j ,\gr.inomy & Crop Science 177, 153—160 (1996)

CII99A Blackwell VHssenschafts-Verliig. Ekriin

ISSN 1)931-2250

Ptasi Produdjon Inspection Centre, Department of Seed Testinf, Ijiimaa, Finland

Post-harvest Evaluation of Nitrogen Sufficiency for Small-grain Cerealsby Measuring Grain Protein Concentration

.1 VlRFANKN and J. PliLTONI^

Authors' address: Mr A, ViRTANRN and Hi J. ProrioNf-.N (Corresponding authf>r). Plant Pnxlucticm lnspectii>nCentre, Depanmcnr of Seed Testing, PO Box 111, FlN-32201 I^jimaa, RnJand

9l!h I fi^rt and ) tables

Ramed I'hctmkr )0, 199?; a^apfeJ .Marth 19, 1996

hbsttact

Nijmn;en (N) fertilizer is an important and expensive input in small •jL;rain ceceal production, and growers thereforeshould aim lo optimi7e its use. Possibilities for usii^ grain protein concentratiori for posr-barvesr evaluation of Nsufficiency were determined in this study Field experiments including spring wheat {'/nlicanr aesltrim L.), spnngharlcy (Henjra/nr imt^ert L) and sprii^ oats (r-tivna sativa L.), and vanous rates of N fertiliarr a|.'^lication wereconducted in southern and westemFinland over 2 years. <irain yield and grain protein were posiuvely correlatedinrf fined ijuadradc regression mtxiels. Both cttdcal and optimutn levels for grain protein concentration weredetermined by Cate-Nelson analysis. Critical values were 12.2 for wheat, 10.2 for biarley and 10.9 for oats, andTiTrcsponding optimum values were I.'i..'i, 11.1 and 12.7, respectively. Tlie accuracy ot'rhe method was tested usingresults from on-farm spring wheat trials. Tbe results indicated that N renifi7.er uptake and grain lield were best inHclds where grain protein concentration exceeded the critical values but not the optimum. Cirowers should usemoft intensive N fertilizatKin management if grain protein concentration does not exceed critical values. Grainpnncin concentratJotis above optitnum values indicate twer-ferulizatHm for maximum grain yield. Analysingprevious research data to identify tbe "critical level" of grain protein concentration is not difficult, and will providepowers, extension personnel, and fertilizer dealers with a cost effective means of evaluaiing rhe efficiency of K useIjv the cn>p and for developing N fertilization recommendations.

Key words: (irain protein, N sufficiency, spririg cereals, barley, oats, wheat.

Introduction which is important in determining yield ptwential,

N'ltrogen (N) fertilization of a crop is the main does not increase to the same extent as nitrate

mtans of manipulating its grf>wth. With increase reductasc activity (L.AVtt.oK et al. 1989, Jov and

in fhc level of N fertilization, the relationship PKLTONEN 1993).

between grain yield and grain protein conccntra As the availability of N is such a cntical factor

»"i IS initially zerti, becomes positive and in crop production, many methods have been

thereafter diminishes through zero eventually proposed for measuritig the efficiency of N

'"'"mit^g tK^tivc (BF.N7,IAN and IJVNI; 1981, uptake and sufficiency of mineraSzablc N in soil

^t- Mia 1979). Use of N fertilizer, in excess of (VFHHILMAN:IM et al. 1982), or total N in either the

Ai; amount needed for maximum yield, will whole plant or its lea\-es (HAGKOVE et aL 1983,

geiKtaBy result in increased grain protein con- ROTH et al. 1989). It has recently been sujgjested

« r .-.jtkm (BENZtAN and LANIC 1981). The likely that a portable chlorophyU meter couid be used

K3 on for this is that the photosynthetic rate, to optimize N fenilizer application (PlXTtiNKN et

0931-2250/96/7703-0153$11.50/0

154 and

Tabte 1. Grain protein and fetacive grain yield data as a function of N fertilizer application rate for spnngwheat, spring barley and oats grtiwn in Rnland, 199.1—1994

Crop

Whuu

Baler

Year, culdvaf andU K

W3&-UViikki

Suioa

Pemio

Kcitkanicmi

k'okcmjki

l9MSl tuViitck.

