Lodging characteristics after physiological maturity of spring maize sowed at different dates and its influencing factors

In the middle-south of Shanxi Province, light and heat resources are abundant leading to a wide range of sowing date for spring maize. A suitable sowing date should achieve high yield and lodging resistance by adapting to the regional meteorological and production characteristics. Therefore sowing date adjustment is an important issue in the popularization and application of mechanical grain harvesting technology for spring maize in this region. A field experiment was conducted in Dongyang Experiment and Demonstration Base of Shanxi Academy of Agricultural Sciences in 2019, consisting of 2 maize cultivars ('JKY3306' and 'ZD88') and 5 sowing date (April 16, April 23, April 30, May 7 and May 30). 'JKY3306' is a screened out cultivar with high yield and suitable for high population and mechanical grain harvesting; while 'ZD88' is a local cultivar. The results showed that lodging rates after physiological maturity of 'JKY3306' at different sowing dates had no significant difference. And lodging rates at the last four sowing dates was always 0. However, the lodging rate after physiological maturity of 'ZD88' increased significantly with the delay of sowing date (P < 0.05). According to the fitting equation, the lodging rate of 'ZD88' sowed at April 30, May 7 and May 14 was respectively increased by 1.3, 2.4 and 3.2 percentage points for every 10 days during grain dehydration period. Through the analysis of influencing factors on lodging resistance, the length of the third and fourth internode, the coefficient of ear height and the gravity center height could be used as the negative effect indexes to evaluate the lodging resistance. And the dry weight per unit length of the fourth internode, the bending strength of the third internode and the wet weight per unit length of the third internode could be used as the positive effect indexes. With the delay of sowing date, the biological yield and economic yield of the two varieties increased significantly at first and then decreased. Spring maize sowed around April 30 can achieve high yield and lodging resistance in this region. Therefore, April 30 is a suitable sowing date to popularize mechanical grain harvesting technology in spring production.