Asiye Saidi - Barafza keshavarze Pars Company. Rafsanjan, Special Economic Zone, Rafsanjan, Iran
Amanollah Javanshah - Iranian Pistachio Research Institute, Rafsanjan, Iran
Ali Heidary Nejhad - Barafza keshavarze Pars Company. Rafsanjan, Special Economic Zone, Rafsanjan, Iran
Samira Aminian - Barafza keshavarze Pars Company. Rafsanjan, Special Economic Zone, Rafsanjan, Iran

Humic acid (HA) represents the organic material most widespread in nature and have positive effects on plant physiology influencing nutrient uptake and root architecture. The role of HA in the environment is extremely important. To date, the methods have been developed for the determination of HAs directly following theextraction process are time consuming. The aim of our work was to the application of UV/vis spectrophotometrymethod to HA determination after its extraction by sodium pyrophosphate alkali solvent. Sodium pyrophosphate is a good choice for soils that contain metalorganic complexes because pyrophosphate anions complex with polyvalent cations to release charged organic matter that can subsequently be dissolved in water. The precisionand accuracy of this method were evaluated. The performance of UV/vis spectrophotometry method wascompared with California Department of Food and Agriculture (CDFA) and International Organization for Standardization (ISO) 3763:1999 methods. The results for the proposed method are comparable or very better than them. Also this methodology is easier and faster than two others.

Humin; Humic acid; UV/vis Spectrophotometry; Precipitation; volumetric method