M.T. Hernandez

No-tillage, crop residue additions, and legume cover cropping effects on soil quality characteristics under maize in Patzcuaro watershed (Mexico)

Abstract Intensive maize ( Zea mays L.) cropping based on conventional tillage practices has resulted in soil quality degradation in the Patzcuaro Watershed in central Mexico. A field experiment with seven soil management treatments was implemented on a sandy loam Andisol to evaluate the impact on soil quality of maize cropping with conventional tillage, no-tillage with varying percentages of surface residue coverage (0, 33, 66 and 100%), and no-tillage with 33% residue coverage together with cover crops of either Vicia sp. or Phaseolus vulgaris L. The treatments of no-tillage under crop residue coverage were established in 1995 and the leguminous species were planted in 1998. By 2000, the alternative management treatments had increased soil enzymes, soil organic C, biodegradable C fractions such as water soluble C, water soluble carbohydrates, and microbial biomass C, and soil wet aggregate stability, compared to the CT treatment. Wet aggregate stability was increased by adopting no-tillage and even further by additional residue. Most soil quality characteristics improved in direct proportion to residue inputs. The use of no-tillage management together with a moderate amount of crop residue (33%) and planted to leguminous species rapidly improved some soil quality characteristics. We conclude that conservation tillage practices can provide an alternative technology contributing to sustainable agriculture in the Patzcuaro watershed of Mexico, which can be extrapolated to similar areas elsewhere in Latin America.

Biopesticide effect of green compost against fusarium wilt on melon plants

Aims:  The biopesticide effect of four green composts against fusarium wilt in melon plants and the effect of soil quality in soils amended with composts were assayed.

Burning Fire-Prone Mediterranean Shrublands: Immediate Changes in Soil Microbial Community Structure and Ecosystem Functions

Wildfires subject soil microbes to extreme temperatures and modify their physical and chemical habitat. This might immediately alter their community structure and ecosystem functions. We burned a fire-prone shrubland under controlled conditions to investigate (1) the fire-induced changes in the community structure of soil archaea, bacteria and fungi by analysing 16S or 18S rRNA gene amplicons separated through denaturing gradient gel electrophoresis; (2) the physical and chemical variables determining the immediate shifts in the microbial community structure; and (3) the microbial drivers of the change in ecosystem functions related to biogeochemical cycling. Prokaryotes and eukaryotes were structured by the local environment in pre-fire soils. Fire caused a significant shift in the microbial community structure, biomass C, respiration and soil hydrolases. One-day changes in bacterial and fungal community structure correlated to the rise in total organic C and NO3−–N caused by the combustion of plant residues. In the following week, bacterial communities shifted further forced by desiccation and increasing concentrations of macronutrients. Shifts in archaeal community structure were unrelated to any of the 18 environmental variables measured. Fire-induced changes in the community structure of bacteria, rather than archaea or fungi, were correlated to the enhanced microbial biomass, CO2 production and hydrolysis of C and P organics. This is the first report on the combined effects of fire on the three biological domains in soils. We concluded that immediately after fire the biogeochemical cycling in Mediterranean shrublands becomes less conservative through the increased microbial biomass, activity and changes in the bacterial community structure.

Agricultural use of leachates obtained from two different vermicomposting processes

The objective of this paper was to investigate the possible agricultural use of the vermicomposting process leachates. Two leachates coming, respectively, from the vermicomposting of cow dung (SCD) and the vermicomposting of green forages (SGF), as well as solution of Hewitt (C) were used at a dose of 1 ml 500 ml(-1) in the foliar fertilization of tomato plants. Treatments were applied 30, 60 and 90 days after planting (DAP). The obtained results showed that foliar fertilization with SCD and SGF increased the morphological and chemical parameters on tomato crop with respect to the plants receiving foliar treatment with SH and C, possibly due to the humic substances content in SCD and SGF. The higher content of humic substances in SGF with respect to the SCD are possibly the responsible of the higher chlorophyll contents observed in the plants receiving the former treatment. This aspect possibly promoted an increase in plant photosynthesis and therefore an increase in fruit quality.

