Strip tillage effect on seedbed tilth and maize production in Northern Italy as case-study for the Southern Europe environment

Europ. J. Agronomy 48 (2013) 50–56

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Strip tillage effect on seedbed tilth and maize production in Northern Italy as case-study for the Southern Europe environment Mattia Trevini, Paolo Benincasa ∗ , Marcello Guiducci Università di Perugia, Dipartimento di Scienze Agrarie ed Ambientali, Borgo XX Giugno, 74 – 06121 Perugia, Italy

a r t i c l e

i n f o

Article history: Received 31 December 2012 Received in revised form 22 February 2013 Accepted 25 February 2013 Keywords: Conservative tillage Ground residue cover Weed Drilling depth Crop emergence Grain yield

a b s t r a c t Strip tillage is a conservative technique widespread overseas with recognized environmental, agronomical and economic benefits. In Europe it has been proposed only recently and is almost unknown by farmers of Italy and other Mediterranean countries, where its compliance with soil and climate environments needs to be evaluated. For this reason, a two-year field trial comparison was carried out between strip tillage, minimum tillage and no tillage for the cultivation of maize in the Po valley, as representative crop and environment for the Italian and Southern Europe intensive agriculture. The aim was to evaluate effects on seedbed quality, weed infestation, and maize performance from crop establishment to final harvest. The experiment was conducted on a sandy-loam soil with high chemical fertility and good water availability for the crop. Strip tillage was carried out by an original passive tool implement hitched to a pneumatic drill operating at a forward speed of around 6 km h−1 . We determined soil penetration resistance, bulk density, water content, clod size distribution, ground residue cover, number of weeds along crop rows and between rows, maize drilling depth, crop emergence, biomass accumulation and grain yield. Strip tillage moved less soil and left higher ground residue cover than minimum tillage, while the seedbed prepared by the two techniques did not differ for suitability to drilling, root exploration and crop growth. In fact, maize grown after strip tillage emerged fast and regularly approximating the wished plant density, experienced a limited weed infestation, and showed high total biomass and grain yields, similar to those obtained with minimum tillage. © 2013 Elsevier B.V. All rights reserved.

1. Introduction Strip tillage consists of seedbed tilth in strips 15–20 cm wide by 15–20 cm deep in correspondence with crop rows alternated to between-row strips of undisturbed soil (Hendrix et al., 2004). Strip tillage belongs to the group of conservation tillage techniques which, contrarily to ploughing, do not overturn soil layers and leave crop residues to cover at least 30% of soil surface. This implies environmental, agronomical and economic benefits such as prevention of runoff and soil erosion, conservation of soil water and organic matter content, safeguard of biodiversity (Morrison, 2002; Sprague and Triplett, 1986), improvement of soil bearing capacity and tractor traction in the undisturbed between-row strip (Hosking and Bloomer, 2006), reduction of inputs (traction power, fuel, labor) and costs (Crosson et al., 1986).

∗ Corresponding author. Tel.: +39 75 5856325; fax: +39 75 5856344. E-mail addresses: [email protected] (M. Trevini), [email protected] (P. Benincasa), [email protected] (M. Guiducci). 1161-0301/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.eja.2013.02.007

Soil strips may be disturbed with either power-take-off powered or passive tool equipments (Hosking and Bloomer, 2006). The formers have got rotating tools, the latters a sequence of tools like cutting disc, row cleaner, shank and roller which, thanks to tractor forward speed, allow soil loosening and seedbed preparation. The intensity of tillage depends on tool type (coulter with or without wings), geometry and arrangement (width, depth, rake angle), forward speed and soil water content (Mitchell et al., 2009; Morris et al., 2007; Pochi and Fanigliulo, 2010). The tillage effect may be evaluated on the basis of indexes like clod size distribution, porosity, bulk density, penetration resistance (Boydafi and Turgute, 2007; Carter, 1990; Schafer and Johnson, 1982; Simmons, 1992), residue incorporation and ground cover (Chen et al., 2004; Roberge et al., 2010). Weed flora evolution is also affected by strip tillage. As for no tillage, the lack of soil overturning causes an increase of weed seeds on soil surface (Demjanová et al., 2009; Hendrix et al., 2004; Swanton et al., 2000). Residual herbicides allow an efficient weed control unless clods that may fall from the disturbed to the undisturbed strip create spots where herbicide spreading is hampered (Hosking and Bloomer, 2006).