Sana

kotkanii.'mi

1993 A mViikki

Suioa

Prrniri

Kotkanicmi

•^listaro

1993 KympfriViikki

Stiiua

Pcmio

Koikanicmi

K^emaki

1994 A mViikki

Suioa

Kuikimieini

Vskki

Sunia

Kudtarucmi

Paramtrtrimeasured

pK

•v-pYP\

PVPY

PYI'1PY

P

YP

YPYPVP

V

PYP

VPYPY

PY

PYP

YPV

PYPYPY

N I

13.049.0

11.576.412.246.6

9.(125.8

11.663.1

11.989.81Ii.S61.811.115.4

8.7

53.29 1

64.09.6

45.5S.2

41 310.268.9

8.8

.54.59.4

61.29.3

49(16.9

36.4

7.96 0 0

10.07729.7

51.7

12.2to.i

9.877.89.4

56.SV.fi

19.5

N2

12.685.112.6

101.312.260.510.677.411.67.34

14394.0

12.294.2

9.7

57.9

9.085.5

9.«

94.89.0

64.98.9

104.1

ro.o818

9.485.0

9.6

86.59.6

62.0

«.376.6

8.7SS.l

11.6KB.O

107

93.19.7

48.4

12.197311.190.59.0

51.6

N3

14.197.8

15.0

108.013.276.613.492.412.3

853

15.0

101915.391.9

12.091.4

1(J.395.511899.7

IO.fi81.0l l . l )

113.1!1U.4

103.5

10.294011.9

91.810.7

76.311.088.0

9.593.6

12.5119.2

12.598.7

11.284.9

12.8106.313.397.4

10.5

81.5

N taie"

N 4

%

15.796.7

15.2104.515.489.4

15.597.1

12.897.R

16 J1111.3

16.098.913.694.1

11.4

97.212.4

108.413.0

93.513.995.411.597.4

11.5101.0

12.1107.4

12.9%.812.99A.t

II.O92.1

12.8116 612 7

96.213.7

85.5

1.3.5103.614.398.613.7

89.7

N5 N6

16.9

100.016.2

umo157

IIIO.O16.7

100.01.3.7 14.5

Mo.ri (01.7

19.2

100.(116 9

KXI.O14.9

IIXI.O

12.5KMUI

13.21O0.O

13.3100.014.2

100.0

12.8KXI.O

12.4HKl.O13.3

100.(113.4

UHI.O14.1

100.0

12.4 12789.4 97.5

15.2100.0

13.51000

13.7

KKVO

15.8100.015.4

100.01.1.2

UX).O

Muimorn

62Kr,

4)122

r.344

Vlii.14.9

100.0 .Vli4

45(IV

AWH,

4 W

S.i45

WilS

f.Kr'J

44.ll'

CtW

7292

705(1

661 >

111100.0 52(.')

59?i

7«MI

595]

62.5;

7451"

Sufficieocy in Smal-grain Cereals 155

Tibk !. Gmtinued

Year, culovar and

Crop site

O i u 1993 VuinaMikki

Suitia

Pernin

Kodufucmi

Ylistani

IWt VimuVUkki

.Suina

Kodtaniemi

Fanmeorrmcasufed

PYPYPVPYP^•

PYP•i

P

Y

N I

12.7

619Ki.n

79.8lo.e46.87.R

15.110.069.7

l l . l )fW.29.')

63.5II.(SIS 2

N2

12.989. S1(1.79f..O10.7

62.2S.2

Bl.O9.9

99.0

1.3.0IO«.6

11.294.09.S

51.1

m

13.291.812.7

103.211.285.49.9

105.511.1

122.2

14.0124.K

13.399.4

m.r7 « l

N rate'

N4

%

13 599.613.3

1(10.4

12.51(14.3

11399.4I2.a

I.V411.MI.?.K99.4I2.<>90.1

Hi Sb r

13.8KKKI

I4.0100.(11.1.6

IW.O11..i

100.01.3.8

KNIO

ISOlOII.O

14.3KKI.O

1.3.(1

Idoii

Maximun)^7 yicM

8805

5572

726(1

5521

()3S7

64a"'

S5I4

S439

\ 50,100, 150 and 2tK) kg N ha m Viikki, Suioa and Pemi<i; 0.40, 80,12(1, and l « l kg N ha in Kotkantemiand ^listaro; 0, .JO, 60, 90, 120, 15() and 180 kgN ha~ in Kokemaki; 'Tercent pmrcin; " Rtlarivc >ield aspercent of nia.ximum N fertilised yieid.

al 1995). i( can be a particularly complexproblem for a grower, however, to estimatepost-harvcsi if N fertilizer application has beenMiccessful and cost effecth'e. GIXK er al. (1982)and CiiHis (1984) showed that post-harvestevaluation of N man^ement by assessirjg thefritica) grain pH»rein concentrabtm ha.<i been avct\ successful tooJ for promotion of impti>vedN [ertilj2er management of wheat in the USA.rhis method could be useful in Finland becausetnc records of grain yield and protein concentra-tion arc generally available to growers. Post-nanest evaluation of N sufficiency could also beu ttl for improved piarming of furure N fertilizer"•••c. It has, moreover, become important tomcinitor N fertilizer use in Eurt>pe for environ-rac'itai reasons.

