Effect of flood and drip irrigation and difference of previous crop residue input on morphological and physiological traits in rice root

ABSTRACT Detailed information on the root system under drip irrigation will help in more efficient irrigation scheduling. Although input of previous crop residues is effective in increasing soil fertility, little is known about its effect on the root system. This study aimed to investigate the effects of irrigation methods (drip or flood) and different management of previous crop residues on root morphological characteristics and its distribution and physiological functions of the rice cultivar ‘Hinohikari’. Experiments were conducted in the paddy field on the university farm (input previous crop residues every year) for both drip and flood irrigation and the paddy and upland field (no input previous crop residues) on the campus of the faculty under flood and drip irrigation. Plant root was sampled with a core sampler (ø 5.5 cm × 30 cm), and root length and surface area were determined using image analysis. Drip irrigation did not change root length compared to flood irrigation, but the root system was heavier and individual root thickness tended to increase compared to flood irrigation. The root depth index was significantly deeper in drip irrigation than in flood irrigation. The bleeding rates were significantly higher in flood irrigation than in drip irrigation. Applying previous crop residues significantly improve root length mainly at the upper soil layers. The mechanisms for enhancing root growth by applying previous crop residues need to be explored individually in flood and drip irrigation, in which physical and chemical properties in soil are largely different. Graphical Abstract