Short communication. Biological fixation of nitrogen and N balance in soybean crops in the pampas region

Biological nitrogen fixation (BNF) is of key importance in the N balance of soybean (Glycine max) crops. A number of authors have suggested that a negative balance may occur under high yield conditions. Few studies have measured the contribution of BNF to soil N in the pampas region. The aims of the present study were to compare three BNF determination methods – two isotopic methods using sorghum or a non-nodulating soybean isoline as a reference crop, and one involving the calculation of the difference in N content between the nodulating and non-nodulating soybean isolines – and to estimate the N balance in soybean crops raised under conventional tillage and no tillage practices. The study was performed in 2004-2005; a complete randomised block design was used with three replicates (plot dimensions 3 × 7 m). The different methodologies estimated BNF to account for 45-58% of total plant N, equivalent to 94 to 123 kg N ha-1. Depending on the methodology for estimating the BNF the soil N balance varied between –7 and 22 kg N ha-1. With an average grain yield of 1,618 kg ha-1 and a BNF accounting for approximately 50% of total plant N (i.e.,115 kg N ha-1), the soil N balance was slightly positive (14 kg ha-1) and independent of the tillage practice. The tillage systems had no effect (P < 0.05) on the mass or number of nodules, shoot biomass production at the R1 or R6 growth stages, the N content, BNF, or grain yield. Since the present results were obtained using non-commercial soybean isolines, further research is required to determine the soil N balance when high yielding soybean crops are raised

Short communication: biological fixation of nitrogen and N balance in soybean crops in the pampas region

Biological nitrogen fixation (BNF) is of key importance in the N balance of soybean (Glycine max) crops. A number of authors have suggested that a negative balance may occur under high yield conditions. Few studies have measured the contribution of BNF to soil N in the pampas region. The aims of the present study were to compare three BNF determination methods ¿ two isotopic methods using sorghum or a non-nodulating soybean isoline as a reference crop, and one involving the calculation of the difference in N content between the nodulating and non-nodulating soybean isolines ¿ and to estimate the N balance in soybean crops raised under conventional tillage and no tillage practices. The study was performed in 2004-2005; a complete randomised block design was used with three replicates (plot dimensions 3 × 7 m). The different methodologies estimated BNF to account for 45-58% of total plant N, equivalent to 94 to 123 kg N ha-1. Depending on the methodology for estimating the BNF the soil N balance varied between ¿7 and 22 kg N ha-1. With an average grain yield of 1,618 kg ha-1 and a BNF accounting for approximately 50% of total plant N (i.e.,115 kg N ha-1), the soil N balance was slightly positive (14 kg ha-1) and independent of the tillage practice. The tillage systems had no effect (P < 0.05) on the mass or number of nodules, shoot biomass production at the R1 or R6 growth stages, the N content, BNF, or grain yield. Since the present results were obtained using non-commercial soybean isolines, further research is required to determine the soil N balance when high yielding soybean crops are raised

Earthworm assemblages in different intensity of agricultural uses and their relation to edaphic variables

The objective of this study was to relate earthworm assemblage structure with three different soil use intensities, and to indentify the physical, chemical, and microbiological soil variables that are associated to the observed differences. Three soil uses were evaluated: 1-Fifty year old naturalized grasslands, low use intensity; 2-Recent agricultural fields, intermediate use intensity, and 3-Fifty year old intensive agricultural fields, high use intensity. Three different sites for each soil use were evaluated from winter 2008 through summer 2011. Nine earthworm species were identified across all sampling sites. The sites shared five species: the native Microscolex dubius, and the introduced Aporrectodea caliginosa, A. rosea, Octalasion cyaneum, and O. lacteum, but they differed in relative abundance by soil use. The results show that the earthworm community structure is linked to and modulated by soil properties. Both species abundance and diversity showed significant differences depending on soil use intensity. A principal component analysis showed that species composition is closely related to the environmental variability. The ratio of native to exotic species was significantly lower in the intensive agricultural system when compared to the other two, lower disturbance systems. Microscolex dubius abundance was related to naturalized grasslands along with soil Ca, pH, mechanical resistance, and microbial respiration. Aporrectodea caliginosa abundance was related to high K levels, low enzymatic activity, slightly low pH, low Ca, and appeared related to the highly disturbed environment. Eukerria stagnalis and Aporrectodea rosea, commonly found in the recent agricultural system, were related to high soil moisture condition, low pH, low Ca and low enzymatic activity. These results show that earthworm assemblages can be good indicators of soil use intensities. In particular, Microscolex dubius, Aporrectodea caliginosa, and Aporrectodea rosea, showed different temporal patterns and species associations, due to the changes in soil properties attributable to soil use intensity, defined as the amount and type of agricultural operations

