@Reynaldo, you could try the soft lysis method. In this method, soil samples (1 g) in duplicate are suspended in 10 mL of extraction buffer (100 mmol/L Tris–HCl (pH‐8·2); 100 mmol/L EDTA (pH‐8); 1·5 mol/L NaCl) and incubated at 37°C for 10–12 h with shaking at 150 rev/min. Samples are re‐extracted in 1 mL of the same extraction buffer. Supernatants are then collected by low speed centrifugation at 2097x g for 10 min. Four millilitres of lysis buffer; 20% (w/v) SDS; lysozyme, 20 mg/mL; protinase K, 10 mg/mL; N‐lauroyl sarcosine, 10 mg/mL; CTAB (cetyltrimethylammonium bromide), 1% (w/v) are added to the supernatant followed by incubation at 65°C for 2 h with vigorous shaking at every 15 min. Samples were centrifuged at 8385 x g for 10 min at 4°C. The upper aqueous phase is extracted with equal volume of phenol : chloroform : isoamylalcohol (P : C : I = 25 : 24 : 1) at 8385 x g for 20 min at 4°C. The upper aqueous phase was again extracted with equal volume of C:I (24:1) at 8385 x g for 10 min at 4°C. DNA was treated by adding 1/10 volume of 7·5 mol/L potassium acetate and subsequently precipitated by adding two volumes of chilled absolute ethanol for 30 min at 4°C. DNA precipitates are then collected by centrifugation at 6708 x g for 10 min, air‐dried and suspended in 20 μl sterile distilled water.