Soil humic acid and aggregation as restoration indicators of a seasonally flooded riparian forest under buffer zone system

Xiao

et al. 2017

Rev. Bras. Ciênc. Solo

ABSTRACT:Residue management in cropping systems may improve soil quality. However, there are few studies on the effects of residue management on soil aggregation and carbon content in the humin (C-HUM), humic acid (C-HAF) and fulvic acid (C-FAF) fractions in South China. Therefore, the effects on soil aggregation and on the C-HUM, C-HAF, C-FAF from incorporating winter cover crop residues in a double-cropped rice (Oryza sativa L.) system in South China fields were studied. The experiment has been conducted since winter 2004. Five winter cropping systems were used: rice-rice-ryegrass (Ry-R-R), rice-rice-Chinese milk vetch (Mv-R-R), rice-rice-potato (Po-R-R), rice-rice-rape (Ra-R-R) and rice-rice with winter fallow (Fa-R-R). The results indicated that the organic C content in the paddy soil under the Ry-R-R, Mv-R-R, Po-R-R, and Ra-R-R systems was significantly higher than the content in the Fa-R-R system at the early rice and late rice maturity stages. The different sizes of aggregates under the five treatments showed similar trends. The Po-R-R systems had the highest percentage of soil aggregates in each size class and the Fa-R-R systems had the lowest percentage of soil aggregates in each size class in the 0.00-0.05, 0.05-0.10, and 0.10-0.20 m soil depth at the early rice and late rice maturity stages. The C-HUM, C-HAF, and C-FAF increased through long-term application of winter cover crop residues. Statistical analysis showed that the C-HAF under the Ra-R-R systems was significantly higher than that in the Fa-R-R systems at the early rice and late rice maturity stages. The C-FAF and C-HUM under the Mv-R-R systems was significantly higher than the C-FAF and C-HUM in the Fa-R-R systems at the early rice and late rice maturity stages. As a result, the soil organic C content, the soil aggregates in each size class, and the C-HUM, C-HAF, and C-FAF increased from application of winter cover crop residues in double-cropped rice systems.

Section: Introductionmentioning

confidence: 97%

Returning Winter Cover Crop Residue Influences Soil Aggregation and Humic Substances under Double-cropped Rice Fields

Xiao

et al. 2017

Rev. Bras. Ciênc. Solo

“…Por último, se optimizaron las estructuras de los complejos formados entre los sitios activos de HA (sHA) y los cationes mencionados anteriormente, utilizando niveles de cálculos PM6 y DFT/LanL2dz iniciando en una distancia de enlace M-sHA de 2 Å. 11,19 La primera optimización de la geometría de los complejos se realizó a nivel PM6. 13 Luego, esta geometría se tomó como punto de partida para el cálculo de la energía a un nivel DFT/LanL2dz.…”

Section: Metodologíaunclassified

“…10 Recientemente, en el año 2017, Kimura y colaboradores estudiaron el efecto de agregación de suelos y su relación con ácido húmicos como indicadores de restauración de un bosque ribereño. 11 En el mismo año, Xu y sus colaboradores estudiaron las estructuras de los acidos húmicos presente en dos suelos típicos de China. 12 En la presente investigación se estudiaron las interacciones de dos modelos de ácidos húmicos con los cationes Al 3+ , Ca 2+ , Mg 2+ , Zn 2+ , K + y NH4 + .…”

Section: Introductionunclassified

Estudio teorico de las interacciones de dos modelos de ácidos húmicos con los cationes Al3+, Ca2+, Mg2+, Zn2+, K+ y NH4+ a un nivel de calculo DFT y un modelo de solvatación PCM

