Compost-N recovery: 15N natural abundance quantitative approach

Caio T. Inácio1, Segundo Urquiaga2, Phillip M. Chalk3

1 Embrapa Solos, Rua Jardim Botânico 1024, Rio de Janeiro, RJ, 22460-000,,

2 Embrapa Agrobiologia, Rodovia BR-465 KM 7, Seropédica, RJ, 23891-000

3 University of Melbourne, Parkville 3010, Melbourne, Victoria


The remarkable influence of organic inputs, such as manure and compost, on d15N values of growing plants suggests the possible use of 15N natural abundance as a tracer of N. Thus, using 15N natural abundance might be possible to estimate compost-N recovery as an alternative method to the use of 15N-enriched materials. The objective of this study was to verify the feasibility of using d15N value to estimate compost-N recovery by plants. Head lettuce, carrots and broccoli were cultivated (randomized blocks) in sequence under increasing levels (0 to 2.5 kg/m², dry matter) of compost application. Pearson correlations were significant and positive between plants d15N and yield (except lettuce, no yield response). A new equation for estimating compost-N recovery by plants was proposed using differences in d15N-plant with and without compost application. The compost-N recoveries were 2-8 % for lettuce, 4-9 % for carrots, and 9-18 % for broccoli. Unrealistic estimates were disregarded and assigned primarily to non-representative sampling because of intra-plant d15N variations. This study showed the theoretical and experimental basis of using d15N values to estimate compost-N recovery by test plants.