The effect of anaerobic digestate derived composts on the metabolite composition and thermal behaviour of rosemary

M A Bustamante,I Nogués,S Jones,S Jones,G G Allison

doi:10.1038/s41598-019-42725-6

Abstract

The study reports on the effect of anaerobic digestate derived composts on the metabolite composition and thermal behaviour of rosemary (Rosmarinus officinalis L.). Plants were cultivated in semiarid soil under four different fertiliser treatments (composts of anaerobic digested cattle (C) or pig slurry (P) at 30t/ha and 60 t/ha, and two control treatments (inorganic fertiliser and no fertiliser application). Samples of leaves and stems were analysed to investigate the effect of treatment on chemical composition and thermochemical properties. Three orthogonal analytical approaches were used, namely: Fourier transform mid infrared spectroscopy (FTIR), gas chromatography/mass spectrometry (GC/MS) and thermochemical gravimetric analysis (TGA). FTIR and GC/MS showed fertiliser treatment resulted in tissue specific changes in sample metabolite composition. Fertiliser treatment was detected to change the thermogravimetric properties of the leaf samples and from inorganic and composted pig slurry digestate treatments had greater ash content and lower proportions of fixed carbon compared with samples from the unfertilised control treatment. This study provides information on how the composition of rosemary might be altered by fertiliser application in regions of poor soil, and has implications for biomass quality when rosemary is grown on semi-wild sites for the purpose of soil improvement.

Highlights

Rosemary (Rosmarinus officinalis L., Lamiaceae) is an aromatic shrub native to the Mediterranean region, and it is grown as a common herb around the world for culinary use
Chemical analysis indicated that both composts were very suitable for their agricultural use (Table 1): the ratio of total organic carbon (TOC) to total nitrogen (C/N) in both composts was below the value of 2025 and the contents of N, P and K were similar to those found in composts derived from livestock manure
The results obtained with Fourier transform infrared spectroscopy (FTIR) and Gas chromatography coupled with mass spectrometry (GC/MS) revealed a clear differentiation between organic and inorganic fertilising treatments on the metabolite content of rosemary plants (Rosmarinus officinalis L.), and these differences are tissue dependant

Summary

Introduction

Rosemary (Rosmarinus officinalis L., Lamiaceae) is an aromatic shrub native to the Mediterranean region, and it is grown as a common herb around the world for culinary use. TGA has been used to characterise organic wastes and composts[20,21], soils[22,23], lignocellulose composition and energy grass feedstock quality[15], and the technique provides valuable information on the kinetics of thermal decomposition[24]. We have used these methods to provide orthogonal, chemically meaningful data for chemometric analyses to visualise chemical/compositional relationships between samples and thereby investigate the effect of fertiliser dose and type on rosemary plants in a global context. This study aims to increase our understanding of the likely compositional effects of organic fertiliser application on rosemary crops and on populations grown in semi-wild regions for the purpose of soil stabilisation

Objectives

Methods

Results

Conclusion