Effects of planting patterns on the lodging resistance characteristics and yield of winter wheat with delaying irrigation at the jointing stage

Winter wheat is the primary cropping system in grain production in the North China Plain. In this study, two planting patterns were applied, including the precision planting pattern (W) and conventional cultivation planting pattern (C), in order to clarify the effect of different planting pattern on lodging resistance of winter wheat with delaying irrigation at the jointing stage. In each planting pattern, the winter wheat was irrigated with 60 mm at the jointing stage (I1), and delaying irrigation 60 mm for 10 d at the jointing stage (I2). The main physical indexes of winter wheat stalk were measured, including the plant height, gravity center height, and fresh weight, as well as the diameter, fresh density, and the wall thickness of the basic secondary internode. A systematic investigation was made on the internode mechanical indexes, such as the bending resistance and bending rigidity of basic secondary internode, lodging resistance index, the creep deformation in the basic secondary internode of winter wheat at heading, filling and dough growth stage. The planting pattern and irrigation schedule were explored for comprehensive optimization on the lodging resistance of winter wheat. The results showed that there was a significant trend to improve the bending resistance strength in the basic secondary internode, and the bending rigidity significantly increased at the heading stage under the wide precision planting pattern with delaying irrigation at the jointing stage. However, the bending resistance strength and bending rigidity in the basic secondary internode, and the fresh weight were significantly reduced at the dough stage in this treatment. The wide precision planting pattern with delaying irrigation at the jointing stage significantly increased the lodging resistance index at the heading stage, and thereby improved the lodging resistance index at the dough stage, where the average lodging resistance index at the heading, filling, and waxing stage were 2.03, 1.58 and 1.87 N/(m·g), respectively. The basic secondary internode of winter wheat had creep characteristics under the proportional load less than its ultimate bending resistance strength. Specifically, the average maximum of creep strain was the highest at the heading stage, and it was still large at the filling stage under the wide precision planting pattern with delaying irrigation at the jointing stage. All of mechanical behavior was in the transition from the deceleration to stable creep stage, where the maximum creep strain ranged from 0.6%-3.7%, and the average maximum of creep strain ranged from 0.7%-2.5%. Combined with the lodging resistance index and creep test, the lodging resistance of winter wheat was the best under the condition of wide precision planting pattern with delaying irrigation for 10 d at the jointing stage. The findings can provide a promising theoretical basis and technical support for water saving and high yield of winter wheat in North China Plain.