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SOIL & WATER MANAGEMENT & CONSERVATION

Tillage Effects on Soil Carbon Balance in a Semiarid Agroecosystem

^a National Inst. of Agricultural Technology (INTA), Anguil, La Pampa 6326, Argentina
^b Faculty of Agronomy, Univ. of Buenos Aires, Av. San Martín 4453, C1417DSE Buenos Aires, Argentina
^c National Inst. of Agricultural Technology (INTA), Anguil, La Pampa 6326 and Faculty of Agronomy, UNLPam., Argentina
^d Faculty of Agronomy, Univ. of Buenos Aires, Av. San martin 4453, C1417DSE Buenos Aires, Argentina

^* Corresponding author (abono{at}anguil.inta.gov.ar).

Tillage systems may affect soil C sequestration, with a potential impact on crop productivity or organic matter mineralization. We evaluated crop yield, C inputs to the soil, and in situ CO₂–C fluxes under no-till and conventional tillage (disk tillage) during the 3- to 6-yr period from the installation of an experiment in an Entic Haplustoll of the Semiarid Pampean Region of Argentina to elucidate the mechanisms responsible for possible management-induced soil organic matter changes. Yield and biomass production were greater under no-till than disk tillage for all the crops included in the rotation (oat [Avena sativa L.] + hairy vetch [Vicia villosa Roth ssp. villosa], corn [Zea mays L.], wheat [Triticum aestivum L.], and oat). This result was attributed to the higher soil water content under no-till. Carbon inputs to the soil averaged 4 Mg C ha^–1 yr^–1 under no-till and 3 Mg C ha^–1 yr^–1 under disk tillage. Soil temperature was similar between tillage systems and CO₂–C emission was about 4 Mg C ha^–1 yr^–1, with significant but small differences between treatments (0.2 Mg C ha^–1 yr^–1). Carbon balance of the soil was nearly equilibrated under no-till; meanwhile, greater C losses as CO₂ than inputs in crop residues were measured under conventional tillage. Organic C in the soil was 5.4 Mg ha^–1 higher under no-till than the disk tillage treatment 6 yr after initiation of the experiment. Results showed that in our semiarid environment, C sequestration occurred under no-till but not conventional tillage. The sequestration process was attributed to the effect of the tillage system on crop productivity rather than on the mineralization intensity of soil organic pools.

Abbreviations: BLUP, best linear unbiased prediction