ADDITION OF COVER CROP RESIDUES AND ORGANIC AMENDMENTS: EFFECT ON NITRIFIERS AND CELLULOLYTIC MICROORGANISMS

Abstract

The addition of cover crops and organic amendments, such as poultry manure and poultry litter, is a source of C and N to the soil. Their decomposition regulates the activity and abundance of soil microorganisms. Our objective was to study the effect of cover crops
and organic amendment additions, applied on soil surface and without the presence of a living vegetal cover, on the abundance and activity of nitrifiers and cellulolytic microorganisms . We conducted an experiment during two consecutive years in Paraná, Argentina (−31° 50,9′ S; −60°32,3′ W). Treatments included the addition of organic amendments (composted poultry litter and poultry manure) and cover crops residues [wheat (Triticum aestivum L.) and white sweet clover (Melilotus albus Medik.)]. Soil water content, activity and abundance of nitrifiers and cellulolytic microorganisms were
determined on soil samples taken at two depths (0-0.05m and 0.05-0.20m). The activity of nitrifiers was 0,01-0,54mg NO3 g-1 (0-0.05m) and the 0,001-0,18mg NO3 g-1 (0.05-0.20m),
the average abundance of nitrifiers was 5,25 log g-1 at both depths, whereas cellulolytic activity showed differences between depths (P <0,0001) with average values of 0,07 mg g-1 (0-0,05m) and 0,05 mg g-1 (0,05-0,2m) and the abundance of cellulolytic showed significant differences between the depths (P <0,025) although with similar values. In contrast, wheat residues, with a high C: N ratio, were associated with initial glucose, abundance of cellulolytic and nitrifiers, and cellulolytic activity. This study allowed us to identify the effect of the addition of the aerial residue of CC and organic amendments, without the contribution of the roots, on the dynamics of cellulolytic and nitrifiers
microorganisms.