In situ simulation was performed on the corn stalks under the mode of planting and returning by nylon bag method. The experiment was conducted to compare the effects of different amounts of straw returning to field on soil total phosphorus

available phosphorus and different forms of organic phosphate. In the experiment

four levels of R0 (0%)

R1 (0.44%)

R2 (0.88%)

R3 (1.32%) and three different returning depths of 0-15 cm

15-30 cm and 30-45 cm were carried out. The results showed that the soil total phosphorus content did not change significantly with the increase of the amount of straw returning to field after 1 year. Compared with R0

the soil available phosphorus in R1

R2 and R3 increased by 27.0%

49.3% and 64.1% respectively in 0-15 cm soil layer. The available phosphorus in 15-30 cm and 30-45 cm soil layers also showed a significant increase with increasing amount of straw returning to soil

and the increasing amount followed by the trend: 0-15 cm>15-30 cm>30-45 cm. Compared with R0

the contents of active organic phosphorus and high-stable organic phosphorus of R1

R2 and R3 in 0-15 cm soil layer showed no significant difference

and the middle active organic phosphorus decreased by 12.8%

26.2% and 36.3% respectively

and the content of stable organic phosphorus increased by 25.1%

53.5% and 61.6%. In 15-30 cm and 30-45 cm soil layers

soil moderate organic phosphorus increased respectively with the amount of straw returning and the content of moderate active organic phosphorus increased and the content of moderate stable organic phosphorus decreased

while there was no significant difference between active organic phosphorus and high stable organic phosphorus. The results showed that maize straw returning to field could increase the content of available phosphorus in soil by promoting the conversion of phosphorus from other forms of soil to available phosphorus. Maize straw returning could supply phosphorus source for direct use in the next season. Meanwhile

it could improve the moderate stability organic phosphorus content and reduce the moderate active organic phosphorus content in the soil.