M. Trevini et al. / Europ. J. Agronomy 48 (2013) 50–56

About crop yield, results on strip tillage vary depending on soil type, season climate and plant species. In fine textured soils strip tillage equalled ploughing for maize yield and improved soil quality (Drury et al., 2003). Similar results were obtained by Licht and Al-Kaisi (2005) except in case of silty or poorly drained soils, where maize yield dropped to the level obtained with no tillage. As compared to other tillage techniques, strip tillage allowed similar yields in cotton (Gencsoylu and Yalcin, 2004; Gemtos et al., 2008), higher yields in sunflower (Sessiz et al., 2008). The final effect of any tillage technique depends much on its effect on initial crop establishment, starting from crop emergence. As compared to conventional tillage, crop emergence was delayed by strip tillage in sugar beet (Morris et al., 2007), not affected in sunflower (Sessiz et al., 2008). Maize emergence rate has been found to increase from a minimum in no tilled soils to a maximum in ploughed soils (Drury et al., 2003). Strip tillage would promote crop emergence with respect to no tillage in wet and cold soils (Licht and Al-Kaisi, 2004). Ultimately, for many aspects strip tillage may be regarded as a compromise between minimum tillage and no tillage (Licht and Al-Kaisi, 2005) Most literature on strip tillage concerns field trials carried out in Northern USA and Canada (Morrison, 2002) and should be validated for other soil and climate environments, preferably using maize as test crop, as it has been the most used there and one of the most widespread all over the world. Scarce research has been delivered to this subject in Europe: it is noteworthy the experiment by Morris et al. (2007), carried out in the English environment, which evaluates seedbed preparation for sugarbeet, but the effects on crop are restricted to seedling emergence. To the best of our knowledge, no experience is available on international literature for Southern Europe environments, except for Gemtos et al. (2008) who used a strip tiller with a rotary tool to prepare seedbed for cotton, which is not properly a widespread crop in Southern Europe apart from Greece. As a further proof of the scarce attention directed to strip tillage in Europe, strip tillers have been proposed only recently by few European companies and never by Italian ones. Therefore, the aim of this work was to evaluate strip tillage carried out by an original passive-tool implement for the cultivation of maize in the Po valley as representative crop and environment for the Italian and Southern Europe intensive agriculture. Strip tillage was evaluated by comparison with minimum tillage and no tillage on the basis of effects on seedbed tilth, ground cover, weed infestation, and maize performance from crop establishment to final yield.

2. Materials and methods 2.1. Experimental design and maize cultivation schedule The trial has been conducted in 2010 and 2011 at the Falivera farm in Quinzano d’Oglio, Brescia Province, middle Po Valley. A randomized block design with 3 replicates was used to compare the following 3 soil tillage techniques aimed at maize seedbed preparation: strip tillage (ST), minimum tillage (MT), and no tillage (NT). Strip tillage in 2011 was carried out in between-row soil strips undisturbed in 2010. Each plot was 80 m long by 16.6 m wide. The strip tiller, provided by the company ma/ag was a first pulled prototype of the factory with four working units. Each working unit consisted of a sequence of row cleaner (to clean the seeding line from clods and residues), adjustable rubber wheel (to detect soil surface and keep a constant working depth) and cutting disc, shank with tine plus a couple of side closing discs (to contain the clods within the strip) and a final roller (to break clods and firm the seedbed). Loading springs and a setting system for each tool allowed to adjust load and tool arrangement according to soil conditions. The tiller, set for a nominal tine working depth of 20 cm, was

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combined with a four-row precision drill with double disc openers for maize rows 70 cm apart, and was hitched to a John Deere 6420 tractor of 120 hp (88 kW). The forward speed was around 6 km h−1 . Minimum tillage in 2010 was carried out with a combined pulled implement ma/ag CDC 32-13, consisting of thirty-two 66cm-diameter discs with either plain or notched blade. Between the two disc ranks, seven ripper shanks were placed and then two rows of wave discs and a final roller for seedbed firming. The tiller, set for a nominal tine working depth of 25 cm, was hitched to a John Deere 7530 tractor of 200 hp (147 kW). In 2011 a more aggressive tiller was used, the ma/ag Combilam I 40/12, consisting of 12 “Mitchel” shanks split in two staggered rows, 3 ranks of wavy disc blade rollers fixed on an auxiliary frame support hitched to the principal frame by means of an adjustable linkage parallelogram and a final basket roller. The tiller, set for a tillage depth of 35 cm, was hitched to a John Deere 8245 R tractor of 245 hp (180 kW). The forward speed was around 12 km h−1 . Both in MT and NT a three-point-hitch sod drill Kinze 3100 with double disc opener was used, set at 8 rows 70 cm apart. In MT the seeder was adjusted by reducing spring load on planter unit to avoid an excessive opener deepening. The soil hosting the experiment was uniform, sandy-loam (57.0% sand, 25.9% silt, 17.1% clay), with 1.9% organic matter, high extractable P and exchangeable K contents in the top 40 cm layer. Previous crops had been rapeseed in fall 2008-spring 2009 and sod seeded maize in summer 2009. High weed infestation was present in 2010 before starting the experiment, with Veronica spp., Matricaria camomilla, Rumex spp., Lolium perenne, Cirsium arvensis, Lamium purpureum, Capsella bursa-pastoris as the most numerous species. Before tillage, weeds were first mown and later killed by a treatment with glyphosate. Then, during maize cultivation one pre-emergence and one postemergence treatment were carried out. In 2011 each plot was split to two sub-plots, one with pre-emergence plus post-emergence control as in 2010, the other with no pre-emergence treatment in order to evaluate the effect of different tillage on initial weed infestation. In this latter sub-plot, weeds were then controlled by one early and one late post-emergence treatment, the former carried out 30 days after emergence (DAS), just after weed counting, in order to bring the whole plot back to a uniform weed free status. Maize (Pioneer PR39F58) was sown on 2 June 2010 and 19 April 2011, contemporarily with tillage at the density of 9.3 seeds m−2 in rows 71 cm apart. In both years mineral fertilization and sprinkle irrigation schedules were performed to completely satisfy nutrient and water requirements. Pests and diseases were controlled successfully in both years by chemicals. Season climate was monitored by the weather station of Monsanto Italia located in Pontevico, around 6 km far from the field trial location. 2.2. Measurements on the soil The effect of tillage techniques on soil quality was evaluated on the basis of several parameters, according to Peruzzi et al. (1999) and ENAMA (2003), by taking measurements on 6 locations per plot and then using the average plot value for statistical analysis. Soil penetration resistance, was measured by a manual 60◦ cone penetrograph (Eijkelkamp Agrisearch Equipment) until 30 cm depth. In ST the measurement was taken only on tilled strips, assuming the soil of undisturbed strips not different from that in NT. Soil bulk density and water content were determined two days after tillage/sowing for the 0–10 cm and 10–20 cm layers, by inserting a standard volume corer horizontally from a side hole and weighing the soil before and after oven drying at 105 ◦ C until constant weight. Clod size distribution for the tilled soil layer was determined for ST and MT on soil samples taken from side holes within 20 cm

