Exploring the relationship between deep roots and shoot growth of wheat under different soil moisture: A large soil column experiment 1

Abstract

The root system is the main organ for crops to absorb water. Crops adjust the growth of underground roots to obtain the most suitable growth state according to environmental changes. However, there is still a lack of research on how deep root systems affect crop growth. Therefore, this study designed a soil column experiment with a 3 m transparent glass tube depth. The soil moisture was controlled to be 50% (W1, water shortage), 70% (W2, suitable), and 90% (W3, surplus) of the maximum field capacity, respectively, and cut off the deep root system under 50 cm at the jointing stage of wheat. To explore the growth state of the deep root system under different soil moisture and its effects on the photosynthetic characteristics, growth characteristics, yield, and water use efficiency of wheat. The results showed that the W1 and W3 treatments increased the length of the deep root system at the heading stage of wheat by 15.5% and 1.3%, respectively, compared with the W2 treatment. The root system of W1 is distributed in deeper soil, while the root system of W3 is more distributed at 50–80 cm. After root cutting, the root system grows fastest under W3, followed by W1, indicating that crop root growth is affected by soil moisture and crop demand characteristics. Unlike the root response, aboveground growth, photosynthetic physiology, and canopy temperature of wheat increased with soil moisture, suggesting that below-ground and aboveground crop growth is not synergistic under soil moisture limitation. Cutting roots reduced wheat yield by 15.3% under W1. However, under W3 treatment, root cutting would reduce the short-term water consumption of wheat, but it would cause the regrowth of underground roots and increase the growth of aboveground parts, increasing the total water consumption of crops. While under W2, cutting the root can reduce the water consumption while maintaining the wheat yield. Therefore, maintaining appropriate soil moisture by adjusting irrigation strategies is an important measure to regulate the growth of wheat underground and above ground and ensure efficient production. At the same time, crops pay more attention to the function of deep root systems when water is scarce.