Phosphorus Fractions of Selected Calcareous Soils of Qazvin Province and their Relationships with Soil Characteristics

Abstract

Informations of phosphorus fractions are important for evaluation of their status in soil and understanding of soil chemistry that influence soil fertility. To obtain such information, amount and distribution of P in different fractions of 20 soil samples of Qazvin province, Iran were determined by sequential extraction methods and their relationships with each other and with soil characteristics were investigated. Total P of different soils ranged from 700 to 1040 mg kg . The clay contents of different samples ranged from 18-52%, CEC -1 from 14.5-33.5 cmol.kg and the active CaCO from 2.9-19.4%. The amount of different P forms i.e. dicalcium -1 3 phosphates (Ca -P), octacalcium phosphates (Ca -P), Al-phosphates (Al-P), Fe-phosphates (Fe-P), occluded-P 28 (O-P) and P as apatite (Ca -P) were determined and found to be ranged from; 1.6-42.3, 72-314, 14.5-54.8, 8.4-34.8, 10 5.9-33.4 and 262-697 mg kg respectively. Simple correlation coefficients showed that Olsen-P had a significant -1 correlation with soluble-P, Ca -P, Fe-P and O-P.A significant correlation was also observed between the P forms 2 themselves, which is presumably a reflection of the existence of a dynamic relation between the chemical forms of an element in soil. Clay with Fe-P and O-P; total P with Ca -P, Al-P and Ca -P; CEC with Al-P and O-P have 8 10 positive significant correlation. Electrical conductivity (EC) with Ca -P and Al-P; organic carbon (OC) with Ca - 8 10 P and active CaCO with Ca -P have negative significant correlation. 3 10