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M. Trevini et al. / Europ. J. Agronomy 48 (2013) 50–56

Table 1 Sieve hole size, size class for soil aggregates and class index. Sieve hole diameter (mm)

Size class

Class index

Ø ≥ 200 100 ≤ Ø < 200 50 ≤ Ø < 100 25 ≤ Ø < 50 10 ≤ Ø < 25 Ø ≤ 10

1 2 3 4 5 6

0.0 0.2 0.4 0.6 0.8 1.0

depth. The soil was air dried for 15 min and then passed through a set of round hole sieves to obtain 6 clod size classes, each with its own index (Ii ) (Table 1). The soil refinement index (RI) (Peruzzi et al., 1999) was calculated as RI= [(Mi × Ii )/Mt ], where Mi = mass of size class i (kg); Ii = index of the size class i; Mt = total soil sample mass (kg). The ground cover residue after tillage was determined by placing a square grid loom at random on the soil surface and counting the number of grid crossings with presence of residues. The percent ground cover (GC%) was then calculated as: GC% = Cr /Ct × 100, where: Cr = number of crossings with presence of residues; Ct = total number of grid crossings. 2.3. Measurements on the crop The population of total weeds and single species was measured in 2011 by counting the number of individuals falling within a 0.25 m2 loom placed eight times per plot core, four on rows and four between rows. Measurements were taken at 30 DAS on sub-plots either with or without pre-emergence chemical control. Maize sowing depth was measured on 6 locations per plot, by digging aside from the emerged plantlet to reveal the seed. Crop emergence was monitored by periodical countings of plantlets starting from 5 DAS until constant number corresponding to total emergence. Crop growth was measured by periodical samplings of 3 plants per plot and oven drying plant material at 105 ◦ C until constant weight. Grain yield was determined by harvesting the 10 core rows of each plot neglecting row edges. Grains were weighed before and after oven drying at 105 ◦ C until constant weight in order to calculate grain water content at harvest and refer yield to standard 14% grain water content. The weight of grains per hectoliter was determined on grain samples oven dried at 60 ◦ C by a Dickey John Gac 2 analyzer. 2.4. Data analysis Data were processed according to a randomized block design except for data on weeds in 2011, where a split-plot design with three blocks was used. Means were compared by LSD (least significant difference) at the 0.05 confidence level, using the software R Development Core Team (2010). 3. Results

Table 2 Percent distribution of clods in size classes and soil refinement index (RI) as recorded in 2010 and 2011 after strip tillage (ST) and minimum tillage (MT). Treatment

2010 ST MT P LSD 0.05 2011 ST MT P LSD 0.05

Clod % distribution in size classes (mm diameter)

RI

50 ≤ Ø < 100

25 ≤ Ø < 50

10 ≤ Ø < 25

Ø ≤ 10

2.47 1.55 0.6988 8.861

5.5 8.58 0.3446 10.730

11.72 14.03 0.2300 5.841

80.28 75.82 0.2555 12.160

0.94 0.93 0.5799 0.066

2.03 1.14 0.4226 3.831

2.76 6.20 0.2476 9.149

16.13 17.68 0.3572 5.639

79.08 74.98 0.3075 12.993

0.94 0.93 0.9040 0.095

Table 3 Soil bulk density and water content (% by volume) as recorded at 0–10 and 10–20 cm depth in 2010 and 2011 for strip tillage (ST), minimum tillage (MT) and no tillage (NT). Treatment

2010 ST MT NT P LSD 0.05 2011 ST MT NT P LSD 0.05

Bulk density (Mg m−3 )

Water content (% by volume)

