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This article in AJ

  1. Vol. 90 No. 2, p. 138-143
     
    Received: Apr 22, 1997
    Published: Mar, 1998


    * Corresponding author(s): radio@ferlav.agro.uba.ar
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doi:10.2134/agronj1998.00021962009000020003x

Soil Carbon Pools under Conventional and No-Tillage Systems in the Argentine Rolling Pampa

  1. Roberto Alvarez ,
  2. Miguel E. Russo,
  3. Pablo Prystupa,
  4. Javier D. Scheiner and
  5. Luis Blotta
  1. Est. Exp. Agropecuária Pergamino-INTA, CC 31 (2700), Pergamino, Argentina

Abstract

Abstract

The Rolling Pampa is the most important cropping region of Argentina, and its soils are subjected to degradation. No-tillage has been proposed to replace the use of the moldboard plow to reduce soil C losses. The effects of no-tillage and plow tillage with and without N fertilization (0 or 90 kg N ha−1) on C inputs and outputs of a Typic Argiudoll and on organic C level and density fractions were studied in a field experiment at the end of 15 yr under a corn (Zea mays L.)-wheat (Triticum aestivum L.)-soybean [Glycine max (L.) Merr.] rotation. Microbial biomass and the rate of organic C mineralization during laboratory incubations were also determined. Nitrogen fertilization had no significant influence on C emission in the field, soil organic matter level or microbial biomass and activity. The annual C budget was negative under both tillage systems, but no-tillage lost about 0.7 to 1.5 Mg ha−1 yr−1 more C than did plow tillage. Carbon in the medium-density fraction (density = 1.6-2.0 g mL−1) of the 0- to 20-cm soil layer was 30% higher (P ≤ 0.05) under no-tillage. Light (density < 1.6 g mL−1) and heavy (density > 2.0 g mL−1) organic fractions, total C, and microbial biomass and activity in the 0- to 20- cm layer were not different in no-tilled and plowed soils, despite different patterns of distribution with depth. The rates of organic C mineralization during laboratory incubations were the same for both tillage systems. We propose that, after an accumulation phase, soil under no-tillage loses higher amounts of CO2-C than under plowing. The use of no-tillage would not significantly affect soil organic matter pools of the region in situations with low erosion losses.

Study supported by a grant from the Univ. of Buenos Aires: UB ACYT AG-089.

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