Silva, LuísBarbosa, SofiaLidon, Fernando CebolaSantos-Silva, JoséConceição, Luís Alcino2024-09-182024-09-182024-08-172073-4395PURE: 99132233PURE UUID: 96bffe0a-5909-4e94-9a75-575af98a88cbScopus: 85202648521WOS: 001305164400001http://hdl.handle.net/10362/172035Publisher Copyright: © 2024 by the authors. The APC was funded by national funds through the Fundação para a Ciência e a Tecnologia, I.P. (Portuguese Foundation for Science and Technology) by the project UIDB/05064/2020 (VALORIZA—Research Centre for Endogenous Resource Valorization) and by national funds from Fundação para a Ciência e a Tecnologia (FCT), Portugal, through the research unit UIDP/04035/2020 (GeoBioTec).Increasing nitrogen use efficiency (NUE) by improving agricultural practices and soil knowledge, and implementing precision agriculture, is essential to reduce the overuse of fertilizers and increase nutrient retention. This study aimed to optimize N management in agriculture by establishing a critical N dilution curve (CNDC) and analyzing variations in NUE and the N nutrition index (NNI) among different crops under various treatments. Using a Bayesian model, the CNDC was determined as %Nc = 3.63 × PDM−0.71. The results showed that plant dry matter (PDM) and plant N content (PNC) varied significantly with crop type and sampling moments. Strong positive correlations are presented by PDM with N uptake (NUp) (0.89) and NNI (0.88), along with an inverse correlation with critical N concentration (−0.95). The study found that crops under irrigation conditions had higher NUp and higher NNI. This study provides valuable insights into the influence of key management decisions on the N nutritional status of annual ryegrass-based forage crops. The results highlight the critical role of accurate and conscious decision-making in improving NUE and crop yields, emphasizing the complex interactions between biomass production and N dynamics in crops. The conclusions allow significant benefits to be realized, contributing to the sustainability of agricultural systems.164144601engcritical nitrogen concentrationcrop yielddata-driven approachsite-specific analysissustainabilityvariable rate fertilizationAgronomy and Crop ScienceSDG 2 - Zero HungerSDG 17 - Partnerships for the Goalsjournal article10.3390/agronomy14081817https://www.scopus.com/pages/publications/85202648521