0–10 cm

10–20 cm

0–10 cm

10–20 cm

1.11 1.19 1.26 0.0848 0.136

1.37 1.43 1.45 0.4715 0.168

9.63 12.19 15.16 0.0269 3.408

14.40 16.15 15.17 0.4807 3.669

1.06 1.11 1.21 0.2101 0.187

1.29 1.19 1.43 0.1170 0.238

12.56 13.80 15.29 0.7513 9.694

13.90 16.69 17.82 0.0189 2.238

half soil profile, while at deeper layers it kept minimum in MT and became intermediate in ST (Fig. 2B). Actually, the penetration resistance was similar in the two years for NT as well as for ST, while it changed much for MT. Clod size distribution in both years was similar in ST and MT, with a very high refinement index, being all clods smaller than 10 cm and more than 70% smaller than 1 cm (Table 2). Bulk density was not significantly different between treatments in both years (Table 3), however lower mean values were recorded for ST and MT over NT. The volumetric soil water content was always minimum in ST, significantly lower than in NT for the upper 10 cm layer in 2010 and lower than in both NT and MT for the 10–20 cm layer in 2011 (Table 3). The ground residue cover in ST was higher than 70% in both years, closer to NT than to MT values (Table 4). 3.3. Tillage effects on weeds In 2011, pre-emergence treatment allowed a successful weed control and weeds at 30 DAS were only sporadic in all treatments (Table 5). Similar success had been achieved by pre-emergence

3.1. Season climate The growing season was pretty rainy for all months in 2010, dry at sowing and from flowering afterwards in 2011 (Fig. 1).

Table 4 Ground residue cover (GRC) in 2010 and 2011 for strip tillage (ST), minimum tillage (MT) and no tillage (NT). Treatment

3.2. Tillage effects on soil Penetration resistance until 15 cm depth in 2010 was maximum in NT, intermediate in MT and minimum in ST (Fig. 2A). In deeper layers, differences were little and not significant. In 2011, penetration resistance was maximum in NT, minimum in MT and ST until

ST MT NT P LSD 0.05

GRC [%] 2010

2011

70.6 37.1 95.8 0.0016 16.56

77.2 23.7 98.2 0.0008 18.03

M. Trevini et al. / Europ. J. Agronomy 48 (2013) 50–56

53

Precipitation (mm)

25

200

20

150

15 100

10

50

5

A ug-11

J ul-11

J un-11

May-11

A pr-11

Mar-11

F eb-11

J an-11

Nov-10

Dec -10

O c t-10

S ep-10

A ug-10

J ul-10

J un-10

May-10

A pr-10

Mar-10

J an-10

F eb-10

Nov-09

O c t-09

Dec -09

0

S ep-09

0

Mean temperature (°C)

30

250

Month Fig. 1. Monthly precipitation and mean temperature between September 2009 and August 2011 as recorded by the weather station of Monsanto Italia located at Pontevico, Brescia Province. Downward arrows indicate maize sowing and harvest dates in the two growing seasons.

Penetration resistance (Mpa) 0

1

2

3

4

5

0 -2

1

2

3

4

5

-2

A

-4 -6

Depth (cm)

0 0

B

-4 -6

-8

-8

-10

-10

-12

-12

-14

-14

-16

-16

-18

-18

-20

-20

-22

-22

-24

-24

-26

-26

-28

-28

-30

-30

ST MT NT

Fig. 2. Penetration resistance measured just after sowing in 2010 (A) and 2011 (B) for strip tillage (ST), minimum tillage (MT) and no tillage (NT). Bars represent ±1 standard error.

control in 2010 (data not shown). On the contrary, in lack of preemergence treatment, the number of weeds was extremely high in NT and much lower in ST, even lower than in MT (Table 5). Either in MT or, especially, in ST the number of weeds was lower between Table 5 Number of weeds as total, along rows and between rows at 30 DAS in 2011 in subplots with or without pre-emergence chemical control (PEC) for strip tillage (ST), minimum tillage (MT) and no tillage (NT). Treatment

ST without PEC ST with PEC MT without PEC MT with PEC NT without PEC NT with PEC Tillage P LSD 0.05 Weed Control P LSD 0.05 T × WC P LSD 0.,05

Presence of weeds (number m−2 ) Total

Rows

Between rows

327.3 1.3 500.3 0.7 1780.3 2.7

280.3 0.7 307.0 0.3 950.7 0.7

47.0 0.7 193.3 0.3 829.7 2.00

0.0046 298.13

0.0325 247.07

0.0004 80.42

0.0001 200.06

0.0002 161.09

0.0001 55.79

0.0007 346.52

0.0096 279.01

0.0001 96.64

rows than along rows (Table 5) mainly due to a reduced presence of dicotyledons between rows (Table 6), in particular Portulaca spp. and C. bursa-pastoris (Table 7). Then, post-emergence weed control at 30 DAS brought back weed population to just around 1 plant m2 (data not shown) as for the subplot with pre-emergence control. 3.4. Tillage effects on maize crop The sowing depth varied with tillage treatment and year with effects on crop emergence (Table 8). Sowing was deeper in ST than in MT in 2010, vice versa in 2011, while it was always the shallowest in NT. Maize emergence in 2010 was high and fast in ST, lower and slower in MT and especially NT (Table 8). The emergence at 16 DAS was 93% of final emergence in ST versus 86% in MT and 85% in NT, and final emergence in ST (8.6 plants m−2 ) approximated to the nominal seed density (9.3 plants m−2 ), while it was significantly lower in MT and NT, the latter with 1.8 plants m−2 less than ST. In 2011, emergence in MT was the fastest (97% of final emergence at 16 DAS) and highest (8.8 plants m−2 ), not much slower but markedly lower in ST and NT, the latter with a final density of 1.8 plants m−2 less than MT. Maize total above-ground biomass accumulation was similar in ST and MT and lower in NT in both years, although differences

