Compost - N recovery : 15 N natural abundance quantitative approach Caio

The remarkable influence of organic inputs, such as manure and compost, on dN values of growing plants suggests the possible use of N natural abundance as a tracer of N. Thus, using N natural abundance might be possible to estimate compost-N recovery as an alternative method to the use of N-enriched materials. The objective of this study was to verify the feasibility of using dN 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 dN and yield (except lettuce, no yield response). A new equation for estimating compost-N recovery by plants was proposed using differences in dN-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 dN variations. This study showed the theoretical and experimental basis of using dN values to estimate compost-N recovery by test plants.