Hie purpose of this studj' was to qtiantify thettlationship between grain yield and proteinconctmtration of spring wheat, spring barley*|W spring oats un(jer northern Europeandimatic cotuditions. The objective was to estab-&h Critical grain fitotein concentration levels for"Sing, post-harvest, to determine sufficiency of Nfertilization.

Materisds and Methods

/wA/ tna/s

Field trials (Series 1) were carried out at fiveUications in southern and western Finland in 1W.\and at three Uicaaons in southern f-inland tn 1994.There were 32 N fertilizer rcspmsc expcnmems,including eight trials of spring wheat, 16 rrials ofspring barley and etght trials of spring <»ats. Theexperiments were planted in three repLcafe blocks.Nttrogeti fertilizer was applied 7 cm deep at sowingand 600 viable wheat seed.<. m ^ were sown and 5(H>viable seeds m"" for baHey and oats u.stng a ro*spacing of 12.5 cm (MKLA and PA.ATCIJ\ 19'74). There

were from five tf> seven N fertilizer application ratesper trial. N ferdliiter was applied in 50kgN ha^'increments between zero ind 200 kg N ha inViikki (6(ri3'N), Suitia (6()'11'N) and Pemio(60"15'N); at 40 kc N ha" ' jncremems between zeroand 160 kgN ha in Kotkaniemt (60 22'N) and^Ttstaro (62'50'N), and 30kgNha~' incrementsbetween zero and 180 kgN h a ' in Kokemaki(6rM3'N). Standard crop protection measures(herbicides am! fungicides) were aj^lied. TTie wheat,barley and oat cu Wvars were selected for iticlusion inthe experiments according to their commercialimportance in die Finnish market at the time of

156 VKTANEN and

wriring, Gtain yield (kg ha ') was detcnnined at15% moisture contctit. Grain protein ctmceotra-tions were analysed using Near Infrared Reflectanceanalyser. Details of the grain yield and grain proteinconcentration measurements were described byPH-TONEN et aL (1995).

TTie critical levels of grain protein were estab-lished using Cate-Nelson aiialysis of varianceprocedures (CATK and NbLSOK 1971, NRLSON andANDERSON 1977). The Cate-Neison 11 model dividedthe dara for critical protein concentrations into twogroups: N fertiLzei responsK-e imi non-responsive,in terms of grain yield. The Cate-Netson III modelseparated the data into three groups: N fertilizerresponsive, transitional and n<'>n-respf>nsive. Cate-Nelsfin in models can be used if there is animprovement in terms of R' in comparison vithCate-Nelsoti II models. Grain yield was expressed aspercetttage yield (Y]/Ym,,.l(M)) where Y| representsthe grain w i d when N j kg ha is applied and Y^^^represents the grain yield at maximum N applicationrate for each experiment.

On-jarm

Data from 22 spring wheat on farms trials (Series2) in southern Finland in 1992 and 199.1 were usedindependently to study the applicabilit\' of criticaland optimal grain protein concentrations to cerealproduction. Spring wheat cuitn'ars and fertilizationlevels were chosen according t<i growers' manage-ment practices. Nitrogen ferrilizer, ^^lied at sowing,ranged between 50 and 145kgN ha"' in 1992 andbetween 80 and 169 kgN ha"' in 1993. Controlplots were not fertilized. Grain yield and grainprotein concentrations were analysed as for Series 1.Grain N yield was calculated using grain dry matteryield and grain N concentration. N fertilizer uptakeefficietvcy was determined from grain N yield minuscontrol plot grain N yield, dmded by applied Nfertilization rate. The spring wheat fields weregn>uped into three categories by grain proteinconcentration according to critical and optimumvalues for grain protein in Series 1. Tlie threecategoties were; fields belou' the critical value (low),fields in berween the critical and optimum values(optimum) and fields over the optimum values(high).

