Objective: The study was to explore the geometric characteristics, spatial and temporal distributive patterns of root systems of spring wheat, millet, grain sorghum, and broomcorn millet. Method: Experimental methods employed were pot culture, soil column culture, chain link mesh box cultivation and field investigation. Result: Differences in root system characteristic patterns of the four cereal crops: Number of seminal root and secondary root was different, maximum striking depth of root systems was different which usually followed the order of grain sorghum > millet > spring wheat > broomcorn millet, maximum root extension was different, maximum root extension often showed an order of grain sorghum > broomcorn millet > millet > spring wheat. The basilar 1-3 node of millet, broomcorn millet and grain sorghum formed 1st round to 3rd round support root after tasselling, while spring wheat did not have support root commonly. Temporal distributive patterns of the four cereal crops in the experiment: root systems of millet, broomcorn millet and spring wheat grew downward gradually along with developing stage, root length and root weight increased persistently, the increase of root length and root weight showed slow-fast-slow patterns. The growth patterns of root weight and total root length of the four cereal crops accorded with S-type growth curve, while the increase per day for root length and root weight of grain sorghum was far larger than that of millet and broomcorn millet. Spatial distributive patterns of the four cereal crops in the experiment: in seedling stage root systems of the four cereal crops grew downward mainly; in each soil layer the absolute root amount increased gradually; root length and root dry weight mostly distributed in the soil layer of 0-40 cm depth; root systems hardly distributed in the soil layer of below 40 cm. Therefore, spatial patterns of the four cereal crops showed a clear T-shape. At jointing stage, root systems kept on growing downward, and the root amount in different soil layers increased distinctly. The spring wheat root weight enhanced notably, and spring wheat root length distribution showed 8-shape approximately. Patterns for root length and weight of the other three crops still showed a T-shape. At heading stage, the root length distributive patterns in different depth soil of millet, broomcorn millet and grain sorghum turned into 8-shape approximately, while the root length distributive patterns in different depths of soil of spring wheat showed an egg-shape. So, the root length of the four cereal crops in the experiment at late heading stage had superiority in middle and bottom soil layer. The vertical distribution of root weight of millet, broomcorn millet, grain sorghum followed the exponential equation y=A.e -bx , but different crops had different b values. The total root length distributive patterns of the four cereal crops in different soil depths at early stage followed the exponential equation y=A.e -bx , but at late stage it followed the multinomial y= ax3+ bx2+ cx+ d. Conclusion: The similarities in spatial distributive patterns of the root systems of the four cereal crops were positive, which provided a theoretical basis for root regulation for cultivation.
