Caio T Inácio1, Segundo Urquiaga2, Phillip M Chalk1, Maria Gabriela F Mata3, Paulo O Souza3. 1. EMBRAPA-Soils, Brazilian Agricultural Research Corporation, Research Center of Soil, Rio de Janeiro, RJ, Brazil. 2. EMBRAPA-Agrobiology, Research Center of Agrobiology, Seropédica, RJ, Brazil. 3. UFRRJ, Soil Science Department, Federal Rural Institute of Agronomy, University of Rio de Janeiro, Seropédica, RJ, Brazil.
Abstract
BACKGROUND: This study was conducted in areas of vegetable production in tropical Brazil, with the objectives of (i) measuring the variation in δ(15) N in soils, organic N fertilizer sources and lettuce (Lactuca sativa L.) from different farming systems, (ii) measuring whether plant δ(15) N can differentiate organic versus conventional lettuce and (iii) identifying the factors affecting lettuce δ(15) N. RESULTS: Samples of soil, lettuce and organic inputs were taken from two organic, one conventional and one hydroponic farm. The two organic farms had different N-sources with δ(15) N values ranging from 0.0 to +14.9‰ (e.g. leguminous green manure and animal manure compost, respectively), and differed significantly (P < 0.05) in lettuce δ(15) N (+9.2 ± 1.1‰ and +14.3 ± 1.0‰). Conventional lettuce δ(15) N (+8.5 ± 2.7‰) differed from hydroponic lettuce δ(15) N (+4.5 ± 0.2‰) due to manure inputs. The N from leguminous green manure made a small contribution to the N nutrition of lettuce in the multi-N-source organic farm. CONCLUSION: To differentiate organic versus conventional farms using δ(15) N the several subsets of mode of fertilization should be considered. Comparisons of δ(15) N of soil, organic inputs and lettuce allowed a qualitative analysis of the relative importance of different N inputs.
BACKGROUND: This study was conducted in areas of vegetable production in tropical Brazil, with the objectives of (i) measuring the variation in δ(15) N in soils, organic N fertilizer sources and lettuce (Lactuca sativa L.) from different farming systems, (ii) measuring whether plant δ(15) N can differentiate organic versus conventional lettuce and (iii) identifying the factors affecting lettuce δ(15) N. RESULTS: Samples of soil, lettuce and organic inputs were taken from two organic, one conventional and one hydroponic farm. The two organic farms had different N-sources with δ(15) N values ranging from 0.0 to +14.9‰ (e.g. leguminous green manure and animal manure compost, respectively), and differed significantly (P < 0.05) in lettuce δ(15) N (+9.2 ± 1.1‰ and +14.3 ± 1.0‰). Conventional lettuce δ(15) N (+8.5 ± 2.7‰) differed from hydroponic lettuce δ(15) N (+4.5 ± 0.2‰) due to manure inputs. The N from leguminous green manure made a small contribution to the N nutrition of lettuce in the multi-N-source organic farm. CONCLUSION: To differentiate organic versus conventional farms using δ(15) N the several subsets of mode of fertilization should be considered. Comparisons of δ(15) N of soil, organic inputs and lettuce allowed a qualitative analysis of the relative importance of different N inputs.
Authors: Teresa Fuertes-Mendizábal; José M Estavillo; Miren K Duñabeitia; Ximena Huérfano; Ander Castellón; Carmen González-Murua; Ana Aizpurua; María Begoña González-Moro Journal: Front Plant Sci Date: 2018-06-22 Impact factor: 5.753