Biochar characteristics and application rates affecting corn growth and properties of soils contrasting in texture and mineralogy
Somchai Butnan a ,Jonathan L.Deenik b ,Banyong Toomsan c ,Michael J.Antal d ,Patma Vityakon a ,⁎
a
Land Resources and Environment Section,Department of Plant Science and Agricultural Resources,Faculty of Agriculture,Khon Kaen University,Khon Kaen 40002,Thailand b
Department of Tropical Plant and Soil Science,University of Hawaii,HI 96822,USA c
Agronomy Section,Department of Plant Science and Agricultural Resources,Faculty of Agriculture,Khon Kaen University,Khon Kaen 40002,Thailand d
Hawaii Natural Energy Institute,University of Hawaii,HI 96822,USA
a b s t r a c t
a r t i c l e i n f o Article history:
Received 25February 2014
Received in revid form 12July 2014Accepted 23August 2014Available online xxxx
Keywords:
Al and Mn phytotoxicities Ash content of biochar
Biochar mediated Mn solubility K luxury consumption Nutrient availability Soil pH
Bene fits of biochar as a soil amendment may vary with its properties,time after its application,and in relation to soil texture and mineralogy.Effects of pyrolysis conditions on biochar properties which,in turn,in fluence soil fer-tility and plant growth in two different soils were investigated.A pot experiment employing two types of euca-lyptus wood derived low (350°C)and high (800°C)pyrolysis t
emperatures,was applied at four ,0,1,2,and 4%w/w,once at the beginning of the experiment to a loamy-sand Ultisol and a silty-clay-loam Oxisol.Two concutive corn crops were grown to investigate biochar temporal effect.Low temperature biochar had lower ash (2.4%)content than its high temperature counterpart (3.9%).Biomass of the first corn crop was signi ficantly depresd under the highest rate of the high temperature biochar compared to control treatment in the sandy Ultisol,but not in the clayey Oxisol.Biomass depression was accompanied by a signi ficant increa in soil pH (5.88)compared to control (4.74),as well as signi ficant increas in tissue K concentrations (43vs 10.8g kg −1),and decreas in tissue Ca (2.8vs 3.8g kg −1)and Mg (1.3vs 2.6g kg −1).Biomass of the c-ond crop incread in most biochar treatments compared to the controls,due to the reduction in phytotoxicity of Al in the Ultisol and Mn in the Oxisol.Both biochars signi ficantly incread soluble Mn concentrations relative to the control (1.39–4.61vs 1.12mg l −1),while they decread tissue Mn concentrations compared to the control (0.08–0.17vs 0.41g kg −1)in the Oxisol.Possible mechanisms underlying biochar mediated increas in soil Mn solubility and decreas in corn Mn uptake were discusd.The results showed clearly that lower temperature biochar gave higher bene fits to both contrasting textured soils than the higher temperature counterpart in both first (32days after biochar application,DAA)and cond (82DAA)cropping cycles.The 1–2%w/w rate of the low temperature biochar was appropriate for the soils,the higher rate being more suited to the finer textured soil.
©2014Published by Elvier B.V.
1.Introduction
Biochar ud as a soil amendment to improve soil fertility and plant growth has been the focus of much rearch in the recent past (Ibrahim et al.,2013).It has shown promi as a sustainable amendment to en-hance soil chemical properties (Glar et al.,2002;Lehmann et al.,2011).Unlike most conventional soil organic materials,which are read-ily decompod,the recalcitrant nature of biochar increas its potential value as a soil amending material for the longer term (Chan et al.,2007).Some biochars contain high quantities of ash,which are enriched with a number of plant nutrients,especially cationic elements,such as K,Ca,and Mg (Deenik et al.,2011;Rajkovich et al.,2012;Yuan et al.,2011).Additionally,ash content plays a major role in controlling soil pH which determines cation exchange capacity (CEC)of variable charged
soils (Sollins et al.,1988)and nutrient availability (Mengel and Kirkby,2001).
The chemical characteristics of biochar produced from a feedstock depend considerably on pyrolysis conditions,especially temperature (Antal and Gronli,2003).At low temperature,biochar chemical compo-sition is clor to the original feedstock while high temperature biochar is clor to graphite (
Masiello,2004).Low temperature biochar has high volatile matter (VM —e.g.,bound carboxylic acid,phenol,ketone,and aldehyde functional groups),but lower fixed C and ash contents than the high temperature counterpart (Bourke et al.,2007).Previous studies showed that biochar with high VM content contributed to N immobili-zation and microbial activity reduction which negatively affected plant growth (Deenik et al.,2010;Spokas et al.,2011).