R««ults and Discussion

Temperatures during the 1993 and 1994 growingseasons (Series 1) were dose to the averse forthe period 1961—1990. Precipitation exceededthe 30 year mean in 1993 and 1994. This weatherprotnoted very high gjaiti yields attd a very gcxxlresponse to N fertilizer. The grain proteincotKentrations, gtaiti yields as percentage ttiaxi-

mtttn yields and die maximum grain yields for aEexperiments are presented in Table 1. There wwekige variations in grain protein concentrationfrom 9.0 to 19.2% in wheat, from 6.9 to 15 8 ".in badey Mid firotn 7.8 to 15.0% in oat Granyields ranged from 674 to 6286 kg N ha"' mwheat, firom 745 to 8345 kg N ha"' in barley andfn»m 990 to 8805kgN ha"' in oats.

Tht tflatiomhp between protein conantratien and pmyield

A quadratic regression model best representedthe relationship between gram prt)tein concentritions and relative grain yieJds at progressivtivincrea.sin}> kvels of N fertilization (Fig. 1). VIKincrease in grain protein concentration, reiatmgrain yield increased almost linearly at the liratrgrain protein levels. At the higher grain pmleinlevels the relative grain yields reached a plateaufor all cereals, and thereafter diminished in wheatand barley. This indicates that when grain priHcmCdncentradon exceeded maximum grain wlconly grain protein concentration was increased 1«supplemental N fertilizer application. This con-firms the results of BRNZIAN and LANK (1''HV

and KnAvn-R (1979).

Data from Kotkatiiemi (1994) control pte(indicated with arrows in Fig. 1) deviated fnmi Jgrain protein — grain ^ield qtiadratic regression,representing extremely low grain yieid but hij;hgrain protein concentration (Fig. 1). Simiiafeffects were also reported by McNr.Ai- and OAVL(1954), FKRNANDKZ and LA!RD (1959), and

BKNZIAN and L\Nf- (1981), but the reason fi'rthis phenoinenon has tH)i yet been adequaid'explained. However, the high grain pttitcinconcentration at extremely low grain yield seem?to be related to the associated reduction in ijrjinyield rather than to efficient N fertilization (l' 'and PKLTONBN 1993).

Ctitical and af^imum ^mn proitin Itvels for gnag )K'«-'

Cate-Nelson 111 models gave higher R^ values fofeach crop if data from Kotkatiiemi (1994) contmiplots were omitted. Hence, Cate-Neison fquidons for N fertilizer responsive, transition if^non-responsive categories were calculated vtith-out this data. The criticaJ and optimtim . raicprotein concentrations for each cereal specie • ^^given in Table 2. Critical values were 12.' ' 1"wheat, 10.2 for badey and 10.9 for oats. ^correspotidir^ c^dmum grain protein concentra-

Hvaluation of N Sufficiency in Small-grain Cereak 157

10 II 11 13 14 15 1« 17 IS 19 20

« 4 l« II 13 13 14 15 1»

I

120^ C

100 -

» -

60

40

»

a

A

' ^

A

AA

y ^ AA

A

m

A

A

»

A

*AA ,^i

^ ^t

' AA

A*

A

A A A

R'-0J9I2

i

:

120 «3

10 II 12 13 U 15 16 17 I«

1- Relationship between relative )-ield, expressed as percentage of maximum N fertilized yield, and grain"-in concentration in (a) spring wheat, (b) barley and (c) oats. Data from 1994 Kotkaniemi ON plotsue squares indicated by arrow) were not included in calculaong the regression equations. Vertical linesicaie critical and optimum grain protein concentraaon from Cate-Nelson analysis

158 VJRTANEN

Table 2. Cate-Nelson equations describing ^ain yieid (Y) in relation to grain protein concentration, mdsuggested critical and optimum grain protein concentrarion values for spring wheat, spring barley and oats inFinland

F^uation R <CriticaI* Transition level'' >Optununi'

atCirain protein concenrrabrmY = 2740 + 1166x, + 508x2where x, = (I if <12.2 and 1 ifwhett x; = 0 if s n . 3 and I if > 1.1.3%»ing barleyGrain pnitein concentrationY = 41.37 + noOx, + 247x2where x, - {I if <10.2 and 1 if 2l(P2where \2 = 0 if sll .O and 1 if > 11.0OatsGrain protein concentrationY = 400.3 + l.S7(l.x, + 743x,where X, = 0 if < 10.9 and 1 if alO.9where x, = 0 if sl2.7 and I if > 12.7

0.57"» 12.2 12.2—1.3.3 15.4

0.61 •** 10.2 10.2—11.0 12.'»

