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Fractions of organic matter in long-term experiments and its relationship with agronomic management

By: Hidalgo, C.
Contributor(s): Alba, F. de [coaut.] | Etchevers, J.D [coaut.] | Fuentes, M [coaut.] | Govaerts, B.
Material type: materialTypeLabelBookAnalytics: Show analyticsPublisher: 2009Description: p. 248.Online resources: Access only for CIMMYT Staff Summary: Humic substances (HS) play an important role in soils and plant nutrition. Carbon (C) content is a good indicator of the potential humic-chemistry of a soil, but the way C is distributed in the soil physical and chemical fractions is important. The effect of agronomic managements (tillage system, residues retention and crop type) on humic fractions distribution was studied in this paper. Soil samples (Cumulic Phaeozem, pHw 6) were collected from a long-term experiment (14 years after being established), conducted at a CIMMYT site in the semi-arid subtropical highlands of Central Mexico. Humic acid (HA), fulvic acid (FA) and humins (HN) fractions in the soil (0-5cm) were determined. Samples were taken from eight treatments, a combination of: zero (ZT) and conventional (CT) tillage; maize and wheat monoculture; and with (+) and without (-) residues retention. Soil humic fractions were extracted by conventional procedures (0.1N NaOH + Na4P2O7.10 H2O pH 10, acidification, pH< 2 ). Carbon content was determined with a TOC analyzer. In general, the largest amount of soil C was found in the HN fraction. In the wheat monoculture soil, C in HN found in the ZT+r and ZT-r treatments nearly doubled (60 %) the C in HA (31 %). The C distribution in HN and HA (51 and 40 % of C) was similar in CT+r and CT-r treatments, though slightly lower in ZT. The removal of residues in both types of tillage (ZT-r and CT-r) for this crop caused no difference in the distribution of C in AH and HN. The maize-cultivated soil showed a different performance. In the treatments using residues (ZT+r and CT+r), regardless of the type of tillage, the HN fraction stored more C (68 and 54 %) than HA (24 and 37 % ). But when the residues were removed from ZT-r the HA fraction accumulated more C (6% more C than in HN) and in CT-r the accumulation was similar (43 and 46 % in HA and HN). The amount of C present in the FA fraction was very low in all treatments (1 to 2 % of soil C). The reported mean residence-times for HN and HA are 1140 and 1235 yr, respectively, therefore these treatments are effective for C sequestration, regardless of the tillage system. However, the low contents of carbon in the HN fraction were associated with low yields and physical and chemical characteristics that hardly favor the soil.
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Conference proceedings CIMMYT Knowledge Center: John Woolston Library

Lic. Jose Juan Caballero Flores

 

CIMMYT Staff Publications Collection CIS-5808 (Browse shelf) Available
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Abstract only

Humic substances (HS) play an important role in soils and plant nutrition. Carbon (C) content is a good indicator of the potential humic-chemistry of a soil, but the way C is distributed in the soil physical and chemical fractions is important. The effect of agronomic managements (tillage system, residues retention and crop type) on humic fractions distribution was studied in this paper. Soil samples (Cumulic Phaeozem, pHw 6) were collected from a long-term experiment (14 years after being established), conducted at a CIMMYT site in the semi-arid subtropical highlands of Central Mexico. Humic acid (HA), fulvic acid (FA) and humins (HN) fractions in the soil (0-5cm) were determined. Samples were taken from eight treatments, a combination of: zero (ZT) and conventional (CT) tillage; maize and wheat monoculture; and with (+) and without (-) residues retention. Soil humic fractions were extracted by conventional procedures (0.1N NaOH + Na4P2O7.10 H2O pH 10, acidification, pH< 2 ). Carbon content was determined with a TOC analyzer. In general, the largest amount of soil C was found in the HN fraction. In the wheat monoculture soil, C in HN found in the ZT+r and ZT-r treatments nearly doubled (60 %) the C in HA (31 %). The C distribution in HN and HA (51 and 40 % of C) was similar in CT+r and CT-r treatments, though slightly lower in ZT. The removal of residues in both types of tillage (ZT-r and CT-r) for this crop caused no difference in the distribution of C in AH and HN. The maize-cultivated soil showed a different performance. In the treatments using residues (ZT+r and CT+r), regardless of the type of tillage, the HN fraction stored more C (68 and 54 %) than HA (24 and 37 % ). But when the residues were removed from ZT-r the HA fraction accumulated more C (6% more C than in HN) and in CT-r the accumulation was similar (43 and 46 % in HA and HN). The amount of C present in the FA fraction was very low in all treatments (1 to 2 % of soil C). The reported mean residence-times for HN and HA are 1140 and 1235 yr, respectively, therefore these treatments are effective for C sequestration, regardless of the tillage system. However, the low contents of carbon in the HN fraction were associated with low yields and physical and chemical characteristics that hardly favor the soil.

Conservation Agriculture Program

English

Lucia Segura

INT2813

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