Background Simian Mountain in Chongqing is an important ecological barrier and main water source of the Yangtze River, and it is also one of the sensitive ecological areas in China. Due to long-term over-cultivation and frequent human activities in recent years, the local ecological conditions are very fragile, which seriously affects the growth of vegetation and has a negative impact on agricultural development, thus the local ecological restoration is very important.Soil water infiltration, as an important factor affecting vegetation growth and groundwater circulation, is a key factor in local farmland vegetation management.Therefore, it is of great significance to study the influence of root distribution on farmland soil moisture infiltration in Simian Mountain of Chongqing to local farmland vegetation management.

Methods Three typical farmlands, namely corn(Zea mays) field, eggplant (Solanum melongena)field and pumpkin (Cucurbita moschata)field, were selected to measure soil water infiltration amount and infiltration rate through double-ring infiltration experiments.After that, the root system was sampled by soil column method. The root length density and root weight density of root samples were calculated by Epson Perfection V370 digital scanner and root analysis software (Win-RHIZO 2008a). The relationship between soil root system and water infiltration was analyzed by grey correlation degree method.

Results 1) The initial infiltration rates were 258, 213 and 285 mm/h in the maize, eggplant, and pumpkin fields respectively, and the average infiltration rates were 154.99, 136.84, and 203.07 mm/h. The infiltration volume and infiltration rate were relatively the highest in the pumpkin field and the lowest in the eggplant field. 2) The amount of water infiltration and infiltration rate of the three types of farmland were the highest in the pumpkin field and the lowest in the eggplant field. 2) The root systems of the three types of farmland were mainly fine roots less than 3 mm in diameter, with a low number of coarse roots. The maximum values of root length density, root weight density, and root pore number for each diameter class were all found at 0-20 cm of soil, with less root content in deeper soils. 3) Plant roots in the soil have a certain influence on water infiltration, and the grey correlation values between each root characteristic index and each soil water infiltration index are all greater than 0.6, and the influence of fine roots on infiltration is greater than that of coarse roots.

Conclusions The root system is closely related to the movement of external water supplies through the soil and is an influential factor in on-farm management that cannot be ignored.