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• Attainable maize yield drives the agronomic optimum of initial N availability (AONav). • Soil texture modifies the curvature of the response models but not the AONav. • For yield environments from 9 to 14 Mg ha-1, the AONav increases by 21 kg N Mg-1. • Fine- and coarse-textured soils show the greatest and the lowest response rates to N. • We could maintain high N use efficiencies by correctly identifying yield environment. The most widely used approach for prescribing fertilizer nitrogen (N) recommendations in maize (Zea Mays L.) in Argentina is based on the relationship between grain yield and the available N (kg N ha−1), calculated as the sum of pre-plant soil NO 3 --N at 0−60 cm depth (PPNT) plus fertilizer N (N f). However, combining covariates related to crop N demand and soil N supply at a large national scale remains unexplored for this model. The aim of this work was to identify yield response patterns associated to yield environment (crop N demand driver) and soil texture (soil N supply driver). A database of 788 experiments (1980−2016) was gathered and analyzed combining quadratic-plateau regression models with bootstrapping to address expected values and variability on response parameters and derived quantities. The database was divided into three groups according to soil texture (fine, medium and coarse) and five groups based on the empirical distribution of maximum observed yields (from Very-Low = <8.5 Mg ha−1 to Very-High = >13.1 Mg ha−1) resulting in fifteen groups. The best model included both, attainable yield environment and soil texture. The yield environment mainly modified the agronomic optimum available N (AON av), with an expected increase rate of ca. 21.4 kg N Mg attainable yield−1, regardless of the soil texture. In Very-Low yield environments, AON av was characterized by a high level of uncertainty, related to a poor fit of the N response model. To a lesser extent, soil texture modified the response curvature but not the AON av , mainly by modifying the response rate to N (Fine > Medium > Coarse), and the N use efficiencies. Considering hypothetical PPNT levels from 40 to 120 kg N ha−1, the expected agronomic efficiency (AEN f) at the AON av varied from 7 to 31, and 9–29 kg yield response kg fertilizer N (N f)−1, for Low and Very-High yield environments, respectively. Similarly, the expected partial factor productivity (PFPN f) at the AON av ranged from 62 to 158, and 55–99 kg yield kg N f −1, for the same yield environments. These results highlight the importance of combining attainable yield environment and soil texture metadata for refining N fertilizer recommendations. Acknowledging the still low N fertilizer use in Argentina, space exists to safely increasing N fertilizer rates, steering the historical soil N mining profile to a more sustainable agro-environmental scenario in the Pampas. [ABSTRACT FROM AUTHOR]

Freezing on-board has made it possible to expand commercial fishing to new species that were not widely utilized until the late 1970s. Shellfish are one of the commercial fishery products that can be harvested from natural beds located in far offshore ocean areas by factory trawler fleet where shellfish is processed and frozen quickly. In this way large volumes of frozen products can be obtained with optimal commercial quality and good sanitary conditions. In Argentina, scallop harvesting followed by on board quick freezing started in 1996. The aim of this presentation is to describe the quick freezing process applied by factory trawlers to scallops harvested from the Argentine Sea and to report the results obtained from the total volatile basic nitrogen (TVB-N) and biotoxin analysis of samples of these products. These data were collected at the National Animal Health and Agri-Food Quality Service (SENASA)-Regional Laboratory at Mar del Plata city, Argentina, and they cover a 14-year time span, from 1997 to 2011. Captured specimens were selected by size according to commercial criteria, and those smaller than 55mm were returned to the sea within 5–10min of capture. Scallops were water vapor-opened in order to separate the adductor muscle from the rest of the soft tissues (viscera, gonads and mantle). Adductor muscles enter a freezing tunnel where a fast flow of cold air induces a shock freezing of the tissue (at −26°C/−30°C), thus allowing to obtain in some 20min individually quick frozen adductor muscle units. The time elapsed since scallops selected by size enter the processing line until the final commercial product is stored is about 30min. This short processing time allows an optimal preservation of all organoleptic characteristics and at the same time prevents phytoplankton biotoxin diffusion from viscera (the primary storage region in the live animal) to muscle. TVB-N determinations were carried out by the Antonacopoulos method. The mean values recorded in the quick frozen scallop muscles ranged from 8.0 to 9.0mg%. Measurements performed in muscle tissue from scallops stored in freezing chambers (−18°C) gave TVB-N values between 12mg% and 13mg%, whereas TVB-N values in adductor muscles stored at 4°C were above 30mg%. Biotoxin determination was performed by the mouse bioassay (MBA) employing the AOAC 959.08 method for Paralytic Shellfish Poison (PSP) and the procedure described by Yasumoto et al. in 1986 for Diarrheic Shellfish Poison (DSP). None of the adductor muscle samples tested had detectable PSP or DSP levels. This was so even on occasions when high PSP concentrations were detected in whole scallop samples. Our results show that the quick freezing process on board Argentinian factory trawler ships are suitable for obtaining a commercial product that fully retains freshness parameters as well as the sanitary characteristics required for human consumption. [Copyright &y& Elsevier]