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No-tillage and conventional tillage effects on durum wheat yield, grain quality and soil moisture content in southern Italy P. De Vita a,c, * , E. Di Paolo b , G. Fecondo b , N. Di Fonzo c , M. Pisante d a ENEA, Italian National Agency for New Technology, Energy & Environmental, Trisaia Research Center, S.S. 106 Jonica, Km 419.5-75026 Rotondella, MT, Italy b CO.T.IR., Consorzio per le Tecniche Irrigue, 66054 Vasto, CH, Italy c Experimental Institute for Cereal Research, Section of Foggia, 71100 Foggia, Italy d Department of Food Sciences, Crop and Soil Sciences Section, University of Teramo, Via Spagna, 1, 64023 Mosciano S. Angelo, TE, Italy Received 28 May 2004; received in revised form 10 January 2006; accepted 27 January 2006 Abstract No-tillage (NT) is becoming increasingly attractive to farmers because it clearly reduces production costs relative to conventional tillage (CT). However, many producers in southern Italy are reluctant to adopt this practice because NT can have contrasting consequences on grain yield depending on weather conditions. The effect of NT and CT on continuous durum wheat (Triticum durum Desf.) under rainfed Mediterranean conditions was studied, over a 3-year period (2000–2002) at two locations (Foggia and Vasto) in southern Italy. Yield, grain quality [thousand kernel weight (TKW), test weight (TW) and protein content (PC)] and soil water content were assessed. Higher yield was obtained with NT than CT in the first 2 years at Foggia. In contrast, mean yield and quality parameters at Vasto were similar for the two treatments, except in the third year in which CT produced more than NT (4.6 Mg ha 1 versus 2.9 Mg ha 1 ). At Foggia, TW and TKW were higher in NT than CT in all years. Highest PC was obtained under CT (19.6% and 15.5% for CT versus 14.7% and 11.4% for NT, respectively, in the growing season 2000–2001 and 2001–2002) indicating that grain was shriveled with low starch accumulation. At Foggia, where this study was part of a long-term experiment started in 1995, a strong correlation was observed between yield and rainfall during the wheat growing season. The coefficient of determination (R 2 ) values for CT and NT were 0.69 * and 0.31 ns, respectively, and the regression straight line crossed around 300 mm of rainfall. These results indicate that NT was superior below this rainfall value, whereas more rainfall enhanced yield in CT. We conclude that NT performed better at Foggia with limited rainfall during the durum wheat growing season. The superior effect of NT in comparison to CT, was due to lower water evaporation from soil combined with enhanced soil water availability. # 2006 Elsevier B.V. All rights reserved. Keywords: No-tillage; Conventional tillage; Durum wheat; Yield; Grain quality; Soil water content 1. Introduction Durum wheat (Triticum durum Desf.) is the main cereal crop in Italy, with >1.6 Mha producing about 4 Tg per year. Production is concentrated in southern and central Italy (the two Italian macro areas under the European cereal subsidy regime) and it has high variability in terms of yield and grain quality. The factors most strongly influencing crop yield, particu- larly grain yield, are soil moisture and N, the former of which depends on rainfall and its distribution during the growing season (Cooper et al., 1987). Typically in www.elsevier.com/locate/still Soil & Tillage Research 92 (2007) 69–78 * Corresponding author. Tel.: +39 0835 974541; fax: +39 0835 974749. E-mail address: [email protected] (P. De Vita). 0167-1987/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.still.2006.01.012

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Page 1: No-tillage and conventional tillage effects on durum wheat yield, grain quality and soil moisture content in southern Italy

www.elsevier.com/locate/still

Soil & Tillage Research 92 (2007) 69–78

No-tillage and conventional tillage effects on durum wheat yield,

grain quality and soil moisture content in southern Italy

P. De Vita a,c,*, E. Di Paolo b, G. Fecondo b, N. Di Fonzo c, M. Pisante d

a ENEA, Italian National Agency for New Technology, Energy & Environmental, Trisaia Research Center,

