Determination of total and available phosphorus in soil samples collected from Tarhuna, Libya using spectrophotometry

Abstract

This study aimed to evaluate the levels of total and available phosphorus in soil samples from Tarhune, Libya using spectrophotometry technique. Twelve representative top layer soil samples were collected from six different sites and pre-treated for analysis. For total phosphorus determination, the samples were digested with a mixture of concentrated HNO3 and HClO4 in a 2:3 ratio, as described in [27, 28]. Meanwhile, available phosphorus was extracted from the samples using 0.5 M NaHCO3, following the method outlined in [29]. Both mixtures were filtered, and ammonium molybdate was added to the filtrate solutions to form a blue phosphorus molybdenum complex. The intensity of the blue color at 830 nm was measured using a spectrophotometer. The results showed that the total phosphorus concentration ranged from 100 to 405 mg/kg, with an average of 212 mg/kg. The available phosphorus concentration fluctuated between 24 and 56 mg/kg, with an average of 42 mg/kg. The study concluded that although the soil samples had a lower total phosphorus content compared to the global mean value, the amounts of available phosphorus were significant. This may be attributed to various factors including natural occurrence, limiting cultivation activities, and rainfall rates.