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On the relationship between N management andgrain protein content in six durum wheat cultivars inMediterranean environmentSalvatore Antonio Colecchia a , Bruno Basso b , Davide Cammarano c , Antonio Gallo a ,Anna Maria Mastrangelo a , Paola Pontieri d e , Luigi Del Giudice d e , Domenico Pignone f

& Pasquale De Vita aa CRA Cereal Research Centre, S.S.16 Km 675, 71122, Foggia, Italyb Department of Crop Systems, Forestry and Environmental Sciences, University ofBasilicata, 85100, Potenza, Italyc Department of Agricultural and Biological Engineering, University of Florida,Gainesville, FL, 1741, USAd Institute of Genetics and Biophysics ‘Adriano Buzzati-Traverso’ (IGB-ABT), CNR, 80131,Naples, Italye Department of Biology, Section of Hygiene, Institute of Plant Genetics (IGV), CNR-Portici, Via Mezzocannone 16, Naples, 80134, Italyf Institute of Plant Genetics (IGV), CNR, Via Amendola 165/A, Bari, 70126, Italy

Accepted author version posted online: 10 Jul 2012. Version of record first published: 01Aug 2012

To cite this article: Salvatore Antonio Colecchia, Bruno Basso, Davide Cammarano, Antonio Gallo, Anna MariaMastrangelo, Paola Pontieri, Luigi Del Giudice, Domenico Pignone & Pasquale De Vita (2012): On the relationship betweenN management and grain protein content in six durum wheat cultivars in Mediterranean environment, Journal of PlantInteractions, DOI:10.1080/17429145.2012.710656

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RESEARCH ARTICLE

On the relationship between N management and grain protein content in six durum wheat

cultivars in Mediterranean environment

Salvatore Antonio Colecchiaa, Bruno Bassob, Davide Cammaranoc, Antonio Galloa, Anna Maria Mastrangeloa,

Paola Pontierid,e, Luigi Del Giudiced,e, Domenico Pignonef and Pasquale De Vitaa*

aCRA Cereal Research Centre, S.S.16 Km 675, 71122 Foggia, Italy; bDepartment of Crop Systems, Forestry and EnvironmentalSciences, University of Basilicata, 85100 Potenza, Italy; cDepartment of Agricultural and Biological Engineering, University of

Florida, Gainesville, FL 1741, USA; dInstitute of Genetics and Biophysics ‘Adriano Buzzati-Traverso’ (IGB-ABT), CNR, 80131Naples, Italy; eDepartment of Biology, Section of Hygiene, Institute of Plant Genetics (IGV), CNR-Portici, Via Mezzocannone

16, 80134 Naples, Italy; fInstitute of Plant Genetics (IGV), CNR, Via Amendola 165/A, 70126 Bari, Italy

(Received 28 May 2012; final version received 4 July 2012)

Grain protein has recently received attention in several countries because of a premium associated to increasedprotein concentration (PC) in grains. Nitrogen (N) fertilizer management with its timing of application and ratesplays a crucial role in increasing PC. The objectives of the present study were to: (1) quantify the effects of

different N fertilizer rates and timing of application on grain yield and grain protein of six durum wheat cultivars,and (2) identify the best cultivar in terms of net return, yield, and protein content in typical pedo-climaticcondition of southern Italy. The field experiments were conducted in Foggia during three growing seasons (2002�2003, 2003�2004, and 2004�2005). Results from this study showed that N application at sowing did not influencethe cultivars performance. N applied at stem elongation increased yield and protein content provided there isadequate soil water for N uptake. In absolute terms, the best combination was the cultivar Svevo managed using104 kg N ha�1 split between tillering and stem-elongation stage. The excessive N splitting reduces yield and does

not provide any improvement in terms of protein content.