It is likely that biochar amendment effects depend upon soil proper-ties,especially soil texture and mineralogy.In the tropics,a large propor-tion of agricultural soils are highly weathered belonging to the order Oxisols and Ultisols,which occupy about 23%and 20%of the tropics worldwide,respectively (Sanchez and Logan,1992).The mineralogy of
Geoderma 237–238(2015)105–116
⁎Corresponding author.
E-mail address:patma@kku.ac.th (P.
Vityakon).
dx.doi/10.derma.2014.08.0100016-7061/©2014Published by Elvier
B.V.
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Geoderma
j o ur n a l h o m e p a g e :w ww.e l s e v i e r.c o m/l o c a t e /g e o de r m a
the soils consists predominantly of low activity clays with variable charged ,kaolinite and oxides and hydroxides of Fe and Al (Naidu et al.,1997).Commonly,a crucial problem of Ultisols and Oxisols is Al toxicity(Lathwell and Grove,1986).Previous studies showed that biochar application reduced Al toxicity in acid soils(Hossain et al., 2010;Major et al.,2010).Chan et al.(2007)reported that application of greenwaste biochar to an acidic Alfisol soil reduced extractable Al con-centration from0.27cmol c kg−1in control to0.12cmol c kg−1in50t biochar ha−1.Nevertheless,excessive application of liming materials in-cluding biochar to coarly textured low buffering capacity soils may lead to abrupt increas in soil pH resulting in deficiencies of some plant nutrients(Kamprath,1971).For example,K deficiency in radish re-sulted from application of poultry litter biochars to an acid soil(Chan et al.,2008),and N and P deficiencies in larch(Larix gmelinii)resulted from application of Japane larch wood biochar(Makoto et al.,2011).
Although there have been some studies on the influence of biochars on soil properties and plant growth in soils differing in texture and min-eralogy,the studies did not show the interaction effects of biochar types(particularly bad on different pyrolysis conditions)and the different soils.For example,Kolb et al.(2009)reported that appli-cation of10%w/w biochar produced from mixed feedstock(bull manure:dairy manure:pine wood=2:1:1)incread total N in a sandy loam Spodosol,but not in a clay loam Alfisol.Meanwhile,Yeboah et al.(2009)reported that application of savannah wood biochar in-cread N and P uptake in corn plants grown in a sandy loam,but uptake decread in a silt loam soil.We propo that biochar materials are char-acterized by physical and chemical properties that would benefit coarly textured soils more than soils withfine texture.Biochars posss high po-rosity and surface area with a potential to beneficially impact soil physical properties by reducing bulk density and increasing water holding capac-ity in sandy soils with high bulk density and low water retention.Chem-ically,biochars have the potential to provide nutrient supply and liming potential through ash components and increa nutrient retention by in-creasing CEC.
The prent rearch addresd two general hypothes:(i)biochars have higher influence on soil properties and plant growth in a coar tex-tured Ultisol soil than in afine textured Oxisol and(ii)bioch
ar produced under higher temperature,and hence lower VM,is more effective at im-proving soil properties and plant growth than a lower temperature (higher VM)biochar,but the effectiveness is short-lived.Therefore,the objectives of this study were(i)to determine effects of pyrolysis condition on biochar properties;(ii)to evaluate the effects of tho biochars and their application rates on soil properties and plant growth in soils con-trasting in texture and mineralogy;and(iii)to determine the time effect on biochar benefits.
2.Materials and Methods
2.1.Soils
Two soils with contrasting texture and mineralogy were ud for this study.The Khorat soil(isohyperthermic Typic Oxyaquic Kandiustults)col-lected from0–15cm depth from a fruit tree rearch plot at Khon Kaen University,Thailand(16°27′50″N;102°48′14″E)and the Wahiawa soil (kaolinitic isohyperthermic Rhodic Haplustox)from the0–15cm depth at the Poamoho Rearch Station,University of Hawaii,USA(21°32′30″N;158°05′15″W).Soils were air-dried and sieved to pass through a 2-mm sieve and stored in polyethylene containers at room tempera-ture.The Khorat soil was shipped to the University of Hawaii where the greenhou experiments were performed.Initial physical and chemical properties of Khorat and Wahiawa soils are shown in Table1.
