Quality and Quantity of Organic Fractions as Affected by Soil Depth in an Argiudoll under Till and No-till Systems

Aims: The aim of this study was to evaluate the long-term effect of tillage systems on the quantity and quality of organic carbon fractions at different soil layers. Study Design: The experimental design was a split plot with three blocks. The long-term effects (25 years) of conventional- (CT) and no-tillage (NT) systems on a Tipic Argiudoll was sampled at 0-5, 5-10, 10-15 and 15-20 cm soil depth. Place and Duration of Study: The field experiment was carried out at Tornquist (38° 07’ 06” S - 62°02’ 17” O) and soil sampling was performed during wheat seeding (June 2011). Methodology: Total soil organic carbon (SOC) content and the following fractions were determined: Coarse particulate (POCc, 105-2000 µm), fine particulate (POCf, 53-105 µm) and mineral-associated (MOC, 0-53 µm) carbon fractions; humic (HA) and fulvic (FA) acids; and total (CHt) and soluble (CHs) carbohydrates. The main physico-chemical properties of HA and FA were analyzed using both FT-IR and fluorescence spectroscopies. Results: After 25 years, total SOC at the 0-20 cm depth was 9% higher in no-tilled than in tilled soils. The POCf was the SOM fraction that turned out to be the most sensitive to tillage effects. The POCc:POCf:MOC ratio at 0-20 cm was similar for NT (3:14:82) and CT (5:10:84); however, differences were found across soil depths. Tilled soils showed higher aromaticity, starting by CH-degradation, in more superficial soil layers. Conclusion: The no-tillage system presented a different pattern which can be related to distribution of crop residues and conditions for humification along the soil depth.

Fil: Galantini, Juan Alberto. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina

Fil: Duval, Matias Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina

Fil: Martinez, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina

Fil: Mora, Maria Veronica. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales; Argentina

Fil: Baigorri, Roberto. Centre d Investigation en Production Animale et Végétale; España

Fil: García Mina, José M.. Universidad de Navarra; España