Soil fertility status, carbon and nitrogen stocks under cover crops and tillage regimes

Arminda Moreira De Carvalho,Robélio Leandro Marchão,Mercedes Maria Da Cunha Bustamante,Kleberson Worslley Souza

doi:10.1590/s1806-66902014000500007

Abstract

The aim of the present study was to evaluate the effects of cover crops on the soil's chemical fertility, in particular its carbon and nitrogen content, in a Typic Acrustox under conventional and no-tillage corn systems. We hypothesized that the no-tillage system associates with cover crops maintains or increases soil carbon and nitrogen stocks and enhance soil fertility. The no-tillage system did not present higher carbon and nitrogen stocks than conventional tillage, but resulted in higher concentrations of exchangeable bases, higher CEC, and higher base saturation in the surface soil layer, mainly under use of Canavalia brasiliensis. Carbon and nitrogen stocks (up to 40 cm depth) differ significantly between the different cover crop species. The use of Mucuna pruriens and Canavalia brasiliensis allows maintain or increase soil C and N stocks. The no-tillage system results in higher accumulation of soil organic matter (0-5 cm), and appears very likely to enhance soil fertility. The use of Canavalia brasiliensis and Mucuna pruriens in succession to corn promotes carbon sequestration and can be used to enhance soil quality in Cerrado agroecosystems.

Highlights

In the Savannas of Central Brazil, or Cerrado biome, the dominant soils are Latosols (Oxisols) and no-tillage systems were introduced in the mid-80s
The samples collected under the no-tillage system had higher mean soil organic matter values in the 0-5 cm soil layer (3.5 dag kg-1) than in the conventional tillage (3.0 dag kg-1)
The results reveal the importance of diversification of soil cover rotation in intense crop cultivation systems in order to maintain soil carbon and nitrogen levels

Summary

Introduction

In the Savannas of Central Brazil, or Cerrado biome, the dominant soils are Latosols (Oxisols) and no-tillage systems were introduced in the mid-80s. Modeling simulations for the Brazilian Cerrado indicated that soil C and N stocks under soybean monoculture with bare fallow declined approximately 20% after 50 years under no-tillage (CORBEELS et al, 2006). A more intensive agriculture combined with NTS practices can enhance C-accumulation rates by increasing biomass production whereby greater amounts of crop residues are returned to the soil (BATLLE-BAYER et al, 2010). The use of nitrogenfixing legumes (e.g. Crotalaria juncea L, and Mucuna pruriens (L) DC) as cover crops in agricultural systems can incorporate more than 200 kg N ha-1 (CALEGARI et al, 2008). Et al (2012) showed advantages of introducing legumes for green manuring as a means of replacing the N lost or removed in harvested grain as well as improving the residue quality to increase the efficiency of N fertilizer use

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