Piacenza Experimental Site

After 1 year of maize cultivation, all field treatments showed an overall TOC depletion in bulk soils (Table 4.7). Similar to Torino, the largest decrease was found for MIN, while a lesser OC reduction was found for TRA and COM-2 (Table 4.7). Also for Piacenza, the failure of compost amendment to enhance SOM content in the first year may be attributed to an extensive priming effect induced by compost organic matter.

Table 4.7 Piacenza experimental site, amount (g kg and relative distribution (%) of organic carbon in bulk samples and water-stable aggregate sizes (mm) in soil under different treatments for 3 years of experimentation

Treatments Bulk Aggregate sizes Sum of fractions

Table 4.7 Piacenza experimental site, amount (g kg and relative distribution (%) of organic carbon in bulk samples and water-stable aggregate sizes (mm) in soil under different treatments for 3 years of experimentation

Treatments Bulk Aggregate sizes Sum of fractions

gkg-1

4.75-1.00

1.00-0.50

0.50-0.25

<0.25

gkg-1

%

gkg-1

%

gkg-1

%

gkg-1

%

gkg-1

%

Control soil

17.2

15.8

54.0

15.7

26.8

14.4

8.5

14.0

10.7

15.4

89.5

Maize

First year

TRA

16.7

12.7

49.1

11.1

16.5

23.4

17.9

20.2

16.5

14.4

86.2

MIN

14.5

14.3

65.5

12.7

15.9

14.3

9.2

14.7

9.4

14.0

96.6

COM-2

15.1

12.2

51.8

9.0

11.0

35.5

22.0

26.0

15.2

15.0

99.3

LSD

1.27

1.0

1.0

1.6

0.9

3.5

0.7

2.5

0.7

NS

Second year

TRA

16.6

17.6

43.7

10.4

23.8

15.5

16.4

15.7

16.0

14.6

87.9

MIN

16.3

16.5

46.5

17.4

29.5

14.5

13.3

13.0

10.7

16.0

98.1

COM-2

17.0

14.8

40.1

15.0

26.5

20.6

18.0

24.3

15.4

16.7

98.2

LSD

0.70

1.0

0.9

0.7

0.3

2.6

0.4

1.7

0.8

0.4

Third year

TRA

18.7

16.7

50.5

16.2

23.8

27.9

16.9

16.8

8.8

17.6

94.1

MIN

22.4

22.3

52.1

21.4

27.8

20.7

11.2

19.8

8.9

21.5

96.0

COM-2

23.5

23.3

60.4

20.1

21.4

25.3

10.4

22.8

7.8

22.7

96.6

LSD

1.30

2.8

1.5

1.8

0.3

5.2

0.6

5.5

0.2

0.7

Wheat

First year

CAT

16.7 (0.4)

16.2a (0.1)

54.4a (0.9)

16.0 (0.4)

23.2b (0.2)

18.1 (0.1)

12.4 (0.1)

16.7a (0.1)

10.0b (0.1)

16.4 (0.4)

98.2

No-CAT

16.3 (0.5)

15.3b (0.4)

49.1b (0.3)

15.6(1.1)

26.2a (0.4)

18.1 (0.9)

12.4 (0.3)

15.1b (0.5)

12.3a (0.4)

15.3 (0.1)

93.8

Second year

CAT

13.4a (0.1)

11.4b (0.2)

33.4b (0.3)

12.2a (0.1)

27.8b (0.3)

19.0a (0.5)

23.3a (0.5)

13.2a (0.3)

15.5 (0.1)

13.2a (0.5)

98.5

No-CAT

12.2b (0.3)

13.2a (0.3)

37.3a (0.5)

11.7b (0.2)

29.3a (0.1)

12.3b (0.5)

18.0b (0.1)

11.3b (0.3)

15.4 (0.1)

12.2b (0.4)

100

Third year

CAT

19.4a (0.5)

17.3 (0.8)

43.5b (0.1)

18.0(0.8)

26.7a (0.1)

26.1a (0.8)

17.2a (0.3)

20.9a (2.1)

12.6a (0.1)

19.0a (0.2)

97.9

No-CAT

17.0b (0.9)

16.5 (0.6)

52.2a (0.5)

16.4(1.2)

25.6b (0.1)

17.5b (1.6)

12.4b (0.1)

16.7b (1.6)

9.9b (0.1)

16.5b (0.4)

97.0

LSD least significant difference for p 0.05 (n = 4), NS not significant. Numbers in brackets for wheat plots represent standard deviation (n = 4). Different small letters in columns indicate significant difference at 0.05 probability level (n = 4)

LSD least significant difference for p 0.05 (n = 4), NS not significant. Numbers in brackets for wheat plots represent standard deviation (n = 4). Different small letters in columns indicate significant difference at 0.05 probability level (n = 4)

However, the experiment's progression in the following 2 years indicates that an increasing trend of OC content in bulk soils was shown by both MIN and COM-2, as compared to TRA. In fact, both MIN and COM-2 had a significant larger OC values than TRA in the third year.

Contrary to Torino, a larger OC content was generally found, throughout the experimentation, for all maize treatments in the smaller 0.50-0.25 and <0.25 mm aggregate fractions (Table 4.7). This result is attributed to the influence of physical properties in the soil aggregate hierarchy and, particularly, of the role played by soil texture. Therefore, the large mass found in macroaggregates for the heavy-textured control soil of Piacenza (Tables 4.1 and 4.4) was somewhat reduced over the years in the deeply plowed TRA and COM-2 treatments, with the latter showing the greatest OC content in the fine size fractions (Table 4.7). On the other hand, the least disturbed MIN treatment kept a OC distribution in size fractions similar to the control Piacenza soil. These findings were further supported by data on the relative (%) amount of OC in soil aggregate sizes, which were strongly correlated to mass distribution of the same size fractions (Table 4.4). Moreover, the difference in OC stabilization among treatments was also revealed by the low OC recovered from fractionation of TRA soil (86%), thus indicating an unstable incorporation of free coarse organic debris in the water-stable aggregates of this soil.

As for wheat plots , while no effect of biomimetic catalyst was observed in bulk soils in the first year as compared to control (No-CAT), OC increased significantly in CAT bulk soils in both the second and third year (Table 4.7). Moreover, a significant increase in OC was found in the sum of size fractions of CAT, as compared to No-CAT, for both the second and third year. This was the consequence of the significantly larger OC content found in the smallest <0.25 mm size fraction of CAT, as compared to No-CAT. Since the association of very fine soil particles promotes the formation of new microaggregates also in already existing macroaggregates (Oades 1984; Six et al. 2004), this result may be explained with the catalyst effect on soil organic components and their association in recently formed microaggregates.

Was this article helpful?

0 0
Organic Gardeners Composting

Organic Gardeners Composting

Have you always wanted to grow your own vegetables but didn't know what to do? Here are the best tips on how to become a true and envied organic gardner.

Get My Free Ebook


Post a comment