Experimental SetUp and Soil Climatic Conditions for Maize Trials

Maize (TO and NA) and sorghum (BA) were grown in the field sites because their large N demand is liable to better reveal the treatment effects. Soil treatments at the TO and NA sites were the following:

1. TRA = traditional soil tillage (moldboard plowing, 30 cm deep), mineral fertilization with urea at the rate of 130 kg ha-1 of N.

2. MIN = minimum tillage (rotary hoeing, 10 cm deep), mineral fertilization with urea at the rate of 130 kg ha-1 of N.

3. GMAN = green manure with hairy vetch (Vicia villosa L.), moldboard plowing, 30 cm deep.

4. COM1 = low rate of compost (equivalent to 130 kg ha-1 of N), moldboard plowing, 30 cm deep.

5. COM2 = high rate of compost (equivalent to 260 kg ha-1 of N), moldboard plowing, 30 cm deep.

6. CONT = no N fertilization, moldboard plowing, 30 cm deep.

Soil treatments at the BA site were the following:

1. TRA = traditional soil tillage (moldboard plowing, 40 cm deep), mineral fertilization with urea at the rate of 130 kg ha-1 of N.

2. COM1 = low rate of compost (equivalent to 130 kg ha-1 of N), moldboard plowing, 40 cm deep.

3. COM2 = high rate of compost (equivalent to 260 kg ha-1 of N), moldboard plowing, 40 cm deep.

4. CONT = no N fertilization, moldboard plowing, 40 cm deep.

A completely randomized design with four replications was adopted for the TO site. Field plots (6 x 8 = 48 m2) were 24 (6 treatments x 4 replications).

A randomized complete block design with four replications was adopted for the NA site. Field plots (6 x 5 = 30 m2) were 24 (6 treatments x 4 replications).

A randomized complete block design with four replications was adopted for the BA site. Field plots (5 x 8 = 40 m2) were 16 (4 treatments x 4 replications).

Fertilization was carried out in spring just before moldboard plowing. Chemical composition of the compost used in all the three sites is reported in Table 3.4. Vetch crop (Vicia villosa L., cv. Haymaker plus) for green manure was sown at TO and NA sites in fall with a seed rate of 280 kg ha-1 and shredded at the same time of fertilizers addition. Phosphorus and K fertilization (P2O5 = 100 kg ha-1; K2O = 200 kg ha-1) was the same on all plots.

Maize crop (Zea mays L., hybrid PR34N43, FAO 500, Pioneer Hi-Bred) was sown at TO and NA at late spring with a density of 7.4 seeds per m2. Sorghum crop (Sorghum bicolor Moench x S. sudanense (Piper) Stapf. cv. BMR333, Societa Italiana Sementi) was sown at BA in late spring with a density of 20 plants per m2. Irrigation was made with a traveling-gun sprinkler irrigation system in TOR and with a drip irrigation tape system in NAP and BAS. Irrigation volumes were

Table 3.4 Chemical

2006

2007

2008

composition of the compost added to plots each year

Dry matter (% f.m.) Organic matter (% d.m.) Organic C (% d.m.) Hemicellulose (% d.m.)a Cellulose (% d.m.)a Lignin (% d.m.)a Ashes (% d.m.) Total N (% d.m.) C/N ratio

61.0

51.1

25.6

11.2

12.2

12.8

aFrom Van Soest et al. (1991)

decided on the basis of crop evapotranspiration calculated by multiplying reference evapotranspiration (Hargreaves and Samani 1985) by crop coefficients (Allen et al. 1998) in TO and NA. At BA, irrigation water was applied every 3-4 days with the aim to maintain soil moisture around field capacity by restoring at each irrigation the amount of lost soil water calculated through TDR readings from probes buried up to 210 cm of depth.

Total amount of water (rainfalls + irrigation) corresponded to 70, 59, and 71% of ETP, respectively, in the 3 years in TO, 76, 77, and 88% of ETP in NA and 103, 97, and 98% of ETP in BA (Table 3.5). A detail of all agronomic techniques is reported in Table 3.6.