S.S. 106 Jonica, Km 419.5-75026 Rotondella, MT, Italyb CO.T.IR., Consorzio per le Tecniche Irrigue, 66054 Vasto, CH, Italy

c Experimental Institute for Cereal Research, Section of Foggia, 71100 Foggia, Italyd Department of Food Sciences, Crop and Soil Sciences Section, University of Teramo,

Via Spagna, 1, 64023 Mosciano S. Angelo, TE, Italy

Received 28 May 2004; received in revised form 10 January 2006; accepted 27 January 2006

Abstract

No-tillage (NT) is becoming increasingly attractive to farmers because it clearly reduces production costs relative to

conventional tillage (CT). However, many producers in southern Italy are reluctant to adopt this practice because NT can have

contrasting consequences on grain yield depending on weather conditions. The effect of NT and CT on continuous durum wheat

(Triticum durum Desf.) under rainfed Mediterranean conditions was studied, over a 3-year period (2000–2002) at two locations

(Foggia and Vasto) in southern Italy. Yield, grain quality [thousand kernel weight (TKW), test weight (TW) and protein content

(PC)] and soil water content were assessed.

Higher yield was obtained with NT than CT in the first 2 years at Foggia. In contrast, mean yield and quality parameters at Vasto

were similar for the two treatments, except in the third year in which CT produced more than NT (4.6 Mg ha�1 versus 2.9 Mg ha�1).

At Foggia, TW and TKW were higher in NT than CT in all years. Highest PC was obtained under CT (19.6% and 15.5% for CT

versus 14.7% and 11.4% for NT, respectively, in the growing season 2000–2001 and 2001–2002) indicating that grain was shriveled

with low starch accumulation.

At Foggia, where this study was part of a long-term experiment started in 1995, a strong correlation was observed between yield

and rainfall during the wheat growing season. The coefficient of determination (R2) values for CT and NT were 0.69* and 0.31 ns,

respectively, and the regression straight line crossed around 300 mm of rainfall. These results indicate that NT was superior below

this rainfall value, whereas more rainfall enhanced yield in CT. We conclude that NT performed better at Foggia with limited

rainfall during the durum wheat growing season. The superior effect of NT in comparison to CT, was due to lower water evaporation

from soil combined with enhanced soil water availability.

# 2006 Elsevier B.V. All rights reserved.

Keywords: No-tillage; Conventional tillage; Durum wheat; Yield; Grain quality; Soil water content

1. Introduction

Durum wheat (Triticum durum Desf.) is the main

cereal crop in Italy, with >1.6 Mha producing about

* Corresponding author. Tel.: +39 0835 974541;

fax: +39 0835 974749.

E-mail address: [email protected] (P. De Vita).

0167-1987/$ – see front matter # 2006 Elsevier B.V. All rights reserved.

doi:10.1016/j.still.2006.01.012

4 Tg per year. Production is concentrated in southern

and central Italy (the two Italian macro areas under the

European cereal subsidy regime) and it has high

variability in terms of yield and grain quality. The

factors most strongly influencing crop yield, particu-

larly grain yield, are soil moisture and N, the former

of which depends on rainfall and its distribution during

the growing season (Cooper et al., 1987). Typically in

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P. De Vita et al. / Soil & Tillage Research 92 (2007) 69–7870

the past, durum wheat-fallow (one crop in 2 years) has

been the cropping system used extensively in a rainfed

farming system. This management system was designed

to enhance water storage, in order to ensure emergence

and establishment of the wheat seedling. This ancient

agronomic practice, involved the use of moldboard

plowing as primary tillage followed by repeated

secondary shallow tillage, aimed to control weeds

and water consumption. Tillage operations necessary to

remove weeds and prevent crust formation cause moist

soil to move to the surface increasing soil evaporation

(Aase and Siddoway, 1982). Still today, farmers

continue to use intensive conventional tillage (CT)

(i.e. moldboard plowing) for continuous wheat produc-

tion in these areas. However, the European Community

agricultural policy has strongly encouraged conserva-

tion tillage practices (and in some instances the

conversion of cropland into set-aside land) in order

to decrease soil loss (European Union, 2000).