Approche quantitative pour laborer une echelle d'evaluation experte d'un indicateur de stabilite structurale

International audienceIn mountains, torrential check dams reduce liquid and solid flows and protect human and material assets at risk. Assessing their structural effectiveness is necessary to choose actions and maintenance strategies. Fuzzy sets can be used to represent needed indicators. Our approach aims at building those fuzzy numbers according to an objective way taking into account internal and external stability of the protective structure. This paper describes a fuzzy evaluation methodology of a scouring indicator. From a structural perspective, this case indeed corresponds to a critical situation associated to soil bearing capacity removal. Classical external stability justification according ultimate (ULS) and service (SLS) limit states are considered as a reference. Gaps between this reference and different scouring scenarios are first interpreted as a measure of scouring indicator. Secondly, the reference is adapted through a reduction of partial coefficients and imprecise loads considered in actions combinations. Finally, the global analysis makes it possible to propose fuzzy sets of scouring impact based on an external stability calculation methodology.En montagne, les ouvrages de correction torrentielle agissent sur les écoulements liquides et solides et protègent les enjeux humains et matériels. L’analyse de leur niveau d’efficacité structurale est nécessaire pour choisir des stratégies et actions de maintenance. Des nombres flous peuvent être utilisés pour représenter les indicateurs de cette efficacité. L’approche proposée vise à rendre objectif le choix de ces nombres en se basant sur une analyse de stabilité interne et externe de la structure. Cet article s’appuie sur l’exemple de l’affouillement en pied d’ouvrage qui correspond à un cas particulièrement critique de suppression des appuis en fondation. Les calculs classiques de vérification de la stabilité externe théorique d’un barrage à l’ELU et à l’ELS (Eurocode 7) sont considérés comme la référence. Son évolution pour un ouvrage donné est d’abord calculée en faisant varier le taux d’affouillement. Dans un second temps, la référence est adaptée en réduisant les coefficients partiels et en tenant compte de l’imprécision sur les cas de charge pris en compte dans les combinaisons d’actions. Finalement, une méthodologie reproductible basée sur ces calculs de stabilité est proposée pour établir les nombres flous associés au taux d’affouillement de pied d’un ouvrage de stabilisation torrentielle

Microbiological activity and carbon mineralization in pampean soils with different agricultural use intensity

ABSTRACT 1 The processes involved in the flows of matter and energy of terrestrial ecosystems depends 2 heavily on soil biological activity, the current conventional agricultural managements could alter 3 the biological mechanisms involved in decomposition and nutrient cycling in agroecosystems. 4 The aim of this study was to compare the activity levels and soil microbial biomass between 5 different agricultural pampean soil uses and its relationship to carbon mineralization. 25 years of 6 agricultural use were compared with 25 years of ecological reserve naturalized where each 7 agroecosystem soil were collected at 61 -125 -183 -236 -302 -368 -431 -488 days for 8 measuring their moisture, organic matter, enzymatic activity, microbial biomass carbon, soil 9 respiration, metabolic quotient, microbial quotient and carbon mineralization rate. The distance 10 between agroecosystems is less than 800 m, thus assuming the same soil and climatic conditions. 11 The data were evaluated by Friedman test finding significant differences in moisture, organic 12 matter, enzymatic activity, soil respiration y microbial quotient (p&lt; 0.01). Difference was also 13 found in the microbial mineralization rate of carbon (p&lt; 0.1). 14 KEY WORDS 15 Microbiological activity; carbon mineralization; soil use. 16 PeerJ PrePrints | https://doi.org/10.7287/peerj.preprints.1608v1 | CC-BY 4.0 Open Access

Trend in rifampicin-, multidrug- and extensively drug-resistant tuberculosis in Italy, 2009\u20132016

Tuberculosis (TB) caused by strains of Mycobacterium tuberculosis that are rifampicin-resistant (RR), multidrug-resistant (MDR) (strains resistant to at least isoniazid and rifampicin) or extensively drug-resistant (XDR) (MDR strains resistant to any fluoroquinolone (FQ) and to at least one second-line injectable drug (SLID): kanamycin, capreomycin or amikacin) is a major threat to TB control globally. All three groups require treatment with second-line drugs (SLDs). We previously reported that MDR- and XDR-TB in Italy occurred mostly in foreign-born persons (FBPs) , but no major information on RR, MDR or XDR trends in FBPs and Italian-born persons (IBPs) were shown. Here, we documented these trends from 2009 to 201