Keywords: durum wheat; nitrogen; fertilization; protein content; grain yield; net return

Introduction

Durum wheat (Triticum durum Desf.) is the maincereal crop in several countries of the Mediterraneanbasin mainly used for pasta, bread, and couscousproduction. Durum wheat market consistently de-mands a grain protein content of 13% or higher, sincethis trait represents the most important factor affect-ing pasta-making properties (Dexter and Matsuo1980; D’Egidio et al. 1990; Ayoub et al. 1994;Troccoli et al. 2000; Clarke 2001). In the typicalsemiarid environments of the Mediterranean areas,continuous durum wheat and durum wheat-fallowsystems are extensively used, causing a decrease of theaverage protein content below 13%. As a conse-quence, nitrogen (N) fertilization is used to increaseprotein content. Numerous experiments over the lastfew decades have investigated the effect of N fertiliza-tion practices (e.g. N form, rate, splitting, timing) onthe fate of the N applied and the strategies to matchplant uptake and utilization during various stage ofgrowth (Borghi 2000; Grant et al. 2001; Blankenauet al. 2002; Rharrabti et al. 2003a, 2003b, 2003c;Lopez-Bellido et al. 2005; Farrer et al. 2006; Ercoli etal. 2008; Basso et al. 2010, 2011, 2012). Increasing Nsupply results in progressive increments of wheatyield and total grain protein content (Spiertz and de

Vos 1983; Ottman et al. 2000; Sardana 2000; Krapp

et al. 2005; Laperche et al. 2007; Ercoli et al. 2008;

Giuliani et al. 2011a, 2011b).The recent introduction of high-yielding wheat

cultivars and of cultivars carrying the genetic bases

for high protein content has prompted an increased

use of fertilizer N (Ortiz-Monasterio et al. 1997). A

single pre-sowing N application is recommended in

arid regions where the crop depends on erratic

rainfall patterns (Arnon 1972; Jackson and Sims

1977). In areas where the amount of rainfall is high

split applications between sowing and up to the early

boot stage can increase grain yield (GY) and protein

content (Mason 1975; Anderson 1985).In semiarid regions, N fertilizers are most com-

monly applied at sowing as for the arid regions.

However, N fertilization can be split in two applica-

tions, one at sowing and the other as top-dressing

before stem elongation.From an agronomic standpoint N application at

an early stage increases GY, but the N fertilization at a

later stage (booting and head-emergence stage) sig-

nificantly increases the amounts of all the protein

fractions, GY, and pasta-making properties. But, in

Mediterranean environments this practice is limited by

the low rainfall recorded between those physiological

*Corresponding author. Email: pasquale.devita@entecra.it

Journal of Plant Interactions2012, 1�9, iFirst article

ISSN 1742-9145 print/ISSN 1742-9153 online

# 2012 Taylor & Francis

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stages. From an economic standpoint, in terms of net

return (NR) and marginal value for each amount of

N applied, it is still not known which N application

and N rate will maximize the return, increase the

yield, and the protein content. High yield and good

pasta-making quality are important features in today’s

durum wheat market. Both can be improved through

N fertilization strategies, such as the rates and

timing of N fertilization (Miceli et al. 1992), but the

cost of fertilizer associated with the application

cost may not always justify the intervention.

Recently, pasta factories recognize an economic pre-

mium to the growers based on the protein content of

the grain.The hypothesis of this study is that the effects of

N rates and time of N application affect qualitative

traits and NR of six durum wheat cultivars under

rainfed Mediterranean conditions. The objectives are

to (1) quantify the effects of different N applications

rates and timing on GY and grain protein for six

highly adopted durum wheat cultivars, and to (2)

identify the best cultivar in terms of NR, yield, and

protein content in a representative area (in terms of

pedo-climatic condition) of southern Italy.

Materials and methods

Trial site

Fields experiments were conducted at Foggia

(41828?N, 15832?E and 75 m a.s.l), in southern Italy,

on a clay-loam soil (Typic Chromoxerert) at CRA

Cereal Research Centre during three growing seasons

(2002�2003, 2003�2004, and 2004�2005). A data

logger was installed to collect daily maximum and

minimum temperatures and rainfall data (Table 1)

while soil characteristics of experimental sites are

reported in Table 2. Vegetative growth of durum

wheat occurred from November to the end of

February and the reproductive period (stem elonga-

tion, heading, grain filling, and maturation) occurred

from March to May.