The first no-tillage (NT) trials in Italy were

conducted in 1968, but it is only in the last decade

that NT technology has experienced a substantial

expansion. This has been based on the need to reduce

crop costs, greater availability on the Italian market of

equipment for sowing on untilled soil, and progress in

the availability of adequate herbicides (Sartori and

Peruzzi, 1994; Sandri and Sartori, 1997).

Conservation tillage, defined here as NT with a crop

residue mulch cover, has considerable potential for

stabilizing production in semiarid zones, but can have

contrasting consequences on water conservation and

yield. Lal et al. (1978) and Osuji (1984) demonstrated

positive effects, whereas Chopart and Kone (1985) and

Wilhelm et al. (1987) found negative effects. This

variability could be due to variations in water balances

both across fields and between different cropping

seasons, leading to positive effects on water storage

and negative effects on water uptake by plants, in

different years.

NT management can increase both water use effi-

ciency and wheat grain yield under dryland conditions

(Bonfil et al., 1999). Clean fallow was also shown to

generally increase soil water storage (Bonfil et al., 1999).

Covering of the soil surface with straw mulch is

another agronomic input with the potential to alleviate

stress by both reducing water evaporation and increas-

ing infiltration (Lal, 1975; Fisher, 1987; Unger et al.,

1991; Rinaldi et al., 2000). In addition, surface

mulching with crop residues reduces temperature,

evaporation, and wind speed gradient and activity at

the soil-atmosphere interface (Hatfield et al., 2001).

However, it is recognized that the production of residues

in semiarid environments may be insufficient to

produce these desired effects. Temperate soils under

NT generally contain greater concentrations of orga-

nic C and microbial biomass, especially in the upper

layer (Cereti and Rossini, 1995; Dick, 1983; Unger,

1991; Potter and Chichester, 1993; Christensen et al.,

1994; Campbell et al., 1989; Arshad et al., 1990;

Logan et al., 1991; Basso et al., 1993). Many

researchers (Hill, 1990; Logsdon et al., 1990; Vyn

and Raimbault, 1993; Cassel et al., 1995) have

reported greater bulk density and soil penetration

resistance and lower total porosity in NT compared

with moldboard plow and chisel plow.

However, the effect of conservation practices is

sometimes contradictory and depends on soil type,

climate and previous management history (Prasad and

Power, 1991).

The long-term effects of CT and NT, under

Mediterranean conditions, have scarcely been studied.

By contrast, NT practices in other areas such as USA,

Australia, and Canada are well documented (Baker

et al., 1996). Tillage effects on wheat yield under

rainfed conditions have been thoroughly studied in the

Great Plains of the USA (Halvorson and Reule, 1994;

Norwood, 1994; Unger, 1994; Wiese et al., 1994).

Furthermore, there is little information in the literature

concerning the effects of tillage systems on durum

wheat grain quality after several years of reduced and

NT practices in Mediterranean dryland conditions.

Several studies have reported that wheat quality is also

influenced by the interaction of a number of other

factors, including cultivar, soil, climate, cropping

practices and grain storage conditions (Randall and

Moss, 1990; Blumenthal et al., 1991; Borghi et al.,

1997). Water stress is associated with increased grain

protein content (Terman et al., 1996), while an excess

of soil moisture can lead to a decrease in grain protein

content (Robinson et al., 1979). Grain protein content

is the result of complex interactions between N and

water availability, yield and temperature, which in

many cases hinder their investigation. Some studies

have analyzed wheat grain protein content as a

function of tillage system, reporting no significant

differences (Baenzinger et al., 1985; Bassett et al.,

1989; Cox and Shelton, 1992). In contrast, Lopez-

Bellido et al. (1998) reported higher grain protein

content for CT than for NT; they also recorded

differences in alveograph parameters between the two

tillage systems. Our objective was to determine the

effects of NT and CT practices on durum wheat yield,

grain quality, and soil water content during several

Mediterranean growing seasons.