0.44*** 10.9 10.9—12.7 I3..S

*** Significant at die O.WI prohabitiiy level; 'Critical leveLi vere calculated from Cate-Nelson [I'Lower ami upper limits of rhe transition level of grain protein concentrations were devek)ped from Can-Nelson 1(1 mfidels;'Mean values forcla.ss > optimum grain ptotein concentration, where there were no monincrease m grain yield.

dons were 13.3 for wheat, 11.1 for lyarley and12.7 for oats. Cate-Ndson equations indicatedthe- capaat)- tor protein concentration to lx-usefvil to predict crop N adequacy. For example,a barley grain protein concentration < 10.2 "/nresutrs in an average grain yield of 4137 kg ha ' .Wnb the help i>f this information, growersproducing barley with low grain protein concen-tration can be advised t( > use more M fcrtiLzer intheir fields. In the "optimum* grain protein class(tO.2—11.0%) there was 1700kgha" ' increasein grain yield compared with the 'low' class,resulting in a total yield of .SK37 kg ha~ \ If grainprotein was ranked 'high' (>11.0 "A), the changeio grain yield was onJy 247 kg ha "' in comparisonwith the 'optimum' class. This indicates over-ferdlization of the barley field for maximum grainyield. TTic mean values for grain proteinconcentration at supra-opdmtim N rates werevery high for wheat (15.4%) and moderate forbaHey (12.9%) and oats (1.3.5%). If high gramprotein is an important factor for milling, bakingor feeding puiposes, one could use knowledge ofpos(-harvest grain protein concentration to guideboth basal and supplemental N fertilizer recom-mendations to increase ff!ait\ protein values.

Cht-farnt triak of spring

Sn eariy moist pcriixi occurred 3 weeks afiei.sowing in 1992. Temperatures in May and Juni1992 were, however, about 1.0 and 1.5 C hightithan the 30 year mean (1961—1990), and plant;suffered from drought until the end of Jul>Therefore, crops matured in mid-yVugust. In turn.the temperatures during crop growth in IW.were ck>st to the mean for the penmi1%1—]99(), but approximately 70mnn morerain fell during crop growth in 1993 than the .'i'year mean.

Mean grain yields and grain protein concenrHtions were 4260 kg ba"' and 14.2 % in 1992 aiul5950 kgha ' and 13.5% in 1993 (data norshown). TSlien the grain protein concentratorwas bek)w ihe taitical value of 12.2 %, Nefficiency was also low (Table 3). Fieldsgrain protein concentration was 'optitnum(12.2—i 3.3%) gave the best grain yield, aWgrain yield improved through fertilizer applicJiO""in both years, but the yield benefit was niofL-apparent tn a good season (1993) than in a doseason (1992). Also, N fertilizer uptake mriuptake efficiency were h^hest in 'optimun;' i"1993, bur not in 1992 when the most efficieni N

F.valuaiion of N Sufficiency in Small-grain Cereals 159

Table .3. Spring wheat data from 22 on-farm trials in 1992 and 1993 grouped to three categories according topain protein concentration

YearGrain protein in

categorj'

Mean Meanaf^lied N Mean fertihzer N

Mean grain Number of fertilizer fertilizer N uptakeyield growers rate uptake" efficiency''

Mean yieldimprovement

byfertilizer N '

1W2

1903

iowoptimum

highlow

optimumh i ^

k g h a " '43.59470540784fi816 3 %6102

35

1448

10

k g h a " '77

127114115119117

k g h a - '264545407569

•K.2735403Ct6360

k g h a '1449193915612{>9535442558

'Calculated from grain N yield minus 0 N plot grain N yield; Calciilated from fertilizer N uptake divided byapplied N fertilization rate; "^C^culatcd from grain yield minus 0 N plot grain yield.

uptake was recorded in the 'high' category. Thisix-sultod in higher grain protein concentrationvalues in 1992 tban in 1993.

Three of the 22 fields in 1992, and four inW?\ were 'low'. ITius. a more efficient Napplication strategy was rccomtnended for thosefields. Only in five (1992) and eight (1993) fieldswa.s there success in optimizing N ferdlizatirmwilhout knowletlge of plant N stattis. Most ofthegrowers (14 in 1992 and 10 in 1993) used toomuch N fertilizer for spring wheat production. Inthe dr\ season of 1992 four more growers failedtodpnmize N fertilization than in J993.

