Abstract
PurposeThe most important factor affecting soil quality is soil humic fraction. Effects of adding carbon in soil humic compounds in arid environments have only been slightly investigated. The change in soil humic acids’ structures in relation with manure and palm compost application and the evolution of humic acids’ structures during palm composting have not been sufficiently investigated. The purpose of this study is to evaluate if date palm compost is suitable for the sustainable increase of soil carbon content with increasing soil humic compounds.MethodsSoil was amended with date palm compost and sheep manure, which represented two treatments, in addition to a control represented by unamended soil. Soil samples were taken from depth layers of 0–20 cm and 20–40 cm. Physicochemical and spectroscopic analyses were used to study humic acids extracted from organic amendment and soil.ResultsThe neutral pH and the C/N ratio of 11.9 revealed that the palm/manure compost was mature. Date palm compost application on soil showed its effectiveness in improving soil quality. Spectroscopic studies of humic compounds extracted from date palm compost and manure, showed the abundance of aromatic structures, confirmed by the low E4/E6 ratio associated with an increase in polycondensation and polymerization. Infrared spectroscopy of humic acids extracted from amended soil revealed its enrichment with aromatic structures.ConclusionsUsing date palm compost for a short term suggests that this compost may be useful as an alternative to increase the soil fertility by increasing the humic acids quantity with enhancing aromaticity degree and functional groups.
Highlights
Due to its role in preventing desertification and erosion, organic matter is a basic component of all agro-ecosystems
Results showed a clear increase of C HA/CFA ratio after incorporation of palm compost and manure. This increase was greater with compost (0.86%) in the surface soil layer (0–20 cm) and with manure (0.55%) in the deeper one (20–40 cm)
The increase of ratio CHA/CFA after compost incorporation can be an indication of enhancing carbon content associated with humic acid compounds (Rivero et al 2004)
Summary
Due to its role in preventing desertification and erosion, organic matter is a basic component of all agro-ecosystems. Organic matter is the result of the combined effect of incorporation, transformation and mineralization of plant and animal residues defined by the local soil and climate characteristics (Horwath 2015). Higher temperature levels accelerate organic matter decomposition; this is likely to cause a serious agriculture problem in the future (Conant et al 2011). Several authors showed that soil in Tunisia suffer from low organic matter levels, especially in arid areas (Gargouri et al 2013). Many organic farms in the Southeast of Tunisia have many problems such as higher soil salinity and low soil fertility (Kouki and Bouhaouach 2009). Agronomists are looking for amendment of the natural ecosystem to improve the soil quality of agricultural land for crop production
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