2.2.Biochars
The biochar feedstock comprid the upper branches of eucalyptus trees(Eucalyptus camaldulensis)remaining from tree cuttings ud for pulp production from the Mancha Khiri Plantation Forest Station,Khon Kaen province,Thailand.The biochars were produced using two different pyrolysis techniques:Thai traditional kiln(TK)and Flash Carbonization™(FC)(Table2).The TK biochar was produced utilizing the traditional prac-tice of local Thai people where the feedstock was subjected to heating (approximately350°C)under low O2for three days,cooled down with water and air dried for another four days.The FC biochar was produced at the Hawaii Natural Energy Institute at the University of Hawaii using the Flash Carbonization process,which involved exposing the feedstock to a controlledflashfire at1MPa pressure for40min with peak temper-ature reaching up to800°C in the reaction canister.Both biochars were crushed and subquently sieved to pass through a2-mm sieve.The TK biochar was transported to Hawaii and both biochars were stored at room temperature prior to laboratory analysis and further u in a green-hou experiment.
2.3.Greenhou Experiment
A pot experiment was conducted under greenhou conditions from August to October2011.A factori
al treatment structure was ud with two soil types(Khorat and Wahiawa soils),two biochar types(TK and FC biochars),and four rates of biochar application(0,1,2,and4%w/w). The14treatment combinations were arranged in a randomized complete block design(RCBD)with three replications for a total of42experimental units.Pots(d=0.16m,v=3016cm3)werefilled with2kg air dried soil and four rates of each biochar were applied to the pots and mixed thor-oughly with the soils.Corn was grown in the pots for two crops,each crop had a duration of39days,and biochars were applied only once be-fore thefirst crop planting.This allowed the study of time effects of bio-char on soil properties and plant wo periods corresponding to thefirst and the following cond crops.The period of thefirst crop was that from biochar application to the harvest of that crop and accom-panying soil sampling at39days after biochar application(DAA),while the period designated as the cond crop was that from the biochar appli-cation to the harvest and soil sampling(82DAA).
Corn eds(var.Hawaiian supersweet no.9)obtained from the Uni-versity of Hawaii Seed Laboratory(Agricultural Diagnostic Services Cen-ter,University of Hawaii)were ud as the test plant.Six corn eds were planted directly into each pot.The edlings were thinned to two plants per pot at ten days after planting(DAP).The pots were watered with deionized(DI)water once a day to70%of water holding capacity (WHC)(20.5and63.4%w/w for Khorat and Wahiawa soils,respectively).
Table1
Initial physical and chemical properties of the Khorat and Wahiawa soils ud for the plant bioassay experiment.
Soil Soil particle
distribution(%)Soil texture Total C Total N pH
(1:5H2O)
CEC a
(cmol c kg−1)
Mineral N
(mg kg−1)
P(mg kg−1)Extractable cations(mg kg−1)
Sand Silt Clay(g kg−1)NO3−NH4+K Ca Mg Al Mn
cis系统Khorat soil79.917.6 2.5Loamy sand 6.9 1.28 5.520.95ND b23.59 5.73141112111.4613.46 Wahiawa soil7.935.656.5Silty clay loam15.3 2.72 6.047.86 1.4028.78 6.263115091610.023516.89
a CEC,cation exchange capacity.
b ND,not detectable.
106S.Butnan et al./Geoderma237–238(2015)105–116
This was performed by weighing pots (pot +soil mixture +water)and adding DI water when necessary to maintain the target water content.Miracle-Gro®fertilizer (24%N:3.5%NH 4+–N and 20.5%CO(NH 2)2–N;8%P 2O 5;16%K 2O;0.02%B;0.07%Cu;0.15%Fe;0.05%Mn;0.0005%Mo;and 0.06%Zn)was applied twice in solution at 1and 25DAP to achieve N fertilizer rates of 100kg N ha −1and 50kg N ha −1,respectively.At 39DAP,the aboveground biomass was harvested,oven-dried at 70°C to constant weight,and weighed.Soil samples were also collected,air-dried and sieved to pass through 2-mm screen for later u in chemical analys.Roots were carefully removed from the rest of the soils.Pieces of biochars attached on the roots were returned to the same pots and were ud to grow the cond crop of corn.The cond crop was planted 4days after the first crop harvest.The procedures of crop management were the same as the first crop.2.4.Biochar,Soil,and Plant Analys
Proximate analysis (VM,ash,and fixed C contents)of biochars was measured following ASTM 1762-84(American Standard of Testing Ma-terial,2001).The contents of VM,ash,and fixed C of TK biochar were 35.79%,2.35%,and 61.86%,respectively;while tho of FC biochar were 14.65%,3.85%,and 81.50%,respectively (Table 2).The ash compo-nents were measured by Hazen Rearch,Inc.,Golden,Colorado,USA.The pH 0of biochars was estimated following Gillman (2007).In brief,nine samples at 2g each of each biochar type were ud.The adsorption sites were saturated with Ca 2+by equilibrating with 20ml of 0.1M CaCl 2for 2h.The excess Ca 2+was removed by centrifugation and discarding of the supernatant.This step was performed 3times employing lower ionic strength (0.002M)of CaCl 2.Thereafter,pH of the biochar samples was adjusted to cover a gradient that includes the expected pH 0employing either an acid 0.1M HCl,or an alkali satu-rated Ca(OH)2.They were left overnight to reach an equilibrium after which the pH was determined and recorded as pH 0.002.To obtain pH at 0.05M (pH 0.05),the suspension was equilibrated with 0.5ml of 2M CaCl 2.ΔpH was calculated as the difference between pH 0.05and pH 0.002.The pH 0is that where ΔpH equals zero.