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P. De Vita et al. / Soil & Tillage Research 92 (2007) 69–78 71

2. Materials and methods

2.1. Study sites

Experiments were conducted at two locations in

southern Italy, Foggia and Vasto, during three growing

seasons (1999–2000, 2000–2001 and 2001–2002). At

Foggia (418280N, 158320E and 75 m a.s.l), the study was

part of a long-term experiment started in 1995 and

conducted at the Experimental Institute for Cereal

Research on a clay-loam soil (Typic Chromoxerert). At

Vasto (428100N, 148380E and 40 m a.s.l.), the study was

conducted at the Experimental Station for Land and

Irrigation Techniques (CO.T.IR.) on a silty clay-loamy

soil (Aquic Haploxerert). A datalogger was installed to

collect the following daily weather data: solar radiation,

minimum and maximum temperature and rainfall at

each location. Soil characteristics of both sites are

reported in Table 1.

2.2. Experimental design and crop management

Two tillage treatments in a continuous durum wheat

system were compared: (i) conventional tillage (CT),

consisting of moldboard ploughing to 30 cm depth

followed by secondary tillage with a soil grubber and

harrow for seedbed preparation, and (ii) no-tillage (NT)

with residue retained on the surface. In NT, crop

residues cut by the combine were chopped and spread

evenly with a combine-attached chopper. NT plots were

seeded with a NT seed drill. Weed were controlled with

glyphosate [isopropylamine salt of N-(phosphono-

methyl)glycine] at a rate of 93.4 g a.i. ha�1 before

planting. At each site, treatments were arranged in a

complete randomized design replicated three times with

plots of 1,500 m2 size. At Vasto, the experimental trial

followed a continuous durum wheat system under CT,

Table 1

Soil characteristics of the two experimental sites (Vasto and Foggia,

Italy)

Soil characteristics Vasto 0–60 cm

depth

Foggia 0–45 cm

depth

Clay (%) 40.7 36

Silt (%) 52.9 17

Sand (%) 6.4 47

pH 8.2 7.8

Exchangeable Ca (g/kg) 122 19

Available P (mg/kg) 14 19

Exchangeable K (mg/kg) 375 111

Total N (g kg�1) 1.4 1.5

Organic C (g kg�1) 16.0 17.3

Bulk density (Mg m�3) 1.25 1.29

while at Foggia site the study was part of a long-term

experiment started in 1995 with the same experimental

design adopted in the present study. During the 1995–

1999 period, only yield data were collected. At each

site the experimental treatments were repeated every

year on the same plots; durum wheat cultivar

‘‘Ofanto’’ was sown on December 10, 12, and 12, in

1999, 2000, and 2001, respectively, at Foggia and

December 3, November 21, and December 2, in 1999,

2000, and 2001, respectively, at Vasto. The seeding

rate was 200 kg ha�1 at Foggia and 230 kg ha�1 at

Vasto. Durum wheat cultivar ‘‘Ofanto’’ was adopted in

these trials for two reasons: (i) it is the most common

cultivar in the experimental areas, and (ii) it is well

suited to the local climate in soils with low N

availability. Nitrogen (90 kg N ha�1) was split applied,

at the rate of 1/3 before sowing (incorporated by disk

harrowing in CT and surface broadcast in NT) as

ammonium phosphate, and 2/3 N top-dressed applied

at the beginning of wheat tillering, corresponding to

Stage 21 of the Zadoks scale (Zadoks, 1974) as

ammonium nitrate. Weeds within the growing season

were controlled by means of specific herbicides:

Tralcossidim (1.7 l ha�1) + Clopiralid + MCPA + -

Fluroxypyr (2.0–2.5 l ha�1).

2.3. Yield and grain quality analysis

Whole plots were harvested mechanically early in

June each year and grain yield determined at 13%

moisture content. Several commercial and technologi-

cal quality parameters were determined. Thousand

kernel weight (TKW) was calculated as the mean

weight of three sets of 100 grains per plot. Test weight

(TW) was measured on three samples of 250 g per plot

and expressed as kg hl�1 obtained with a Shopper

chondrometer. Grain N content was determined by

means of the standard Kjeldahl method. Grain protein

concentration (PC) was calculated after multiplying

Kjeldahl N by 5.7 and expressed on a dry weight basis.

