Materials and Methods 821 Experimental Setup

Bacteria diversity has been investigated in soils collected from the experimental sites of Torino, Napoli, and Piacenza (see Chap. 3) where the following soil management practices were applied for maize cropping:

COM: traditional tillage (35 cm) and organic matter amendment consisting of

20 t/ha of compost and corresponding to 260 kg N/ha. TRA: traditional tillage (35 cm) and chemical fertilization corresponding to 260 kg N/ha.

MIN: minimal tillage (10 cm) and chemical fertilization as for TRA; and for wheat cropping.

CAT: traditional tillage (35 cm) and spread of water soluble iron-porphyrin as catalyst for the in situ photo-oxidative polymerization of SOM (see Chaps. 1 and 4). Soil surface was amended before seeding by 1 g iron-porphyrin (dissolved in 5-10 l water)/m2.

NoCAT: traditional tillage (35 cm) without any catalyst amendment.

The experimental design was at randomized blocks with either four replicates (TRA/MIN/COM) or three replicates (CAT/NoCAT). Each plot was sampled for both bulk and rhizospheric soil.

Rhizosphere soil was obtained by hand scrubbing, in sterile conditions, the 2 mm portion of soil tightly adhered to the roots of three plants per plot and pooling the collected soil in one sample per plot. Five subsamples of bulk soil per plot were collected at 35 cm depth, and pooled on site. Soil samples were sieved at 2 mm and stored at -80°C for RNA extraction and at -20°C for DNA extraction. The sequence of operations to extract both DNA and RNA from soils and obtain meaningful information from the nucleic acids on the effects of soil treatments on soil biodiversity are listed in Fig. 8.1.

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