Soil pH was determined in a 1:5soil to DI water ratio.Soil total C and N contents were determined using a Shimadzu TOC-VCSH high-nsitivity combustion TOC analyzer (Shimadzu Corp.,Kyoto,Japan).
Mineral N (NH 4+and NO 3−
)was extracted by 2M KCl extraction.Ammo-nium was subquently determined by salicylate –hypochlorite method (Gentry and Willis,1988)and NO 3−by Cd reduction method (Mulvaney,1996)using an EasyChem Discrete Autoanalyzer (EasyChem,Systea Scienti fic,Oak Brook,IL).Phosphorus was extracted with Bray-2solution
(Jones,2001)and determined on a Shimadzu UV –VIS spectrophotometer (UVmini 1240,Systea Scienti fic,Oak Brook,IL)at an absorbance of 820nm.Basic cations (K +,Ca 2+,and Mg 2+)were extracted by 1M NH 4OAc at pH 7(Pansu and Gautheyrou,2006),and Al 3+by 1M KCl (Bertsch and Bloom,1996),while soluble Mn was measured in a satu-rated paste extract (Porter et al.,2004).Cations were determined by in-ductively coupled plasma spectrophotometry on a Thermo Jarrell Ash Atom Scan 16instrument (Franklin,MA).Soil cation exchange capacity (CEC)was measured by 1M NH 4OAc extraction method at pH 7(Pansu and Gautheyrou,2006),and NH 4+concentration for calculation of CEC was determined colorimetrically using a flow-injection analyzer (FIAstar®5012,FOSS Tecator,Sweden).
Shoot and root biomass of corn were measured by weighing from each pot after they were oven-drie
d at 70°C for 72h or till achieving the constant weight.The shoot tissue samples were ground and sieved to pass through a 2-mm screen.Plant nutrient concentrations (K,Ca,Mg,and Mn)were determined by combusting 0.5g oven-dried tissue,digesting in 1M HCl,and measuring on an inductively couple plasma spectrophotometer.2.5.Statistical Analysis伤感英文名
Three-way analysis of variance (ANOVA)was ud to determine the effect of soil type,biochar type and application rate,time after biochar application,and their interactions on corn biomass,corn shoot tissue nutrient concentrations,and soil properties.The treatment means were compared using Tukey's Studentized Range Test.The differences between initial pH and Al in the Khorat soil versus tho in control treat-ment in the first crop were compared using paired t-test.All statistical analys were performed using SAS software version 9.1(SAS Institute,Cary,NC).Plotting,fitting,and equations of regression analysis,as well as calculations of coef ficient of the determination (r 2)were performed using SigmaPlot software version 12.3(SYSTAT software,Inc.,Chicago,IL).In all analys,differences were considered to be signi ficant at p ≤0.05.3.Results
3.1.Biochar Properties
FC biochar had higher fixed carbon (fC)content,ash content,and ash constituents of mineral oxides,b
ut lower VM content than TK biochar (Table 2).Among the elements in ash some of which are sources of plant macro-nutrients,Ca and K constituted the two highest contents,
Table 2
Chemical properties of Thai traditional kiln (TK)and Flash Carbonization ™(FC)biochars ud for the plant bioassay experiment:(a)proximate analysis values (VM,ash,and fC contents)
and elemental contents in biochar ash;(b)pH,charge property (pH 0),extractable mineral N (NO 3−and NH 4+如何找客户
).(a)Proximate analysis and ash components Biochar
Proximate analysis (%)Elemental content in ash a (g kg −1)VM b
Ash fC c Si Al Fe Ca Mg K P TK biochar 35.79 2.3561.860.720.140.50 5.410.43 5.100.50FC biochar
14.65
3.85
81.50
1.04
0.33
2.29
10.42
0.59
7.81
0.86
(b)pH,charge property,and mineral N contents Biochar
pH
Charge property Extractable mineral N (mg kg −1)(BC d :H 2O =1:5)
pH 0NO 3−NH 4+TK biochar 6.52 6.380.323.96FC biochar
8.92
8.13
ND e
11.87
a Dry weight basis of biochar.
b VM,volatile matter.
c fC,fixe魔芋烧鸭的做法
d C.d BC,biochar.
e
ND,not detectable.
