 10, 20, 45 days after sowing the SA and WS rice crops

Day after sowingFertilizer types

Notes: (SA) Summer-Autumn; (WS) Winter-Spring

- The experimental treatments were shown in the (Table 2.5)

Table2.5:Treatmentsofthefieldexperimentinfourecologicalzonesofacid sulphatesoils Ordinal Treatments Description

Determining the agronomic targets

Determination of agronomic targets(detailed in the thesis).

Determiningtheactualyieldistheyielddeterminedatthetimeofharvest on an area of5m2and converted to 14%humidity

Determining the amount of NPK of rice absorbed from fertilizer

Determine the protein content by the Kjeldahl distillation method.Analyze the phosphate using the color comparison method Measurepotassium(K)withanatomicabsorptionspectrometer.Calculatenutrient absorption arebased on leaf stem biomass and seeds with NPK content in the stems andriceseeds

Determining the possibility of supplying NPK from the soil

The soil's ability to provide nutrients (Dobermann and Fairhurst,

2000) is described as the ability to provide N fromINSsoil (indigenous

nitrogensupply)isthetotalamountofproteintheplantabsorbsinvacant

lotN(0N),butfertilizePandK(thewayofdeterminingPandKissimilar to determiningN)

INS=Thetotalamountofproteinabsorbedfromthestemsandriceseeds of the PK

lot;PS(indigenous phosphorus supply) = the total amount of phosphorus

absorbed from the stems and rice seeds of

theNKlot;IKS(indigenouspotassiumsupply)=thetotalamountofphosphorusabsorbed from the stems and rice seeds of theNPlot

Data processing

Using Excel software to draw charts, using SPSS software tocompare average differences and analyze variances by Duncanaudit

2.5.3 Content 3: Avail’s effectiveness assessmentmethod

Experimental treatment design for fertilizer P (DAP) mixed to Avail

The experiment of applying fertilizer P mixed with Avail was carriedout in parallel at 04 experimental stations (section 2) Theexperimentwascarriedouton3differenton-farmresearchhouseholdsof eachecological region, 03 time duplicates on a plot area of 25m2 Theformula offertilizer N and K2O in the Summer-Autumn season (80N + 30K2O) and(100N + 30K2O kg/ha) in the Winter-Spring season, usingthe variety OM

5451 as the experiment Fertilizer was applied at 3 times of 10, 20 and 45days after sowing time with specific amounts in (Table 2.6)

Table 2.6: The amount of base fertilizer N, and K applied at three times of

10, 20, 45 days after sowing the SA and WS rice crops

Day after sowingFertilizer types

Table 2.7: Phosphorus fertilizer rates and phosphorus application blended with Avail

Ordinal Treatments Description

4 30P2O5+Avail - Application of Avail (2‰) coated on 30 kg

P 2 O 5 /ha

Note:Using2litersofAvail@ polymersolutionof 2‰concentrationcoatedfor1tonofDAP.

Evaluation of the influence of Avail on acid sulfate soils

Determining the influence of fertilizer P mixed to Avail for yieldcomposition and rice yield Determining the influence of fertilizer P mixed

to Avail for P content and absorption of rice plants

Chapter 3: RESULT AND DISCUSSION 3.1 Changes in soil surface and its chemical characteristics on acid sulfate soil in Mekong Delta after 20 years ofuse

3.1.1 Changes in acid sulfate soilsurface

3.1.1.1 At Hong Dan-Bac Lieu (2015 compared to1992)

Accordingtotheresultofevaluatingtheacidsulfatesoilsurfaceat HD-BL,there has not been significant changes in the generating layer between the tworesearch times The soil surface is divided into 4 mainlayers,withthegeneratinglayerfromthegroundto200cmdepth(Ah/AB, Bgj1, Bj2, Cr).The active acid sulfate layer appears deeper than 50cm, and has Jarosite straw yellow dots(2.5Y 8/6-8/8) and acid sulfate producing matters above 140cm The soil name classifiedaccording to FAO-WRB is unchanged between the two research times (Sali-Endo- OrthiThionic Fluvisols) (Figure3.1)

Figure 3.1: Soil profile in Hong Dan-Bac Lieu (2015 compared to 1992)

3.1.1.2 At Phung Hiep-Hau Giang (2015 compared to1992)

TheresultcomparingtheacidsulfatesoilsurfaceatPH-HGbetweenthetwoperiods (Figure 3.2) showedthat thesoil surfacehad 4maingenerating layersand ABshifting layer (1992).Theevaluated soil surfacein2015consisted of4layers (Ah; Bgj1; Bgj2;Cr),whilein1992,itwas5layers (Ah;AB;Bgj;Cgj; Cr).AtBgj layerin2015,the depthwas30 cm,shallowerthan thatin1992,due to the 8 cmintegrationfrom ABlayertoBgj layer.Atthetworesearchtimes,the depth of theactiveacidsulfate layerdidnotchange,below50cm,withjarosite spots (2.5Y8/8) and theacidsulfategeneratingmatterspyrite,below110cmdepth.Theacidsulfate

soil surface at PH-HG was categorized, according to FAO-WRB, as heavilyactive acid sulfate soil (Epi-Orthi Thionic Fluvisols).

