Document Type : Research Paper
Former Graduated Student, Faculty of Agriculture, University of Tabriz
Assistant Professor, Faculty of Agriculture, University of Tabriz
Associated Professors, Faculty of Agriculture, University of Tabriz
Information about forms of phosphorus (P) is important for the evaluation of P status in soil and also understanding of the soil fertility and plant nutrition. To obtain such information and to determine the relationship between the P forms from soil characteristics, amount of different organic and inorganic P forms of 20 soil composite samples of Eastern Azerbaijan Province, Iran were determined by sequential fractionation method. According to the results, the amount of total P in soils ranged from 534 to 1061 mg kg-1 with an average of 771.3 mg kg-1. Inorganic P concentrations was as follows: Apatite (Ca10-P) > octacalcium phosphate (Ca8-P) > aluminum phosphate (Al-P) > iron phosphate (Fe-P) > dicalcium phosphate (Ca2-P). Organic phosphorus concentrations was as follows: Moderately labile organic P (MLOP) > labile organic P (LOP) > Non labile organic P (NLOP). Results showed that calcium carbonate equivalent (CCE) with octacalcium phosphate and iron phosphate, pH with octacalcium P, iron phosphate, available phosphorus and organic carbon with moderately labile and non- labile organic P had significant correlations. Total calcium and total organic P had significant relationships with organic carbon. Total calcium phosphate and total inorganic P also showed significant correlations with the calcium carbonate equivalent. Ca2-P, Ca8-P, Fe-P, Al-P, LOP and MLOP had positive and significant relationship with the available-p, and between different forms of phosphorus Ca2-p had highly significant correlation with available phosphorus. Also, significant correlations were obtained between various types of phosphorus, which is presumably a reflection dynamic relationship between them in the soil. Regression analysis showed that calcium carbonate equivalent presumably is an important effective soil characteristic on distribution of P forms in studied soils.