In conclusion, the results from this studyshowed that with the help of cntical grain proteinonccntration values, growers pniducing small-grain cereals with low protein concentration canbe advised to use a more intensive N fertilizationprogram to optimize grain yield formation.Protein concentration above the optimum valuesindicates over-fertilization for maximum grain

In years of drought (e.g. 1992 for springgrain yields are usually low and grain

protein cotKcnttation will generally be high.However, in such years, the N tiptake efficiencyfor optimum grain yield will be also lower. Thus," was conciuded that critical levels of grainprottin concentration are applicable in both goodind poor seasons. However, there are situationsfor which the model has not been validated Forfample, when Aere is N deficiency, leading toextremely low grain yield formation, but miner-a l b l N is available in soil (e.g. Kotfcanienii

plots in 1994), the frequendy observed

high grain protein concentration is a result ofyield k>ss due to N deficiency. Such situationswere rare berween 1968—1988 in southernFinland (Pi:i.Tf)Ni-:N et al. 1990). Analyzingprevious research data to identif\- the 'criticallevel' of grain protein concenttation is notdifficult, and will provide growers, extensionpersonnel, and fertilizer dealers with a costcffecdvt means of evaluating the efficiency ofN use by the crop and for developing NfertiUzarion rccommendanons. Information onpost-harvest grain protein concentration f>f small-grain cereals can easily be ohtained by growers asgrain protein determination is often a routinemarketing requirement.

Zusanunenfassung

Nachemteauswertung fat ausreichendenSdckstofiT bei Getieide atif der Grundlageeiner Messung der KomeiweiBkonzentration

Stickstoff (N)-Diinger ist ein wichtiger undkostenextensiver Aufwand in der CJetreidepro-duktion; die Anbauer solhen daher seine .Anwen-dung optimiercn. In dieser Arbeit wurden dieMoglichkeiten untersucht, die Komeiweifikon-zentration in einer Nachemteausweming hinsicht-lich einer ausreichenden Mcnge an N zu ermitteln.Die Feldexperimente umfaBten Sommerweizen(Triticum atstiimm L.), Sommetgerste {Hordeumvul^trr L.) und (Sommer-) Hafer (.Avem sativaL ) unter Verwendung verschiedener Mengen anN-Dunger; die Versuche wurden im sudlichen

160 VlRTANEN and Pt!.TOKK

und westlichen Finnland uber 2 Jahre durchge-fuhrt. Kornertrag und KomeiwetU waren positivkorreliert und lieBen sich in einer quadratischenRegression erfassen. Kritische tind opdmaleKonzentrationen des KomeiweifSes wurden mitder Cate-Nelson-Analysc bestimmt. KritischeWerte wurden mit 12,2 fur Weizen, 10,2 furGerste und 10,9 ftir Hafer nachgewiesen; diedazu korrespondierenden opdmalen Werte be-trugen 13,3, 11,1 und 12,7. Die Zuverlassigkeitder Methodc wurde unter Verwendung von aufFarmen durchgefuhrten Versuchen mit Sommer-weizen uberprufr. Die Fjgebnisse weisen dar-aufhin, dafi N-Dungcrauftiahme und Kornertragam besten auf Feldcm waren, auf denen dieKomciweifikonzcntrauon die kntischen Wcrtc,aber nicht die optimalen uberschritt. Die An-baucr sollten ein intensiveres N-Diingungsvcr-fahren verwenden, wenn die KomeiweiCkonzen-tration nicht die kritischen Werte uberschreitet.Die Komeiweifikonzentration ober-halb deroptimalen Werte weisen daraufhin, daB eineUberdiingung bezuglich maximalcr Kornertragevorlicgt. Die Analyse voriicgender Forschungs-etgebnisse zur Identifikadon des "kritischenGehaltes'* bezuglich der KomeiwciBkonzentni-tion erwiesen sich nicht als schwierig und gehendamit den Anbauern, der Beratung und denDurigerverkaufem eine kosteneffektivc Bestim-mung zur Auswertung der N-Effizienz durch dieKulturpflanzc sowie Hinweise zur Kntwicklungvon F^mpfehlungen fur die N Diingung.

References

testing to wheat farmers'. J. Agron. Edut. ]J10.3—106.

, D. G. WF5TFALI, A. E. LiinttTCK, and |. J-GoRlS, 1982: Cirain protein content as an indicatnr <.:'N sufficiency for winter wheat, y^on. |. 7

AN. B.. and P. LANF, 1981: Interrelationshipbetween N C4>ncentrati(m in graui, grain yield andadded femliser nitn^en in wheat experiments ofSouth-ea.M F.nglancl. j . Sd. Food .''igtic. 32, 35—43.

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