Experimental design

Since there is no predetermined hierarchy among thestudied factors, the experiment was arranged in arandomized complete block design with three replica-tions using a factorial design with durum wheatgenotypes and N treatments as factors.

Six N treatments were applied at three different Nrate (80, 104, and 128 kg N ha�1 as urea) and split intwo different ways, one called ‘normal’ in which N issplit between tillering and stem elongation, andanother called ‘split’ with N applied at sowing,tillering, and stem elongation (Table 3). The area ofeach plot was 10.2 m2 (eight rows, each 7.0 m longand 0.17 m apart). Since the soil contained sufficientamounts of plant available P (�100 kg P ha�1)and K (�450 kg ha�1), phosphorous and potassiumfertilizer were not applied. Weeds were control-led by means of specific herbicides: Tralcossidim(1.7 l ha�1) �Clopiralid�MCPA�Fluroxypyr(2.0�2.5 l ha�1). The experiment was sown on 10th,12th, and 12th December in 2002, 2003, and 2004,respectively, with a seeding rate of 200 kg ha�1,the preceding crop was durum wheat. Plants wereharvested after the physiological maturity at themiddle of June.

Durum wheat cultivar

Six durum wheat genotypes (Lesina, Creso, Svevo,Simeto, Duilio and, Ciccio) were chosen because theyrepresent the most popular cultivars in Apulia, themain durum wheat growing area of Italy. Svevo,released in 1996 and developed between the ‘SocietaProduttori Sementi’ (Bologna, Italy) and Barilla, ischaracterized by a high protein content and a highyellow index of its semolina; Ciccio, released in 1996is an early durum wheat cultivar with high yieldpotential, good resistance to common diseases andlodging; Creso was the first significant semi-dwarfcultivar released in Italy in 1974 and still growntoday. Creso has a high yield potential and, at thesame time, good grain quality for pasta-making;Simeto, released in 1988, represents the most popular

Table 1. Monthly rainfall and mean maximum and minimum temperatures for three growing seasons compared to long-termdata for Foggia (Italy).

2002�2003 2003�2004 2004�2005 Long-term data 1955�1994

Tmax(8C)

Tmin(8C)

Rainfall(mm)

Tmax(8C)

Tmin(8C)

Rainfall(mm)

Tmax(8C)

Tmin(8C)

Rainfall(mm)

Tmax(8C)

Tmin(8C)

Rainfall(mm)

November 22.2 11.0 17.7 20.5 11.1 5.4 18.3 9.8 121.6 16.7 6.9 61.4

December 14.9 8.5 130.8 14.5 5.8 164.6 15.9 8.6 53.8 12.8 3.9 59.9January 15.0 7.4 171.6 13.8 5.7 45.7 12.4 4.4 79.4 11.3 2.5 48.0February 11.3 3.4 24.8 16.3 4.6 15.4 11.5 4.1 74.2 12.5 2.7 42.9

March 17.7 5.5 37.2 17.4 6.0 23.7 18.0 5.5 55.2 15.4 4.1 46.4April 20.5 7.5 37.4 20.6 10.3 51.9 21.8 8.7 22.0 19.1 6.2 46.8May 29.5 14.5 12.2 24.4 10.8 48.4 28.2 14.2 1.2 24.7 10.4 37.1

June 35.0 19.8 56.6 30.3 16.6 99.0 32.2 16.9 69.6 29.5 14.6 32.0Sum 488.3 454.1 477 374.4

2 S.A. Colecchia et al.

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cultivar grown in Italy. It has a high yield potentialand kernels have excellent qualitative characteristics,a very high thousand kernel weight (TKW) and agood attitude to industrial transformation; Lesina,released in 1998 is a very early durum wheat cultivarwith high yield potential, very good resistance tocommon diseases and to lodging; Duilio, released in1984, is characterized by a very high yield potential,determined by a good balance of yield components(ear fertility, TKW, and number of ears per metersquare). Furthermore, due to its high yield stability,Duilio is well suited to every kind of cultivation area.

