Organic and Inorganic Forms of Phosphorus in a Calcareous Soil Planted with Four Species ofEucalyptusin Southern Iran

Distribution of inorganic phosphorus fractions in some soil profiles of Zagros forest of Iran

“…The highest decrease in NaHCO 3 -P was observed in Deli profile where it decreased from 50.6 in A horizon to 6.5 mg kg −1 in Btk1. Although values similar to those of the present study are common in agricultural fields (Adhami et al 2006;Mostashari et al 2008) they are higher than those reported in virgin ecosystems such as those reported by Samadi and Gilkes (1998); Khanmirzaei et al (2009) and Ma et al (2009). In eight of the ten profiles, NaHCO 3 -P was higher than 20 mg kg −1 and in three profiles it was even higher than 40 mg kg −1 .…”

“…The highest content of NH 4 OAc-P (i.e., 81.9 mg kg −1 ) was observed in A horizon of Deli profile, a Calcic Haploxeralfs with 850 mm annual precipitation. Khanmirzaei et al (2009) reported that NH 4 OAc-P was 26-42.5 mg kg −1 in a calcareous soil under eucalyptus plantation. Adhami et al (2006) found that Ca 8 P (the same as NH 4 OAc-P in the present study) and MgCl 2 -P ranged from 15 to 366 and from not detectable -102 mg kg −1 , respectively, in 18 calcareous soils of the Fars province.…”

“…Labile and moderately labile inorganic P fractions are produced at the expense of primary Ca-P minerals (hydroxy and flouroapatite) and the extent of primary Ca-P compounds turnover to labile and moderately labile pedogenic Phosphorus fractions other than instantly soluble P could be important in natural ecosystems. Khanmirzaei et al (2009) reported that probably NH 4 OAc-P and NaOH-P (attributed to Ca 8 -P and Fe-P, respectively (Jiang & Gu 1989)) are labile inorganic P pools under eucalyptus plantation. Ma et al (2009) reported that Ca 8 -P and Fe-P concentration in the rhizosphere of Zygophyllum xanthoxylum and Atraphaxis bracteata were significantly less than those of corresponding bulk soil, which indicates the bioavailability of these fractions.…”

“…Although inorganic P fractionation in highly calcareous soils of Iran has been studied (Adhami et al 2006;Mostashari et al 2008;Khanmirzaei et al 2009) little attention has been paid to the distribution of inorganic P fractions in the soil profile of natural ecosystems, where subsurface P might be important in ecosystem's sustainability. One of such natural ecosystems is Zogros forest, which is under an international biodiversity conservation project.…”

“…In this situation, Ca-P is the main soil P fraction (Walker & Syers 1976;Khanmirzaei et al 2009); and may constitute up to 80% of inorganic P fractions that could be divided into labile, pedogenic, and lithogenic Ca-P compounds. Labile and moderately labile inorganic P fractions are produced at the expense of primary Ca-P minerals (hydroxy and flouroapatite) and the extent of primary Ca-P compounds turnover to labile and moderately labile pedogenic Phosphorus fractions other than instantly soluble P could be important in natural ecosystems.…”