Identifying N fertilizer regime and vegetable production system in tropical Brazil using (15) N natural abundance

Natural abundance analysis of the role played by 15 N as indicator for the certification of organic-system deriving food

BACKGROUND

The natural abundance of stable isotope ¹⁵ N (δ¹⁵ N) in production systems has emerged as an alternative to distinguish organic products from conventional ones. This study evaluated the use of δ¹⁵ N values recorded for nitrogen fertilizers, soil and plant tissue in order to set the differences between organic and conventional agricultural production systems applied to rice, potatoes, apple and banana crops.

RESULTS

Values of δ¹⁵ N recorded for N sources ranged from +5.58‰ to +18.27‰ and from -3.55‰ to +3.19‰ in organic and synthetic fertilizers, respectively. Values recorded for δ¹⁵ N in food from organic rice, potatoes and banana farms were higher than values recorded for δ¹⁵ N in conventional farms; the same was observed for values recorded for δ¹⁵ N in leaves from the four crops.

CONCLUSION

Results have allowed for differentiation between production systems due to values of δ¹⁵ N recorded in leaves of all crops and food, for rice, potatoes and banana trees. © 2021 Society of Chemical Industry.

15N Natural Abundance Evidences a Better Use of N Sources by Late Nitrogen Application in Bread Wheat

This work explores whether the natural abundance of N isotopes technique could be used to understand the movement of N within the plant during vegetative and grain filling phases in wheat crop (Triticum aestivum L.) under different fertilizer management strategies. We focus on the effect of splitting the same N dose through a third late amendment at flag leaf stage (GS37) under humid Mediterranean conditions, where high spring precipitations can guarantee the incorporation of the lately applied N to the soil-plant system in an efficient way. The results are discussed in the context of agronomic parameters as N content, grain yield and quality, and show that further splitting the same N dose improves the wheat quality and induces a better nitrogen use efficiency. The nitrogen isotopic natural abundance technique shows that N remobilization is a discriminating process that leads to an impoverishment in 15N of senescent leaves and grain itself. This technique also reflects the more efficient use of N resources (fertilizer and native soil-N) when plants receive a late N amendment.

The relative isotopic abundance (δ13C, δ15N) during composting of agricultural wastes in relation to compost quality and feedstock

Variations in the relative isotopic abundance of C and N (δ¹³C and δ¹⁵N) were measured during the composting of different agricultural wastes using bench-scale bioreactors. Different mixtures of agricultural wastes (horse bedding manure + legume residues; dairy manure + jatropha mill cake; dairy manure + sugarcane residues; dairy manure alone) were used for aerobic-thermophilic composting. No significant differences were found between the δ¹³C values of the feedstock and the final compost, except for dairy manure + sugarcane residues (from initial ratio of -13.6 ± 0.2 ‰ to final ratio of -14.4 ± 0.2 ‰). δ¹⁵N values increased significantly in composts of horse bedding manure + legumes residues (from initial ratio of +5.9 ± 0.1 ‰ to final ratio of +8.2 ± 0.5 ‰) and dairy manure + jatropha mill cake (from initial ratio of +9.5 ± 0.2 ‰ to final ratio of +12.8 ± 0.7 ‰) and was related to the total N loss (mass balance). δ¹³C can be used to differentiate composts from different feedstock (e.g. C₃ or C₄ sources). The quantitative relationship between N loss and δ¹⁵N variation should be determined.

Isotope ratio mass spectrometry in combination with chemometrics for characterization of geographical origin and agronomic practices of table grape

BACKGROUND

Although table grape is one of the most cultivated and consumed fruits worldwide, no study has been reported on its geographical origin or agronomic practice based on stable isotope ratios. This study aimed to evaluate the usefulness of isotopic ratios (i.e. ² H/¹ H, ¹³ C/¹² C, ¹⁵ N/¹⁴ N and ¹⁸ O/¹⁶ O) as possible markers to discriminate the agronomic practice (conventional versus organic farming) and provenance of table grape.

RESULTS

In order to quantitatively evaluate which of the isotopic variables were more discriminating, a t test was carried out, in light of which only δ¹³ C and δ¹⁸ O provided statistically significant differences (P ≤ 0.05) for the discrimination of geographical origin and farming method. Principal component analysis (PCA) showed no good separation of samples differing in geographical area and agronomic practice; thus, for classification purposes, supervised approaches were carried out. In particular, general discriminant analysis (GDA) was used, resulting in prediction abilities of 75.0 and 92.2% for the discrimination of farming method and origin respectively.

CONCLUSION

The present findings suggest that stable isotopes (i.e. δ¹⁸ O, δ² H and δ¹³ C) combined with chemometrics can be successfully applied to discriminate the provenance of table grape. However, the use of bulk nitrogen isotopes was not effective for farming method discrimination. © 2016 Society of Chemical Industry.