Yield and grain quality analysis

The entries were characterized for agro-morphologi-cal and qualitative traits. Heading date (HD, daysafter first April) was recorded when about half of theculms showed emerging spikes (growth stage 55,Zadoks et al. 1974), while the plant height (PH) wasmeasured during the milk-waxy maturation. Wholeplots were mechanically harvested and GY deter-mined at 13% moisture content. Several commercialand technological quality parameters were deter-mined. TKW was calculated as the mean weight ofthree sets of 100 grains per plot. Test weight (TW)was measured on three samples of 250 g per plot andexpressed as kg hl�1 obtained with a Shopperchondrometer. Grain N content was determined bymeans of the standard Kjeldahl method. Grainprotein concentration (PC) was calculated after

multiplying Kjeldahl N by 5.7 and expressed on adry weight basis.

Economic analysis

The NR was calculated for each cultivar, N level andapplication time. The most common criteria adoptedby Italian pasta companies to establish the premiumprice for more protein is 10 eurocents every 2.0 gkg�1 of proteins exceeding the minimum content of130 g kg�1, reaching a maximum of 1.5 Euro ifprotein content is�160 g kg�1.

The yield NR was calculated as follows:

NR ¼ Yh � ðGp þ PpÞ � Costs

where Yh is the yield harvest (t ha�1), Gp is grainprice (Euro t�1), Pp is the protein premium. Costs arethe total costs (Euro ha�1) including sowing, fertiliz-ing, harvesting, weed and pests control, and so on.The detailed description of GY price, and total costsis showed in Table 4.

The marginal value for each amount of N givenrespect to the baseline of 80 kg N ha�1 is calculatedas follows:

MV ¼NRNx � NRNy

DN

where NRNx is the NR of the subsequent N applica-tion; NRNy is the NR of the previous N application;and DN is the difference of N between the twoapplications.

Statistical analyses

Data from combined years were analyzed usingANOVA and Fischer’s protected least significantdifference at pB0.05. All data were statistically analy-zed with a statistical software package (Statistica,Statsoft, 1995).

Results

Weather conditions

Weather conditions for the three years of the experi-ment and for the period 1955�1994 are summarized

Table 2. Soil properties in the beginning of 3-year of

experiment at Foggia (Italy).

Properties Dept (cm) 0�45

Organic matter (%) 1.96pH water 8.01Sand (%) 10.9Silt (%) 38.9

Clay (%) 50.2Total CO3 (%) 7.15Active CO3 (%) 5.76

K2O ppm 950P2O5 ppm 30N organic (%) 0.191

Table 3. Amount and timing of N fertilization at the growth stages GS 21, GS 31 and GS 37 (decimal code according toZadoks et al. 1974).

Fertilizer N (kg N ha�1)

Nitrogen treatments Sowing (GS 21) Tillering (GS 21) Stem elongation (GS 37) Total N supply (kg N ha�1)

N80 ‘‘normal’’ � (0) 32 (40) 48 (60) 80N104 ‘‘normal’’ � (0) 41.6 (40) 62.4 (60) 104

N128 ‘‘normal’’ � (0) 51.2 (40) 76.8 (60) 128N80S ‘‘split’’ 24.0 (30) 24 (30) 32 (40) 80N104S ‘‘split’’ 20.8 (20) 31.2 (30) 52 (50) 104N128S ‘‘split’’ 25.6 (20) 38.4 (30) 64 (50) 128

Note: value �%.

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in Table 1. During the three years growing season

rainfall was higher than the historical rainfall. It

ranged from 454 to 488 mm (about 100 mm higher

than the mean value of long-term rainfall data �374

mm). During the first year (2002�2003) the 62% of

total rainfall was recorded in two December and

January. In the third year (2004�2005) the rainfall

was better distributed respect to the second and first

years. During the reproductive period (February�April), temperatures varied widely during the three

years (Table 1). In particular, the second year was

characterized by above average temperature with

March monthly maximum temperature 38 higherthan the long-term records.