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S.Butnan et al./Geoderma 237–238(2015)105–116
while Mg and P were the two lowest in both biochars.In addition,Fe and Ca contents were significantly lower in TK than FC biochars while extractable NH4+was greater in TK than FC and extractable NO3−was found only in TK biochar.As a conquence of higher ash content in FC than TK biochar,higher pH was found in the former(pH8.92)than the latter biochar(pH6.52).
冰心的散文集Pyrolysis temperature influenced pH0of biochars ud in this study as en in a higher pH0value in FC biochar than in TK biochar(Table2). pH0is the pH at which the net charge(of variable charged materials) equals to zero(Uehara and Gillman,1981).
3.2.Plant Respons
3.2.1.Corn Above-ground Biomass
Corn biomass responded differently(p≤0.01)to soils of different textures and mineralogy(Table3).In the Khorat soil,application of FC biochar immediately negatively affected corn biomass especially at the highest(4%)rate relative to the control(Fig.1a).However,in the Wahiawa soil,there were no signific
ant effects of both biochars in the first crop relative to the control(Fig.1b),but significant positive effects appeared only later in the cond crop under the higher rates(2and4%) (Fig.1d).It is notable that in the cond crop,both biochars produced positive effects in both soils at all rates with the exception of the FC bio-char at the low(1%)rate(Fig.1c and d).Contrary to our hypothesis,the effects of the biochars on corn biomass were not only short-lived,but also carried over from thefirst to the cond crop as shown initially by the significant(p≤0.001)time effect on the biomass(Table3).This showed that the time after biochar application exerted significant influ-ence on the biomass.The above results as well as thefindings that corn biomass of the cond crop in the controls in both soils were significant-ly depresd compared to tho of thefirst crop(Fig.1a vs c and b vs d)also testified to this time effect.
Corn biomass also responded differently(p≤0.001)to the two bio-char types produced under different temperature regimes as well as to the three-way interactions of soils×biochar type×time(p≤0.05) (Table3).Overall,the TK biochar produced higher corn biomass than the FC biochar in both soils and cropping cycles(Fig.1).In thefirst crop cycle,TK biochar produced average corn biomass of13.2g pot−1, while FC biochar produced11.8g pot−1.Similarly,in the cond crop, average corn biomass under TK biochar was10.1g pot−1,while that of FC biochar was8.2g pot−1.In addition,in the Khorat s
oil,FC biochar at the highest rate(4%)significantly depresd the biomass in thefirst crop,while the TK did not cau any significant effect compared to the control(Fig.1a).Furthermore,in the cond crop,the highest rate of FC biochar also significantly depresd corn biomass below the same (4%)and lower(2%)rates of the TK biochar(Fig.1c).In addition,this highest rate of FC biochar also brought about a growth depression below tho of its lower rates.
3.2.2.Tissue Nutrient Concentrations and Ratios
In general,all lected tissue macro-nutrient(K,Ca,Mg)concentra-tions were significantly affected by type and rate of biochar in the Khorat soil in both thefirst crop and cond crop periods,except K which significantly changed in both soils in the longer term(Table4).
In the Khorat soil in thefirst crop,tissue K concentrations incread, while Ca and Mg concentrations decread with increasing rates of both biochars(except for1%FC biochar),however significant differences compared to the control were only found at the highest rate(4%)of FC biochar(Table4).In the cond crop,significant increas in K con-centrations over the controls were obrved under4%FC biochar in both soils.In the Khorat soil,Mg concentrations were much lower than the TK counterpart at the highest rate of FC biochar.This decrea was substantiated by significantly lower
Mg uptake by plants under FC (12.1mg pot−1)compared with TK(32.6mg pot−1)biochar.In addi-tion,the4%rate of FC also depresd the Mg concentration below that of the lower rate(2%).