2.4. Soil analysis

For each location and during two growing seasons

(2000–2001 and 2001–2002) soil water content was

measured on a monthly basis using the gravimetric

method, based on the conventional oven-dry weight and

multiplied by the bulk density (Qiu et al., 2001). At

Vasto, soil samples were taken at five depths (0–5, 5–10,

10–20, 20–40 and 40–60 cm), while at Foggia, soil

samples were taken at a depth of 0–15, 15–30 and 30–

45 cm. Only water in the profile as a whole is discussed,

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P. De Vita et al. / Soil & Tillage Research 92 (2007) 69–7872

not the individual increments. Soil physical properties

(bulk density, sand %, silt % and clay %) and soil

chemical properties (pH, total N and organic C) were

determined on each plot at the beginning and end of

the study.

2.5. Crop water use

On the basis of measured soil water content, seasonal

crop water use (WU) was estimated according to the

following water balance equation:

WU ¼ �DSWCþ R� D (1)

where ‘‘DSWC’’ is the variation, between seedling and

harvest date, of the volumetric soil water content at 0–

0.60 and 0–0.45 m depth layer, respectively, at Vasto

and Foggia, R the amount of rainfall, and D is the water

lost due to deep percolation, all expressed in mm. The D

term was calculated according to a water balance

approach, using daily values of evaportranspiration

(ET) and rainfall, and starting from measured soil water

content at sowing. Whenever field capacity was

exceeded, deep percolation water was calculated.

Water use efficiency (WUE) was calculated as the ratio

of grain yield and water used by the crop (Roygard

et al., 2002).

Table 2

Monthly rainfall and mean maximum and minimum temperature for three g

Foggia (1955–1994) and Vasto (1965–1993), Italy

1999–2000 2000–2001

Tmax

(8C)

Tmin

(8C)

Rainfall

(mm)

Tmax

(8C)

Tmin

(8C)

Rain

(mm

Foggia

November 17.8 8.5 55 20.9 10.3 36

December 14.8 6.6 31 17.4 7.5 16

January 12.8 2.8 12 15.6 7.4 27

February 15.0 4.2 30 15.8 5.3 18

March 18.5 5.4 33 22.4 12.1 11

April 22.7 10.8 64 20.8 8.6 77

May 29.1 14.6 61 27.5 13.7 16

Sum 286 201

Vasto

November 15.7 6.5 105 19.1 7.8 26

December 12.7 3.8 53 14.7 4.5 55

January 10.2 1.5 41 13.3 3.8 104

February 11.8 2.4 50 13.0 2.5 23

March 15.2 3.0 24 20.4 7.5 16

April 19.0 8.0 59 17.3 6.1 61

May 23.8 12.8 24 22.4 11.8 43

Sum 356 328

2.6. Statistical analysis

Data from individual years and from combined years

were analyzed using ANOVA using Fischer’s protected

least significant difference at P < 0.05. All data were

statistically analyzed using a statistical software

package (Statistica, StatSoft Inc., Tulsa, OK, USA).

3. Results and discussion

3.1. Weather conditions

Weather conditions are summarized in Table 2.

Vegetative growth of durum wheat occurred from

November to the end of February and the reproductive

period (stem elongation, heading, grain filling, and

maturation) occurred from March to May. As is typical

of the Mediterranean climate, quantity and distribution

of rainfall were highly variable, but concentrated from

the end of autumn (fall) to the beginning of spring.

Rainfall (November–May) varied among the 3 years

(Table 2), with ranges from 201 to 362 mm at Foggia

and 328 to 417 mm at Vasto.

