OBSOLETE urea nitrogen exposure true PECO_GIT:3 plant_experimental_conditions_ontology EO:0001025 OBSOLETE A nitrogen macronutrient exposure (PECO:0007284) involving exposure of plant to urea (CHEBI:16199) as the primary or sole source of nitrogen. urea nitrogen treatment (narrow) PECO:0001025 cooperl 2013-04-12T19:19:27Z