Agriculture 4.0: Development of a new technology for phosphorus speciation in soils

Abstract

Despite the high concentrations of P in the soil, supplementation through fertilization is essential to ensure agricultural productivity. This occurs because only a small fraction of the total P present in the soil is available to plants (solution-P and labile-P). The largest fraction (non-labile P) is firmly bound in soils due to precipitation with Ca ions (in calcareous soil) and adsorption by Fe and Al oxides (in acidic soil). Some strategies, such as the action of microorganisms, have been considered to make P bound to the soil available. However, the decision to apply any type of management is always guided by quantitative knowledge, which makes it essential to determine labile and non-labile P concentrations in agricultural soils. The methods traditionally used for these determinations are time-consuming, involve a large amount of hazardous chemical reagents and generate post-analysis waste. Laser-induced breakdown spectroscopy (LIBS) is a photonic technique that allows direct analysis in a few seconds, without the use of chemical reagents and does not generate post-analysis residues. In terms of instrumental configuration, LIBS is quite versatile with the availability of benchtop and portable instruments, which can enable the in-situ analyzes required by Agriculture 4.0. In this context, the present proposal aims to develop quantitative methods to estimate labile and non-labile P species in different samples of Brazilian soils using LIBS. Two instruments, a hLIBS (commercial portable instrument) and an SD-LIBS (electric discharge-assisted benchtop instrument), will be evaluated and the results will be compared. It is expected that the developed methods provide excellent analytical tools capable of providing relevant data for the application of effective managements, which allow a greater use of P fixed in the soil and avoid the excessive application of phosphate fertilizers, whose worldwide source is depleting. (AU)