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

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.

A Rapid Method for Assessing the Environmental Performance of Commercial Farms in the Pampas of Argentina

“…While C depletion can largely be explained by increasing cropping under conventional tillage, no-till not only seems to prevent C depletion but also to boost a long-term C gain in soils. This behavior can be confirmed through experimental results (Alvarez et al, 1999Alvarez, 2001;Chagas et al, 1995;Miglierina et al, 2000;Studdert and Echeverría, 2000).…”

Carbon balance in maize fields under cattle manure application and no-tillage cultivation in Northeast Thailand

“…CO 2 flux from a non-tilled field was higher than from a tilled field in Argentina (Alvarez et al 1998) and slightly higher than from tilled fields in New Zealand (Aslam et al 2000) and Scotland (Vinten et al 2002). Alvarez et al (1998) reported from incubation experiments that the CO 2 flux was the same from soils with notillage and soils with tillage, and that the accumulation of labile organic matter caused a high CO 2 flux in the no-tillage treatment. In the NT treatment in our experiments, we hypothesize that the low input of labile organic matter because of the low biomass of maize and weeds resulted in a low CO 2 flux.…”

Soil organic matter, biota and aggregation in temperate and tropical soils - Effects of no-tillage

“…Aggregates physically protect SOM by (1) forming a physical barrier between microorganisms plus microbial enzymes and their substrates, (2) controlling food web interactions, and (3) influencing microbial turnover [97]. A closer look at the processes involved in aggregate formation and stabilization in temperate versus tropical soils illustrates the close relationship between soil biota and SOM dynamics.…”

“…9). This more pronounced aggregation increase does, however, not seem to lead to an [3,26,[30][31][32]35,38,59,65,77,79,109,111,113,114,139,164,172,173,177,194,Paustian and Elliott,unpublished,214,219,220,241] for (sub)tropical soils and from [2,11,22,42,50,[54][55][56]58,67,72,78,84,85,89,93,95,96,104,105,133,134,136,146,…”