Long-term combined chemical and manure fertilizations increase soil organic carbon and total nitrogen in aggregate fractions at three typical cropland soils in China
Y.T.He a ,W.J.Zhang a ,M.G.Xu a ,?,X.G.Tong b ,F.X.Sun a ,J.Z.Wang a ,S.M.Huang c ,P.Zhu d ,X.H.He a ,e
a
Ministry of Agriculture Key Laboratory of Crop Nutrition and Fertilization,Institute of Agricultural Resources and Regional Planning,Chinese Academy of Agricultural Sciences,Beijing 100081,China b
College of Resources and Environment,Northwest A &F University,Yangling,Shannxi 712100,China c
Institute of Plant Nutrition,Resources and Environment,Henan Academy of Agricultural Sciences,Zhengzhou 450002,China d
Centre of Agricultural Environment and Resources,Jilin Academy of Agricultural Sciences,Changchun 130033,China e
School of Plant Biology,University of Western Australia,Crawley,WA 6009,Australia
H I G H L I G H T S ?Assessed the effects of 17years fertilization on SOC,TN and its fractions.
?Manure increased all indexes but straw return had no effects on all indexes at GZL.?Chemical fertilization had no effects on TN but decreased MBC in GZL and QY.
?cfPOC was the most sensitive indicator and MOC,MTN was the main sequestrated form.?
Straw return was site-dependent and manure was the best for improving soil quality.
a b s t r a c t
a r t i c l e i n f o Article history:
Received 25January 2015
Received in revised form 26May 2015Accepted 2June 2015
Available online 25June 2015Editor:D.Barcelo
Keywords:
Long-term fertilization Particulate organic carbon Mineral associated organic C
Microbial biomass carbon and nitrogen Luvic Phaeozems Calcaric Cambisol Ferralic Cambisols
Soil organic carbon (SOC),total nitrogen (TN),microbial biomass carbon (MBC)and nitrogen (MBN)are impor-tant factors of soil fertility.However,effects of the combined chemical fertilizer and organic manure or straw on these factors and their relationships are less addressed under long-term fertilizations.This study addressed changes in SOC,TN,MBC and MBN at 0–20cm soil depth under three 17years (September 1990–September 2007)long-term fertilization croplands along a heat and water gradient in China.Four soil physical fractions (coarse free and ?ne free particulate organic C,cfPOC and ffPOC;intra-microaggregate POC,iPOC;and mineral associated organic C,MOC)were examined under ?ve fertilizations:unfertilized control,chemical nitrogen (N),phosphorus (P)and potassium (K)(NPK),NPK plus straw (NPKS,hereafter straw return),and NPK plus manure (NPKM and 1.5NPKM,hereafter manure).Compared with Control,manure signi ?cantly increased all tested parameters.SOC and TN in fractions distributed as MOC N iPOC N cfPOC N ffPOC with the highest increase in cfPOC (329.3%)and cfPTN (431.1%),and the lowest in MOC (40.8%)and MTN (45.4%)under manure.SOC sig-ni ?cantly positively correlated with MBC,cfPOC,ffPOC,iPOC and MOC (R 2=0.51–0.84,P b 0.01),while TN with cfPTN,ffPTN,iPTN and MTN (R 2=0.45–0.79,P b 0.01),but not with MBN,respectively.Principal component analyses explained 86.9–91.2%variance of SOC,TN,MBC,MBN,SOC and TN in each fraction.Our results demon-strated that cfPOC was a sensitive SOC indicator and manure addition was the best fertilization for improving soil fertility while straw return should take into account climate factors in Chinese croplands.
?2015Elsevier B.V.All rights reserved.
1.Introduction
In cropland soil,the preservation or improvement of soil quality and productivity is of major importance.Soil organic carbon (SOC)is closely associated with a wide range of physical,chemical and biological
properties,and thus has been recognized as a key component of soil quality (Reeves,1997).Fertilizer application has been widely used as a common management practice to increase soil carbon (C)sequestration and SOC level.For instance,to increase soil fertility and obtain a satisfac-tory yield,manures have been used for nearly 4000years in China,Japan and Korea (Dormaar et al.,1988).In addition,in cropland soils SOC also represents a potential sink of atmospheric CO 2.As a result,under-standing the impact of chemical fertilizer and manure application
Science of the Total Environment 532(2015)635–644
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Xu).https://www.doczj.com/doc/8d16210503.html,/10.1016/j.scitotenv.2015.06.0110048-9697/?2015Elsevier B.V.All rights
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on SOC and its fractions could provide valuable information for main-taining or implementing environmentally sustainable management practices for agroecosystems.
In general,the readily decomposable labile C is sensitive and re-sponds more quickly to changes in management practices than recalci-trant C and thus is used as an early indicator of SOC changes(Campbell et al.,1997).The microbial biomass plays a critical role in regulating the C and N cycling processes in soils,and microbial biomass carbon(MBC) and nitrogen(MBN)are sensitive indicators for changes resulting from agronomic practices and other perturbations of soil ecosystems though they are only a small part of SOC and total nitrogen(TN).Numerous studies have reported the effects of fertilization on MBC or MBN,but no consistent results have been obtained(B?hme et al.,2005;Zhong and Cai,2007).For example,organic manure tends to increase MBC by direct C input and/or the change of microbial community composition (Sun et al.,2004),while chemical fertilization have often produced con-tradictory effects(He et al.,2013;Sarathchandra et al.,2001).This un-certainty is partly attributed to the short-time study and to variations in soil type,climate condition,and crop system under different fertiliza-tions.In addition,the structure composition of the different fertilizers, the changes in soil enzyme activities and abundance and function of the soil microbial community under different fertilizations also contrib-ute to the contradictory effects(Giacometti et al.,2013,2014).There-fore,it is important to assess the effects of different fertilizations on MBC or MBN in variable soil types at a long-time scale to better under-stand soil C transformation or accumulation.
