Monitoring Organic Matter Humification during the Composting of Date Palm Wastes Using Chemical and Spectroscopic Analyses for Arid Soil Quality Improvement

Abstract

ABSTRACT Soil organic matter (SOM) is the most important factor that affects soil quality. In arid areas, lack of SOM causes a major problem and farmers need to add organic amendments to restore the soil quality. Organic waste composting is an efficient and sustainable way to produce organic resource for soil amendment. The main objective of this study was to evaluate the effectiveness of compost derived from co-composting of date palm residues with goat manure to ameliorate soil quality in arid region in the southeast of Tunisia. Palm tree wastes were co-composted with goat manure (1/3 v:v) for 120 days. Chemical properties and structural changes of humic acids (HA) during the composting process were investigated using physicochemical and spectroscopic analyses: spectroscopic ultraviolet/visible (UV) analysis and Fourier Transform Infrared (FTIR) Spectroscopy. HA fractions extracted from different steps of composting process were monitored by measuring humification ratios CHA/CFA and E4/E6. Soil was amended with produced compost and manure during 3 months, and soil property evolution was evaluated using chemical and spectroscopic analyses. Results revealed that the date palm compost displayed neutral pH, a C/N ratio of about 12 and high levels of nutrients. FTIR spectra of HA extracted from produced compost and manure showed the abundance of aromatic structures with a high condensation and polymerization confirmed by a low E4/E6 ratio related to the increase in polymerization and polycondensation and a high CHA/CFA humification rate that improved the elevation of the humification degree. The application of the produced palm compost in soil improved soil quality by increasing levels of SOM and nutrients and showed a marked improvement of humification rate. The FTIR spectra of soil HA showed a clear increase in aromatic structures that improved soil stability. The input of palm compost is an efficient way to ameliorate arid soil quality by supplying highly humified organic matter restitution.