Determinação da concentração de fósforo em latossolo amarelo por imagens digitais no município de Itacoatiara-AM

Abstract

The objective of this work was to quantify the concentration of phosphorus available in the yellow latosol - type soil of the pineapple crop by means of a colorimetric method based on image analysis. The images of soil extracts were obtained using commercial scanner and free software. The determination of phosphorus is based on the reaction between orthophosphate ions (PO 3) and 2- molybdate (MoO4 ) in strongly acid medium, forming the molybdophosphoric complex, which is reduced by ascorbic acid to molybdenum blue. After color formation, absorbance is measured using a UV/VIS spectrophotometer in 660 nm. Simultaneously the extracts / phosphorous patterns were transferred to a microplate on the scanner, scanned and analyzed with the ImageJ program. The vector norm is used as the analytical response, which is related to the concentration of phosphorus (mg/dm³) that is determined from the linear model of the standard curve. Samples were collected in the Village of the Remanso New, municipality of Itacoatiara-AM, during the winter and summer periods of the region. Extraction of available phosphorus in the extracts was performed with Melich 1 extractor in the proportion of 1:10. Filtration of extracts, volume study of standard solutions on the microplate and area of the analyzed images contributed to the final analysis results. A relationship between the time of analysis of the patterns and the correlation of the standard curves. The concentrations of phosphorus in the samples collected in the dry period were higher than those collected in the rainy season, both by the reference method and by the proposed method. LD and LQ values were lower by digital images. After application of the T-test it was found that there was no significant difference between the two methodologies for a 95% confidence level (calculated = 0.4705 and t critical = 2.7764) and the relative standard deviations were less than 3.0 %.