The second study-year (2000–2001) was character-

ized by a long drought stress period. The first year

(1999–2000) was almost normal and the third year was

rowing seasons (2000–2002) compared to long-term data recorded at

2001–2002 Long-term data

fall

)

Tmax

(8C)

Tmin

(8C)

Rainfall

(mm)

Tmax

(8C)

Tmin

(8C)

Rainfall

(mm)

17.7 8.6 56 16.7 6.9 61

11.9 4.3 55 12.8 3.9 60

12.6 4.8 47 11.3 2.5 48

17.8 7.6 11 12.5 2.7 43

19.4 8.3 22 15.4 4.1 46

21.0 9.1 110 19.1 6.2 47

25.9 12.8 61 24.7 10.4 37

362 342

14.7 7.6 96 15.3 9.5 70

9.5 2.6 51 11.4 6.2 87

9.9 0.0 29 10.0 4.9 51

13.9 3.9 52 10.8 5.2 48

15.6 5.8 26 13.4 7.2 53

17.1 7.9 111 16.9 10.2 51

22.2 12.3 52 21.6 14.6 38

417 398

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P. De Vita et al. / Soil & Tillage Research 92 (2007) 69–78 73

Table 3

Grain yield and qualitative parameters obtained at Vasto (Italy) during three growing-seasons (2000–2002)

Growing season Treatment Yield

(t ha�1)

Test weight

(kg hl�1)

Thousand kernel

weight (g)

Protein

content (%)

1999–2000 No-tillage 4.5 75.2 39.8 14.0

Conventional tillage 4.2 77.5 39.6 12.9

F value n.s. n.s. n.s. n.s.

2000–2001 No-tillage 4.5 71.5 45.1 13.8

Conventional tillage 4.7 73.8 43.7 13.4

F value n.s. n.s. n.s. n.s.

2001–2002 No-tillage 2.9 b 65.8 b 30.2 16.3 a

Conventional tillage 4.6 a 72.3 a 37.7 13.5 b

F value ** ** n.s. **

n.s.: not significant.** Values significant at P < 0.01 level probability.

normal (2001–2002) compared with long-term rainfall

data. During the grain filling period (April–May),

temperatures varied widely for each site and study-year

(Table 2). Mean temperature at Foggia was always

higher than at Vasto. For each location, the second

study-year was characterized by above average tem-

perature with an unexpected increase in March (Table 2)

leading to a significant shortening of the durum wheat

production cycle.

3.2. Yield and grain quality

At Vasto, there were no effects of tillage treatment

during the first 2 years (1999–2000 and 2000–2001) in

Table 4

Grain yield and qualitative parameters obtained at Foggia (Italy) during th

Growing season Treatment Yield

(t ha�1)

1999–2000 No-tillage 3.34 a

Conventional tillage 2.94 b

F value *

2000–2001 No-tillage 1.65 a

Conventional tillage 0.90 b

F value **

2000–2002 No-tillage 2.13

Conventional tillage 2.65

F value n.s.

n.s.: not significant.* Values significant at P < 0.05 level probability.

** Values significant at P < 0.01 level probability.*** Values significant at P < 0.001 level probability.

either wheat yield or quality (Table 3). In contrast,

grain yield during the same period at Foggia was

greater under NT than CT (Table 4). In the third year

(2001–2002), wheat yield was lower under NT than

CT at Vasto and not different between tillage systems

at Foggia. The low yield under NT in the third year

may have been associated with the development

of fungal disease, like powdery mildew (Blumeria

graminis f. sp. tritici) and leaf rust (Puccinia recondita

f. sp. tritici), that caused senescence during grain

filling stage with low values of TW and TKW. This

discrepancy among years was due to high precipitation

(111 mm versus 51 mm for the long-term average) in

April 2002.

ree growing-seasons (2000–2002)

Test weight

(kg hl�1)

Thousand kernel

weight (g)

Protein

content (%)

78.8 a 41.5 a 12.8 a

76.5 b 38.3 b 11.6 b

** ** **

77.2 a 40.5 a 14.7 b

73.6 b 30.2 b 19.6 a

* *** *

73.9 a 35.5 a 11.4 b

70.1 b 29.3 b 15.5 a

* * *

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P. De Vita et al. / Soil & Tillage Research 92 (2007) 69–7874

For the 1999–2000 and 2000–2001 growing seasons

at Vasto, grain quality parameters were similar between

the two tillage systems (Table 3). Test weight values

were less than market requests (TW � 80 kg hl�1),

while PC values met the industry’s standards

(PC � 12.5%). No relationship was found between

TW and PC, confirming that TW was mainly affected

by shape and size of the kernels (Troccoli and Di

Fonzo, 1999) in response to the climatic conditions

during grain filling stage. In the third year, lower yield

under NT than under CT was also associated with

lower grain quality. Low values of TW and TKW

indicated that grain was shriveled with low starch

accumulation (Troccoli et al., 2000), resulting in

higher PC in NT than CT.