For agronomic analyses, soil samples were collected before sowing and after harvest from all fields and for all years in three soil layers (0-15, 15-30, 30-60 cm) and the N-NH4 and N-NO3 content was determined.

For Torino, soil mineral N was extracted by shaking 100 g of moist soil with 300 ml of 1 M KCl solution for 1 h. Subsequently, the samples were filtered through a Whatman no. 1 paper, and then the extracts were frozen until analysis. NO3— — N and NH4+ — N concentrations were determined by colorimetry with a continuous flow analyzer (Evolution II, Alliance Analytical Inc., Menlo Park, CA).

For Napoli, soil mineral N was extracted with Hach standard kit reagents (Hach DR 2000, Hach Company, Loveland, CO) and the extracts were analyzed by the spectrophotometer at 500 (NO3— — N) and 425 (NH4+ — N) nm. Mineralization of soil organic N was estimated by N uptake in nonfertilized control, plus soil mineral variation between crop sowing and harvest (Meisinger 1984; Bhogal et al. 1999; Fiorentino et al. 2009). Plant samples were collected at harvest and oven-dried at 70°C to constant weight. A sub-sample of dry biomass was analyzed for N content (Kjeldhal method at NA and elemental analyzer at TO and BA).

Analysis of variance was applied to determine differences among treatments in total biomass, N content, and N uptake. Data were analyzed for separated sites and treatments as main factor, while year was the repeated measure. When effects were significant, means were separated using a Sidak post hoc test.

Table 3.5 Water supply during cropping years in the three sites

Year

Rainfalls

Irrigation

Total water supply

ETP

Water

Torino

2006

309

160

469

667

0.70

2007

229

140

369

628

0.59

2008

432

40

462

654

0.71

Napoli

2006

148

275

423

555

0.76

2007

5

345

350

453

0.77

2008

109

362

471

538

0.88

Battipaglia

2007

26

512

538

522

1.03

2008

3

458

461

475

0.97

2009

71

362

433

442

0.98

Table 3.6 Schedule (day/month) of maize and sorghum agronomic operations at the three sites

Torino

Napoli

Battipaglia

Operations

15/3, 2006

11/11,2005

-

Seedbed preparation and

26/10, 2006

3/11, 2006

vetch sowing

23/10, 2007

7/11, 2006

17/5, 2006

4/5, 2006

-

Vetch sampling and

17/5, 2007

10/5, 2007

chopping

17/5, 2008

21/5, 2008

18/5, 2006,

5/5, 2006

-

Vetch incorporation

4/5, 2007

12/5, 2007

19/5, 2008

21/4, 2008

18/5, 2006

4/11, 2005

27/4, 2007

Main tillage according to

4/6, 2007

8/11, 2006

30/4, 2008

experimental protocol

19/5, 2008

11/10, 2007

8/5, 2009

18/5, 2006

17/5, 2006

24/5, 2007

Fertilization and seedbed

4/6, 2007

24/5, 2007

10/6, 2008

preparation

19/5, 2008

5/5, 2008

11/6, 2009

19/5, 2006

22/5, 2006

31/5, 2007

Maize or sorghum sowing

4/65, 2007

8/6, 2007

14/6, 2008

19/5, 2008

6/5, 2008

13/65, 2009

8/6, 14, 2006

16/6, 20/7, 2006

24/6, 16/7, 2007

Weed control

6/6, 25, 2007

20/6, 23/7, 2007

27/6, 7/7, 2008

19/6, 2008

18/6, 22/7, 2006

22/6, 6/7. 2009

2006: 160 mm x 4

2006: 275 mm x

12

2007: 512 mm x

19

Irrigations

2007: 140 mm x 3

2007: 345 mm x

12

2008: 458 mm x

21

2008: 40 mm x 1

2008: 362 mm x

11

2009: 362 mm x

22

22/9, 2006

7/9, 2006

4/9, 2007

Harvest

10/10, 2007

9/9, 2007

9/9, 2008

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