Meanwhile,SOC fractions are characterized by differential stabilities and turnover rate,thus also been extensively used as sensitive indica-tors to provide insight into the consequences of management practices that could not be gleaned from studies of total SOC.Six et al.(2002)pro-posed a physical fractionation procedure and the associated conceptual SOC model that separated the bulk SOC pool into four conceptual aggre-gate fractions according to different protection mechanisms.These four conceptual fractions are(1)coarse free and(2)?ne free particulate or-ganic C(cfPOC and ffPOC,unprotected SOC inter-aggregate),(3)intra-microaggregate particulate organic C(iPOC,physically protected SOC) and(4)mineral associated organic C(MOC,chemically and biochemi-cally protected SOC).This conceptual model could give an opportunity to understand the effect of soil microbial activities during SOC biodegra-dation under different management practices(Six et al.,2002).In addi-tion,this physical fractionation technique has been employed to separate SOC fractions that stabilize C and thus could have important implications for soil C sequestration at a long-time scale.In a44year ?eld experiment,both cattle manure and crop residue treatments in-creased SOC and most of these increases(up to72%)were stored in MOC fraction(Courtier-Murias et al.,2013).However,limited informa-tion still exists regarding the long-term impacts of different fertiliza-tions on SOC physical fractions,particularly in cropland soils in China.
The quality and quantity of SOC have been suggested as major fac-tors affecting soil N dynamics,and one of the major roles of organic matter in soil fertility is to release N and other nutrients for crop growth (Hart et al.,1994).Changes in N content in soil fractions therefore may be a good indicator of soil fertility and plant N supplying capabilities of a given soil.For instance,studies have reported changes in N contents within different density fractions under different fertilization manage-ments(Compton and Boone,2002).However,less is known about the responses of TN content in physical fractionations under long-term dif-ferent fertilizations.
Along a water and heat gradient from north to south,black soil (Luvic Phaeozems for FAO classi?cation,Leptic Phaeozems for WRB classi?cation),?uvo-aquic soil(Calcaric Cambisol for FAO classi?cation and Fluvic Cambisol for WRB classi?cation)and red soil(Ferralic Cambisols for FAO and Ferric Acrisols for WRB classi?cation)are main soil types distributing from northwest,central and south of China, where also the important agricultural regions are located.To develop ef-?cient soil fertility management practices,long-term experiment net-works have been established since1990to examine the effects of continuous applications of chemical fertilizer and the combination of chemical fertilizer and manure on crop yield and soil fertility over these https://www.doczj.com/doc/8d16210503.html,ing soils under?ve17years long-term(September 1990–September2007)fertilizations(chemical fertilizer with or with-out organic manure)from three sites(~500km away from each site), the aims of this study were thus to address the effects of the sole chem-ical fertilization and the combined fertilization of chemical fertilizer and organic manure on(1)variations of MBC and MBN;(2)variations of SOC and TN accumulations in the whole soil and different physical frac-tion pools;(3)relationships between MBC or MBN,fraction pools and SOC or TN accumulations.Here,we paid special attention on the distri-bution and accumulation of SOC and TN in soil physical fractions.The expected results could identify the key fractions and the best fertilizer management practices for SOC accumulations under different fertilizer managements across different cropping systems in China.
2.Materials and methods
2.1.Site description
Along a water and heat gradient from north to south of China,three selected long-term?eld fertilization sites(established since September 1990)are located in Gongzhuling(GZL),Jilin,northeast China; Zhengzhou(ZZ),Henan,central China;and Qiyang(QY),Hunan,south-ern https://www.doczj.com/doc/8d16210503.html,rmation on basic,geography,climate and soil chemical properties of these three sites in1990is brie?y given in Table1.
2.2.Cropping systems and plant harvest
Two years before the establishment of these three long-term fertili-zation sites,local crops as follows were cultivated without fertilization to reduce soil fertility variability.The cropping system differed in these three sites:a mono-maize cropping(late April to late September)
Table1
General description of geography and soil properties(0–20cm in1990)at the three17years(1990–2007)long-term experimental sites in China.
Gongzhuling Zhengzhou Qiyang
Location43°30′,124°48′34°47′,113°40′26°45′,111°52′
Climate Mild-temperate,semi-humid Warm-temperate,semi-humid Subtropical,humid monsoon
Cropping system Single-cropping,maize Double-cropping,maize/wheat annually Double-cropping,maize/wheat annually Precipitation(mm)5256321250
Mean temperature(°C) 4.514.318.0
FAO soil classi?cation Luvic Phaeozems Calcaric Cambisol Ferralic Cambisol
Soil texture Clay loam Light loam Light loam
Clay content(%)31.013.435.2
Bulk density(g cm?3) 1.24 1.41 1.19
Initial SOC(g kg?1)13.5 6.707.89
Total N(g kg?1) 1.420.67 1.07
pH(soil:water=1:2.5)7.28.3 5.7
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at GZL,and a wheat –maize double-cropping at both ZZ (mid-October to early June for wheat and mid-June to late September for maize)and QY (early November to early May for wheat and early April between wheat strips to July for maize).No irrigation was given to crops at GZL and QY,but two or three times of irrigations at ZZ to wheat and once to maize (about 75mm each time)depending on precipitation.Pesticides (3kg ha ?1carbendazim for wheat rust at a jointing stage,3.75kg ha ?1omethoate for aphids at wheat grain ?lling stage,45kg ha ?1carbofuran for corn borer at trumpet stage)were applied during growth when needed.Weeds were removed by hand.All above-ground biomass were manually harvested and then separated as grains and straws,which were oven dried to constant weight.
2.3.Experimental design and fertilization rates
The ?eld experiments were in a randomized block design with 3replications in ZZ (plot size 45m 2),2replications in QY (plot size 196m 2)but no replication in GZL (plot size 200m 2).Five treatments were examined in this study:(1)unfertilized control;(2)chemical ni-trogen (N)and phosphorus (P)plus potassium (K)(NPK);(3)NPK plus straw (NPKS);(4)NPK plus manure (NPKM);(5)150%NPKM (1.5NPKM).
