Abstract
Biochar-based fertilizers are a new attractive alternative to P supplementation for crops, as they can gradually release the nutrient, avoiding losses and improving soil quality. In this regard, the evaluation of the P amount in biochar-based fertilizers is extremely important for their quality control. Analytical techniques that require sample solubilization are not very efficient for this task, as biochar is difficult to solubilize. Laser-induced breakdown spectroscopy (LIBS) is a promising technique to respond to this demand, as it enables a direct analysis of solid samples, avoiding the complicated process of sample solubilization. In this work, a novel method based on spark discharge (SD) coupled to LIBS was evaluated for P determination in biochar-based fertilizers prepared from three different biomasses. To overcome calibration problems in LIBS analysis, a matrix-matching procedure accomplished by the addition of eucalyptus biochar to calibration standards was used in experiments. This procedure minimized matrix effects and allowed us to achieve a satisfactory accuracy even when applied to similar but different matrices. Furthermore, the developed method is simple, fast, direct, does not generate post-analysis residues and appears appropriate for the quality control of sustainable biochar-based fertilizers and other biochar products.
Highlights
Phosphorus (P) is a macronutrient that plays a fundamental role in the energy metabolism of plants, whereas its deficiency causes reduced plant growth and chlorosis and necrosis in leaves [1]
The spark discharge (SD)-Laser-induced breakdown spectroscopy (LIBS) spectra measured for the three samples (Figure 1) featured four P atomic lines in the spectral range from 250 to 262 nm
Similar spectra were acquired from the calibration standards
Summary
Phosphorus (P) is a macronutrient that plays a fundamental role in the energy metabolism of plants, whereas its deficiency causes reduced plant growth and chlorosis and necrosis in leaves [1]. The deficiency of P in agricultural soils is remediated by the application of phosphate fertilizers that are derived from the extraction, grinding and treatment of igneous or sedimentary rocks and are usually applied in high amounts, less than 50% of P in them is taken up by plants [2,3]. The possibility of using biochar from different agricultural byproducts to produce controlled-release fertilizers was proposed [4,5]. Biochar confers several benefits to agricultural soils, such as an increase in biodiversity and retention of water and nutrients [6,7]. In this context, the International Biochar Initiative (IBI)
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