Grain quality at Foggia was affected by tillage

treatments during all three growing seasons (Table 4).

Specifically, TW and TKW were greater under NT than

CT each year. Protein content, in contrast, was similar

between tillage systems during the first year (1999–

2000), but lower under NT than CT in the second and

third years. The high value of PC under CT during

2000–2001 indicated that the grain was shriveled with

low starch accumulation (Troccoli et al., 2000).

At Foggia, where yield data were available since

1995, a strong correlation was observed between yield

and precipitation during the wheat cycle (Fig. 1).

Regression lines crossed at 300 mm of rainfall, a point

at which below NT was superior to CT and at which

above CT was superior to NT. The lower yield under NT

than CT at Vasto in 2001–2002 with high rainfall

confirmed this relationship. Similar results were found

under barley by Azooz and Arshad (1998), where in a

dry-year barley yield increased with NT, while in a wet

year yield was greater with CT. Again our results agree

well with the data of Lopez-Bellido et al. (1996) and

Lopez-Bellido and Lopez-Bellido (2001) for similar

environmental conditions; in fact, we found higher

Fig. 1. Correlation between grain yield and rainfall during durum

wheat cycle (November–May) at Foggia, Italy.

durum wheat yield under NT than CT in dry seasons,

while the opposite was true in wet seasons. In

northwestern Canada, barley grain yield was greater

under NT than CT in drier years, but lower in wetter

years (Arshad et al., 1999). Bonfil et al. (1999) found no

difference among tillage techniques with seasonal

rainfall (from wheat planting to harvest) of 320 mm

in Israel. At Vasto, where the precipitation during the

wheat cycle was always around 400 mm, no correlation

was found between yield and precipitation.

3.3. Soil water content

At Foggia, soil water content was significantly

greater under NT than CT, at the beginning of the

wheat cycle, during each of the two growing seasons

(Fig. 2). Higher soil water content under NT than CT

indicated reduced water evaporation during the

preceding period. This condition guaranteed an earlier

and more uniform emergence in NT than in CT

(Fig. 3), where whole plot emergence was delayed. In

2000–2001, soil water content was always greater

under NT than under CT, but differences declined

towards the end of the crop cycle (Fig. 2).

Fig. 2. Soil water content under conventional tillage (CT) and no-

tillage (NT) during 2000–2001 and 2001–2002 growing seasons at

Foggia, Italy. *Significant difference at P < 0.05 level probability

between tillage treatments.

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P. De Vita et al. / Soil & Tillage Research 92 (2007) 69–78 75

Fig. 3. Emergence conditions of durum wheat on December 15, 2000 at Foggia, Italy under conventional tillage (left) and no-tillage (right).

In 2001–2002, soil water content under NT started

off more similar to that in CT, but became greater than

CT throughout the year. Across growing seasons, soil

water content under NT was about 20% greater than

under CT.

At Vasto, soil water content results were similar to

those at Foggia (Fig. 4), but the magnitude of difference

in soil water content between tillage systems was less

than at Foggia.

At Foggia, differences in soil water content between

NT and CT could be partly attributed to differences in

Fig. 4. Soil water content under conventional tillage (CT) and no-

tillage (NT) during 2000–2001 and 2001–2002 growing seasons at

Vasto, Italy. *Significant difference at P < 0.05 level probability

between tillage treatments.

bulk density, 1.42 Mg m�3 under NT and 1.16 Mg m�3

under CT. Differences in bulk density due to tillage

system was an annual additive effect during 7 years. As

reviewed earlier, the effects of tillage on bulk density

and therefore on porosity distribution is conflicting

(Kay and Van den Bygaart, 2002). However, under NT it

was expected that a better and more uniformly

distributed wheat root system existed in the 0–15 cm

depth (Barzegar et al., 2004; Wilhelm, 1998) due to

better soil structural conditions, improved by higher

content of organic C in comparison to CT (19.7 g kg�1

versus 18.7 g kg�1). At Vasto, soil bulk density differed

only slightly at 0–40 cm depth; being 1.37 Mg m�3

under NT and 1.33 Mg m�3 under CT.