The annual fertilization rates were summarized in Table 2.At each site,an equivalent total amount of N was applied to all treatments ex-cept an extra N from wheat straw under NPKS at QY.In all sites the chemical sources of N,P and K were urea,calcium triple superphosphate and potassium sulfate,respectively.The manure was horse manure from 1990to 1998and cattle manure from 1999to 2007at ZZ,whereas pig manure from 1990to 2007at both GZL and QY.For the two manure treatments,30%of the total N was from the chemical fertilizer and the rest 70%from the manure.The additional added chemicals P and K in the manure and straw were not adjusted.Chemical fertilizers were applied before seeding,with 30%for wheat and 70%for maize with no topdressing at ZZ and QY,while one-third of the chemical N and the total P and K were applied at sowing,and the rest of N as top-dressing at the jointing stage at GZL.Meanwhile,the entire amount of manure and straw were once applied before wheat seeding.
2.4.Soil sampling
Soil samples at 0–20cm depth were collected in September 2007using a 10cm diameter soil auger.A total of 9soil cores from each plot were collected with 3cores as one composite sample,which was then divided into two subsamples.One subsample was stored at 4°C prior to the MBC and MBN analyses;another was air-dried and ground for the determination of soil chemical and physical properties. 2.5.Determination of MBC and MBN
The determination of MBC and MBN was in accordance with chloro-form fumigation extraction method (Vance et al.,1987)and the conver-sion factor of 0.45for both MBC and MBN.The amount of total organic C (TOC)in the extracts was measured using an automatic TOC analyzer (vario TOC cube,Elementar,Hanau,Germany).2.6.Determination of SOC physical fractions
Determination of soil physical fractionations was in accordance with Gale et al.(2000)and Six et al.(2000).In this study four physical frac-tions were adopted (Tong et al.,2014):(1)the coarse free particulate organic C (cfPOC,N 250μm,unprotected SOC);(2)the ?ne free POC (ffPOC,53–250μm,unprotected SOC);(3)the intra-microaggregate POC (iPOC,N 53μm from the heavy fraction of ffPOC,physically protected SOC)and (4)the mineral associated organic C fraction (MOC,b 53μm,chemically and biochemically protected SOC).2.7.Analyses of carbon and nitrogen in soils
Concentrations of SOC and TN in bulk and fraction soils were deter-mined by the wet oxidation with K 2Cr 2O 7and the semi-micro Kjeldahl methods using air-dried soil samples.2.8.Statistical analyses
One-way ANOVA was performed to test different fertilization effects on soil physicochemical properties,soil microbial properties and physi-cal fractions.Pearson linear correlations between MBC,MBN or soil physical fractions and SOC or TN were determined.Principal compo-nents analysis (PCA)was undertaken to identify soil fertility between fertilizations.Statistical signi ?cant differences were judged by LSD test at P b 0.05.Graphs were prepared using SigmaPlot 10.0.All the statisti-cal analyses were conducted using the SPSS 17.0.3.Results and discussion
3.1.Soil organic carbon and total nitrogen
Generally,signi ?cantly higher both SOC and TN among the three sites patterned as GZL N QY ≈ZZ for the same fertilization,while among ?ve fertilizations for each site as:1.5NPKM N NPKM N NPKS ≈NPK ≈Control,except a higher SOC under NPNKS at ZZ and a lower SOC under the Control at QY (Fig.1a,b,e,f,i,j).Compared with the Control,NPK plus manure (NPKM or 1.5NPKM,hereafter manure)ap-plications signi ?cantly increased SOC (42.6–97.5%)and TN (37.8–109.7%)at all three sites.These trends could attribute to greater C and
Table 2
Annual fertilization rates of N,P and K (kg ha ?1)at the three 17years (1990–2007)long-term experimental sites in China.Treatments a
Gongzhuling Zhengzhou
Qiyang Inorganic b N –P –K (kg ha ?1)
Organic N
(kg ha ?1)Inorganic N –P –K (kg ha ?1)Organic N
(kg ha ?1)Inorganic N –P –K (kg ha ?1)Organic N
(kg ha ?1)Control 0–0–0
00–0–0
00–0–0
0NPK 165–36–680353–78–1460300–53–1000NPKS c 112–36–6853238–78–146115300–53–10039NPKM d 50–36–68115238–78–14611590–53–1002101.5NPKM
75–54–103
172.5
356–117–220
173.5
135–79–149
315
a
Treatment codes:NPK:inorganic nitrogen,phosphorous and potassium,the chemical sources of N,P and K were urea,calcium triple superphosphate and potassium sulfate,re-spectively;NPKS:NPK plus straw return;NPKM:NPK plus manure;1.5NPKM:1.5times NPKM.b
Inorganic N fertilizer is as urea,P as calcium superphosphate,K as potassium sulfate.c
Straw rates (3.2to 7.5Mg ha ?1year ?1)varied with N concentration and sites (1/2wheat straw and 1/2corn straw were returned at Qiyang while only maize straw was returned at Gongzhuling and Zhengzhou).d
The manures were pig manure since 1990at Gongzhuling (23.0Mg ha ?1year ?1)and Qiyang (42.0Mg ha ?1year ?1),but horse manure from 1990to 1998and cattle manure from 1999to 2007at Zhengzhou (12.9Mg ha ?1year ?1).All such manure amounts at these three sites were averaged in the fresh weight during 1990to 2007.