Agronomical evaluation

In Table 5 are summarized the effects of year (Y),cultivars (G), N treatments (T), and their interactionsfor all traits evaluated in the study. Considering themain factors, all traits showed statistically significantvariations. Among the first-order interactions, Y�Gand Y�T interaction showed significance for allparameters evaluate with the exceptions of TW andPC. On the other hand, G�T and Y�G�T interac-tions were statistically significant only for TKW para-meter indicating that the study did not show changes incultivar rankings for most attributes. HD values weresignificantly higher in the year with the lowest GY,while the best mean values of TW and TKW wererecorded in the second study-year (2003�2004).

The timing of the N treatments had not significanteffect on durum wheat GY over the three years as awhole for 80 and 104 kg N ha�1 while a significantdifference was observed at 128 kg N ha�1 rate (Table5). The best GY response was obtained from N128

treatment when 40% of the total N fertilizer rate wasapplied at the beginning of the tillering stage and therest 60% at the stem elongation stage. Splitting the

Table 4. Total costs (Euro ha�1) including sowing, fertiliz-ing, harvesting, weed and pests control, and durum wheatgrain price.

2004 2005

Plough (t ha�1) 120 120

Seeds and sowing (t ha�1) 120 120N Fertilizer cost (t kg�1) 0.23 0.32N Distribution (t ha�1)

‘‘Normal’’ 30 30

‘‘Split’’ 45 45Weed control (t ha�1) 60 60Harvest (t ha�1) 60 60

Grain price (t t�1) 190.89 137.48

Table 5. Effects of year (Y), cultivars (G), N treatments (T), and their interactions for all traits evaluated in the study.

FactorsHeading date

(days from first April)Plant

height (cm)Grin Yield(Mg ha�1)

Test weight(kg hl�1)

1000-kernelsweight (g)

Protein content(% d.m.)

Year (Y)2002�2003 32.92 A 65.37 C 2.975 C 78.39 C 44.32 C2003�2004 24.23 C 77.78 B 3.747 B 82.45 A 47.49 A 13.3

2004�2005 26.77 B 84.12 A 4.165 A 82.01 B 46.76 B 13.8Lsd 0.05 0.2239 0.4 2.975 78.39 44.32N rate and timing (T)

N80 27.67 C 75.09 B 3.443 D 80.92 B 47.84 A 13.2 CN80S 28.11 AB 75.74 B 3.549 CD 81.60 A 46.34 B 13.1 CN104 27.81 BC 74.91 B 3.572 BCD 80.80 BC 46.33 B 13.6 BN104S 28.02 AB 75.83 B 3.695 B 80.97 B 45.81 BC 13.4 BC

N128 28.00 AB 77.31 A 3.831 A 80.98 B 45.72 BC 13.8 ABN128S 28.22 A 75.65 B 3.683 BC 80.44 C 45.09 C 14.1 ALsd 0.05 0.3167 1.47 0.1352 0.4695 0.88 0.43

Cultivars (G)Svevo 26.93 D 83.06 A 3.805 A 80.91 C 42.22 E 14.4 ACiccio 26.69 D 75.56 C 3.731 A 82.30 A 45.81 C 12.5 E

Creso 33.04 A 69.81 E 3.134 C 81.56 B 44.85 D 14.0 ABSimeto 27.96 B 72.69 D 3.564 B 79.50 D 48.89 B 13.7 BCLesina 25.85 E 75.19 C 3.783 A 80.62 C 50.51 A 13.4 CD

Duilio 27.37 C 78.24 B 3.757 A 80.81 C 44.85 D 13.3 DLsd 0.05 0.3 1.5 0.14 0.47 0.88 0.43Significant interactionY�G *** *** *** *** *** ***

Y�T ** *** *** NS ** NSG�T NS NS NS NS *** NSY�G�T NS NS NS NS *** NS

NS: Not significant; level of statistical significance:**pB0.01,***pB0.001.