To further investigate interactions among the cations,ratios of con-centrations of Ca:K and Mg:K were considered(Table5).Significant treatment effects on such ratios were found only in the Khorat soil in both cropping cycles.Tissue Ca:K and Mg:K ratios significantly de-cread with increasing rates of both biochars in thefirst crop while in the cond crop,significant decreas of Ca:K and Mg:K ratios were found only at the highest rate of FC biochar compared to2%FC biochar. There were significant polynomial relationships between extractable soil K concentration and tissue Ca concentration in both thefirst and cond crops.In thefirst crop,tissue Ca concentrations were significant-ly reduced by increasing extractable soil K concentration(r2=0.67; p≤0.01)(Fig.2a).Meanwhile,in the cond crop,tissue Ca concentra-tions incread with soil K concentrations up to a threshold level of 32.5mg K kg−1beyond which they decread(r2=0.43;p≤0.01) (Fig.2b).
Tissue Mn concentrations showed decreasing trends relative to the controls under increasing rates of both biochars in both soils at both times(Table4).The decreas were significant under the highest rates(4%)of FC biochar.It was notable that in the Wahiawa soil in the cond crop,application
of both types of biochars significantly de-cread tissue Mn concentration below that of the controls,and Mn con-centration of the control in the cond crop was2.6times higher than that of thefirst crop(Table4).Mangane to Ca ratios were all below the critical point of80(dos Anjos Reis,2002)in thefirst cropping cycle suggesting the abnce of Mn toxicity(Table6).In the cond planting,however,Mn:Ca reached121in the control treatment indicat-ing toxic conditions with both biochars significantly lowering Mn:Ca ratio compared with the control.
3.3.Soil Properties
In thefirst crop cycle,soil pH was not affected by biochar amend-ment except in the Khorat soil amended with the highest rate of FC biochar(Table7a).On the other hand,in the sandy soil,pH of the un-amended(control)treatment was significantly lower than the initial pH.Meanwhile,in the cond crop,significant pH increas over the control were found in higher rates of both biochars in both at the highest rate of FC and TK biochars in both soils,and at2%rate of the FC biochar in the Wahiawa soil(Table7b).Soil pH showed a trend of higher values under FC compared with TK biochar with a significant increa at the highest rate for the FC biochar in the Khorat soil only.
Extractable K and Ca concentrations mostly incread in thefirst crop with increasing biochar rates i
n both soils with the exception of that under1%TK biochar in the Wahiawa soil.However,the increa was significant only at the4%rate for the FC biochar compared to their respective controls(Table7a and b).Similarly,Mg concentrations
Table3
Analysis of variance(ANOVA)showing the effects of soil types,biochar types,biochar
application rates,time after biochar application,and their interactions on corn biomass,
soil pH,and soil Mn concentration.
Source of variance df Corn biomass Soil properties
pH Mn狗英语怎么读
Soil(S)1*****–
Biochar type(Bt)1********结婚用英语怎么说
Biochar rate(Br)3*********
Time(T)1******ns
S×Bt1ns**–
S×Br3ns*–
S×T1***ns–
Bt×Br3******
Bt×T1ns****
Br×T3***ns***
S×Bt×T3*ns–
*p≤0.05;**p≤0.01;***p≤0.001;and ns=not significantly different(F-test).
108S.Butnan et al./Geoderma237–238(2015)105–116
also showed a signi ficant increa at the highest application rate of FC biochar in the Khorat soil (Ta
ble 7a).In the cond crop,K,Ca,and Mg concentrations in the Khorat soil were greatest at the highest rate of FC biochar,and the Ca and Mg concentrations under FC biochar were signi ficantly higher than tho of TK biochar at the same rate.Mean-while,in the Wahiawa soil in the cond crop period,K concentration reached a maximum at the highest rate of FC biochar and it was greater than the lower rates (1%TK and 2%TK and FC biochars)(Table 7b).Cal-cium concentration in the Wahiawa soil was greatest at the highest rate of FC biochar,however,Mg concentrations showed signi ficant decreas in all biochar amended treatments,compared to the controls.
Two elements known to have potential phytotoxic effects in acid soils are Al (in Khorat soil)and Mn (in Wahiawa soil)(Porter et al.,2004).Aluminum concentrations in the Khorat soil in the first crop decread signi ficantly below the control with increasing rates of both biochars (Table 7a).However,in the cond crop,signi fi-cant decreas in Al concentration below the control were only found under 2%and 4%rates of FC biochar.At the end of the first crop,soil pH showed a signi ficant negative effect (r 2=0.89;p ≤0.001)on ex-tractable Al in the Khorat soil (Fig.3a).This effect persisted through to the cond crop where high soil Al concentration showed a negative ef-fect on shoot (r 2=0.42;p ≤0.01)(Fig.3b)and root (r 2=0.49;p ≤0.01)(Fig.3c)biomass.For the Oxisol,Mn concentrations in the sat-urated paste extract were above 0.5mg L −1,the concentration consid-ered toxic (Porter et al.,2004),and showed a general increa with the addition of biochar (Table 7b).