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N inputs through the input of manure and/or root biomass due to better crop growth.Similar results have been reported from other long-term (10to 100years)fertilizations in cropland soils (Blair et al.,2006;Giacometti et al.,2013;Purakayastha et al.,2008).It is worth to note that a higher annual C addition with manure from NPKM to 1.5NPKM produced signi ?cant increase of sequestrated C (13.8–23.9%)and N (15.5–52.2%)at all three sites.These ?ndings indicated that the tested soils have further potentials to sequestrate considerable C and N,suggesting the signi ?cance of more organic C input from manure could build up SOC and TN pool in our study soils.
The sole chemical fertilization (NPK)generally had no effects on SOC and TN except a 22.8%increase of SOC at QY (Fig.1).The lack of re-sponse of SOC to chemical fertilizer might be due to a lower C input,while the non-response of TN might be due to the N loss via leaching,denitri ?cation or some other process such as ammonia volatilization in the cropland (Ju et al.,2009).Meanwhile,the return of straw had no in ?uence on TN at the three sites,while it signi ?cantly increased SOC at ZZ (39.5%)and QY (24.8%),but not at GZL,indicating that soil C sequestration could be enhanced,but not N sequestration,when crop
residues had been incorporated into soil.The irresponsible status of SOC at GZL might be due to the low decomposition of straw added under a lower climate temperature in north China,or to an induced SOC decomposition through the straw return.
3.2.Microbial biomass carbon and microbial biomass nitrogen
The highest MBC and MBN were observed at both GZL and in QY,but not at ZZ for the same fertilization (Fig.1c,d,g,h,k,l).Meanwhile,at all three sites a signi ?cant increase and a maximum amount of MBC and MBN were under the NMKM and 1.5NPKM treatments (Fig.1),which were similar to the pattern reported by other studies in the long-term (15–30years)fertilization experiments in other cropland soils (Liang et al.,2012;Manna et al.,2006).Compared with the Control,MBC was 16.0%–159.6%higher,and MBN was 80.6%–119.1%higher under manure treatments at the three sites.Tu et al.(2006)found that an increase in easily decomposable organic C was likely contributed to the enhanced microbial biomass.Therefore,MBC and MBN were mostly enhanced by the regular supply of the readily metabolizable C and N
under
Fig.1.Effects of 17years (1990–2007)fertilizations on soil organic carbon (SOC),total nitrogen (TN),microbial biomass carbon (MBC)and nitrogen (MBN)of bulk soils at three long-term ?eld sites in China.Data (means ±SD,n =3)with different letters denote signi ?cant differences between fertilizations in the same site (a,b,c,d,e)and between sites for the same fertilization (x,y,z)at P b 0.05.Abbreviations:NPK:inorganic nitrogen,phosphorous and potassium;NPKS:NPK plus straw return;NPKM:NPK plus manure;1.5NPKM:1.5times NPKM.GZL:Gongzhuling;ZZ:Zhengzhou;QY:Qiyang.
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manure treatments.NPKS treatment had no effects on MBC and MBN at GZL,but signi?cantly increased at ZZ,compared with the Control,which were probably due to the lower decomposition of straw in a lower cli-matic temperature at GZL and a suitable temperature and precipitation for microbial growth at ZZ.In contrast,QY is characterized by a higher temperature and humidity,which could lead to a faster straw decompo-sition,and then to a loss of straw-derived C and a release of N,thus MBC was not impacted while MBN was signi?cantly increased under NPKS (Tong et al.,2014).
Meanwhile,MBC under NPK was signi?cantly increased at ZZ (48.2%),but signi?cantly decreased at GZL(90.4%)and QY(24.3%), compared with the Control(Fig.1).The stimulated effects of NPK fertil-ization to MBC at ZZ might mainly be because of an enhanced growth of crops.At ZZ,crop yield was285%higher under NPK fertilization than under the control,which might result in an accumulation of MBC through increased root turnover and exudates in soils.Zhong and Cai (2007)also found that MBC was signi?cantly increased by NPK applica-tion in a13year long-term fertilization in China.However,the decreased MBC under NPK at GZL and QY might attribute to serious soil acidity due to a long-term N fertilization.Indeed,our previous study found that NPK treatment signi?cantly increased soil exchange-able acidity dominated by Al and elevated acidi?cation rates at QY dur-ing the decreasing of soil pH(Cai et al.,2014).In this present study,the pH was not signi?cantly changed at ZZ but signi?cantly declined from 7.64under the control to6.19under NPK at GZL,and from5.70under the control to4.44under NPK at QY after17years chemical fertilization. Therefore,the lower pH induced Al toxicity could suppress microbial ac-tivities and growth of soil microorganisms,and thus consequently lead to a reduction in microbial biomass.
3.3.Soil organic carbon and total nitrogen in physical fractions
Averagely,the recoveries of soils after the fraction procedure were 97.3%,99.3%and97.2%under different fertilizations for GZL,ZZ and QY,respectively.The MOC fraction accounted for the largest(77.4–87.2%)portion and ffPOC for the smallest(0.13–0.52%)portion
of
Fig.2.Effects of17year(1990–2007)fertilizations on soil organic carbon(means±SD)of each soil aggregate fractions at three long-term?eld sites in China.Data(means±SD, n=3)with different letters denote signi?cant differences between fertilizations in the same site(a,b,c,d,e),between sites for the same fertilization(x,y,z)and between fractions in the same site under the same treatment(α,β,γ,δ)at P b0.05.Abbreviations:cfPOC:coarse free particulate organic carbon;ffPOC:?ne free particulate organic carbon;iPOC:intra-microaggregate particulate organic carbon;MOC:mineral associated organic carbon;See Fig.1for fertilization treatments and sites abbreviations.
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soils.Additionally,the average recovery of SOC after the fraction procedure were 91.4%,107.7%and 90.3%and the recovery of TN were 85.6%,90.2%,104.3%under different treatments in GZL,ZZ and QY,respectively.
