Dynamics of humic fractions and microbial activity under no-tillage or reduced tillage, as compared with native pasture (Pampa Argentina)

Abstract

Humic fractions, arginine ammonification and soil respiration were monitored in spring, summer and autumn 1999 in natural pasture soil and in no-tillage or reduced-tillage soil under maize. The Typic Argiudoll soils, typical of the Argentine rolling pampa, can be structurally unstable, particularly when conventionally tilled, a form of soil management affecting the humification process. The no-tillage soil had a lower content of fulvic acids than the reduced-tillage soil in spring and summer, probably because the humification process was favored by residue management in no-tillage soil, with a significant increase in the most stable fraction. Both arginine ammonification and CO 2 were significantly correlated with the humic acids and humin contents. No significant correlation was found with fulvic acids,probably due to the lability and high variability of this fraction. A high correlation was found between arginine ammonification and CO 2 . The highest index values were generally observed in natural pasture soil, whereas notillage soils showed a higher index value than reducedtillage soils throughout, confirming the hypothesis that humification is more intense in the presence of organic residues.

Tillage System Affects Soil Organic Carbon Storage and Quality in Central Morocco

“…This is consistent with results obtained by Szajdak et al [65]. The relative decrease in FA under NT compared to CT was probably due to the humification process which was favored by residue management under NT and resulted in a significant increase of the most stable fraction (HA and HU) [66].…”

Distribution of organic carbon in the stable soil humic fractions as affected by tillage management

“…Several investigators (Lichtfouse et al 1995;Wanniarachchi 1997;Spaccini et al 2000;Doane et al 2003) using d 13 C techniques to investigate C dynamics in soil humic fractions recovered variable proportions of corn-derived C in the soil humic fractions, and this was suggestive of differences in C dynamics among the fractions. Gonza´lez et al (2003) also demonstrated that humic fractions do respond dynamically to different tillage practices. Further, the problem of artifact production can be reduced by using mild extracting agents, such as neutral sodium pyrophosphate (Swift 1996) and by removing particulate organic matter before extraction of humic substances.…”

Spatiotemporal heterogeneity of soil fertility in the Central Monte desert (Argentina)

“…To analyze the dynamics of SOM and N fractions the following indices were estimated: C mineralization index (CO 2 -C/SOM-C) (Abril et al, 2005), humification index (HA/SOM), humus type (HA/FA) (Gonzá lez et al, 2003), and available N index (NO 3 -N/total N) (Sparling, 1998). To determine spatial and temporal heterogeneity, data from the different sites (Under P, Under L, Gap P, and Intercanopy) and sampling dates (dry and wet seasons) were analyzed statistically using ANOVA and comparison of means by LSD test (p < 0.05).…”