4 S.A. Colecchia et al.

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same total N rate between sowing (20%), tillering(30%), and stem-elongation (50%) caused lower yield(N128S), with 3.8 and 3.6 t ha�1, respectively. TheN128S treatment had similar yield response of 104 kgN ha�1 N rate (N104 and T104S treatments).

Yield components (TW and TKW) also behavedin a similar way, with differences between thedifferent N splitting treatments. Higher TW wereobserved for N80S which was significant differentfrom all the other treatments. On the other hand, PHtrait was less sensitive to N fertilizer rate andsplitting, all the treatments did not show any sig-nificant difference except for N128. The rate andsplitting of N fertilizer application also influencedgrain protein content (Table 5), which was alwayshighest when 128 kg N ha�1 rate was applied at thetillering and stem elongation stage. Application of the80 kg N ha�1 rate prompted a significant decline ingrain protein content in both split procedures (N80

and N80s).The main effect of genotypes was significant for

all traits evaluated (Table 5). For the HD, thecultivars have showed mean values quite similar forfive to six genotypes that ranged around two days(from 25.9 to 27.8 days after first April) with theexception of Creso (33 days after first April). Cresowas the only genotype that showed a mean value ofPH lower than 70 cm (69.8 cm). Mean GY variedfrom 3.134 (Creso) to 3.805 t ha�1 (Svevo), TWvaried from 79.5 (Simeto) to 82.3 kg hl�1 (Ciccio),and TKW ranged from 42.22 (Svevo) to 50.51 g(Lesina).

In Figure 1A are shown the effects of Y and Ntreatments (T) on GY and PC; the effect of Nfertilizer rate and timing on GY was more markedin the last two years that were characterized by betterrainfall distribution. In particular, during the 2004�2005 growing season the best performances wererecorded at 104 and 128 kg N ha�1 rate while thelowest and significant means were observed at 80 kgN ha�1 rate. In the second year (2003�2004), instead,the mean GY performances over the six N treatmentswere quite similar and not significant. Figure 1Bshows the effects of N treatments and application onPC during two growing-seasons. The results show

that significant differences are only at 104 and 128 kgN ha�1 rate while for all other N treatments anysignificant difference was observed. In all the cases,the mean PC was higher than Industry’s standards(�13%).

Regarding the Y�G interaction it was found tobe significant although it was generally a noncross-over type of interaction (Figure 2A). In general, thecultivars were more responsive to improved climaticconditions during the study-period with the exceptionof the late Creso cultivar for which a constant yieldperformance every year was recorded. With regard tothe PC (Figure 2B) Svevo and Creso were thecultivars with the highest mean values of proteincontent in the grains (average value 14.4 and 14.0%for Svevo and Creso, respectively). The highestabsolute values were observed in the second yearand for the same cultivars (15.0 and 14.5% for Svevoand Creso, respectively). The lowest values in bothfirst and in second year were observed for the cultivarCiccio (12.4 and 12.5% for 2004 and 2005, respec-tively).

Economic evaluation

The results of economic analysis (Figure 3) showedrather uniform a behavior among the different ratesof N during the first year for both timing of Napplications with a NR ranging from 413.3 Euroha�1 (Svevo, N104s) to 169.6 Euro ha�1 (Creso,N104). Creso recorded the lowest values of NRalthough a high grain protein content was recorded(Table 5). The cultivar Ciccio, despite the fact that isthe cultivar with lower protein content (Figure 2B), itprovided a higher NR due to the high GY. In thesecond year, NR ranged from a maximum value of259.7 Euro ha�1 (Lesina N128s) and a minimumvalue of �66.2 Euro ha�1 (Creso, N80). At higher Nrate (N104 and N128) the NR was similar amongcultivars. Svevo (259.3 Euro ha�1 at N104) andCiccio (229.5 Euro ha�1 at N128) recorded meanvalues higher with Normal N timing application whileCiccio (245. Euro ha�1 at N104s) and Lesina (259.7Euro ha�1 at N128s) performed better when N wassupplied in split application.