As expected,manure application (NPKM and 1.5NPKM)signi ?cantly increased SOC and TN in all four soil physical fractions compared with the Control at the three sites (Figs.2and 3).At GZL and QY,the SOC and TN in all four soil physical fractions under NPKM and 1.5NPKM were even signi ?cantly higher than those under NPKS and NPK treat-ments.Other studies also observed signi ?cant increase in SOC and TN of soil fractions under manure treatments (Purakayastha et al.,2008;Sleutel et al.,2006).Among the four soil physical fractions,the increase under manure treatments was highest in cfPOC fraction for SOC (189.2–650.6%,averaged 329.3%)and TN (185.2–841.0%,averaged 431.1%),but lowest in MOC fraction for SOC (17.1–56.7%,averaged 40.8%)and TN (3.3–74.7%,averaged 45.4%)(Figs.2and 3).In a long-term 100year ex-periment at Rothamsted,Blair et al.(2006)reported that the manure application had increased liable organic C by an average of 353%,which was close to the increase rate of this study.The cfPOC was mainly derived from plant material,which might haven been subject to partial microbial decomposition.Sleutel et al.(2006)found the combined SOC in the cfPOC and ffPOC made up 10–13%of the total SOC under different fertilization treatments in a 42year long-term cropland fertilization in Hungary.In the present study,the average proportion of these fractions varied between 9.8–22.5%and 4.7–16.7%of the bulk soil SOC and TN across the three test sites (Fig.S1),which correspond fairly with their results.In addition,there was a clear increasing trend of the proportion of the amount of SOC and TN presenting in the cfPOC and cfPTN fraction under manure,chemical fertilization or straw return treatments at the three sites,and the maximum proportion increase was under manure (from 6.9to 13.6%at GZL,6.0to 12.9%at ZZ and 5.3to 19.6%at QY)(Fig.S1).The highest increase of SOC in the cfPOC fraction in our study con ?rmed that cfPOC was a good indicator for the change in SOC under fertilizations,especially under manure management (Figs.2).
Due to a larger organic C input through straw,the straw return treat-ment also generally increased SOC and TN in each fraction at ZZ and
QY
Fig.3.Effect of 17year (1990–2007)fertilizations on total nitrogen of each soil aggregate fractions at three long-term ?eld sites in China.Data (means ±SD,n =3)with different letters denote signi ?cant differences between fertilizations in the same site (a,b,c,d,e),between sites for the same fertilization (x,y,z)and between fractions in the same site under the same treatment (α,β,γ,δ)at P b 0.05.Abbreviations:cfPTN:coarse free particulate total nitrogen;ffPTN:?ne free particulate total nitrogen;iPTN:intra-microaggregate particulate total nitrogen;MTN:mineral associated total nitrogen;See Fig.1for fertilization treatments and site abbreviations.
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(except for the ffPOC and ffPTN at ZZ),but not at GZL except for an increase in ffPOC and ffPTN,compared with the control(Figs.2and3). Compared to NPK,however,NPKS signi?cantly decreased SOC in each fraction at GZL(Fig.2a,b,c,d).These results indicated that the returned straw might have stimulated the original soil old C decomposition,and such decompositions could be offset by the new straw C amendment, hence the SOC accumulation was similar under the straw return and the control at GZL.
Chemical fertilizer signi?cantly increased SOC of cfPOC(57–197%), ffPOC(95–166%)and iPOC(26–65%),but had no effects on MOC at all three sites and on ffPOC at ZZ(Fig.2).Meanwhile,the TN of the four fractions was all increased under NPK except iPTN and MTN at GZL (Fig.3).In general iPOC was thought to be stored in aggregates to pre-vent from the decomposition of microorganisms.Chemical fertilizer contained a large amount of available N that could stimulate the growth of crop as well as the activities of microorganism that might enhance the decomposition of iPOC fraction(Liu et al.,2010).The balanced NPK fer-tilization might have a stronger stimulation effect on crop growth, which could return more residues to soil than on SOC decomposition and N loss,leading to an increased SOC and TN in the cfPOC,ffPOC
or
Fig.4.Relationships between soil organic carbon(SOC)and microbial biomass carbon(MBC)of the bulk soil,cfPOC,ffPOC,iPOC or MOC of each soil physical fraction;and between total nitrogen(TN)and microbial biomass nitrogen(MBN)of the bulk soil,cfPTN,ffPTN,iPTN or MTN of each soil aggregate fraction under three17years(1990–2007)long-term fertilization sites in China(**P b0.01and***P b0.001).See Fig.1for fertilization treatments and site abbreviations,see Figs.2and3for SOC and TN fractions.
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iPOC fraction.The organic C in the iPOC fraction across these three sites ranged7.3to15.7%of the total SOC(Fig.S1),which were similar to a range of7.3to12.0%observed by Sleutel et al.(2006).MOC was associ-ated with mineral and mainly sequestrated in soil in the form of humus, and the SOC and TN in the MOC and MTN fractions held the largest pro-portion of the total SOC(63.2–81.4%)and TN(73.1–90.0%)(Fig.S1). Meanwhile,the C input under NPK might not form enough complex or-ganic compounds associated with mineral,which accounted for the non-response of SOC in the MOC fraction under chemical fertilization (Tong et al.,2014).The increase of TN in the MTN fraction under NPK at ZZ and QY was more likely due to the residue return through a stim-ulating effect on crop growth,whereas an unchanged TN in both the iPTN and MTN fractions under NPK at GZL might be attributed to a large extent on a higher TN concentration in the bulk soil at GZL than at ZZ and QY.
