The use of double-cropping in combination with no-tillage and optimized nitrogen fertilization reduces soil N2O emissions under irrigation.

The irrigation systems of the Ebro valley can lead to high N2O emissions. The effects that crop diversification, such as double-cropping in combination with conservation tillage and different N fertilizer ratios, has on soil N2O emissions have not been extensively studied in this region. The goal of this research was to measure N2O soil emissions and determine the tillage practices and N fertilization rates that provide the lowest emissions when combined with double-cropping systems. The work compared monocropping maize (MC) versus legume-maize double-cropping (DC) with two tillage systems (conventional tillage, CT; and no-tillage, NT), and three mineral N fertilization rates (zero, medium and high). Pea for grain (2019), vetch for green manure (2020), and vetch for forage (2021) were the legumes employed. The N2O emissions ranged from 0 to 15.5 mg N2O-N m-2 d-1 and were concentrated in the fertilization periods. Soil temperature and water filled pore space (WFPS) content significantly influenced soil N2O emissions. For both cropping systems, the conditions with the highest N2O emissions were soil temperatures above 20 °C and a WFPS of 50-60 %. The use of legumes facilitated reduced N fertilization in DC without affecting crop yield and led to reduced N2O emissions in this cropping system. DC reduced the emission factor (EF), which in all cases was lower than the default IPCC EF (1 %). With DC, a medium N fertilization rate produced similar yields to the high rate commonly applied by farmers, and also entailed lower N2O emissions. The no-tillage system, although producing higher levels of N2O, achieved lower yield-scaled N2O emissions due to greater crop yields. This work underlines the advantages of using double-cropping no-tillage systems combined with medium rates of N fertilization to reduce soil N2O emissions.

Recombination in the wheat stem rust pathogen mediated by an indigenous barberry species in Spain.

The comeback of wheat stem rust in Europe, caused by Puccinia graminis f. sp. tritici, and the prevalence of the alternate (sexual) host in local areas have recently regained attention as a potential threat to European wheat production. The aim of this study was to investigate a potential epidemiological link between the aecia found on an indigenous barberry species and stem rust infections on nearby cereals and grasses. Aecial infections collected from Berberis vulgaris subsp. seroi were inoculated on a panel of susceptible genotypes of major cereal crop species. In total, 67 stem rust progeny isolates were recovered from wheat (51), barley (7), and rye (9), but none from oat, indicating the potential of barberry derived isolates to infect multiple cereals. Molecular genotyping of the progeny isolates and 20 cereal and grass stem rust samples collected at the same locations and year, revealed a clear genetic relatedness between the progeny isolated from barberry and the stem rust infections found on nearby cereal and grass hosts. Analysis of Molecular Variance indicated that variation between the stem rust populations accounted for only 1%. A Principal Components Analysis using the 62 detected multilocus genotypes also demonstrated a low degree of genetic variation among isolates belonging to the two stem rust populations. Lastly, pairwise comparisons based on fixation index (Fst), Nei's genetic distances and number of effective migrants (Nm) revealed low genetic differentiation and high genetic exchange between the two populations. Our results demonstrated a direct epidemiological link and functionality of an indigenous barberry species as the sexual host of P. graminis in Spain, a factor that should be considered when designing future strategies to prevent stem rust in Europe and beyond.

Influence of Agronomic Factors on Mycotoxin Contamination in Maize and Changes during a 10-Day Harvest-Till-Drying Simulation Period: A Different Perspective.

Agronomic factors can affect mycotoxin contamination of maize, one of the most produced cereals. Maize is usually harvested at 18% moisture, but it is not microbiologically stable until it reaches 14% moisture at the drying plants. We studied how three agronomic factors (crop diversification, tillage system and nitrogen fertilization rate) can affect fungal and mycotoxin contamination (deoxynivalenol and fumonisins B1 and B2) in maize at harvest. In addition, changes in maize during a simulated harvest-till-drying period were studied. DON content at harvest was higher for maize under intensive tillage than using direct drilling (2695 and 474 µg kg-1, respectively). We found two reasons for this: (i) soil crusting in intensive tillage plots caused the formation of pools of water that created high air humidity conditions, favouring the development of DON-producing moulds; (ii) the population of Lumbricus terrestris, an earthworm that would indirectly minimize fungal infection and mycotoxin production on maize kernels, is reduced in intensive tillage plots. Therefore, direct drilling is a better approach than intensive tillage for both preventing DON contamination and preserving soil quality. Concerning the simulated harvest-till-drying period, DON significantly increased between storage days 0 and 5. Water activity dropped on the 4th day, below the threshold for DON production (around 0.91). From our perspective, this study constitutes a step forward towards understanding the relationships between agronomic factors and mycotoxin contamination in maize, and towards improving food safety.

Barberry plays an active role as an alternate host of Puccinia graminis in Spain.

Stem rust, caused by Puccinia graminis, is a destructive group of diseases. The pathogen uses Berberis species as alternate hosts to complete its life cycle. B. vulgaris and the endemic species B. hispanica and B. garciae are present in Spain. The objective of this study was to investigate the functionality of the indigenous barberry as alternate hosts. Field surveys were conducted in 2018 and 2019 in Huesca, Teruel and Albacete provinces of Spain. Aecial samples on barberry were analysed via infection assays and DNA analysis. B. garciae was predominant in Huesca and Teruel provinces, often found in the field margins of cereal crops. Aecial infections on B. garciae were observed in May and uredinial infections on cereal crops in June. Scattered B. hispanica bushes were occasionally found near cereal crops in Albacete, where aecial infections on B. hispanica were observed in June when most cereal crops were mature. Infection assays using aeciospores resulted in stem rust infections on susceptible genotypes of wheat, barley, rye and oat, indicating the presence of the sexual cycle for P. graminis f. sp. tritici, f. sp. secalis and f. sp. avenae. Sequence analyses from aecial samples supported this finding as well as the presence of Puccinia brachypodii. This study provides the first evidence that indigenous Berberis species play an active role in the sexual cycle of P. graminis under natural conditions in Spain.

A resource-based modelling framework to assess habitat suitability for steppe birds in semiarid Mediterranean agricultural systems.

European agriculture is undergoing widespread changes that are likely to have profound impacts on farmland biodiversity. The development of tools that allow an assessment of the potential biodiversity effects of different land-use alternatives before changes occur is fundamental to guiding management decisions. In this study, we develop a resource-based model framework to estimate habitat suitability for target species, according to simple information on species' key resource requirements (diet, foraging habitat and nesting site), and examine whether it can be used to link land-use and local species' distribution. We take as a study case four steppe bird species in a lowland area of the north-eastern Iberian Peninsula. We also compare the performance of our resource-based approach to that obtained through habitat-based models relating species' occurrence and land-cover variables. Further, we use our resource-based approach to predict the effects that change in farming systems can have on farmland bird habitat suitability and compare these predictions with those obtained using the habitat-based models. Habitat suitability estimates generated by our resource-based models performed similarly (and better for one study species) than habitat based-models when predicting current species distribution. Moderate prediction success was achieved for three out of four species considered by resource-based models and for two of four by habitat-based models. Although, there is potential for improving the performance of resource-based models, they provide a structure for using available knowledge of the functional links between agricultural practices, provision of key resources and the response of organisms to predict potential effects of changing land-uses in a variety of context or the impacts of changes such as altered management practices that are not easily incorporated into habitat-based models.