Wheat root systems and water utilization in a semi-arid region

Abstract

The deep and thick soil layer on a semi-arid loess plateau provides ideal natural conditions for the full growth of plant roots. Under these field conditions, the average depth of winter wheat (Triticum aestivum L.) roots is about 3.7 m, and the maximum depth is up to 5 m. In the growing period, the average rate of root penetration downward is approximately 1.5 cm per day. There is a linear relationship between the depth (Y) and day (X), i.e., Y=8.89+1.5X. The progress of the root system obeys the fifth order growth model: Y=8.17−20.68X+1.06X²-0.013X³+6.7X10-5X⁴-1. 1X10-7X⁵(R=0.9959 * *), (Y - root biomass, kg/ha., X - number of days after seeding). The increase in the number and in the biomass of roots appears in two peaks, one before winter and the other in spring. The maximum root biomass occurs at the stage of heading. Root growth progress comes earlier than the above-ground shoot, showing the relationship between the root and the shoot in nutrition and water supply. The vertical distribution of the number and biomass of roots follows a negative index model: Y=Ae^-Bx(R>0.95 * *). The roots decrease with the increase of soil layers. Although the roots are fewer in the deeper soil, they are located in a favorable moisture environment and play an important role in the formation of wheat yield in dryland fields. The high-yielding wheat is characterized by large, well-developed root systems in deeper soil layers. Techniques such as fertiliser input, irrigation and rotation with deep-root crops can promote the penetration of roots downward to deeper soil. Wheat with deep and well-developed roots can absorb more water and nutrition from the larger soil volume, especially in deeper soil layers. The water efficiency and yield of wheat are highest in three seedling types.