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Combining no-till with rye (Secale cereale L.) cover crop mitigates nitrous oxide emissions without decreasing yield
No full textNo-till (NT) often increases soil carbon (C) sequestration compared with conventional tillage (CT), yet its net
effect on N2O emissions is controversial. Cover crops (CCs) adoption is promoted in NT systems because CCs
growth curbs nitrate losses via leaching. However, incorporating CC residues into the soil may have positive or
negative effects on N2O emissions depending on CC species and agro-ecosystem management. A better understanding
of how tillage practices and CC species affect N2O emissions is therefore needed for the development of
productive agroecosystems that contribute to climate change mitigation. The objectives of this three-year
(2015–2017) field experiment on a Udertic Haplustalf soil in the Po Valley were to compare N2O emissions and
crop yield of soybean under NT and CT, and to examine how contrasting residues from two CCs (rye, Secale
cereale L. vs hairy vetch, Vicia villosa Roth) affect N2O emissions in NT soybean and maize. We hypothesized that
N2O emissions would be lower with NT than with CT and with rye residues than with vetch ones. Nitrous oxide
was continuously sampled using automatic chambers during three periods (emergence, N-fixation and maturity)
over the soybean-cropping season in 2015 and during the entire cropping maize season in 2017. The DNDC
model was calibrated (2015 data) and validated (2017 data), and then used to estimate the annual cumulative
N2O emissions in different treatments. Overall, N2O emissions in NT were 40–55% lower than in CT, for both in
situ measurements (Period I) and modelled estimations. These differences could be ascribed to the higher waterfilled
pore space (WFPS) and soil nitrate availability in CT than in NT. No-till also increased SOC content (28%;
0–5 cm) and earthworm abundance (5 times) compared with CT. Within NT systems, N2O emissions were
20–36% lower with rye CC than with vetch CC (P < 0.05), which was a consequence of the lower availability of
soil mineral N under rye than under vetch due to the high C/N ratio of rye residues. Yield of soybean and maize
under NT was higher with rye CC than with vetch CC. The combination of NT and rye CC that led to the lowest
N2O emissions and highest yields should be recommended in the Po Valley region
Superficiale o sotterranea, la goccia conviene
No full textLe tecniche di microirrigazione (sia superficiale, sia sotterranea) garantiscono su mais e pomodoro un evidente risparmio della risorsa idrica e rese agronomiche paragonabili o superiori all’irrigazione per aspersione. Anche sul fronte della concentrazione di nitrati nel terreno i vantaggi sono indiscutibil
Soil type and cropping system as drivers of soil quality indicators response to no-till: A 7-year field study
No full textConventional agricultural practices (CAP) highly impacted soil functions involved in the provision of multiple
ecosystem services. No-till (NT) has been repeatedly indicated as a key way to enhance soil fertility and biodiversity,
while having a positive effect on the environment and climate change. However, experimental evidence
to date shows contrasting effects of NT on physical parameters of soil fertility, as well as on soil organic
carbon (SOC) storage and soil biodiversity especially if different soil types and cropping systems are considered.
The objectives of the present 7-year field study were: (i) to unravel the effect of NT on SOC, soil bulk density,
and water stability index (WSI) of soil aggregates across five different soil types (Silty Clay, Silty Clay Loam, Clay
Loam, Silt Loam, and Sandy Loam) and cropping systems (silage vs grain production), (ii) to examine how soil
fauna (i.e. microarthropods and earthworms) is affected by NT practices under those soil-crop conditions, and
(iii) to assess relationships among responses of soil physical indicators (i.e. soil bulk density and WSI), SOC, and
soil fauna.
Our results showed that soil bulk density was generally not affected by 7-year NT across all soil types. At the
same time, NT increased WSI. It follows that NT may increase stable rather than artificial tillage-derived porosity
due to reduced soil disturbance, and increased SOC and biological activity. However, reduced importance for
boosting aggregates stability should be attributed to NT where initial SOC is high, clay and silt are predominant
soil fractions, and the rate of crop residue is low.
Our findings suggest that NT may enhance SOC stock (on average 0.66 Mg C ha−1 year−1) in the 0–30 cm soil
layer. However, we found (i) a tendency of NT to decrease SOC concentration in the 15–30 cm soil layer (on
average −1.18 g C kg−1), and (ii) no SOC increase induced by NT if crop residues were not left onto the soil
surface.
Nevertheless, NT practices promoted (i) the microarthropods adaptation measured with the QBS-ar index
(105.5 vs 64.7), and (ii) the increase of earthworm abundance (412 vs 123 individuals m−2), which are fundamental
for enhancing nutrient cycling and soil porosity.
Correlations among soil fauna (i.e. QBS-ar and earthworm density), soil physical parameters (i.e. soil bulk
density and WSI), and SOC (i.e. concentration and stock) corroborates the hypothesis that soil fauna adaptation
and proliferation are main detectors of soil quality and sensitive indicators of changes in soil tillage
Cover crops, compost, and conversion to grassland to increase soil C and N stock in intensive agrosystems
No full textAbstract: Organic fertilization or conversion to grassland may increase soil organic carbon (SOC) and soil total nitrogen (STN). However, responses of net SOC and STN accumulation are sometimes inconsistent and little is known about temporal patterns when those strategies are stopped. We (a) assessed the effects of rye (Secale cereale L.) and hairy vetch (Vicia villosa Roth) cover crops (CCs) on SOC and STN during a 4-year “enriching” period (EP), and a following 2-year “depleting” period (DP); (b) compared these strategies with compost application and conversion to permanent fescue (Festuca arundinacea Schreb.); and (c) determined the responses of maize (Zea mays L.), soybean (Glycine max L. Merr.), and sunflower (Helianthus annuus L.) yields. Crop yield increased only in maize with compost and hairy vetch, which downsizes the role of these strategies to support productivity. SOC and STN increased with 4-year compost (+ 10.2 Mg C ha−1; + 0.5 Mg N ha−1), rye (+ 8.8 Mg C ha−1; + 0.6 Mg N ha−1), and hairy vetch (+ 6.9 Mg C ha−1; + 0.6 Mg N ha−1). Afterwards, SOC stock loss during 2-year DP tended to be higher than annual C input where there were CCs, and accounted for about 70% of annual C input where there was compost. High SOC loss highlights the weak effect of CCs for long-term SOC stabilization. Conversely, STN increased even during DP, which indicates a more lasting effect. Green manuring with CCs may be relevant for enhancing SOC and STN, although the beneficial effects are short-lived. Conversion to grassland remains the reference strategy. Graphic abstract: [Figure not available: see fulltext.
