Soil Phosphorus Forms and Profile Distributions in the Tidal River Network Region in the Yellow River Delta Estuary

Abstract

Modified Hedley fraction method was used to study the forms and profile distribution in the tidal river network region subjected to rapid deposition and hydrologic disturbance in the Yellow River Delta (YRD) estuary, eastern China. The results showed that the total P (Pt) ranged from 612.1 to 657.8 mg kg−1. Dilute HCl extractable inorganic P (Pi) was the predominant form in all profiles, both as absolute values and as a percentage of total extracted Pi. The NaOH extractable organic P (Po) was the predominant form of total extracted Po, while Bicarb-Pi and C.HCl-Po were the lowest fractions of total extracted Pi and Po in all the P forms. The Resin-P concentrations were high in the top soil layer and decreased with depth. The Pearson correlation matrix indicated that Resin-P, Bicarb-Pi, NaOH-Pi, and C.HCl-Pi were strongly positively correlated with salinity, TOC, Ca, Al, and Fe but negatively correlated with pH. The significant correlation of any studied form of organic P (Bicarb-Po, NaOH-Po, and C.HCl-Po) with geochemical properties were not observed in the study. Duncan multiple-range test indicated that the P forms and distribution heterogeneity in the profiles could be attributed to the influences of vegetation cover and hydrologic disturbance.

Forms and vertical distributions of soil phosphorus in newly formed coastal wetlands in the Yellow River Delta estuary

“…The total organic carbon (TOC), Ca, Al, and Fe ranged at 1.5–16.7, 32.7–69.0, 53.1–81.0, and 16.7–44.4 mg g −1 , respectively (Table ). The soils in this study were classified according to their organic matter (C org < 20%) and taken as the mineral soils (Yu et al, ). As the organic matter is easily dissolved in water, it was lost during the long transportation process from the Loess Plateau to the estuarine coastal wetland via the YR.…”

“…has been identified as the climax vegetation species in the delta wetlands. The main soil types are typical saline alluvial soils (Fluvisols, Food and Agriculture Organization; Yu et al, ).…”

“…For better understanding of different geochemical or ecological significance of P forms, Tiessen and Moir promoted a modified Hedley fractionation scheme, which extracted P i and P o of increasing chemical stability (Fabre, Gauquelin, Vilasante, Ortega, & Puig, ). This modified procedure and the measurements of soil parameters and the content of have been specifically described by Yu et al (). A laser particle analyzer (Malvern Mastersizer 2000F) was used for the measurement of grain size.…”

“…Phosphorus (P) attached to sediment is initially eroded from upland regions and transported to waterbodies in the P cycle (Bruland & DeMent, ). The P sediment and river water may travel through wetlands in most of wetlands and muddy coasts before reaching the ocean to complete the cycle (Yu et al, ). P entering these coastal wetlands, which is partitioned into organic or inorganic forms, will be partitioned into labile and refractory components to understand the soil P availability in the study of its biogeochemistry (Levy & Schlesinger, ).…”

“…As one important nutrient element, P forms have a close linkage with soil quality, further directly influencing land degradation, especially in the coastal zone (Gao et al, ; Tian, Zhai, Zhao, & Mu, ). Previous studies have used sequential fractionation to partition the soil P into inorganic, organic, and microbial forms (Levy & Schlesinger, ), which subdivided into the plant‐available forms (including Resin‐P i , NaHCO 3 ‐P i , and NaHCO 3 ‐P o ) and the refractory forms (including NaOH‐P i , NaOH‐P o , Dil.HCl‐P i , Conc.HCl‐P i , Conc.HCl‐P o , and Residual‐P; Yu et al, ). Across different mineral weathering and soil development gradients, the organically bound fractions and the geochemically bound fractions in soil P, which were used to describe the contribution of biological process, were easily separated by the Hedley, Stewart, and Chauhan () fractionation (Cross & Schlesinger, ; G. Wang et al, ).…”