Generally,for the same fertilization at the same site,higher TN in fractions generally ranked as MTN N iPTN N cfPTN N ffPTN at the three sites(Fig.3),while signi?cantly higher SOC in fractions ranked as MOC N iPOC N cfPOC N ffPOC at GZL,MOC N cfPOC≈iPOC≈ffPOC at ZZ except in ffPOC at NPKM and1.5NPKM,and MOC N cfPOC N iPOC N ffPOC at QY except under Control and NPKS(Fig.2).In addition,for the same fertilization among these three sites,higher cfPOC or cfPTN patterned as QY N GZL N ZZ,while in the other three fractions as GZL N QY N ZZ(Figs.2and3).3.4.Relationships between SOC and TN with MBC,MBN or fraction organic
C or N
The SOC signi?cantly positively correlated with MBC,cfPOC,ffPOC, iPOC and MOC(R2=0.51–0.84,P=0.01–0.001,Fig.4a,b,c,d and e), while the TN signi?cantly positively correlated with cfPTN,ffPTN, iPTN and MTN(R2=0.45–0.79,P=0.01–0.001,Fig.4g,h,i and j)respectively,but not with MBN(Fig.4f).This meant that both mi-crobial biomass and physical fractions were the components of bulk soil and they could indicate long-term changes of SOM and TN due to fertil-ization treatments.Chung et al.(2008)found that the SOC of the MOC fraction did not linearly relate with the C input and that the MOC fraction exhibited a C saturation behavior,namely,MOC might not have potential to further sequestrate soil C in soil.The signi?cantly pos-itively linear relationship between the SOC or TN of each physical frac-tions and the total SOC or TN of the bulk soil in the present study demonstrated that all of these fractions were not saturated.As a result, a potential is plausible for each physical fraction to sequestrate more C and N under different fertilizer managements at these three tested soils.
Meanwhile,SOC also signi?cantly positively correlated with TN (Fig.5a),and SOC in each fraction signi?cantly positively correlated with TN in each fraction across all three sites(R2=0.52–0.96,P= 0.01–0.001,Fig.5b,c,e and f).The C:N ratio signi?cantly decreased in the order of ffPOC(15.1)N cfPOC(14.4)≈iPOC(14.2)N MOC
(6.6).
Fig.5.Relationships between soil organic carbon(SOC)and total nitrogen(TN),microbial biomass carbon(MBC)with microbial biomass nitrogen(MBN)of the bulk soil,and between SOC with TN of each physical fractions under three17years(1990–2007)long-term fertilization sites in China(**P b0.01and***p b0.001).See Fig.1for fertilization treatments and site ab-breviations,see Figs.2and3for SOC and TN fractions.
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The C:N ratio is indicative of the capacity of a soil to store and recycle nutrients.In general,soil C:N ratio decreases with increasing of degra-dation and humi ?cation of organic matter.As a decomposition pro-ceeds,C is released during respiration and some of the mineralized N is lost through leaching or gaseous emissions while some other parts of mineralized N is reincorporated into the SOM pool (Chapin et al.,2002).The decrease of C:N ratio in the four fractions in this study indi-cates that MOC was most humi ?ed,and N was more stored than C in this fraction,which also showed the procession of SOC accumulation and sequestration in soil.
Principal components analyses (PCA)showed that overall the prin-cipal components (PC1and PC2)explained 86.9%,89.6%and 91.2%of
the variance of soil fertility (SOC,TN,MBC,MBN,SOC and TN in each fraction)in GZL (Fig.6a),ZZ (Fig.6b)and QY (Fig.6c),respectively.Soil fertility under fertilizations with the addition of manure was clearly separated with that under the chemical fertilization at all three sites,while under straw return was similar to the control at GZL,to NPKM at ZZ and to NPK at QY,which was well con ?rmed in all above-mentioned results in this study.4.Conclusions
Our results demonstrated that continuous 17year applications of manure signi ?cantly increased SOC and TN concentrations,MBC,MBN,and the SOC and TN in soil physical fraction of cfPOC,ffPOC,iPOC and MOC at three cropland sites of China along a heat and water gradient.Straw return might also have similar effects on SOC,TN,MBC,MBN and the SOC and TN in each soil physical fraction like the manure appli-cation,except in the low temperature and humidity site of GZL in north-east of China.Chemical fertilization had showed relatively less effects on the total SOC and TN accumulation in the whole and each soil fraction.As a general rule,cfPOC was the most sensitive indicator to C changes and MOC,MTN was the main form that C and TN sequestrated in soil under long-term fertilizations.MBC,SOC and TN in aggregate fractions were signi ?cantly linearly correlated to total SOC and TN in the bulk soil.The overall PCA showed that manure fertilization was the best fer-tilization management strategy while straw return should be taken into account climate factors in cropland soils in China.
