Two new plant nutrient nanocomposites based on urea coated hydroxyapatite: Efficacy and plant uptake

Macronutrient delivery to plants, particularly nitrogen, is problematic because of losses occurring during fertilization. Currently, nanotechnology is being considered as a solution to improving nutrient use efficiency. In this study, we report the synthesis and plant uptake of two plant nutrient nanocomposites based on urea coated hydroxyapatite (UHA) and potassium encapsulated into (i) a nanoclay, montmorillonite (MMT) or (ii) cavities present in Gliricidia sepium stem resulting in a wood chip containing macronutrients. Soil leaching behaviour, efficacy and plant uptake of the nutrients were tested in a pot experiment using Festuca arundinacea during a period of 60 weeks. Two nanocomposites displayed slow release behaviour particularly for nitrogen, in soil leaching tests compared to the conventional formulations. Both nanoformulations displayed efficient plant nutrient uptake highlighting the improved nutrient use efficiency. These data clearly revealed that urea fabricated into its nanoscale provide platform for development of efficient fertilizer formulations

Behavioural indicators of welfare in farmed fish

Behaviour represents a reaction to the environment as fish perceive it and is therefore a key element of fish welfare. This review summarises the main findings on how behavioural changes have been used to assess welfare in farmed fish, using both functional and feeling-based approaches. Changes in foraging behaviour, ventilatory activity, aggression, individual and group swimming behaviour, stereotypic and abnormal behaviour have been linked with acute and chronic stressors in aquaculture and can therefore be regarded as likely indicators of poor welfare. On the contrary, measurements of exploratory behaviour, feed anticipatory activity and reward-related operant behaviour are beginning to be considered as indicators of positive emotions and welfare in fish. Despite the lack of scientific agreement about the existence of sentience in fish, the possibility that they are capable of both positive and negative emotions may contribute to the development of new strategies (e. g. environmental enrichment) to promote good welfare. Numerous studies that use behavioural indicators of welfare show that behavioural changes can be interpreted as either good or poor welfare depending on the fish species. It is therefore essential to understand the species-specific biology before drawing any conclusions in relation to welfare. In addition, different individuals within the same species may exhibit divergent coping strategies towards stressors, and what is tolerated by some individuals may be detrimental to others. Therefore, the assessment of welfare in a few individuals may not represent the average welfare of a group and vice versa. This underlines the need to develop on-farm, operational behavioural welfare indicators that can be easily used to assess not only the individual welfare but also the welfare of the whole group (e. g. spatial distribution). With the ongoing development of video technology and image processing, the on-farm surveillance of behaviour may in the near future represent a low-cost, noninvasive tool to assess the welfare of farmed fish.Fundação para a Ciência e Tecnologia, Portugal [SFRH/BPD/42015/2007]info:eu-repo/semantics/publishedVersio