居住的英文4.Discussion
4.1.Biochar Characteristics as Affected by Pyrolysis Conditions
Pyrolysis temperatures signi ficantly in fluenced chemical properties of biochars.Similar to previous reports,fC,ash,and VM contents of bio-chars were primarily affected by pyrolysis temperature (Abdullah et al.,2010;Deenik et al.,2010).High fC and ash,but low VM contents of FC biochar were results of its high production temperature relative to tho of the TK biochar.Ash is a principal factor determining elemental contents and pH value of biochars (Yuan et al.,2011).Higher elemental contents of FC compared with TK biochars were the results of higher ash content from elevated temperatures.Yuan et al.(2011)reported that al-kalinity and pH of biochars incread with increasing pyrolysis temper-atures.In addition,the higher pH of FC than TK biochars was the result not only of higher ash contents in the former biochar,but also progres-sive loss of acidic surface functional groups (mainly carboxylic acids)and VM under high production temperature (Mukherjee et al.,2011;Singh et al.,2010).
The variability of types and contents of elemental constituents of ash in biochars was in fluenced mainly by feedstock type and pyrolysis tem-perature (Antal and Gronli,2003).Eucalyptus wood has b
een reported to have Ca and K as its major elemental components (Abdullah et al.,2010).This supports the high contents of Ca and K relative to other ele-ments in both biochars.In addition,the higher melting points of the two elements than other elements contributed to their
persistence,
Fig.1.Different application rates of Thai traditional kiln (TK)and Flash Carbonization ™(FC)biochars affecting corn shoot dry weight:(a)the Khorat soil in the first crop;(b)the Wahiawa soil in first crop;(c)the Khorat soil in the cond crop;(d)the Wahiawa soil in the cond crop.Bars with the same lower ca letter within the same soil type and crop and tho with the same upper ca letter within a soil type but different crops are not statistically different (p ≤0.05;Tukey's Studentized Range Test).Error bars reprent SEM.
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S.Butnan et al./Geoderma 237–238(2015)105–116
and hence to their higher contents compared with other elements lost during pyrolysis(Abdullah et al.,2010;Wu et al.,2011).Elemental con-tent of the TK biochar was also affected by the cooling down process employing water.The u of water in the cooling down process has been reported to leach out some mineral elements from biochars,for example,substantial removal of Ca from biochars via water leaching has been reported by Wu et al.(2011).This earlierfinding supports our results which showed significantly lower contents of Fe and Ca in TK compared to FC biochars.The TK biochar not
only had lower ash con-tent,but also lost some of the ash constituent elements through water leaching during the cooling down process.The cooling down step in-volved placing the TK biochar in the open air and applying water to hasten cooling.Lower extractable NH4+concentration in FC than TK bio-chars was likely the result of N loss due to higher temperature during pyrolysis of FC biochar.At the relatively low temperature reached in the traditional kiln process,a large proportion of N is still retained in biochar structure and NH3loss is reduced(Hansson et al.,2004).Pres-ence of NO3−in TK biochar was likely due to oxidation of NH4+.
Biochar charge properties were also affected by pyrolysis tempera-ture.The pH0of a variable charged ,soil or biochar)is the pH at which its net surface charge equals zero.When pH is higher than pH0,net negative surface charge results and conquently the bio-char acquires cation exchange capacity(CEC)(Uehara and Gillman, 1981).The TK biochar had lower pH0than the FC biochar,hence at the same pH of the environment where the biochars exist,the TK biochar would be expected to have higher CEC than the FC biochar.Lower pH0 in the TK compared to the FC biochar was a result of lower production temperature prerving acidic functional groups that potentially con-tribute to CEC(Lau et al.,1986;Solar et al.,1990).Results of this study were consistent with Gaskin et al.(2008),Kloss et al.(2012),and Singh et al.(2010),who reported that CEC of biochars
decread with increasing production temperature.In addition,it is likely that the pro-duction process of the TK biochar leads to substantial surface oxidation during the cooling down pha of the pyrolysis process which involves applying water to hasten cooling.This process can enhance surface ox-idation or aging of the biochar(Spokas,2010)leading to increasing CEC. The cooling down process can be likened to the production of activated carbon from charcoal via the u of water vapor to increa its adsorp-tion capacity(Budinova et al.,2006).On the other hand,FC biochar was cooled down in a aled chamber(Antal,2004)and hence unlikely to have undergone oxidation.