Figure 3.2: Soil profile in Phung Hiep-Hau Giang (2015 compared to 1992)

3.1.1.3 At Tan Thanh-Long An (2015 compared to1992)

Thesoil surfaceatTT-LAin bothresearch timeswasdividedinto6generatinglayers.Thesoilsurfacein2015hadlayersofAp;AB;Bg;Bgj;Cgj;Cr,andAp; Ah;Bg; Bgj;Cgj;Cr in1992 (Figure 3.3).TheAhlayerin1992changedintoABlayerin2015,becausethesoillayerwasmodified via

accumulationofmineralsinsoilandchangesinthecolorofthesoilmatrix

Figure 3.3: Soil profile in Tan Thanh-Long An (2015 compared to 1992)

TheBg,BgjandCgjlayersin1992hadstronggleyification,rusted brown olivedots changed in to yellow olive ones (2.5Y 5/4; 6/8).However,in2015,withtheconservativedykesystem,thesoilhaddry

andsubmergedalterationinthemodelof3crops/year,resultinginmore rusted dotsand diverse colors of dots (2.5YR 6/8 and 7.5YR 2.5/1) Thesoilsurfacehadtheactiveacidsulfatesoildeeperthan50cmandthelayer

containingacidsulfategeneratingmattersPypitedeeperthan120cm.The

soilclassificationaccordingtoFAO-WRBwasslightlyactiveacidsulfate soil (Endo-OrthiThionic Gleysols), which did not change its name after a period ofcultivation

3.1.1.4 At Thanh Hoa-Long An (2015 compared to1992)

The soil surface in TH-LA after the two research periods (Figure 3.4)had 6 generating layers, but the name of the layers has changed: soil profile

in 2015 with generating layer (Ah; AB; Bgj; Bg; Cr), soil profile in 1992including layers (Ah; Bg; Bgj; BC; Cr)

Figure 3.4: Soil profile in Thanh Hoa-Long An (2015 compared to 1992)

The soil surface in 2015 showed that the ground Ah layer hadrusteddotsalongtheroottube,darkyellowincolor(7.5YR6/8),because the agriculturalcultivation, the soil was usually dired and ventilated, leading to oxidization of Fe2+

betweenthetworesearchperiods,whichwasgleyicandhadJarositedots (2.5Y 8/6) atthe depth of 25-45cm Thus, the soil name did not change through time andkept as heavily active acid sulfate soil (Epi-Orthi ThionicFluvisols)

3.1.1.5 At Tan Phuoc-Tien Giang (2015 compared to1992)

20yearsofcultivationhadsomedifferences but notsignificant.Thesoil

AB;Bgj1;Bgj2;Cr),whilein1992,the

numberof layerswas6 (Ah;AB;Bg; Bgj;Bj;Cr) Thecultivating layerAh(0-30cm)and the AB shiftinglayer (30-45cm) in1992had norusteddots, thisindicated that statusof thesoilwas wetandthe matrixwasfromdarkandslightbrown(7.5YR2/1)tobrownishgrey(10YR6/2).However,in2015,the ground layer Ah (0-35cm) had dark greymatix (Gley1 3/N),rustedreddishyellowdots(7.5YR6/8),simultaneously,the ABlayer(35-55cm)wasgrey(Gley15/N)withtheverticalclayaccumulationandrustedyellowishr

ed dots(7.5YR5/8) duemetabolismofmetaloxides

Figure 3.5: Soil profile in Tan Phuoc-Tien Giang (2015 compared to 1992)

To sum up, the assessment of soil survey results between the twoperiods (2015 compared to 1992) on 05 profiles acid sulfate soil in theMekong Delta showed that there is a small change in morphology as:background color of soil, color of rust spots, the maturity of the soil.However, the sulfuric diagnostic layer and diagnostic materials did notchange,sothesoilnamesof05acidsulfatesoiltypesintheMekongDelta classified by FAO-WRB did not change after 20 years ofcultivation

3.1.2 ChangesofchemicalpropertyofacidsulfatesoilintheMekong Delta after 20 yearscultivation

Results of soil analysis by generating layers of 5 soil profiles in2periods showed that: pHH2O(1:2.5)generating layers of 5 soil profiles intheyear(2015comparedto1992)didnotsignificantfluctuation.ThesoilpH value of thesurface layer of 5 soil profiles is low (pH<5), assessing thelevelofacidityfrommoderatetoveryacidic,andalsoadverseeffectsthe growth anddevelopment of rice (Shamshuddin et al.,2013)