Abstract
Little attention has been paid to the accumulation of soil organic matter (SOM) in the fringes of the mid-latitude desert. In this paper, soil samples from a long-term field experiment conducted from 1990 to 2013 at a research station in Urumqi, China by different fertilizer treatments, were used to determine soil properties and soil dissolved organic matter (DOM) by chemical analysis, fluorescence excitation emission matrix (EEM) spectroscopy, and high resolution-transmission electron microscopy (HR-TEM). The binding features of DOM under the addition of Ca2+ were analyzed using a two-dimensional (2D) Fourier transform infrared (FTIR) spectrometer further to explore the response of the DOM to increasing concentrations of Ca2+. Long-term application of chemical fertilizers and goat manure increased soil organic carbon (SOC) by 1.34- and 1.86-fold, respectively, relative to the non-fertilized control (8.95g.kg-1). Compared with the control, application of chemical fertilizers and manure significantly increased the concentrations of Ca, Mg, Si, humic and fulvic acid-like substances in DOM but decreased the amounts of trivalent metals (Al and Fe) and protein-like substances. Although crystalline Al/Fe nanoparticles and amorphous or short-range-order Si/Al nanoparticles existed in all DOM samples, crystalline Ca/Si nanoparticles were predominant in the samples treated with goat manure. Although organic matter and Si-O-containing nanoparticles were involved in the binding of Ca2+ to DOM, application of chemical fertilizers weakened Ca2+ association with components of the amide II group (1510 cm-1) and Si-O linkage (1080 cm-1), whereas application of goat manure enhanced the affinity of Ca2+ for Si-O linkage. Our results suggested that the enrichment of Ca in gray desert soil possibly helps accumulate SOM by forming crystalline Ca/Si nanoparticles in addition to Ca2+ and organic matter complexes.
Highlights
It is well recognized that soil organic matter (SOM) is the key component in sustaining soil fertility and conserving environmental quality [1, 2]
The decreased concentrations of trivalent metals (Al and Fe) of dissolved organic matter (DOM) in all fertilizer treatments implied that trivalent metals occurred in low levels in the desert soil and were diluted by organic matter due to complex formation
The results indicated the high possibilities of the existence of Ca-Si-O nanoparticles in the NPKM and M treatments, which was later confirmed by the High resolution-transmission electron microscopy (HRTEM) results
Summary
It is well recognized that SOM is the key component in sustaining soil fertility and conserving environmental quality [1, 2]. Intensive research aimed at enhancing SOM contents or soil. 2D-FTIR Exploration of Ca2+ and DOM Complexes in Gray Desert Soil. Fertilizer Efficiency Monitoring Station for providing relevant data generated from these experiments
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