Abstract:Alternate furrow irrigation is a biological water-saving technique and extensively applied to agricultural production in the arid and semi-arid region. There are the irrigated and non-irrigated root-zones alternately under alternate furrow irrigation. Because crop roots firstly sensed the variation of soil water and had a process of adaptation, their morphology characteristics and structure distribution under alternate furrow irrigation were studied to reveal the adaptive mechanism of roots system in the soil environment. Taking the roots both at ridge and slope as the research object, the minirhizotrons was used to investigate the changes of root length (living roots/dead roots), diameter, volume density, surface area, root tip number and diameter class as well as the correlations between each parameter of roots and soil moisture, soil temperature, water use efficiency (WUE). In the period of 52-78 day after the sowing of maize, the experiment was not influenced by rainfall (total precipitation is 5 mm in two times) and this period was chosen for the analysis of root morphology characteristics and structure distribution. Results showed maize roots were mainly distributed at ridge at the early growing stage, and its root production rate was greater than that at slope. Meanwhile, root metabolism was rapid with the higher root mortality rate. Alternate furrow irrigation had greater effect on the morphology indexes of maize roots at slope than at ridge, and after the re-watering in the non-irrigated root-zone at slope, the average root diameter was decreased, while the daily average root production rate, the volume density per unit soil area, the root tip number and surface area of the living roots were increased, and these indexes were gradually reduced with the decrease of soil moisture in the irrigated root-zone. At ridge, the average root diameter of the living roots is similar to that at slope, and the change trend of daily average root production rate, the volume density per unit soil area, the root tip number and surface area of the living roots is also similar to those at slope, but the values of these indexes were lower than those at slope. After the re-watering in non-irrigated root-zone at slope, the root mortality rate, root diameter, volume density, root tip number and surface area of dead roots were decreased, and the root mortality rate and diameter were gradually reduced with the decrease of soil moisture, while the root volume density, root tip number and surface area were gradually increased with the decrease of soil moisture. Root system was divided into four diameter classes based on the root morphology, and root morphological characteristics of different diameter classes were analyzed. In the distribution of root length and volume density, the roots with diameter( 2.5-4.5)×10-1mm accounted for the greatest proportion, while in the distribution of root tip number and surface area, the roots with diameter (0-2.5)×10-1mm accounted for greater proportion. Correlation analysis and significant test showed that the living and dead root tips and root mortality rate were significantly correlated with soil moisture, soil temperature and WUE. There are significant positive correlations between some morphological indexes of roots (root production rate, volume density of living roots, et al.) and soil moisture and soil temperature only at slope. Results indicated that alternate furrow irrigation regulated root morphology more significantly at slope than at ridge.