Soil quality of Mollisols quantified by the pore size distributions

GHIBERTO, P.; IMHOFF, S.; LIBARDI, PL.; PIRES DA SILVA, A.; TORMENA, C.; PILATTI, M.A.

Montevideo

Congreso; 19th ISTRO Conference; 2012

ISTRO

Indicators that summarize the porous system behavior and, as consequence, the state of the structure are useful to assess the soil quality. The objectives of the research were: (i) to evaluate indicators of the porous system state of Argiudolls and Hapludolls of Argentina, and to determine their physical quality, (ii) to find a pores distribution curve that can be used as reference. Undisturbed soil samples were collected in A and B horizons with a wide variation in texture, organic matter (OM) and soil bulk density (Bd). These samples were subjected to different matric potential to determine 60 water release curves that were used to calculate: pores size distribution, porosity in the domain of macropores (PORp), total capacity of air (ACt), available water for crops (CAD), stability index (SI), among others. The analysis of the indicators permitted to gather the studied soils in four groups according to the air supply and the water drainage, and to determine a water release curve of reference. The parameters of this curve, with a total porosity value of 0.528 m3 m-3, allowed to determine that PORp=0.036 m3 m-3, ACt=0,157 m3 m-3, field capacity=0.371 m3 m-3, wilting point=0.140 m3 m-3 and CAD=0.231 m3 m-3. These indicators point out that the ability to quickly drain excess of water is not adequate. The high content of silt and the low tenor of organic matter seem to be responsible for the excess of small pores, the low PORp and the high instability of the soil structure. Fifty six cases had SI