C. Bayer et al., Organic matter storage in a sandy clay loam Acrisol affected by tillage and cropping systems in southern Brazil, SOIL TILL R, 54(1-2), 2000, pp. 101-109
Soil organic matter decline and associated degradation of soil and environm
ental conditions under conventional tillage in tropical and subtropical reg
ions underline the need to develop sustainable soil management systems. Thi
s study aimed first to evaluate the long-term effect (9 years) of two soil-
tillage systems (conventional tillage: CT, and no-tillage: NT) and two crop
ping systems (oat (Avena strigosa Schreb)/maize (Zea mays L.): O/M; and oat
+common vetch (Vicia sativa L.)/ maize+cowpea (Vigna unguiculata (L.) Walp)
: O+V/M+C without N fertilization on total organic carbon (TOC) and total n
itrogen (TN) concentrations in a sandy clay loam Acrisol in southern Brazil
. The second objective was to assess soil potential for acting as an atmosp
heric CO2 sink. Under NT an increase of soil TOC and TN concentrations occu
rred, in both cropping systems, when compared with CT. However, this increa
se was restricted to soil surface layers and it was higher for O+V/M+C than
for O/M, The O+V/M+C under NT, which probably results in the lowest soil o
rganic matter losses (due to erosion and oxidation) and highest addition of
crop residues, had 12 Mg ha(-1) more TOC and 0.9 Mg ha(-1) more TN in the
0-30.0 cm depth soil layer, compared with O/M under CT which exhibits highe
st soil organic matter losses and lowest crop residue additions to the soil
. These increments represent TOC and TN accumulation rates of 1.33 and 0.10
Mg ha(-1) per year, respectively. Compared with CT and O/M, this TOC incre
ase under NT and O+V/M+C means a net carbon dioxide removal of about 44 Mg
ha(-1) from the atmosphere in 9 years. NT can therefore be considered, as i
t is in temperate climates, an important management strategy for increasing
soil organic matter. In the tropicals and subtropicals, where climatic con
ditions cause intense biological activity, in order to maintain or increase
soil organic matter, improve soil quality and contribute to mitigation of
CO2 emissions, NT should be associated with cropping systems resulting in h
igh annual crop residue additions to soil surface. (C) 2000 Elsevier Scienc
e B.V. All rights reserved.