Analysis of organic fractions as indicators of soil quality under natural and cultivated systems

DUVAL M.; GALANTINI J.A; IGLESIAS J. O.; CANELO S.; MARTINEZ JUAN MANUEL; WALL L.

SOIL & TILLAGE RESEARCH

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2013 vol. 131 p. 11 - 19

0167-1987

Soil organic matter (SOM) or carbon (SOC) is the most important component of the soil and it iscomposed of fractions with different lability. Particulate organic carbon (POC) and carbohydrates (CH),among others, are the most sensitive to changes in crops and soil management practices. The purpose ofthis study was to analyze different soil parameters aimed for the evaluation of management practiceseffects under widely different soil and climatic conditions. Soils were located along a West?East transectin the most productive region of the Argentinean pampas: [West] Bengolea and Monte Buey (Co´ rdoba),Pergamino (Buenos Aires) and Viale (Entre Rios) [East]. Three treatments were defined according to landuse: ??Good agricultural practices?? (GAP): sustainable agricultural management under no-till; ??Pooragricultural practices?? (PAP): non-sustainable agricultural management under no-till; ??Naturalenvironment?? (NE): rangelands long as reference situation. Samples were taken at 0?10 and 10?20 cm depths. SOC was determined in different particle size fractions: 105?2000 mm (coarse particulateorganic carbon, POCc), 53?105 mm (fine particulate organic carbon, POCf), and 53 mm (mineral-associated organic carbon, MOC). Total (CHt) and soluble (CHs) carbohydrate contents were alsodetermined. The SOC level in NE was decreasing from the East (27.3 g kg1 in Viale) to the West(13.3 g kg1 in Bengolea), following the rainfall and texture gradient among sites. The POCc/SOC andPOCc + POCf/SOC ratios in the NE showed differences among sites, suggesting different dynamicdepending on the environmental characteristics at the different locations. The SOC levels in the upperlayer of agricultural soils were 16?44% lower than natural ones. Carbon stocks were estimated for anequivalent mass of soil (950 and 2350 Mg ha1) in order to consider differences in bulk densities amongdifferent treatments. Mean values were significantly different (p < 0.001) for the different managementpractices: NE (26.6 Mg ha1) > GAP (20.1 Mg ha1) > PAP (16.3 Mg ha1). In general, labile organicfractions showed differential sensitivity. Fractions with an intermediate dynamic, as POCf (53?100 mm)and CHt, seem to be better indicators to detect the short- and medium-term management effects thanmore dynamic fractions.