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M. Trevini et al. / Europ. J. Agronomy 48 (2013) 50–56

Table 6 Number of graminacee and dicotyledon weeds as total, along rows and between rows at 30 DAS in 2011 in lack of pre-emergence chemical control for strip tillage (ST), minimum tillage (MT) and no tillage (NT). Graminaceae (number m−2 )

TESI

ST MT NT P LSD 0.05

Dicotyledons (number m−2 )

Total

Rows

Between rows

Total

Rows

Between rows

7.00 25.7 9.7 0.3232 32.17

0.0 14.7 8.3 0.2927 22.17

7.0 11.0 1.3 0.3151 15.25

320.3 474.7 1770.7 0.0054 622.31

280.3 292.3 942.3 0.0371 513.43

40.0 182.3 828.3 0.0004 170.77

Table 7 Number of the three most present dycotyledons along rows and between rows at 30 DAS in 2011 in lack of pre-emergence chemical control for strip tillage (ST), minimum tillage (MT) and no tillage (NT). Treatment

ST MT NT P MDS 0.05

Portulaca spp. (number m−2 )

Chenopodium spp. (number m−2 )

Capsella bursa-pastoris (number m−2 )

Rows

Between rows

Rows

Between rows

Rows

Between rows

69.0 133.3 929.3 0.0077 412.34

8.3 81.0 797.3 0.0001 112.51

35.6 43.3 3.0 0.0970 39.99

3.0 33.3 0.7 0.1899 44.46

172.3 93.7 3.7 0.0836 149.42

23.0 52.0 0.7 0.1037 49.25

Table 8 Maize sowing depth, number of plants emerged at 16 DAS (E16) and final emergence (E final) in 2010 and 2011 for strip tillage (ST), minimum tillage (MT) and no tillage (NT). Tillage

ST MT NT P LSD 0.05

2010

2011

Sowing depth (cm)

E 16 (plants m−2 )

E final (plants m−2 )

Sowing depth (cm)

E 16 (plants m−2 )

E final (plants m−2 )

6.0 3.2 2.4 0.0003 0.69

8.0 6.4 5.8 0.0004 0.47

8.6 7.4 6.8 0.0038 0.66

4.8 6.5 4.0 0.0599 2.01

7.1 8.5 6.4 0.1800 2.00

7.5 8.8 7.0 0.0193 1.19

Table 9 Total above-ground dry biomass, grain yield at standard 14% water content, grain weight per hectoliter and water content at harvest in maize cultivated in 2010 and 2011 by strip tillage (ST), minimum tillage (MT) and no tillage (NT). Tillage

ST MT NT Tillage P LSD 0.05 Year P LSD 0.05 T×Y P LSD 0.05

Total biomass [Mg d m ha−1 ]

Grain yield (14% H2 O) [Mg ha−1 ]

Grain weight per hectoliter [kg hl−1 ]

Grain water content [%]

2010

2011

Mean

2010

2011

Mean

2010

2011

2010

2011

17.77 15.37 13.80

20.74 20.58 15.96

19.26 17.98 14.89

8.80 8.65 6.83

13.29 15.03 11.56

11.05 11.84 9.19

75.10 73.87 73.20

73.34 73.81 72.42

22.70 26.02 28.48

27.42 24.97 28.28

0.0737 3.388

0.0047 2.046

0.0008 1.644

0.1633 3.783

0.5009 7.489

0.161 3.485

0.0003 1.342

0.0021 2.845

0.1484 2.325

0.8227 4.928

between the formers and the latter were significant only in 2011 (Table 9). No significant differences were recorded between treatments for mean plant height and weight (data not shown). Grain yields at harvest were not significantly different among treatments in both years, although mean values for MT and ST in the two years were about 2 Mg ha−1 higher than for NT (Table 9). Non relevant, although significant, differences were recorded among treatments for grain weight per hectoliter and water content at harvest (Table 9). 4. Discussion Data on soil parameters indicate that strip tillage made seedbed similar to that prepared by minimum tillage. Differences in

0.2127 2.476

0.0358 0.950

0.1036 5.551

0.0113 1.634

penetration resistance observed between strip tillage and minimum tillage in the two years were mainly due to changes in minimum tillage (Fig. 2). In this treatment, penetration resistance recorded in 2010 was quite high probably because the implement used was equipped with plain blade disc roller that could have caused an underground soil compaction. The much lower penetration resistance recorded for minimum tillage in 2011 can be explained from one hand with the more aggressive tiller and its deeper setting, from the other hand with the residual effect of tillage carried out in 2010. On the contrary no residual effect from previous year could be expected for strip tillage, because strips disturbed in 2011 corresponded to undisturbed between-row strips of 2010. The different soil water content recorded between minimum tillage and strip tillage might have affected penetration resistance,