Supplementary data to this article can be found online at https://www.doczj.com/doc/8d16210503.html,/10.1016/j.scitotenv.2015.06.011.Acknowledgments
We acknowledge our colleagues for their unremitting efforts to the long-term experiments.Financial support was from the National Natural Science Foundation of China (41371247)and National Basic Research Program of China (2011CB100501).References
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幼儿园中班整合教案：蛋和蛋制品 江苏省淮安市金湖县闵桥中心幼儿园徐承勤 活动目标 1．通过活动知道蛋是有营养的，对自己身体有好处。 2．在认识蛋的过程中，进一步发展观察力和语言表达能力； 3．在自助餐中形成文明的好习惯；享受生活的乐趣。 活动准备1．教师：鸭蛋；鸡蛋、鹌鹑蛋、鸽子蛋、鹅蛋各——个；蛋制品(茶叶蛋、蛋糕、蛋饼、蛋卷、荷包蛋、炒蛋、蒸蛋等)若干。 2.幼儿：每人一只碗，一把勺，一块毛巾；—-只蛋。(幼儿自带鸡蛋、鸲鹑蛋、鸭蛋) 活动过程实录 1.导入活动：引起兴趣，认识蛋的种类。 (1)师：今天我们小朋友都带了—只蛋宝宝，现在请大家先看一下你带的蛋宝宝是什么样的，叫什么名字，是哪一种小动物生出来的，然后告诉你旁边的小朋友。 (2)师：下面谁愿意把你带的蛋宝宝介绍给大家听呢? 幼A：我带的是鸡蛋，是鸡妈妈生的。 幼B：我带的是鸭蛋，是鸭妈妈生的。 (3)师：小朋友带的蛋真多，有鸡蛋、鸭蛋、鹌鹑蛋等等，我也带了一只，是什么颜色的?是什么蛋呢?是哪一种小动物生出来的呢? 幼：老师带来的蛋是白色的；是鸽蛋，是鸽子妈妈生的。 (4)、师：现在请小朋友看一看、再摸一摸你们带来的蛋，和旁边的小朋友比一比，有什么相同的地方和不同的地方。 幼A：我的蛋比他的蛋大。我的蛋是白色的，他的蛋是肉色的。 幼B：蛋壳都很光滑。 师：小朋友带来了各种各样的蛋，它们的颜色不同，有大有小，但是都是很光滑的，我们知道鸡蛋是鸡妈妈生的，鸭蛋是鸭妈妈生的。 2．认识蛋白和蛋清. (1)师：这光滑的蛋壳里到底藏了些什么东西呢?你们打开来看看就知道了，大家注意了，一只手按住杯子，另一只手拿好蛋，将蛋的中间部分对准杯口，稍重一点一磕，然后将蛋对准杯子掰开，好，我们开始。 (2)师：你们看到了什么? 幼：蛋白和蛋黄。 师：哪一部分是蛋黄？哪一部分是蛋白？ 幼：黄色的是蛋黄，透明的是蛋白。 师：哦，不管什么蛋，里面都有黄颜色的叫蛋黄，透明的粘糊糊的叫蛋清，烧熟了就成为蛋白，现在请小朋友把你们打好的蛋放人中间的盆子里。 3．粗浅介绍蛋的营养价值。 (1)师：小朋友你们每天都吃蛋吗?为什么要吃蛋呢? 幼A：有营养，吃了会长高。 幼B：吃了身体好。 师：我们小朋友每天至少吃一只蛋，但不能吃得太多，吃多了不容易消化没烧熟的蛋不要吃，里面会有很多细菌，吃了我们的肚子会痛的。 4．让幼儿讨论蛋的吃法及做成哪些蛋制品。 (1)师：平时蛋有很多种吃法，你吃过哪些蛋做的菜。 幼：荷包蛋，蛋汤，炒蛋。 (2)师：好，老师现在就把你们刚刚打开来的蛋做一份炒蛋给你们尝一尝。（教师现场操作)好，除了炒蛋还可以做成哪些菜? 幼：番茄炒蛋，蒸蛋，茶叶蛋。 (3)师：蛋除了可以做菜还可以做好吃的点心，你们还知道有哪些吗？ 幼：蛋饼，鸡蛋糕；蛋卷。 5．自助餐。
第十一章蛋和蛋制品的微生物 第一节鲜蛋内微生物污染的来源 一、卵巢和输卵管内污染 当母禽感染了病原微生物，并通过血液循环侵入卵巢和输卵管，在蛋的形成过程中进入蛋黄或蛋白。通过这一途径污染的主要是雏鸡白痢沙门氏菌、鸡败血霉形体、禽白血病病毒、减蛋综合症病毒和禽关节炎病毒等。在蛋壳形成之前，泄殖腔内细菌向上污染至输卵管，也可导致蛋的污染。 二、产蛋时污染 母禽泄殖腔的细胞可粘附在蛋壳上。当蛋从泄殖腔(40—42℃)排出体外时，由于外界空气的冷却作用，引起蛋内收缩，使附在蛋壳上或空气中的微生物，随着空气穿过蛋壳而进人蛋内。 三、蛋产出后的污染 健康母禽产下的蛋与外界环境接触，蛋壳表面可污染大量的微生物。通常一个外表清洁的鲜蛋，其蛋壳表面约有400万500万个细菌，一个肮脏的鲜蛋，其壳上的细菌可高达14000万—90000万个。蛋壳上有许多大小为4—40um的气孔与外界相通，微生物可经这些气孔而进入蛋内，特别是贮存期长或经过洗涤的蛋，蛋壳外黏膜层的天然屏障作用遭到破坏，在高温、潮湿的条件下，环境中的微生物更容易借水的渗透作用侵入蛋内。温度低、湿度高时，污染到蛋壳上的霉菌很快生长，菌丝可穿过蛋壳而长入蛋内。 四、鲜蛋内微生物污染的控制 为防止母禽内源性感染并经蛋传播病原微生物，必须搞好饲养管理、环境卫生、免疫接种、定期检疫和疾病的及时诊断治疗，以保证母禽的健康。 