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

Table 2

Mean soil phosphorus concentrations by fraction in tidal river network region soils listed as mg P kg⁻¹ soil. Means were averaged from 18 soil samples in each type. Duncan multiple-range test was conducted with 17 degrees of freedom. The signification of different forms of phosphorus was described in [8].

P extract	BRB	RB	TB	TCB	Geochemical significance	Ecological significance
Resin-P	9.6^c	11.0^c	14.6^b	16.6^a	Nonoccluded, rapid turnover	Plant available
Bicarb-Pi	4.2^c	4.9^bc	5.8^b	7.1^a		Easily plant available,
Bicarb-Po	30.0^b	40.8^a	17.7^c	37.6^a		Easily mineralized
NaOH-Pi	4.0^b	5.4^a	5.7^a	6.2^a	Nonoccluded, slow turnover	Lesser plant available
NaOH-Po	32.0^b	43.9^a	25.7^bc	22.1^c		Not directly plant available
D.HCl-Pi	420.2^a	417.4^a	423.5^a	414.6^a	Occluded, slow turnover
C.HCl-Pi	45.0^c	61.6^b	73.8^a	78.0^a
C.HCl-Po	30.1^a	22.0^c	22.7^bc	28.6^ab
Residual-P	36.9^c	42.0^b	46.9^a	47.1^a
Pi	520.0^c	542.4^b	570.2^a	569.5^a
Po	92.1^b	106.7^a	66.1^c	88.2^b
Pt	612.1^c	649.2^ab	636.3^b	657.8^a

The a, b, c represent significant differences between means for groups, while means for groups in homogeneous subsets are displayed as ab and bc (𝑃=0.05,𝑛=18).