Author(s):
Fangueiro, D. 
; Gusmão, M. ; Grilo, J. ; Vasconcelos, E. ; Cabral, F.
Date: 2010
Persistent ID: http://hdl.handle.net/10400.5/2618
Origin: Repositório da UTL
Subject(s): animal slurry; nitrogen mineralization; soil incorporation; particle size
Description
RAMIRAN International Conference Animal manures are rich in organic matter and nutrients, namely nitrogen (N) and, consequently, widely applied to
soil as organic fertilizers. However, a large part of the nitrogen contained in animal manures is in the organic form
and so not directly available for plants. Indeed, organic N has to be mineralized prior to plant uptake (Rees and
Castle, 2002). Several manure characteristics as the C:N ratio (Chadwick et al., 2000), the lignin content
(Kristensen, 1996) and the NH4 +/organic N ratio (Beauchamp and Paul, 1989) have been suggested as indicators of
the plant-available N. More recently, Fangueiro et al. (2008) showed that the potential of N mineralization (PNM) of
cattle slurry is inversely correlated with slurry particle size: finest fractions are the particle-size fractions from which
N mineralization occurs in slurries whereas coarser fractions are associated with immobilization. Furthermore,
Moller et al. (2002) reported that animal diet and anaerobic decomposition during storage in slurry channels and
stores affect the slurry particle size distribution. Such information is of great interest since the finest slurry particle
size should infiltrate the soil more easily and quickly relative to the coarser slurry particle size that should remain
close to soil surface. Furthermore, mechanical slurry separation is now performed in many pig and dairy farms in
order to improve slurry management in terms of nutrients utilization and reducing costs related to slurry storage.
Slurry separation by screw press leads to a nutrient rich organic solid fraction (0.7– 3.2 mm particles) that may be
composted and a liquid fraction that can be used for fertigation.
In the present study, three types of slurry (pig, duck and cattle) were separated into 4 slurry particle size
fractions (>2000 um, 2000-500 um, 500-100 um, <100 um) in order to assess the influence of the type of slurry and
slurry particle size on the PNM after soil incorporation.
