Innovations in agriculture, including application of chemical fertilisers, have allowed food production to keep pace with the growing population. Nevertheless, this has come at a significant environmental cost. Improving plant nutrient use efficiency (NUE) is critical in tackling greenhouse gas emissions, improving biodiversity and increasing productivity in agricultural systems to meet the requirements of the growing world population. Biostimulants are compounds from various sources that can regulate plant physiological processes and increase nutrient uptake and utilisation. Consequently, integrating use of plant biostimulants with conventional agriculture may facilitate reduced fertiliser use while maintaining crop yields. Here, we discuss the current research on biostimulants in the context of improved macro- and micronutrients use efficiency. While most of the reviewed studies report a positive effect of biostimulants on NUE within the studied crop, there is a need for a more systematic approach, including precise calculations of NUE and conducting trials under both optimum and sub-optimum nutrient conditions. Overall, plant biostimulants appear to be a promising addition to sustainable agriculture practices, with multiple benefits from both social and environmental perspectives.

Eight rumen additives were chosen for an enteric methane-mitigating comparison study including garlic oil (GO), nitrate, Ascophyllum nodosum (AN), Asparagopsis (ASP), Lactobacillus plantarum (LAB), chitosan (CHI), essential oils (EOs) and 3-nitrooxypropanol (3-NOP). Dose-dependent analysis was carried out on selected feed additives using a meta-analysis approach to determine effectiveness in live subjects or potential efficacy in live animal trials with particular attention given to enteric gas, volatile fatty acid concentrations, and rumen microbial counts. All meta-analysis involving additives GO, nitrates, LAB, CHI, EOs, and 3-NOP revealed a reduction in methane production, while individual studies for AN and ASP displayed ruminal bacterial community improvement and a reduction in enteric CH₄. Rumen protozoal depression was observed with GO and AN supplementation as well as an increase in propionate production with GO, LAB, ASP, CHI, and 3-NOP rumen fluid inoculation. GO, AN, ASP, and LAB demonstrated mechanisms in vitro as feed additives to improve rumen function and act as enteric methane mitigators. Enzyme inhibitor 3-NOP displays the greatest in vivo CH₄ mitigating capabilities compared to essential oil commercial products. Furthermore, this meta-analysis study revealed that in vitro studies in general displayed a greater level of methane mitigation with these compounds than was seen in vivo, emphasising the importance of in vivo trials for final verification of use. While in vitro gas production systems predict in vivo methane production and fermentation trends with reasonable accuracy, it is necessary to confirm feed additive rumen influence in vivo before practical application.

Seaweed is a resilient macrophytic plant thriving in intertidal zones. These are rapidly gaining attention due to their autotrophic nourishment, rapid growth, and minimal land requirement for cultivation. Seaweed is used in various food and non-food sectors, thus possessing immense potential as a valuable bioresource with high commercial value. However, utilizing seaweed as a bioresource comes with various challenges at processing levels, particularly at cost-effective downstream processing. Hence, this review highlights the advancement in seaweed biomass processing together with its application in food, nutraceuticals, pharmaceuticals, cosmetics, and non-food sectors. Additionally, the advancements in seaweed cultivation and the applications of seaweed in agriculture as a biostimulant, biofuel production, and packaging material are also reviewed. Finally, this review addresses the need for technology intensification, public awareness, and financial investment to enhance the commercialization and integration of seaweed-based products into the bioeconomy. The potential of seaweed to contribute to climate change mitigation and the circular economy is underscored, calling for further research and development to optimize its multifaceted applications.

Nitrogen (N) is the most important macronutrient used in modern agricultural systems to enhance crop yields; however, a significant amount of applied N is not taken up by the crop and is lost to the environment. Improving the nitrogen use efficiency (NUE) of crops can curb these environmental losses while concurrently delivering economic gains. Plant biostimulants have potential to improve NUE in agronomic settings. In this research, a granular N-containing fertilizer coated with the biostimulant PSI-362, an extract from the brown seaweed Ascophyllum nodosum, was applied to grass managed under different production systems to assess its impact on NUE. The role of soil type, pH, phosphorus (P) and potassium (K) on the efficacy of the biostimulant in improving NUE was assessed using lysimeters filled with six different soils. A significant increase in grass yield (29%) was found with PSI-362 addition at a 75% N rate over the 75% N control (8478 kg of dry matter (DM) ha⁻¹ vs. 6772 kg of DM ha⁻¹) over two years of trials under a simulated grazing platform of six rotations. The NUE increased to 96.6% for the PSI-362-treated grass compared to 82.8% for controls. Field-based evaluations demonstrated no decrease in yield and quality from harvested and grazed grass treated with the biostimulant when the N rate was reduced by 20 to 25%. Based on these results, the application of PSI-362 allows a reduction in nitrogen input by up to 25% without losses of grass yield or quality.

The inclusion of rumen buffers in ruminant feeds has gained widespread adoption for the prevention of rumen acidosis, thereby avoiding the negative production and health consequences of low rumen pH and resulting in improved feed efficiency. Benchmarking and quality controlling the performance of rumen buffer materials is of significant interest to feed mills and end-user producers. The aim of this study was to evaluate, develop and optimise a laboratory protocol to consistently and robustly evaluate rumen buffering materials in order to predict their in vivo efficacy. Three different methods were evaluated for determining the buffering potential of carbonate buffer materials: (a) 2 and 8 h static pH, (b) 8 h fixed HCl acid load addition and (c) 3 h acidotic diet simulation using acetic acid. Buffer material, threshold pH, test duration and interactions between all three variables were significant (p < 0.001) in evaluating the performance of the buffer materials. The acidotic diet simulation was found to provide a different ranking of materials to the 8 h fixed HCl acid load methodology. The results highlight the importance of method selection and test parameters for accurately evaluating the potential efficacy of rumen buffer materials.

Nitrogen is a macronutrient that is applied in substantial amounts as a chemical fertiliser to conventional agricultural systems. However, loss of nitrogen from agricultural systems to the environment, in the form of gases (N₂O) and leachate (NO₃), is detrimental to the environment. As such, improving the nitrogen use efficiency (NUE) of crops is an essential component of sustainable agriculture. Biostimulants are a category of products that improve NUE when applied to crops and/or soil. Here, we examined the effects of PSI-362, an Ascophyllum nodosum biostimulant mixed with and applied on calcium ammonium nitrate (CAN) granules, on grass yield, quality traits, and environmental impacts in lysimeter trials under natural weather conditions. By using PSI-362, it was possible to reduce nitrogen application by 25% without a significant loss in yield compared to a conventional 100% N system. We also observed an increase in NUE under a 75% N with PSI-362 co-application fertilisation regime, and a significant increase in crude protein content compared to the 100% N fertilisation controls. Furthermore, this reduced nitrogen application also resulted in reduced nitrogen loss through leachate (NO₃) and N₂O to the atmosphere. The total NUE for PSI-362 + fertiliser granules ranged from 58.7% to 78.6% depending on the biostimulant dose, which was significantly better than the fertiliser alone. Our results showed that this biostimulant, which can easily be incorporated into conventional agronomic practices, allows for a more sustainable approach to pasture-based systems.