A

0.0

1.0

2.0

3.0

4.0

5.0

6.0

80 104 128 80s 104s 128s

Yie

ld (

t h

a-1 )

N Treatments

2003 2004 2005

B 0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

80 104 128 80s 104s 128s

Pro

tein

co

nte

nt

(% d

.m.)

N Treatments

2004 2005

Figure 1. Effects of year and N treatments on grain yield (A) and protein content (B) at Foggia (Italy). Vertical bars representLSD (pB0.05%).

Journal of Plant Interactions 5

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Overall, the marginal value for 2003�2004 showlow negative or positive values respect to the N80

chosen as baseline with a variation between �2.13

and �3.70 Euro kg�1 N ha�1. For the ‘normal’ Napplication N104 had negative marginal values forSvevo (�0.58 Euro kg�1 N ha�1), Ciccio (�0.75Euro kg�1 N ha�1), and Creso (�0.32 Euro kg�1 Nha�1) and positive for Simeto, Lesina, Duilio with1.4, 2.34, 3.70 Euro kg�1 N ha�1, respectively,

(Figure 4A). N128 showed low positive marginalvalues only for Svevo, Ciccio, and Creso and negativefor the other three cultivars (Figure 4A). For the‘split’ N application N104 is positive for the first fourcultivars (Svevo, Ciccio, Creso, and Simeto) and

negative for the other two (Lesina and Duilio), whileN128 showed opposite behavior (Figure 4B). In 2004�2005 the marginal values are more variable rangingbetween �3.12 and �7.53 Euro kg�1 N ha�1. N104

had most of the positive marginal values for both N

applications (‘normal’ and ‘split’) except for Duilio

(‘split’ N) where it showed a negative value of �0.30

Euro kg�1 N ha�1. The highest N application (128

kg N ha�1) showed only a high marginal value for

Lesina (‘split’ N) with 4.68 Euro kg�1 N ha�1, while

for all the other cultivars and N applications was

either very low or negative (Figure 4C,D).

Discussion

Nitrogen fertilizer application guidelines are normally

based on supplying the difference between the avail-

able N in the soil and the potential uptake by the

crop. However, the economically optimum nitrogen

rate amount will vary depending on grain prices,

fertilizer costs, and yield potential. Therefore, there is

0.0

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Svevo Ciccio Creso Simeto Lesina Duilio

Yie

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t h

a-1)

N Treatments

2003 2004 2005

0.0

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16.0

Svevo Ciccio Creso Simeto Lesina Duilio

Pro

tein

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nt

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Figure 2. Effects of year and cultivars on grain yield (A) and protein content (B) at Foggia (Italy). Vertical bars represent

LSD (pB0.05%).

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Figure 3. Net return evaluated for six durum wheat cultivars and two N treatments during 2003�2004 (A and B) and2004�2005 (C and D).

6 S.A. Colecchia et al.

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a need to adopt agronomic and economic models thatdetermine the optimum nitrogen rate and timing andare useable by growers and their advisers to achievehigher yield and grain PC (El-Sheemy 1991; Petracet al. 1999; Martre et al. 2006).

Nitrogen fertilizers are most often effective whenapplied at sowing, but where the yield expectation ishigh and the season is longer, split applicationsbetween sowing and up to the early boot stage canalso increase GY and protein percentage (Mason1975; Lopez-Bellido et al. 2006).

The economic return from late season applied Ndepends on the cost of the additional N and applica-tion, the resulting yield, the protein increase, and theprotein premium when the wheat is sold. The cost offertilizer-N will vary depending on year and regionand is greatly influenced by energy prices. Nitrogenfertilizer rate and timing are the major managementtools available after planting to manipulate wheat toproduce higher yields per hectare. Our findingsindicated that the excessive splitting of N rate over3 N rate (80, 104, and 128 kg N ha�1) showed only aminimum significant difference among the treat-ments. In particular, at high N levels (128 kg Nha�1) the timing and splitting of N fertilizer applica-tion influenced both GY and grain protein contentconfirming a number of studies for which the splitand late application of N promotes a build-up ofgrain protein content rather than an increase in GY(Sowers et al. 1994; Ayoub et al. 1995; Ercoli et al.2009). Alcoz et al. (1993), Mossedaq and Smith(1994), and Sowers et al. (1994) also report anincrease in wheat yield when fertilizer N is appliedat the start of stem elongation when soil water is

