Background The Ordos Plateau is a typical arid and semi-arid grassland area. Over reclamation of grassland is one of the main causes for shrub encroachment and desertification in the Ordos Plateau. Soil moisture is a key factor for restoration of abandoned cropland in arid and semi-arid areas. The characteristics of soil water infiltration are closely related to soil moisture in different soil layers, and the soil water infiltration in different soil layers can affect vegetation succession process in abandoned croplands. In order to better understand changes of soil water infiltration with vegetation succession in abandoned croplands, the characteristics of soil water infiltration on abandoned croplands with different abandoned years in soft hill and hard ridge in the Ordos Plateau were investigated.

Methods In soft hill and hard ridge of the Ordos Plateau, croplands with different abandoned years (12 kinds of abandoned cropland) were selected, and double ring infiltration device was used to measure soil infiltration parameters, and Kostiakov-Lewis model was used to simulate soil infiltration process of these abandoned croplands with different abandoned years.

Results 1) In soft hill, the initial infiltration rate decreased over abandoned years, but it did not show significant difference among different abandoned years. The final infiltration rate and the total infiltration height declined over abandoned years, reached the lowest values in 15th year, and then increased over abandoned years, and the final infiltration rate and the total infiltration height showed a significant decrease in 10th year. 2) In hard ridge, the initial infiltration rate, the final infiltration rate and the total infiltration height were positively correlated with abandoned years before it reached split point in 10th year (for the initial infiltration rate) and 15th year (for the final infiltration rate and the total infiltration height), thereafter declined with further increase of abandoned years, and there were significant increase from 10th to 15th year. 3) In soft hill, there was no obvious change in a value over abandoned years, but K value showed a decreasing trend with the increase of abandoned years. There was no significant change in a value over abandoned years, K value increased with the increase of abandoned years, reached the highest value in 10th year, and then declined. K value showed a significant increase from 10th year to 20th year in hard ridge.

Conclusions With increase of abandoned years, the soil water infiltration decreased and soil water might increase in shallow soil layers in soft hill; soil structure and soil water infiltration capacity were improved in hard ridge. These results implied that the water and soil preservation capacity gradually improved in croplands over abandoned years without human disturbance, and the results may provide scientific basis in decision-making for restoration of abandoned croplands in Ordos Plateau.