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but in our opinion the effect was limited as compared to the effect of different soil compactness accounted for by tillage techniques. In fact, soil penetration resistance was higher in MT than in ST also in 2010 although MT showed a significantly higher water content. Results are in line with those obtained by Gemtos et al. (2008) in the comparison between strip tiller and conventional tillers (plough or heavy cultivator) and by Grant and Lafond (1993) in silty-sandy soils, while Licht and Al-Kaisi (2004) on clay-silty soils observed that strip tiller caused a penetration resistance in the 20 cm topsoil similar to no tillage and higher than chisel. About clod size distribution (Table 2), it is worth to underline that one slow passage with the strip tiller gave the same fine tilth of two minimum tillage passages at double speed. This was unexpected since clod size has been demonstrated to decrease with increasing number of passages (Schafer and Johnson, 1982) and forward speed (Boydafi and Turgute, 2007), although this may not stand strictly in sandy soils (Morris et al., 2007). Differences observed for bulk density between no tillage and the two tillage techniques (Table 3), although not significant, were expected because tillage generally causes a decrease of bulk density (Boydafi and Turgute, 2007; Dwyer et al., 1996) except sometimes for sandy soils (Ezeaku et al., 2011; Sessiz et al., 2008). Similarly, the lower soil water content recorded for strip tillage with respect to no tillage (Table 3) was expected in virtue of the greater soil airing caused by soil disturbance. On the contrary, it was not expected that strip tillage might cause a water content generally, although not always significantly, lower than minimum tillage since the former disturbed less soil than the latter. This result would be in contrast with findings by Licht and Al-Kaisi (2005) who observed a higher, although non-significant, water content in strip tillage over minimum tillage by chisel plow. A tentative explanation for our evidence is that soil rising in disturbed strips alternated to undisturbed strips created a ridge-and-furrow-like shape for soil surface increasing the surface exposed to evaporation for disturbed strips. The high percent ground residue cover observed for strip tillage (Table 4) confirms this technique is highly conservative as compared to minimum tillage, which in 2011 was even under the 30% threshold. Our ground cover values were higher than those observed by Vetsch et al. (2007) for corresponding tillage treatments. As far as weed infestation is concerned (Table 5), our data indicate that, by using residual herbicides in pre-emergence, weeds can be controlled successfully in any tillage treatment both in rows and between rows. On the contrary, in subplots of 2011 where pre-emergence chemical control was omitted weed infestation increased markedly for all treatments but was particularly high for no tillage where the bad initial crop establishment reduced maize competitive ability. Our results for strip tillage are substantially in agreement with literature. The high presence of C. bursa-pastoris observed for strip tillage (Table 7), particularly in crop rows, confirms evidences by Baker and Griffis (2005). Hendrix et al. (2004) observed a low weed emergence in strip tillage and no tillage as compared to ploughing, and Anderson (2008) observed a halved weed emergence in strip tillage and no tillage as compared to minimum tillage carried out by chiesel. On the other hand, our high weed population observed for no tillage is in contrast with evidences by Hendrix et al. (2004) and Anderson (2008), but this can be explained by our worsened maize establishment. However, a high population of Portulaca oleracea in no tillage was also observed by Chauhan and Johnson (2009) as a consequence of higher seed exposure to light. Maize drilling depths (Table 8) indicate drills performed differently depending on seedbeds created by tillage techniques. Based on 2-year results it can be argued that drilling at 6 cm depth was the most appropriate for our soil type and water content. This depth was achieved by strip tillage in 2010 and minimum tillage in 2011.

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The shallow drilling achieved for minimum tillage in 2010 was due to the high soil penetration resistance and to the shallow setting of drill probably worsened by the fact that row cleaners moved some soil below gauge wheels so reducing the actual opener depth. The shallow drilling achieved in no tillage in 2010 was due to high soil penetration resistance but also to not appropriate drill setting, which was improved in 2011. The poor emergence (Table 8) observed for no tillage was thus a consequence of shallow drilling and soil compactness, and maybe also of a lower soil temperature. In fact, Licht and Al-Kaisi (2004, 2005) recorded lower soil temperatures for no tillage as compared to strip tillage and minimum tillage and Sharratt et al. (2006) found that high ground residue cover delayed soil warming. However soil temperature was not measured in our experiment. Moreover, the presence of unburied seeds and scaled emergence promoted predation. A reduced maize density for no tillage compared to strip tillage was also observed by Hendrix et al. (2004), who explained this evidence by a higher pre-emergence weed infestation. About maize total biomass and grain yield (Table 9), the higher values recorded in 2011 for all treatments are consequence of the earlier sowing date, which, together with appropriate irrigation management, guaranteed maize vegetative growth in optimal condition and flowering at due period. Strip tillage promoted maize growth more than it could be expected from results reported by other authors. Licht and Al-Kaisi (2004), did not find remarkable differences on total biomass between strip tillage and no tillage, while results obtained by Vyn and Janovicek (2001) varied with year, locality and fertilization rate. The good grain yields obtained in the two years for strip tillage, not different from those obtained for minimum tillage, represent a positive result. Vyn and Janovicek (2001) reported maize yields for strip tillage similar to or lower than those observed with other techniques. The yield obtained by Hendrix et al. (2004) for strip tillage was higher than for conventional tillage in a first year, vice versa in a second one. Gencsoylu and Yalcin (2004) obtained higher yields than with conventional tillage and lower than with other conservative techniques in one year, no significant differences in another year. Licht and Al-Kaisi (2005), in clay soil did not observe differences between tillage techniques. It is worth to underline that in most of experiments above, including our one, the high experimental error caused non-significant differences between treatments even if mean values were much different. The effect of tillage on grain weight per hectoliter and grain water content (Table 9), although significant in 2011, is negligible and indirect, due to the effect of tillage on sowing conditions and consequent emergence rate and growth (Archer and Reicosky, 2009; Vetsch et al., 2007).