adequate for N uptake after application. In adding,our experience evidenced as the N application atsowing date did not influence in any way the cultivarsperformance suggesting the possibility to delay Nfertilization and focusing on the critical stage of thecrop that in these semiarid conditions is representedby the end of tillering and beginning of stemelongation.

The proper N management and the economicsuccess of N fertilization depend on the growingseason rainfall. The highest yield was obtained in2004�2005, when rainfall was more uniformly dis-tributed during the growing season. In addition, thehigher rainfall between February and May influencedthe crop N uptake and higher protein content. Themarginal value of the fertilization for this growingseason showed that 104 kg N ha�1would have beenthe best amount of N to apply either as ‘normal’ or‘split’. Higher N fertilization rates did not cause anysignificant increase in yield and protein because it islikely that the excess N is leached during thosemonths of higher rainfall, causing environmentaland economic losses. In 2003�2004, the marginalvalues were not significantly higher respect to thebaseline because the lower rainfall during February�May period will not cause excessive crop N uptake.

In economic terms the interaction between T andG showed differences more marked among thecultivars, particularly for the 2003�2004 growingseason with an extremely low incidence of proteinpremium on NR that, instead, appeared closelyrelated to GY. Similar conclusions were reported byVaughan et al. (1990) showing that at moderateprotein premiums of $1.10 Mg�1 per 2.5 g kg�1

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Figure 4. Marginal value evaluated for six durum wheat cultivars and two N treatments during 2003�2004 (A and B) and

2004�2005 (C and D).

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above 120 g kg�1, N applied with the aim of

increasing grain was not profitable unless the costof application was included as part of a tillage

practice. On the contrary the NR evaluated for the

2004�2005 was most significantly associated with rateand timing of N fertilizer applied.

Results from this study show that N application at

sowing date did not influence the cultivars perfor-mance suggesting the possibility to delay N fertiliza-

tion and focusing on the critical stage of the crop thatin these semiarid conditions is represented by the end

of tillering and beginning of stem elongation. Napplied at stem elongation has been demonstrated

to increase yield and protein provided there isadequate soil water content to uptake N (Alcoz

et al. 1993; Mossedaq and Smith 1994; Sowers et al.

1994). In absolute terms the best combination was thecultivars Svevo managed using 104 kg N ha�1

divided between tillering and stem-elongation stage.The excessive N splitting reduces yield potential

without advantage in PC terms.The proper N management from this point of

view appears strictly dependent on the location and

year of the study. The lack of universal N fertilizerprescription suggests that to achieve N optimization

for yield and grain protein a system approach to

evaluate the interactions of climate, soil, cultivars,and agronomic managements may be required.

Comparing the two applications against the three

split application at the same rates, research indicatesthat (1) yields are not increased with the split, (2)

excessive splitting reduces yield potential withoutadvantage in PC terms, and (3) in these local

conditions late heading cultivars are less productivethan the most common and early ones.

In conclusion, our study underlines the impor-

tance of selecting the proper durum wheat cultivar tomaximize the NR for farmers and the need to manage

N fertilization to improve wheat yield and grainquality. Despite the fact that the study was carried

out for a limited number of years, we feel confident

that results observed in the field trial on yield andprotein response to N management are representative

of a large area of the Tavoliere plane and can betransferred over space and time due the lower erratic

nature of Mediterranean climate.

Acknowledgements

This study was supported by the Ministry of Agricultural,

Food and Forestry Policies (MIPAF) of Italy, as special

grant SICERME2 and Apulia Region with the project PIF

124 ‘Filiera cerealicola Legacoop’.

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