Espinosa-Fuentes¹,

Colpas-Castillo²,

Fuentes³

2017

Quim. Nova

. In this paper, two models of humic acids, the Temple-NortheasternBirmingham (TNB) and Kolla models, were studied. Also, the complexation reaction of the structures formed by the interaction of the TNB and Kolla models with Al 3+ , Ca 2+ , Mg 2+ , Zn 2+ , K + and NH 4 + cations, common in agricultural soils, was studied. These calculations were made for the complexes, at PM6 and DFT / LANL2DZ level of theory, both in vacuum and in aqueous medium. We found a strong affinity between Kolla and TNB models, and Al 3+ , Ca 2+ , Mg 2+ , Zn 2+ , K + and NH 4 + cations, influenced by the solvent that affected the interaction sites; the solvent increased the rate of reactivity and affinity for the cations in nucleophilic regions and decreased it in electrophilic regions of the structures. Calculations of molecular electronic potential, MEP and atomic charges, the local smoothness, Fukui functions and the HSAB principle adequately described the HA/cations interactions which were affected by the number of hydrogen bonds. The most reactive sites were the hydroxyl, phenolic, carbonyls oxygens and nitrogens at both vacuum and aqueous medium, especially carbonyl oxygens. These results are consistent with the properties of HA that make them attractive as components of agricultural soils.Keywords: TNB; Kolla HA models; reactivity descriptors; DFT; HSAB; PCM; metal cations. INTRODUCCIÓNLas ácidos húmicos (HA) aumentan la fertilidad, la retención de minerales, la acidez del agua adsorbida y el transporte de contaminantes a través del suelo, también afectan la química de la atmósfera a través del ciclo del carbono. 1-3 La gran mayoría de los estudios realizados con sustancias húmicas y fúlvicas se han enfocado en suelos 4 debido a la propiedad que tienen estas sustancias para recuperar suelos erosionados e infértiles; otro aspecto positivo son sus propiedades ambientales, bioquímicas, y terapéuticas. Aunque existen discrepancias entre las estructuras propuestas para los HA, estas poseen semejanzas en cuanto al número y tipo de grupos funcionales presentes. 5 Los estudios reportados sobre sustancias húmicas son relativamente escasos, debido a su gran diversidad y ambigüedad estructural. Asimismo, las interpretaciones de las propiedades químicas teóricas de dichas sustancias han sido muy sesgadas en cuanto a predicción de su utilidad e interacción con los principales cationes metálicos de interés vital. Entre los estudios más sobresalientes encontramos: En el año 2007 a Troul y colaboradores, los cuales estudiaron las interacciones de acidos fulvicos con benceno y Al (III). 6 En el mismo año, De Castro y colaboradores reportaron un estudio teórico de la complejación de Zn (II) y Cd (II) con ácidos fulvicos. 7 En el 2008, André y colaboradores estudiaron la regioselectividad de Al (III) frente a sustancias con grupos catecol. 8 En el año 2009, Burk y colaboradores estudiaron las interacciones de cesio con sustancias orgánicas de naturaleza aniónica provenientes del suelo. 9 En el año 2014, Aquino y colaboradores reportaron las regione...

Soil Use and Management

“…The role of carbohydrates in improving soil structure is variable (Bronick & Lal, ), while HAs and FAs are linked to minerals and soil aggregates with aromatic C or aliphatic alkyl‐C (Golchin et al ., ), resulting in a functional role in soil aggregation, porosity and stabilization (Šimanský & Bajčan, ). Thus, the quantitative and qualitative variations in HA and FA composition result in changes in the quality of aggregate formation and its role in soil stabilization (Kimura et al ., ).…”

Section: Introductionmentioning

confidence: 97%

“…The main ecosystem service provided by riparian forests is the protection of both aquatic and terrestrial ecosystems, buffering them against physical, chemical and biotic disturbances (Naiman & Decamps, ). Riparian forests ensure water drainage and erosion control through the effects of plant roots and soil aggregation (Bronick & Lal, ; Kimura et al ., ), which also control soil porosity. The latter drives soil water drainage and aeration through macro‐ and micropore balances (Six et al ., ).…”

Section: Introductionmentioning

confidence: 99%

Riparian reforestation with a single exotic species restores soil aggregation and porosity but not humic substances

Santos

Scotti

2018

A degraded riparian area in the Uberaba River basin (Brazil) was restored by local landowners using a monoculture of the exotic species Syzygium cumini (L.) Skeels over 15 years. To assess this riparian restoration, we compared this experimental site (ES) with a disturbed site (DS) and a preserved site (PS) with regard to soil organic matter, humic and fulvic acids (HA and FA), glomalin, soil aggregation and porosity. The results did not show significant differences between ES and PS with regard to soil aggregation and porosity. The cation exchange capacity and the HA and FA contents of ES were significantly different from those in PS and DS. Whereas the HA content of ES was less than that in PS, FA was significantly increased. The order of aromatic composition of humic substances by site was PS > ES > DS and contrasted with the aliphatic composition, which was DS > ES > PS. A principal component analysis based on all variables demonstrated that ES was closer to PS than to DS but that there was no overlap among sites, as PS was driven by humic aromatic substances and the experimental site by fulvic and aliphatic compounds. We concluded that there was a functional recovery of ecosystem services related to soil aggregation and porosity, but the qualitative differences in organic matter formation between the restored and preserved sites were not consistent with ES being fully restored.