Phosphorus Availability and Potential Environmental Risk Assessment in Alkaline Soils

Soil phosphorus (P) is an essential element that is often limiting in ecosystems. Excessive use of P fertilizers has led to P loss from soil and introduction into the environment. However, the behavior and potential risk assessment of P in alkaline soils is not well studied. Therefore, soil sampling was performed in alkaline soils in the northern Nile Delta, Egypt. Three analytical procedures (i.e., Mehlich 3 (P-M3), Olsen (P-Olsen), and Bray 1 (P-Bray) solutions) were used to evaluate P availability and potential environmental risk from P loss. Selected soil properties were determined using standard methods. Mean values of P extracted were in the order P-M3 > P-olsen > P-Bray, and were significantly correlated with each other. The P-M3 was the highest in silt clay loam and lowest in sandy and loamy soils. To predict potential P loss from the soils, degree of P saturation (DPS), soil P storage capacity (SPSC), and P stability ratio (P-sat) were calculated. Results showed the highest DPS was recorded in sandy textured soils, indicating that they have lower sorption capacity, whereas the SPSC was highest in silt clay textures; hence, it is likely they would act as a P sink. P-sat was highest in sandy soils, which indicated a high risk for P leaching. Principal component analysis (PCA) performed on the data identified four principal components that described 83.8% of the variation between P and the studied soil parameters. The results indicated that silt was the critical soil characteristic associated with both P sorption and extractability in different textures of soil. The second component confirmed the positive association between the different soil P extraction methods (P-M3, P-Olsen, and P-Bray).