Phosphorus Dynamic in the Soil-Plant System ... 311993). However, some researchers have found no textural effects on litter
decomposition (Scott et al., 1996). Although the effect of soil texture on the
stabilization of SOM fractions has been investigated by some authors
(Stevenson, 1994; Rosell & Galantini, 1997), little information is available on
its influence on the distribution and properties of SOM components and
related N and S mobility and availability in the fine textured soil fractions (silt
and clay), especially in semiarid regions. Soil texture influences the soil
microenvironment and SOM mineralization in several ways. It has been
reported that the higher the clay content, the more stabilization of the topsoil
and the content of organic matter is enhanced (Balesdent et al., 2000). Soil
texture can be related to changes in P fractions and transformation. O'Halloran
et al. (1985) found that up to 90% of the spatial variability in total P content of
a Mollisol was explained by texture. A similar study showed that significant
proportions of variability of all P fractions, except for H 2 SO 4 - P in a Brown
Chernozemic loam, could be attributed to changes in sand content (O’Halloran
et al., 1987). Increasing silt plus clay content has been significantly correlated
with larger soil resin-P, NaHCO 3 - Pi/Po and NaOH-Pi/Po pools. The HCl-P pool
was positively correlated with sand content (O'Halloran et al., 1987). There is
evidence that P transformation in soils were closely linked to microbial
activity and C dynamics, which affect P mineralization and immobilization
(Hedley et al., 1982). For example, a loam soil supported higher microbial
biomass than the sandy loam and sandy soils (Cooper & Warman, 1997).
Huffman et al. (1996) indicated that soil texture had a greater effect on P
transformation than did the combined effects of residue addition, residue
placement and nutrient addition, because soil texture affected the labile Pi,
labile Po, and microbial P pools. Several authors have found a similar pattern
in Pampean soils of Argentina (Buschiazzo et al., 1998; Hevia et al., 2003;
Galantini et al., 2004). Soil texture affects N and P availability by influencing
SOM accumulation (Schimel et al., 1985, Kuhn et al., 2012), soil microbial
activity (Hassink et al., 1993) and physicochemical equilibriums (McDowell et
al., 2003). However, different pools of SOM are differently affected by soil
texture (Galantini et al., 2004, Kuhn & Armstron, 2012). Since soil texture
affects SOM storages through direct and indirect mechanisms, total SOM may
not be a universal predictor of soil quality (Plante et al., 2006). The precise
nature of the impact of soil texture on phosphorus (P) equilibrium and
dynamics on P availability is still unknown (Salas et al., 2003; Zheng et al.,
2003; Kooijman et al., 2005).
Soil texture can modify P equilibrium and availability as a consequence of
its mineral physicochemical properties, its influence on phosphate adsorption-