Taking the soils under three different reclamation modes

i.e. reclamation filled by Yellow River sediments

reclamation filled by lake sediments

and beforehand reclamation

in the Jining region as the research objects

spatial distribution characteristics of various forms of inorganic phosphorus (Ca2-P

Ca8-P

Al-P

Fe-P

O-P

Ca10-P) in soils under different reclamation modes were studied

and the reasons for low phosphorus availability in reclaimed soils were investigated. The result shows that: (1) Total phosphorus content in reclaimed soils under different reclamation modes was between 0.42 to 0.77 g/kg

and available phosphorus content was between 0.65 to 5.22 mg/kg

total phosphorus content was higher in reclaimed soils

but plant-available phosphorus content was lower. (2) In reclaimed soils

contents of sparsely plant-available inorganic phosphorus (Ca10-P and O-P) were the highest

and the contents of Ca8-P and Ca2-P

which are plant-available

were the lowest. For the contents of various forms of inorganic phosphorus

there were slight differences among different reclamation modes. Compared with normal soils

the proportion of Ca8-P in reclaimed soils decreased

accounting for about 3% of total phosphorus

but the proportion of sparsely plant-available O-P increased

accounting for about 32% phosphorus. (3) Total inorganic phosphorus and various forms of inorganic phosphorus accumulated in surface soils

phosphorus content and availability decreased with increasing soil depth

with the content and availability in soils under the modes of reclamation filled by Yellow River sediments and reclamation filled by lake sediments being higher than that in soils under the mode of beforehand reclamation.(4) There was a significant negative correlation between plant-available phosphorus and soil compactness

r=-0.554*(p＜0.05)

and there was an extremely significant positive correlation between plant-available phosphorus and Ca10-P

r=0.650**(p＜0.01). In reclaimed soils

a greater compactness and a lack of effective source of phosphorus could account for the lower phosphorus availability. In comparison

phosphorus conditions in soils under the mode of beforehand reclamation were worse because this mode got greater mechanical compaction.