Cover crops during transition to no-till maintain yield and enhance soil fertility in intensive agro-ecosystems
No full textIntroducing no-till and cover crops in arable agro-ecosystems leads to the restoration of soil fertility, through the increase of soil organic matter (SOM), soil total nitrogen (STN), and available phosphorus (P), therefore maintaining or enhancing crop yield and reducing costs. Although the effects of those practices have been widely examined, many studies show conflicting results and little is known about the combined effects of no-till (NT) and cover crops (CCs) under intensive arable cropland in the Po Valley (Northern Italy). The objectives of this study were: (i) to evaluate if NT management coupled with CCs negatively affects yields during the transition period and how yields evolve; (ii) to assess SOM, STN, and P dynamics in the 60-cm soil depth layer; and (iii) to evaluate the effects of different types of winter cover crops on yield and soil parameters. A six-year field experiment was established in Piacenza, on a silty-clay soil under temperate climate conditions. The crop sequence was: winter wheat, maize, maize, soybean, winter wheat, and maize. The four experimental treatments were: (1) conventional tillage (CT) as control; (2) NT with CC of rye (NT-R); (3) NT with CC of hairy vetch (NT-V); and (4) NT with a mixture of CCs (rye, hairy vetch, crimson clover, Italian rye-grass and radish) [NT-M]). Dry biomass yield of CCs ranged between 2.2 and 3.1 Mg ha−1 for rye; 1.9 and 3.0 Mg ha−1 for hairy vetch; and 1.9 and 3.2 Mg ha−1 for mixture. In the present study, yields of winter wheat, maize, and soybean were generally not reduced with NT-CCs since the first year after conversion. The different composition and thickness of cover crop mulch showed an opposite yield response to rainfall pattern: under NT-R, a negative correlation was observed between grain yield and rainfall, while under NT-V this correlation was positive. After six years, SOM and STN concentrations in the 0-30 cm soil layer increased in NT-CCs. SOM concentration was +30%, +23% and +20% higher than CT for NT-R, NT-M and NT-V, respectively. STN was +28% higher under NT-R and NT-V, and +21% higher under NT-M, than CT. Conversely, P concentration was not influenced by the NT-CCs system, although we observed a tendency to increase under NT-V. In the 30-60 cm soil, layer, the tillage systems did not affect SOM and STN. We concluded that introducing NT with winter CCs into intensive arable agricultural systems is an effective strategy for enhancing soil fertility in fine-textured soils under temperate climates, without penalizing yields
May conservation tillage enhance soil C and N accumulation without decreasing yield in intensive irrigated croplands? Results from an eight-year maize monoculture
No full textIntensive management of agroecosystems has been widely indicated as major responsible for soil degradation, thus negatively impacting on relationships between agriculture and climate change. Conservation tillage (i.e. no-till and minimum tillage) has been recommended for enhancing soil organic carbon (SOC) and total nitrogen (STN) stocks while having a positive impact on food security, biodiversity, water quality and the environment. Nevertheless, positive responses were mainly reported in hot and semiarid climates, with rainfed crops and low N fertilization rates. Therefore, the main objective of this study was to test the adoption of conservation tillage in intensive maize cropping systems under temperate soil, with high N fertilization rate (> 200 kg N ha−1 yr−1) and organic matter input (i.e. manure distribution and high biomass return), and with permanent optimum water moisture due to irrigation. We conducted an 8-year field experiment on a maize (Zea mays L.) monoculture to assess: (i) the effect of no-till (NT) and minimum tillage (MT), on grain yield and biomass return as compared with conventional tillage (CT); (ii) how tillage systems affect the evolution of SOC and STN levels over time under these conditions; (iii) soil aggregation processes and mechanisms leading to SOC and STN changes in the long-term. Results showed that MT increased maize grain yield (+7 %) and total biomass (+10 %) compared with CT. Conversely, NT reduced maize grain and biomass production during the initial 5-year transition, but afterwards increased maize yield up to that of CT. At the end of the experiment, SOC sequestration was increased under NT and MT by 1.45 and 1.52 Mg C ha−1 yr−1 compared with CT, respectively. Also, STN accumulation was higher under NT and MT than under CT (+0.15 and +0.17 Mg N ha−1 yr−1, respectively). Most of such a SOC and STN increase was located into C- and N-rich macroaggregates. Within those macroaggregates (large macroaggregates, LM; small macroaggregates, sM), we found that C and N pools associated to mM accounted for between 41 and 65 % of total C and N content in NT and MT systems across the different soil layers, which is beneficial for long-term C and N stabilization in soils. Thus, introducing conservation tillage within intensive agricultural context devoted to maize monoculture as that of the Po Valley should be recommended to: (i) maintain (or even increase) maize yield, and (ii) enhance SOC and STN accumulation and stabilization
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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