Effect of solid waste compost on microbiological and physical properties of a burnt forest soil in field experiments

Abstract The restoration of soil microbial activities is a basic step in the reclamation of burnt soils. For this reason, the ability of municipal solid waste compost to accelerate the re-establishment of bacterial and fungal populations, as well as to re-establish physical properties in a burnt soil, was evaluated in a field experiment. Four treatments were performed by adding different doses of compost (0, 0.5, 1 and 2 kg compost m–2 soil) to a burnt Calcic Rodoxeralf soil, and the changes in microbial populations, salt content, aggregate stability and bulk density were evaluated for 1 year. Initially, the addition of compost had a negative effect on soil microbial populations, but 3 months after compost addition, the number of viable fungal propagules increased in all the amended soils. This positive effect lasted until the end of the experiment. From 30 days onwards, all the amended soils showed a greater total number of bacterial cell forming units than the unamended burnt soil. Organic amendment increased the percentage of 2- to 4-mm aggregates, although the effect on the stability of the 0.2- to 2-mm aggregates and on bulk density was less noticeable.

Polyphenolic profile as a useful tool to identify the wood used in wine aging

Although oak wood is the main material used in cooperage, other species are being considered as possible sources of wood for the production of wines and their derived products. In this work we have compared the phenolic composition of acacia (Robinia pseudoacacia), chestnut (Castanea sativa), cherry (Prunus avium) and ash (Fraxinus excelsior and F. americana) heartwoods, by using HPLC-DAD/ESI-MS/MS (some of these data have been showed in previous paper), as well as the changes that toasting intensity at cooperage produce in each polyphenolic profile. Before toasting, each wood shows a different and specific polyphenolic profile, with both qualitative and quantitative differences among them. Toasting notably changed these profiles, in general, proportionally to toasting intensity and led to a minor differentiation among species in toasted woods, although we also found phenolic markers in toasted woods. Thus, methyl syringate, benzoic acid, methyl vanillate, p-hydroxybenzoic acid, 3,4,5-trimethylphenol and p-coumaric acid, condensed tannins of the procyanidin type, and the flavonoids naringenin, aromadendrin, isosakuranetin and taxifolin will be a good tool to identify cherry wood. In acacia wood the chemical markers will be the aldehydes gallic and β-resorcylic and two not fully identified hydroxycinnamic compounds, condensed tannins of the prorobinetin type, and when using untoasted wood, dihydrorobinetin, and in toasted acacia wood, robinetin. In untoasted ash wood, the presence of secoiridoids, phenylethanoid glycosides, or di and oligolignols will be a good tool, especially oleuropein, ligstroside and olivil, together verbascoside and isoverbascoside in F. excelsior, and oleoside in F. americana. In toasted ash wood, tyrosol, syringaresinol, cyclolovil, verbascoside and olivil, could be used to identify the botanical origin. In addition, in ash wood, seasoned and toasted, neither hydrolysable nor condensed tannins were detected. Lastly, in chestnut wood, gallic and ellagic acids and hydrolysable tannins of both the gallotannin and ellagitannin type, can be used as chemical markers.

Polyphenols in red wine aged in acacia (Robinia pseudoacacia) and oak (Quercus petraea) wood barrels

Polyphenolic composition of two Syrah wines aged during 6 or 12 months in medium toasting acacia and oak 225L barrels was studied by LC-DAD-ESI/MS. A total of 43 nonanthocyanic phenolic compounds were found in all wines, and other 15 compounds only in the wines from acacia barrels. Thus, the nonanthocyanic phenolic profile could be a useful tool to identify the wines aged in acacia barrels. Among all of them the dihydrorobinetin highlights because of its high levels, but also robinetin, 2,4-dihydroxybenzaldehyde, a tetrahydroxydihydroflavonol, fustin, butin, a trihydroxymethoxydihydroflavonol and 2,4-dihydroxybenzoic acid were detected at appreciable levels in wines during aging in acacia barrels, and could be used as phenolic markers for authenticity purposes. Although longer contact time with acacia wood mean higher concentrations of phenolic markers found in wines, the identification of these wines will also be easy after short aging times due the high levels reached by these compounds, even after only 2 months of aging.

Long-term effects of devegetation on composition and activities (including transcription) of fungal communities of a semi-arid soil

A stable plant cover is essential in the semi-arid soils of the Mediterranean area to maintain their fertility and functionality. In a semi-arid area, we have studied abundance, structure, and presence of active species of fungal communities of a devegetated soil (disturbed soil) and vegetated soil (undisturbed soil). Disturbed soil was covered by small spontaneous vegetation (5–10%) compared to undisturbed soils (70%), and this decreased the content of the total organic C, microbial biomass, microbial activity (adenosine triphosphate), and fungal counts. The composition and activities of fungal communities were also investigated by direct extraction of DNA and RNA from soil. Denaturing gradient gel electrophoresis analysis of 18S ribosomal DNA and 18S ribosomal RNA profiles indicated that total and active fungal communities were changed after vegetation removal.