At Foggia, greater bulk density under NT would

have increased soil water capacity, which in association

with reduced water evaporation from the soil surface

due to residue, would have enhanced available water

for the crop. Furthermore, NT can increase water

storage replenishment of deeper layers as compared

with CT (Bonfil et al., 1999). Gantzer and Blacke

(1978) reported an increase of earthworm population

and biochannels in NT system compared with CT,

resulting in higher infiltration of water. Moreover,

Douglas et al. (1980), found macropores of earthworm

channels to be the prime cause for the difference

between CT and NT tillage systems. Seasonal WU at

Vasto was 434 and 415 mm (2000–2001) and 471 and

448 mm (2001–2002), respectively, for CT and NT

treatments. At Foggia, WU was 245 and 271 mm

(2000–2001) and 420 and 407 mm (2001–2002),

respectively, for CT and NT treatments. The water

balance did not indicate drainage, so that all rainfall

was considered useful for the crop. In the Mediterra-

nean climate of southern Italy, soil water evaporation is

important before complete crop soil cover. Rinaldi et al.

(2000) found out, in an experiment with weigh

lysimeters, water saving of about 12% when mulched

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P. De Vita et al. / Soil & Tillage Research 92 (2007) 69–7876

with wheat straw residue. Moreover, NT with straw

mulch can increase both WUE and grain yield (Bonfil

et al., 1999). At Foggia, greater WUE occurred with NT

(6.1 kg ha�1 mm�1) than with CT (3.7 kg ha�1 mm�1)

in 2000–2001, which was extremely dry, while no

significant differences were found in other years, where

mean WUE values were 10.8 and 8.1 kg ha�1 mm�1,

respectively, in 2000–2001 and 2001–2002 at Vasto and

5.8 kg ha�1 mm�1 at Foggia in 2001–2002.

Soil organic C at Foggia was greater with NT than

CT at 0–15 cm (19.7 g kg�1 versus 18.7 g kg�1) and at

15–30 cm (18.7 g kg�1 versus 15.0 g kg�1). The situa-

tion was reversed in the deeper layers (30–45 and 45–

60 cm), where organic C was greater in CT. These

results agree with those of other authors who observed

an effect of tillage operations on improved soil quality

indices (Dick, 1983; Lal et al., 1998), including soil

organic C storage (Dick, 1983; Lamb et al., 1985; Dao,

1991; Unger, 1991; Edwards et al., 1992; Eghball et al.,

1994; Bruce et al., 1995; Potter et al., 1998).

Conversely, increased losses of soil organic C have

been documented with CT (Lamb et al., 1985; Studdert

et al., 1997). At Vasto, no differences in content or

distribution of organic C were found, between NTand CT

(data not shown). The reason why many of the soil

properties recorded at Vasto were not significantly

different could be due to the young age of the trial. Many

of such soil modifications start 4–5 years after the

beginning of the tillage system adoption, as reported by

several authors (Rhoton, 2000; Carter and Rennie, 1982).

4. Conclusion

Superior yield and WUE occurred with NT when

precipitation was <300 mm during the wheat cycle

(November–May). Under these conditions, the NT

treatment expressed its superior nature for wheat yield

ensuring also a good level of grain quality. This is

important, since better quality of durum wheat in many

Mediterranean regions is inversely related to yield so

that the concept of quality is strictly associated to the

capacity of the soil management system to guarantee

acceptable and stable production by farmers with time.

The results presented here, show the importance of

saving soil moisture, through a reduced tillage system,

particularly in semi-arid environments, characterized

by low annual rainfall and high environmental

evapotranspiration demand. NT with residue retention

increased organic C in the upper layer of the soil, which

could lead to higher root density. This last characteristic

of crop in semi arid regions allows the ready absorption

of water minimizing water loss by evaporation.

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