Phosphorus (P) fractionation is the validation of the nature, solubility and relative bioavailability of P. A sequential P extraction was used to determine the distribution of plant-available P fractions in soils. The relationships of these P fractions to soil properties and foliar P contents were also determined. Results of this study showed substantial differences in soil properties among orchards. Higher amounts of soil organic matter (SOM), cation exchange capacity (CEC) and major plant nutrients were found under orchard soils when compared with control soil. Most of the soil variables varied among orchard species as loquat > citrus > guava. The orchard soil exhibited a slightly higher soil pH. Overall, the P fractions were higher in all types of orchard soils and lowered in the control soils. Among tree species, P fractions in soils were achieved as loquat > citrus > guava. The extracting agents differed for P in the order residual P > HCl-P > NaOH-P > NaHCO₃-P > H₂O-P. Mostly higher amounts of the P fractions were achieved in the topsoil. The average amount of extractable P was found significantly higher in those soils of fruit orchards where the total amount of P was actually higher. The higher r² values between P fractions versus SOM, clay and CEC of soils predicted a strong interrelationship among these soil variables. Leaf N contents of loquat and guava trees were consistently higher, and leaf P contents varied as loquat > citrus > guava. Potassium and Ca contents were higher in citrus than in the other two species. Micronutrients were found as Fe > Zn > Mn > Cu in the leaves. Regression models indicated a sufficient relationship between Hedley P fractions and the foliar P contents in tree species. This study indicates that the above soil properties can be used to ascertain soil P fractions, and that can influence the bioavailability of P from orchard soils.

Lead (Pb) is an environmental pollutant, and its concentration in the soil environment has received greater attention. Studies on the interrelation of Pb and major soil properties using different extraction methods have been poorly documented. The lead extraction method is important to be identified, which may accurately reflect Pb extractability from soils. Therefore, a study was conducted to investigate the Pb pollution of roadside soils. Four extractants: ammonium acetate (NH₄OAc), hydrochloric acid (HCl), diethylenetriaminepentaacetic acid (DTPA), and sodium hydroxide (NaOH). Soil samples were sieved for three particle sizes: finer to coarser particles (0.5 to 2 mm). Results showed that there were substantial differences for Pb concentrations among sampling sites depending on the extracting reagents: HCl > DTPA > NH₄OAc > NaOH. The extractability of Pb from soil was apparently enhanced with the increasing strength of a reagent used for the soil solution. The NH₄OAc extractable Pb concentrations in the surface soil samples from the Abbottabad area ranged from 67.9 to 246.7 mg kg⁻¹, and in Haripur, the Pb concentrations ranged from 97.6 to 242.5 mg kg⁻¹. At 20% HCl solution, the average Pb concentrations were 2.6 times higher than the NH₄OAc solution in the topsoil of Abbottabad area. The roadside soils contained Pb concentrations higher than the permissible limits. The control soil samples (from a distance of 200 m) exhibited Pb concentrations in the relative range of 28.5 to 61.7 mg kg⁻¹. Pb concentrations in the topsoil and subsoil were found to be apparently inconsistent. The concentration of Pb was higher in the soil containing a higher amount of organic matter and clay content. The soil pH and particle size were inversely related to extractable Pb in the soil. Higher Pb pollution in the soil could be associated with the higher traffic density.