Table4
Nutrient concentrations in corn shoot tissue in the Khorat and Wahiawa soils as affected by application of different rates of Thai traditional kiln(TK)and Flash Carbonization™(FC)bio-chars in thefirst crop(T1)and cond crop(T2)periods.
Treatment Selected tissue nutrient concentration(g kg−1)
K Ca Mg Mn
T1T2T1T2T1T2T1T2
Khorat soil
Control10.8c†19.3b 3.84ab 3.48 2.58a 1.19b–d0.134a0.281ab 1%TK biochar15.4c14.5b 3.23ab 3.76 2.12b 1.16d0.083b0.297a
2%TK biochar20.6bc14.3b 3.03b 4.63 1.87bc 1.77ab0.061b–d0.142bc 4%TK biochar30.8b15.1b 3.08ab 4.70 1.65cd 1.75a–c0.056b–d0.126bc 1%FC biochar20.4bc17.2b 3.99a 4.10 1.97bc 1.46a–d0.067b–c0.166a–c 2%FC biochar28.7b15.5b 3.17ab 5.88 1.45d 1.89a0.037c–d0.179a–c 4%FC biochar43.0a31.5a 2.76c 3.58 1.32d 1.17cd0.034d0.041c
p-Value b.00010.00030.00520.055b.00010.0015b.00010.0022
F-test********ns**********
C.V.(%)17.3712.6210.3217.607.3910.6117.0227.51
Wahiawa soil
Control44.331.2b 2.97 3.38 2.22 2.960.159a0.408a
1%TK biochar44.032.5b 2.90 3.75 2.25 2.860.140ab0.169b
+2%TK biochar43.627.9b 3.18 3.52 2.20 2.790.136ab0.163b
4%TK biochar44.343.7ab 3.37 3.72 2.28 2.210.103ab0.156b
1%FC biochar56.146.2ab 3.14 3.58 2.39 2.690.125ab0.121b
2%FC biochar47.035.9ab 3.58 3.60 2.45 2.260.096b0.093b
4%FC biochar50.053.9a 3.41 3.93 1.94 2.500.084b0.078b
p-Value0.0900.0160.40940.9620.2800.5840.0060.0004
F-test ns*ns ns ns ns*****
C.V.(%)11.0613.9212.4716.669.9117.9812.7725.04
*p≤0.05;**p≤0.01;***p≤0.001;and ns=not significantly different(F-test).
T1=thefirst crop period(39days after biochar application or at the harvest of thefirst crop),T2=the cond crop period(82days after biochar application or at the harvest of the cond crop).
†Means within a column followed by the same letter are not significantly different at p≤0.05(Tukey's Studentized Range Test).
Table5
Corn tissue Ca:K and Mg:K ratios in the Khorat and Wahiawa soils as affected by different
application rates of Thai traditional kiln(TK)and Flash Carbonization™(FC)biochars in
thefirst crop(T1)and cond crop(T2)periods.
Treatment Tissue Ca:K ratio Tissue Mg:K ratio
T1T2T1T2
Khorat soil
Control0.356a†0.164bc0.239a0.053b
1%TK biochar0.211b0.261a–c0.139b0.081ab
2%TK biochar0.147cd0.327ab0.091c0.111a
4%TK biochar0.100de0.328ab0.053d0.118a
1%FC biochar0.195bc0.256a–c0.096c0.085ab
2%FC biochar0.111ed0.380a0.051de0.114a
4%FC biochar0.067e0.114c0.032e0.041b
p-Value b.00010.006b.00010.0005
F-test***********
C.V.(%)10.4419.977.3113.88
Wahiawa soil
Control0.0670.1080.0500.064
1%TK biochar0.0660.1150.0510.088
2%TK biochar0.0730.1160.0510.088
4%TK biochar0.0760.0710.0510.051
1%FC biochar0.0730.0750.0560.056
2%FC biochar0.0770.1450.0530.068
4%FC biochar0.0680.0730.0390.046
p-Value0.660.470.170.05
F-test ns ns ns ns
C.V.(%)14.6741.3413.7619.18
**p≤0.01;***p≤0.001;and ns=not significantly different(F-test).
†Mean within column followed by the same letter are not significantly different at
p≤0.05(Tukey's Studentized Range Test).
110S.Butnan et al./Geoderma237–238(2015)105–116