为了减少鲜蛋的外来微生物污染，母禽产蛋地方应清洁和干燥，最少每天收集一次鲜蛋，剔除破壳蛋和不合格蛋，将鲜蛋迅速置于温度1～5℃、相对湿度70%～85%环境中贮藏，大头向上放置。一切与鲜蛋接触的用具均应清洁干燥。运输过程中避免蛋壳破损。 第二节污染微生物对鲜蛋的作用 一、蛋内污染微生物的种类 （一）细菌荧光假单胞菌、绿脓杆菌、变形杆菌、产碱类杆菌、亚利桑那菌、产气杆菌、大肠杆菌、沙门氏杆菌、枯草杆菌、微球菌、锈球菌和葡萄球菌等。（二）病毒禽白血病病毒、禽传染性脑脊髓炎病毒、减蛋综合征病毒、包涵体性肝炎病毒、禽关节炎病毒、鸡传染性贫血病毒、小鹅瘟病毒和鸭瘟病毒等。（三）霉菌毛霉、青霉、曲霉、白地霉、交链孢霉、芽枝霉和分枝霉等。 二、影响蛋内污染微生物繁殖的因素 （一）鲜蛋的放置方法及贮存时间鲜蛋应钝端向上放置贮存，因为蛋黄的比重比蛋白轻，若锐端向上，蛋黄向上漂移，易与壳内膜接触，蛋壳上污染的微生物易避开蛋白中的抗微生物因素，便可从该处直接进入蛋黄内，并迅速繁殖。鲜蛋在室温条件下贮存1—3周后，蛋白内的溶菌酶便失去活性，此后侵入的细菌易进入蛋黄。久贮的蛋，蛋白的水分大部分转入蛋黄，使蛋白收缩，蛋黄膨胀，蛋黄膜易与壳内膜接触，穿过壳内膜的微生物也可直接进入卵黄。 （二）微生物的特性革兰氏阴性菌进入蛋内后很容易在蛋内繁殖。这是因为它们对蛋白中的抑菌因素有抵抗作用。例如，来源于土壤和水的荧光假单胞菌，进入蛋内产生绿脓酮素，能与抑菌的伴清蛋白竞争结合金属离子，使伴清蛋白失
幼儿园中班科学：蛋和蛋制品 活动简析： 蛋和蛋制品是中班幼儿熟悉与感兴趣的，本次活动形式新颖，多样化。幼儿每人带一只不同品种的蛋，人人参与。在动手打蛋的环节中，又锻炼了幼儿的动手能力。通过比较各种品种的蛋来培养幼儿的观察力。教师又当场制作炒蛋，引起幼儿极大的兴趣。最后一环节，让幼儿在布置好的餐桌和柔和的音乐中进行自助餐，给幼儿美的享受，从中体会到生活的乐趣。 活动目的： 1、在认识蛋的过程中，进一步发展观察力和语言表达能力。 2、通过活动知道蛋是有营养的，对自己身体有好处。 3、在自助餐中形成文明的好习惯，享受生活的乐趣。 活动准备： 1、教师：鸭蛋、鸡蛋、鹌鹑蛋、鹅蛋各一个，电炒锅三只。 2、幼儿：每人一只碗、一把勺、一只蛋。 3、鹅及蛋制品的。 4、自助餐物品：桌布、盘子及各类蛋制品。 活动过程： 1、导入活动，引起兴趣，认识蛋的种类。 （1）师：“今天我们小朋友都带了一只蛋宝宝，请你们看一看你带的蛋宝宝是什么样的，叫什么名字，是哪一种小动物生出来的，然后告诉你旁边的小朋友。” （2）请个别幼儿上来介绍自己的蛋宝宝。 （3）老师介绍鹅蛋宝宝，看鹅生蛋的课件。
（4）请小朋友摸一摸蛋宝宝，有什么感觉？（蛋壳摸上去是凉凉的，很光滑） （5）和旁边的小朋友比一比，你们的蛋宝宝一样吗？ （6）教师小结：“小朋友带来了各种各样的蛋，它们的颜色不同，有大有小，但是它们的壳都是很光滑的。” 2、认识蛋白和蛋清。 师：“这光滑的蛋壳里到底藏了些什么东西呢？你们打开来看看就知道了。” （1）请小朋友自己动手打蛋。 （2）你们看到了什么？ 小结：“不管什么蛋，里面都有黄黄的、圆圆的叫蛋黄，透明的粘糊糊的叫蛋清，烧熟了就是蛋白。” 3、粗浅介绍蛋的营养价值。 师：“小朋友每天都吃蛋吗？为什么要吃蛋呢？” 小结：“我们每天要吃一个蛋，但不能吃得太多，吃多了不容易消化，没烧熟的蛋也不能吃，里面会有许多细菌，吃了我们的肚子会痛。” 4、让幼儿讨论蛋的吃法及做成哪些蛋制品。 （1）你吃过哪些蛋做的东西？ （2）看蛋制品课件 （3）现场做炒鸡蛋。 5、自助餐。 边吃边告诉自己的好朋友或者客人老师，蛋的味道怎么样？ 活动延伸： 1、练习做蛋壳贴画 2、让幼儿收集各种动物的蛋的图片
第三章禽蛋与蛋制品加工 第一节禽蛋的基本知识 1.气室： 2.系带： 3.胚珠: 4.光线透视法： 5.蛋由（）（）（）三大部分构成。 6.蛋壳由（）（）（）及（）所组成。 7.胶质膜保护期（）周。 8.蛋白由内向外分为三层（）（）（）。 9.一般鸡鸭蛋的厚度在（）mm,鹅蛋厚度在（）mm. 10蛋壳的密度为（），蛋白的密度为（），蛋黄的密度为（），新鲜全蛋的密度为（）。 11.新鲜蛋白的PH为（），新鲜蛋黄的PH为（）。 12新鲜蛋白的热凝固温度为（），蛋黄为（），混合蛋为（）。 13.蛋的冰结点为（），蛋黄为（）。鲜蛋在（）时就会冻结，下降至（）时就会冻裂。 14.鲜蛋的感官鉴定方法有（）和（）。
15.蛋的各不同结构化学组成。 16.鲜蛋的感官鉴定方法。 17.次劣蛋产生的原因 18.常见次劣蛋有哪些.
第二节蛋的贮藏保鲜方法 1.涂膜贮藏法： 2.简易贮藏法主要有（）（）和（）。 3.石灰水贮藏的鲜蛋不宜用来加工皮蛋或咸蛋。（） 4.水玻璃贮藏方法所需水玻璃溶液浓度一般为（）波美度。 5.涂膜贮藏法最常用的涂膜剂有（）（）（） 及（）。 6.涂膜剂涂布的方法有（）和（）两种。 7.冷藏蛋出库时应每隔2-3小时室温升高1℃，当低于外界温度（）时 即可出库。 8.常用的鲜蛋贮藏保鲜方法有哪些。 9.石灰水贮藏鲜蛋的原理。 10.冷藏法贮藏鲜蛋的原理。
第三节蛋制品加工 1.常见的蛋制品有（）（）（）（）及（）。 2.咸蛋的加工原理。 3.咸蛋的加工方法有（）（）（）。 4.咸蛋加工常用辅助材料有（）（）（）（）。 5.咸蛋盐水加工方法。 5.糟蛋加工原理。