5. Conclusions Results obtained in the two years for soil parameters demonstrate that strip tillage allowed a seedbed preparation not different from minimum tillage but moved less soil volumes and left higher ground residue cover, which implicates well-known economic and environmental benefits. Seedbeds prepared by strip tillage and minimum tillage showed similar suitability to drilling, root exploration and crop growth. In fact, maize grown after strip tillage emerged fast and regularly approximating the wished plant density, experienced a limited weed infestation, and thus showed high total biomass and grain yields, similar to those obtained with minimum tillage. On the other hand we have to point out that maize growth and yield were also quite high for no tillage, and this perplexes on the actual convenience of tilling the soil instead of drilling directly on undisturbed soil, at least for our experimental

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environment (sandy-loam soil with high chemical fertility and good water availability for the crop). Acknowledgment Authors wish to thank the company ma/ag agricultural equipment of Casalbuttano (Cremona Province), which developed the strip tiller prototype. References Anderson, R.L., 2008. Residue management tactics for corn following spring wheat. Weed Technology 22, 177–181. Archer, D.W., Reicosky, D.C., 2009. Economic performance of alternative tillage systems in the northern corn belt. Agronomy Journal 101, 296–304. Baker, J.M., Griffis, T.J., 2005. Examining strategies to improve the carbon balance of corn/soybean agriculture using eddy covariance and mass balance techniques. Agricultural and Forest Meteorology 128, 163–177. Boydafi, M.G., Turgute, N., 2007. Effect of tillage implements and operating speeds on soil physical properties and wheat emergence. Turkish Journal of Agriculture and Forestry 31, 399–412. Carter, M.R., 1990. Relative measures of soil bulk density to characterize compaction in tillage studies on fine sandy loams. Canadian Journal of Soil Science 70, 425–433. Chauhan, B.S., Johnson, D.E., 2009. Seed germination ecology of Portulaca oleracea L.: an important weed of rice and upland crops. Annals of Applied Biology 155 (1), 61–69. Chen, Y., Monero, F.V., Lobb, D., Tessier, S., Cavers, C., 2004. Effects of six tillage methods on residue incorporation and crop performance in a heavy clay soil. Transaction of the ASAE 47 (4), 1003–1010. Crosson, P., Hanthorn, M., Duffy, M., 1986. The economics of conservation tillage. In: Sprague, M.A., Triplett, G.B. (Eds.), No Tillage and Surface Tillage Agriculture, The Tillage Revolution. A Wiley Interscience publication, John Wiley and Sons Inc., USA, pp. 409–437. ˇ Matana, J., 2009. Effects of ´ S., Demjanová, E., Macák, M., Dalovic, I., Majerník, F., Tyr, tillage systems and crop rotation on weed density, weed species composition and weed biomass in maize. Agronomy Research 7 (2), 785–792. Drury, C.F., Tan, C.S., Reynolds, W.D., Welacky, T.W., Weaver, S.E., Hamill, A.S., Vyn, T.J., 2003. Impacts of zone tillage and red clover on corn performance and soil physical quality. Soil Science Society of America Journal 67, 867–877. Dwyer, L.M., Ma, B.L., Stewart, D.W., Hayhoe, H.N., Balchin, D., Culley, J.L.B., McGovern, M., 1996. Root mass distribution under conventional and conservation tillage. Canadian Journal of Soil Science 76, 23–28. ENAMA, 2003. Agricultural machinery functional and safety testing service. Test protocol n. 03 rev. 2.1 – Soil tillage machines. Rome, Italy. Ezeaku, C.A., Adamu, S., Onwualu, A.P., 2011. Maize response to tillage and organic manure in a sandy loam soil in north east Nigeria. In: Proc. of the Tillage for Agricultural Productivity and Environmental Sustainability Conference, Ilorin, Nigeria, February 21–23, pp. 371–378. Gemtos, T.A., Cavalaris, C.C., Karamoutis, C., Fountas, S., 2008. Evaluation of strip tillage for cotton production in Greece. In: Proc. of the International Conference on Agricultural Engineering, Hersonissos, Crete, Greece, June 23–25, 2008, Oral Presentation no. 160. Gencsoylu, I., Yalcin, I., 2004. Advantages of different tillage systems and their effects on the economically important pests, Thrips tabaci Lind. and Aphis gossypii Glov. in cotton fields. Journal of Agronomy and Crop Science 190, 381–388. Grant, C.A., Lafond, G.P., 1993. The effects of tillage systems and crop sequences on soil bulk density and penetration resistance on a clay soil in southern Saskatchewan. Canadian Journal of Soil Science 73, 223–232.

