Change of soil quality based on humic acid with date palm compost incorporation

Abstract

Purpose The 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. Methods Soil 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. Results The 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. Conclusions Using 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.

Assessing Factors Controlling Structural Changes of Humic Acids in Soils Amended with Organic Materials to Improve Soil Functionality

“…Conversely, due to the high level of labile SOM in FYM, the aromaticity of HAs from the relatively fresh (0.5-year-old) sample, T1, was as low as in the unamended treatment, T9. However, when FYM is decomposed over a long period of time, as in T10 and T12, it can be an important source of complex aromatic compounds, which is in agreement with other studies [5]. The NMR spectra revealed that the structural characteristics of HAs were strongly influenced by site, field age, the quantity of aromatic compounds in the amending material and frequency of organic amendment.…”

“…In the long-term samples (T9-T10 and T11-T12), the shoulder almost completely disappeared to merge with the peak at 1630 cm −1 . Taking T7 and T8 aside, these observations could be attributed to a linear condensation (with age) of secondary amides into more humified aromatic C compounds such as phenols [5,51]. Humified aromatic OM, due to its high content of diverse functional groups, is critical for stabilising soil structure and facilitating the sorption of contaminants and the retention of plant nutrients in soil [13,52,53].…”

“…The remaining detritus is then transformed by humification into humic substances (HSs) [4]. This increases the aromatic characteristics of SOM, thus making HSs highly resistant to further decomposition and a potential long-term sink for C in soil [5].…”

“…Biochar and brown coal waste (BCW) are carbonised organic materials which have high proportions of recalcitrant OM, and by extension higher levels of HAs with aromatic characteristics, compared with other organic amendments such as farmyard manure (FYM) and composts [17][18][19]. Thus, the differences in the contents of aromatic compounds or degree of humification in such materials create significant variation in the structure of HAs [5,7,20]. In addition, this is influenced by the field age of OM, amendment dosage, and amendment frequency [7,15,16,21].…”

Influences of Nitrogen Application Levels on Properties of Humic Acids in Chernozem Amended with Different Types of Organic Materials

“…The HAs extracted from a soil amended with municipal sewage sludge for seven years had a higher concentration of aliphatic and N-containing groups, but a lower concentration of polysaccharides than those from the unamended soil based on the FTIR spectroscopy [13]. Infrared spectroscopy of HAs extracted from the soil amended with date palm compost or sheep manure revealed the enrichment with aromatic structures in HAs [14]. It was seen that the structure of HAs in amended soils might be affected at varying extents depending on the nature and origin of OMs [15].…”