02426naa a2200229 a 450000100080000000500110000800800410001902200140006002400390007410000210011324501270013426000090026152017340027065000190200465000130202365000240203665000200206065000150208070000170209570000170211277300670212921779092025-08-11       2025    bl uuuu     u00u1 u    #d  a1806-96577 a10.36783/18069657rbcs202401822DOI1 aINACIO, C. de T.  aUsing the 15N natural abundance for a quantitative approach to N recovery from organic fertilizers.h[electronic resource]  c2025  aThe influence of organic inputs, such as manure and compost, on the 15N values of growing plants suggests it may be possible to use of 15N natural abundance (NA) as a nitrogen (N) tracer. This study aimed to verify the feasibility of using the TM15N values to estimate compost-N recovery by plants. A field experiment was carried out by growing head lettuce, carrots and broccoli in sequence under increasing levels of compost (randomized complete blocks, six doses, four replicates). The compost was produced on-farm using horse bedding manure and vegetable waste. We found a positive and significant correlation between vegetables yield × TM15N-plant as well as between N-harvested × TM15N-plant, alongside the response to the increasing levels of compost. Positive and significant (α = 0.05) correlations were found for carrots (R = 0.91 and 0.95) meanwhile, no significant correlations were found for broccoli (R = 0.60 and 0.66). Lettuce did not respond to compost levels. We applied an equation to estimate compost-N recovery by carrots based on the variation pattern that was found in TM15N-plant. A positive and significant correlation between TM15N-plant and plant yield (or N harvested) is the first condition to obtain valid estimates. The estimated compost-N recovery for carrots was from 4.7 to 9.1 %, respectively, at 0.5 and 2.0 kg m-2 of compost (dry basis). Sources of uncertainty are also discussed, and include intra-plant 15N fractionation, which might require further studies of sampling strategies. This study shows the theoretical and experimental basis of using compost (dry basis). Sources of uncertainty are also discussed, and include intra-plantN to estimate organic fertilizer-N recovery by crops.  aAnimal manures  aComposts  aNutrient management  aPlant nutrition  aVegetables1 aURQUIAGA, S.1 aCHALK, P. M.  tRevista Brasileira de Ciência do Sologv. 49, e0240182, 2025.