Hendrix, B.J., Young, B.G., Chong, S.K., 2004. Weed management in strip tillage corn. Agronomy Journal 96, 229–235. Hosking, W., Bloomer, D., 2006. Strip tillage: a reduced cultivation system for field crop production. Farmer Guidelines developed by LandWISE under SFF Project: “Controlling the Strip”. LandWISE 2006, http://www.landwise.org.nz/wp-content/uploads/STF-Guide-A5-booklet.pdf (Download 17 February 2013). Licht, M.A., Al-Kaisi, M., 2004. Strip tillage effect on seedbed soil temperature and other soil physical properties. Soil & Tillage Research 80, 233–249. Licht, M.A., Al-Kaisi, M., 2005. Corn response, nitrogen uptake, and water use in strip tillage compared with no tillage and chisel plow. Agronomy Journal 97, 705–710. Mitchell, J., Shrestha, A., Campbell-Mathews, M., Giacomazzi, D., Goyal, S., Bryant, D., Hererra, I., 2009. Strip tillage in California’s Central Valley. University of California. Division of Agriculture and Natural Resources. Publication 8361/January 2009. p. 1–8. http://anrcatalog.ucdavis.edu/pdf/8361.pdf (Download 18 September 2012). Morris, N.L., Miller, P.C.H., Orson, J.H., Froud-Williams, R.J., 2007. Soil disturbed using a strip tillage implement on a range of soil types and the effects on sugar beet establishment. Soil Use and Management 23, 428–436. Morrison, J.E., 2002. Strip tillage for “no-till” row crop production. Applied Engineering in Agriculture 18, 277–284. Peruzzi, A., Raffaelli, M., Di Ciolo, S., 1999. Proposal of methodology for the evaluation of the quality of work of the operative machines for soil tillage. Journal of Agricultural Engineering 3, 156–167. Pochi, D., Fanigliulo, R., 2010. Testing of soil tillage machinery. In: Dedousis, A., Bartzanas, T. (Eds.), Soil Engineering. Soil Biology Book Series, vol. 20. Springer, Berlin, pp. 147–168. R Development Core Team, 2010. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. Version 2.12.1, 2010, ISBN 3-900051-07-0. URL http://www.R-project.org/ Roberge, R.C., Crowe, T.G., Roberge, M., 2010. Comparison of clearing performance for row cleaners on a strip tillage implements. In: Proc. of the 27th World Congress of the International Commission of Agricultural and Biosystems Engineering (CIGR), Québec City, Canada, June 13–17, 2010, paper no. CSBE100791, http://www.csbe-scgab.ca/docs/meetings/2010/CSBE100791.pdf (Download 17 February 2013). Schafer, R.L., Johnson, C.E., 1982. Changing soil condition – the soil dynamics of tillage. In: Unger, P.W., Van Doren Jr., D.M. (Eds.), Predicting Tillage Effects on Soil Physical Properties and Processes. ASA Special Publication, pp. 13–28, no. 44. Sessiz, A., Sogut, T., Alp, A., Esgici, R., 2008. Tillage effects on sunflower (Helianthus annuus) emergence, yield, quality and fuel consumption in double cropping system. Journal of Central European Agriculture 9 (4), 697–710. Sharratt, B., Zhang, M., Sparrow, S., 2006. Twenty years of tillage research in subarctic Alaska I. Impact on soil strength, aggregation, roughness, and residue cover. Soil & Tillage Research 91, 75–81. Simmons, F.W., 1992. Tillage and compaction effects on root distribution. In: Reetz Jr., H.F. (Ed.), Proc. of the Roots of plant nutrition Conference. Champaign, Illinois, GA, pp. 6l–68l. Sprague, M.A., Triplett, G.B., 1986. No Tillage and Surface Tillage Agriculture, The Tillage Revolution. A Wiley Interscience Publication, John Wiley and Sons Inc., USA. Swanton, C.J., Shrestha, A., Knezevic, S.Z., Roy, R.C., Ball-Coelho, B.R., 2000. Influence of tillage type on vertical weed seedbank distribution in a sandy soil. Canadian Journal of Plant Science 80 (2), 455–457. Vetsch, J.A., Randall, G.W., Lamb, J.A., 2007. Corn and soybean production as affected by tillage systems. Agronomy Journal 99, 952–959. Vyn, T.J., Janovicek, K.J., 2001. Potassium placement and tillage system effects on corn response following long-term no tillage. Agronomy Journal 93, 487–495.