AFM Microbial Biomass and Activity

The results of microbial counts were confirmed by evaluating active fungal biomass (AFM), microbial carbon (Cmic), and soil respiration. The soils of Torino and Napoli showed statistically significant differences for microbial and fungal biomass and CEM in 2008 and for all investigated parameters in 2007 (Table 6.1). In the third year (2008) of experimentation (Table 6.1), active fungal biomass (AFM) and microbial carbon (Cmic) were significantly affected by compost amendment (COM-2). Moreover, when considering the variability within groups, a significant effect was observed for soil (bulk/rhizo) and site (Napoli/Torino), as well as for

Table 6.1 Levels of significance (p values from ANOVA) for effects of compost amendments on microbial biomass and activity in bulk soil and rhizo soil at Napoli and Torino sites, and differences between years

AFM Cmic Respiration CEM

Table 6.1 Levels of significance (p values from ANOVA) for effects of compost amendments on microbial biomass and activity in bulk soil and rhizo soil at Napoli and Torino sites, and differences between years

AFM Cmic Respiration CEM

dF

P

dF

P

2007 (Three-way)

2007 (Two-way)

Treatments (TRA-COM)

1

0.201

0.524

0.624

Treatments (TRA-COM)

1

0.239

Soil (Bulk-Rhizo)

1

0.164

<0.001

0.039

Site (Napoli-Torino)

1

<0.001

Site (Napoli-Torino)

1

0.002

<0.001

0.001

Treatments x site

1

0.594

Treatments x soil

1

0.469

0.550

0.735

Treatments x site

1

0.149

0.723

0.850

Soil x site

1

0.625

<0.001

0.022

Treatments x soil x site

1

0.611

0.374

0.891

2008 (Three-way)

2008 (Two-way)

Treatments (TRA-

2

0.013

0.019

0.068

Treatments

2

0.001

COM-MIN)

(TRA-COM-MIN)

Soil (Bulk-Rhizo)

1

<0.001

<0.001

0.002

Site (Napoli-Torino)

1

<0.001

Site (Napoli-Torino)

1

<0.001

<0.001

0.147

Treatments x site

2

0.035

Treatments x soil

2

0.007

0.104

0.405

Treatments x site

2

0.687

0.012

0.079

Soil x site

1

<0.001

<0.001

<0.001

Treatments x soil x site

2

0.019

0.089

0.091

2007-2008 (Three-way)

2007-2008 (Two-way)

Years (2007-2008)

1

<0.001

<0.001

<0.001

Years (2007-2008)

1

0.734

Site (Napoli-Torino)

1

0.004

0.084

<0.001

Site (Napoli-Torino)

1

<0.001

Soil (Bulk-Rhizo)

1

<0.001

<0.001

0.001

Years x site

1

<0.001

Years x site

1

<0.001

<0.001

<0.001

Years x soil

1

<0.001

<0.001

0.095

Site x soil

1

<0.001

<0.001

<0.001

Years x site x soil

1

0.001

0.028

0.028

dF degree of freedom, AFM active fungal mycelium, CmC Microbial carbon, CEM coefficient of endogenous mineralization, TRA conventional tillage, COM compost amendment, MIN minimum tillage. Values in bold are statistically significant dF degree of freedom, AFM active fungal mycelium, CmC Microbial carbon, CEM coefficient of endogenous mineralization, TRA conventional tillage, COM compost amendment, MIN minimum tillage. Values in bold are statistically significant rhizosphere x site interaction (Table 6.1). The interaction treatment x soil was significant only for AFM in 2008, while the interaction treatment x site was significant only for Cmic COM-2 significantly reduced AFM in the Torino bulk soil (Fig. 6.4), while no significant effect was detected in the bulk soil of Napoli (Fig. 6.4). In the maize rhizo soil of both Napoli and Torino, a significant reduction

Bulk-soil

Rhizo-soil

JS 20-M on

Hfc a a

aba riaJH

Rhizo-soil

Na 07 Na 08 To 07 To 08

Fig. 6.4 Active fungal mycelium, microbial C, microbial respiration, and water content (mean ± SE) of soil sampled from Napoli (Na) and Torino (To) experimental sites. TRA conventional tillage, COM-2 compost amendment, MIN minimum tillage. Left-hand-side figures report values for bulk-soil; Right-hand-side figures report values for rhizo-soil. Different letters indicate significant differences between treatments (ANOVA-Holm-Sidak test; p < 0.05) within site and year in the amount of active fungal mycelium was detected in 2008, as compared to TRA and MIN (Fig. 6.4). Moreover, in both 2007 and 2008, COM-2 reduced microbial biomass of bulk soil and rhizo-soil in Napoli, though differences were statistically significant only in 2008 (Fig. 6.4). In Torino, the microbial biomass of COM-2 bulk soil in 2007 was significantly lower than in both TRA and MIN, while in 2008 the rhizo-soil microbial biomass of COM-2 was significantly lower than in MIN (Fig. 6.4). For both Napoli and Torino, the bulk-soil microbial biomass was significantly larger in 2007 than in 2008, though the difference for rhizo-soil microbial biomass between the 2 years was significant only for Napoli (Fig. 6.4).

Soil respiration was significantly affected by soil (bulk/rhizo) or site as well as by soil-site interaction (Table 6.1). A soil respiration significantly lower than MIN and TRA was found for COM-2 in Torino bulk soil in 2007 and in Napoli rhizo soil in 2008, respectively (Fig. 6.4). In 2008, the coefficient of endogenous mineralization (CEM) was significantly affected by both treatment and site (Fig. 6.5), and by

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