Distribution and vertical stratification of carbon and nitrogen in soil under different managements in the pampean region of Argentina

C.R. ALVAREZ; A. COSTANTINI; A. BONO; M.A. TABOADA; F.H. GUTIERREZ BOEM; P.L. FERNÁNDEZ; P. PRYSTUPA

REVISTA BRASILEIRA DE CIêNCIA DO SOLO

SOC BRASILEIRA DE CIENCIA DO SOLO

Lugar: Vicosa; Año: 2011 vol. 35 p. 1985 - 1994

0100-0683

One of the expected benefits of no-tillage systems is a higher rate of soil Csequestration. However, higher C retention in soil is not always apparent when notillageis applied, due e.g., to substantial differences in soil type and initial C content.The main purpose of this study was to evaluate the potential of no-tillagemanagement to increase the stock of total organic C in soils of the Pampas regionin Argentina. Forty crop fields under no-tillage and conventional tillage systemsand seven undisturbed soils were sampled. Total organic C, total N, their fractionsand stratification ratios and the C storage capacity of the soils under differentmanagements were assessed in samples to a depth of 30 cm, in three layers (0–5, 5–15 and 15–30 cm). The differences between the C pools of the undisturbed andcultivated soils were significant (p < 0.05) and most pronounced in the top (0–5 cm) soil layer, with more active C near the soil surface (undisturbed > no-tillage> conventional tillage). Based on the stratification ratio of the labile C pool (0–5/5–15 cm), the untilled were separated from conventionally tilled areas. Much of thevariation in potentially mineralizable C was explained by this active C fraction (R2= 0.61) and by total organic C (R2 = 0.67). No-till soils did not accumulate moreorganic C than conventionally tilled soils in the 0–30 cm layer, but there wassubstantial stratification of total and active C pools at no till sites. If the Cstratification ratio is really an indicator of soil quality, then the C storage potentialof no-tillage would be greater than in conventional tillage, at least in the surfacelayers. Particulate organic C and potentially mineralizable C may be useful toevaluate variations in topsoil organic matter.